Essential Biology for Cambridge ® IGCSE 2nd Gareth Williams Richard Fosbery Series Editor: Lawrie Ryan Edition Library; p112: BIOLOGY ATES/Science 3 Great Clarendon Photo MEDIA/Science Library; p118: Photo ADAM Library; p113: BIOPHOTO HART-DA VIS/Science ASSOCI- Photo Library; p118: © satit_srihin/istock; p119: © gregepperson/istock; p122: © jo unruh/istock; Street, Oxford, OX2 6DP, United p123: Kingdom © Nathan Benn/Ottochrome/Corbis; p123: © RGB Ventures/SuperStock/ Alamy; p123: © Eric Carr/Alamy; p124: Blend Images - Ariel Skelley; p124: © RichOxford University Press is a department of the University of Oxford. It ard Levine/Demotix/Corbis; p125: Charmaine A Harvey; p125: © FAYYAZ AHMED/ furthers the University’s objective of excellence in research, scholarship, epa/Corbis; and education by publishing worldwide. Oxford is a registered trade p128: Inc./Alamy; of Oxford University Press in the UK and in certain other © Gareth Williams to practical Library; paper and practice questions © OUP 2015 Library; p140: p147: © Gareth Williams and OUP right of Gareth asserted by Williams him to be identified as author of this work BIOPHOTO in accordance with the Copyright, Designs Act © PHOTOTAKE SYRED/Science Fosberry; p141: p147: Peter Richard Muller/CULTURA/Science Fosberry; p150: AJ Pho- PHOTO/HOP Photo Library; p155: ASSOCIATES/Science MEHAU Photo KULYK/Science Library; p156: Photo Library; BIOPHOTO ASSOCI- has Photo Library; Freema/Alamy; p159: p161: PROF Richard S. CINTI/Science Fosberry; p164: Photo © Library; Photofusion p160: Picture © Li- 1988. brary/Alamy; First p137: ANDREW and Michael Patents istock; p140: Original ATES/Science been p134: 2015 p156: The Library; bikeriderlondon; Richard AMERICAIN/Science illustrations Photo MichaelTaylor/Shutterstock; 2015 to Alternative p138: countries Photo Text CNRI/Science mark published in p167: ASTRID andamp;amp; HANNS-FRIEDER MICHLER/Science 2009 Photo Library; p168: © JohnPitcher/istock; p170: JEROME WEXLER/Science Photo This All in edition rights a retrieval without as published reserved. the the system, prior expressly in No or reproduction Library; this Oxford publication transmitted, by in law, the University any of licence rights scope in writing by reprographics outside Department, of permission permitted appropriate 2015 part of may form or Oxford or above Press, at the reproduced, by any terms be address sent come or the UK; p179: with © must this same not circulate this work in any other form Library; above. and you must on any Library Cataloguing ©Janine 19 8 7 835516 6 5 Paper used made from conforms Printed in Publication 4 3 in the wood to in the production grown in of this Britain book sustainable environmental Great make-up authors AMI p190: © Library; by is regulations Bell and a natural, forests. Bain of The the Ltd, recyclable product manufacturing country of ence process by and on for origin. p202: Cover publishers research work and on Publshing wish and the publisher photographs image: © Michael Markanja/istock; mesa/istock; Services, Natural brary; to thank Julietta commenting on Watson the for p6: p4: DA VID Visions; p9: Science © p8: Juanvi Photo in Alternative are grateful this & © MERS/Science ADRIAN Patricia to to practical the paper following Fogden/CORBIS; p4: SCHARF/Science © Photo Photo Mark Inc.; / © and p181: LIVING p181: ART EN- Photo EYE Library; OF p186: © Frank SCIENCE/Science Walker/Alamy; Photo Library; p189: DR JEREMY Library; BURGESS/Science p188: Photo Arnold, STEVE Inc./Alamy; p190: SUSUMU GSCHMEISSNER/Science NISHINAGA/Science Photo CNRI/Science Library; p33: p9: p2: © Library; p8: Oxford for Photo Library; M.H. p4: GREGORY © p3: kon- DIMIJIAN/ SHARP/Science © Photo Photo Birkhead; p18: p21: Carolina DA VID THOMAS p33: Library; Mike Li- p10: AUBREY/Science Samworth.; Photo Molloy; p63: Supply, Photo © GoGo Photo Library; p58: p56: MARTIN ROSENFELD DR GO- Library; Pho- Images Library; DESIGN/Science p12: Co/Visu- p21: NCMIR/Science p43: M.H. STAM- Library; Library; DEERINCK, p11: SINCLAIR Photo Biological Photo LAGUNA ASSOCIATES/Science IslandLeigh/istock; p12: BROWN/Science p47: Library/Cordelia Library; SVENSSON/Science SYRED/Science p29: Photo Library; p63: © Nigel Cattlin p46: Photo Li- Ecoimages/Foto- DOHRN/Science IMAGES LTD/Science / Alamy; p64: © Roel Smart/istock; p66: GEOFF KIDD/Science Photo Library; p73: © lo/istock; p74: © Maica/istock; p74: © image BROKER / Alamy; p74: GUSTOIMAGES/Science Photo Library; p77: BIOPHOTO AS- SOCIATES/Science brary; p80: IAN Photo Library; BODDY/Science p77: BIOPHOTO Photo Library; ASSOCIATES/Science p85: EYE OF Photo Li- SCIENCE/Science Photo Library; p86: CNRI/Science Photo Library; p87: © Les Stone/Corbis; p87: Eco Images; Sturt; p90: p91: Alamy; CHUCK Photo p90: LOUISA PRESTON/Science BROWN/Science SYRED/Science Science Photo Library; p94: Library; Photo p92: BIOPHOTO Library; Gene Photo p91: Cox; Library; Gene p94: DR ASSOCIATES/Science Cox; p92: JEREMY Photo p91: Noel POWER BURGESS/ Library; p94: BIOPHOTO ASSOCIATES/Science Photo Library; p96: BIOPHOTO ASSOCIATES/Sci- ence Photo p195: PROF. P. MOTTA/DEPT. Library; OF p193: D. ANATOMY/UNI- ANATOMICAL TRA VELOGUE/Science Library; Library; p97: p200: Photo DR G. Library; Photo p199: Library; JAMES p199: ANA- MOSCOSO/Science STEVENSON/Sci- Photo Library; p201: istock; p204: OF DR J. P. p210: ABEILLE/Science © sean HEALTH/Science Photo Library; p218: sprague Photo / Library; MICHEL Photo Alamy; p214: DELARUE, Library; p210: © p209: © monkeybusi- NIAID/NATIONAL video1/istock; ISM/Science p214: Photo INSTI- CNRI/Sci- W ALKER/Science Photo Library; p219: Library; Dimarion/Shutterstock; p220: D. p219: Photo Library; p221: PASCAL GOETGHELUCK/Science Photo PHIL- Library; © Martin ence Photo Shields/Alamy; ence Photo Library; p227: © p224: © PeterAustin/istock; CuboImages srl/Alamy; p229: p226: DA VID REVY , ISM/Sci- NICHOLLS/Sci- to megasquib/istock; p6: johnaudrey/istock; BARRINGTON Photo Photo p58: AND Library; A. © BJORN Samworth.; BIOPHOTO Science Library; Paul permission Scientic/Mike AUBREY/Science Library; Library; p43: ISM/Science p54: p56: Photo Photo Mike p11: p12: POWER Photo Corporation/Alamy; REVY , Photo section. Shadow_Hawk/istock; Photo Kostich/istock; Alamy; DA VID Library; Library; p19: MURTI/Science brary; p10: BICKER/Science Unlimited, AND Library; Library; p229: BIOPHOTO ASSOCIATE/Science Photo Library; p232: © book. Rinek/istock; Carrasco Library; SHARP/Science lia; inhauscreative/istock; Underwood/Corbis; her manuscript TED KINSMAN/Science Photo Library; p10: © Lupos/istock; p10: STUART WILSON/ J.C. © DUR- Well- Kent Science Photo Library; p7: M.I. W ALKER/Science Photo Library; p8: Heather Angel to Photo Peter nessimages/istock; Glasgow Ian p21: p187: TRA VELOGUE/Science Photo TUTES GreenGate the his authors reproduce PAL Photo & JOHN p177: BlueSkyImage/Shutterstock; p201: MAURO FERMARIELLO/Science Photo Library; p223: Connell als p179: Underwood LTD/Science IMAGES/Science p193: p199: LIPS/Science assistance / Gjorgiev/Shutterstock; 1 M.I. © © FERMARIEL- p175: 8 2 ence The MAURO Data Acknowledgements The HEALTH DALE/Science TOMICAL Page Vladimir p180: p174: available 0 9 Library; Audras/Onoky/Corbis; Wiedel/Photofusion; blickwinkel/Alamy; VERSITY; 10 Photo Eric p176: Levine/Alamy; PHILLIPS/Science 978 © acquirer. Photo Data Library; ANIMAL p186: © Library; British p177: p175: impose DARWIN condition Photo Richard CATTLIN/Science Library; TERPRISES, LLC/Science Photo Library; p185: DR JEREMY BURGESS/Science Photo Rights p187: You NIGEL Photo MOREDUN concerning to p171: LO/Science HAM/Science Press, agreed Enquiries should stored means, University under organization. the be CLOUDS HILL IMAGING LTD/Science Photo Library; Shaw/Alamy; p233: anAnthony/istock; p236: Kim p236: © brary; JEROME p234: FRANCIS Fenemma/Visuals STEVE LEROY , Unlimited, karlumbriaco/Fotolia; p237: WEXLER/Science p237: ALLEN/Science Photo p234: BIOCOSMOS/Science Inc./Getty; MAURO Photo Library; p236: © Photo Mirko p238: Science Library; Zanni/Getty; FERMARIELLO/Science Library; Christi- Photo Photo Li- Library; p238: FLETCHER andamp;amp; BAYLIS/Science Photo Library; p238: TONY CAMA- CHO/Science John Photo Giustina; Library; p240: (c) driftlessstudio/istock; ence Photo Library; rishwad/istock; Adrian p262: Muttitt POWER p265: p244: p253: p260: / JOHN Michele © Elliot ANDREW Image Alamy; AND p240: 2008 MAXIMILIAN STOCK SYRED/Science p260: SM ROSENFELD SYRED/Science All Nichol/Alamy; Source; p261: MOSS/Science Westmorland Photo LTD/Science p253: Photo Raq IMAGES Library; Photo Photo Rights Library; p240: Reserved; HUGH Library; LTD/Science Library; © Olha p266: © SPENCER/Sci- p254: © Photography/Getty; p264: (c) p241: Photo am- p261: Library; Rohulya/istock; © chas53/istock; p266: © Nigel Cattlin/Visuals Unlimited/Corbis; p270: © CARLOS BARRIA/Reuters/ Corbis; p270: Thomas John Sukpaiboonwat/Shutterstock; Marent/Getty; Potter/Alamy; Photo Library; ence Photo p275: p277: SOHM/VISIONS OF Library; Photo DR p280: Library; BENSCH/Reuters/Corbis; p283: PETER LTD/Science Photo DIRK Library; Fosberry; © p285: kozmoat98/istock; Library; WIERSMA/Science p281: SHEILA © WILL p284: Photo MARTIN © Library; MARTIN Corbis. Photo p285: Rights p282: © © p278: © JOE BOND/Sci- p280: DENI Library; p283: p284: BOND/Science All Library; Library; p271: p274: NUNUK/Science p280: Photo Library; paulprescott72/istock; p286: DA VID Photo Coret/Corbis; Photo jeanro/istock; andamp;amp; TERRY/Science Olivier SCOONES/Science p285: Photo frei-impuls/istock; © p276: BURGESS/Science Library; p282: © p272: chiarito/istock; SCIENCES/Science Richard © davide p281: AT p271: osiris59/istock; JEREMY Photo SOULABAILLE/LOOK tock; © © AMERICA/Science HESELTINE/Science Science p272: JOHN MCINTYRE/ p281: © YVES FABRIZIO George Clerk/is- ROSENFELD IMAGES Photo Library; Lourens Reserved.; p285: Smak/Alamy; p286: Michael & Patricia Fogden/Getty; p286: Richard Fosberry; p287: © Enjoylife2/istock; p287: © GoodOlga/istock; tock; p288: p289: © © p288: Juniors National Erick Margarita Bildarchiv/Alamy; Geographic Image Images/Shutterstock; p289: p288: SCUBAZOO/Science © mkos83/is- Photo Library; Collection/Alamy. p104: RIA NOVOSTI/Science Photo Library; p105: Photo Researchers, Inc. /Science Artwork Photo Library; p108: BIOPHOTO ASSOCIATES/Science Photo Library; p108: Photo Library; p110: BIOPHOTO ASSOCIATES/Science Photo by Greengate effort has © ChristianAnthony/istock; p112: STEVE been made to Services contact all and OUP. copyright holders, but if any have Library; inadvertently p111: Publishing CNRI/ Every Science GSCHMEISSNER/Science been overlooked, the publishers Photo necessary amendments at the first opportunity. will be happy to make the Contents Introduction Unit 1 1 Characteristics of living Characteristics 1.2 Classication Features of of Vertebrates 1.5 Invertebrates 1.6 Ferns 1.7 Dichotomous Starvation 7.5 Digestion 78 7.6 Teeth 80 living organisms 7.7 Mouth, 7.8 Small intestine and absorption 84 7.9 Large intestine and intestinal 86 Unit 2 2.1 oesophagus Structure Different 2.4 Levels owering plants keys 8 Plant transport Transport Water 8.3 Transpiration 94 of cells 8.4 Translocation 96 Practice 98 types of of cell organisation Movement Osmosis Active in in and plant out of cells and animal cells transport Transport 24 9.1 Circulation 100 26 9.2 The 102 Chemical 9.3 Heart 9.4 Blood 9.5 Coronary 9.6 Blood 9.7 Blood 9.8 Lymph heart and molecules 106 heart disease (CHD) 108 110 32 in defence 112 and for tissue uid 114 questions 116 10 Diseases and immunity 118 38 biological molecules questions 10.1 Disease 10.2 Defence 118 10.3 Aspects 10.4 Controlling 40 against disease 120 Structure 5.2 Factors and action of enzymes enzyme Practice Plant and pH 6.1 Photosynthesis 6.2 What 6.3 Products of Unit 11 Gas spread 122 of disease questions exchange 124 126 in humans 128 11.1 The gas 11.2 Gas exchange exchange 11.3 Breathing 11.4 Rate system 128 needed 132 52 photosynthesis? photosynthesis photosynthesis and Practice 54 54 for 130 50 nutrition of 46 the 48 questions is immunity action: temperature Enzymes Practice 46 affecting of 44 Enzymes Rate 104 42 5.1 6.4 exercise vessels 38 DNA Practice 6 100 36 molecules tests humans 28 Unit Biological in 34 questions Biological questions 9 Practice Unit 92 22 questions Practice 5.3 90 20 30 5 systems uptake 18 Osmosis Unit 90 8.2 3.2 4.3 88 8.1 28 4.2 questions 16 Diffusion 4.1 disease 14 3.1 4 82 12 organelles Practice Unit stomach 10 Unit 3.4 and 18 2.3 3.3 76 8 Cells Cell 3 74 deciency 6 questions 2.2 Unit needs nutrient 2 Unit Practice and 4 Practice and energy 2 organisms 1.4 Balancing 7.4 classication organisms 1.1 1.3 and 7.3 Unit 12 of breathing 134 136 Respiration 138 56 12.1 Aerobic 12.2 Anaerobic respiration 138 58 respiration 140 60 Practice production depth questions questions 142 6.5 Glasshouse 62 6.6 Leaves 6.7 Mineral requirements 66 13.1 Excretion 144 Practice questions 68 13.2 Kidney structure 146 13.3 Kidney function 148 13.4 Kidney Unit Unit 7 7.1 Animal A 13 Excretion nutrition balanced diet 70 dialysis Sources of nutrients and kidney transplants 150 70 Practice 7.2 144 64 questions 152 72 iii Contents Unit 14 Coordination and control 14.1 Nervous 14.2 Neurones 14.3 Synapses 14.4 Sense 14.5 The 14.6 Hormones 14.7 Controlling conditions 14.8 Controlling body 14.9 Tropic and and in response humans reex arcs drugs organs eye 154 Unit the body Unit 15 18.1 Variation 232 18.2 Mutations 234 158 18.3 Adaptive 236 160 18.4 Natural 162 18.5 Selective 15.2 Heroin 15.3 Alcohol questions and Practice Smoking the and misuse of health Asexual 16.2 Flower 16.3 Pollination 16.4 Fertilisation 16.5 The male 16.6 The female 16.7 Fertilisation 16.8 Pregnancy and sexual reproduction and seed formation system Pyramids 19.3 Shortening 19.4 Nutrient 174 19.5 The 176 19.6 Populations, 178 19.7 Human Methods reproductive and environment 244 ow 244 of numbers and biomass 246 the food chain 248 Control care of of Sexually system implantation nitrogen 250 cycle 252 communities and 254 populations Practice 256 questions 258 20 Biotechnology and genetic engineering 260 184 20.1 Microorganisms 186 20.2 Enzymes 188 20.3 Fermenters 264 190 20.4 Genetic engineering 266 Practice questions 268 Human inuences and and biotechnology biotechnology 260 262 194 21 on ecosystems 270 196 and birth 21.1 Food 21.2 Habitat supply 270 21.3 Pollution 274 21.4 Water 276 21.5 The 21.6 Acid 21.7 Sustainable 21.8 Sewage 21.9 Endangered destruction 272 200 202 cycle birth greenhouse effect 278 206 fertility transmitted pollution 204 control rain 280 208 infections (STIs) questions resources 282 210 treatment and recycling 284 212 Inheritance species 286 214 21.10 genes and Conservation 288 Practice 290 Chromosomes, 17.2 Protein 17.3 Mitosis 17.4 Meiosis 17.5 Inheritance 17.6 Monohybrid 17.7 Codominance 226 17.8 Sex 228 synthesis and genes inheritance linkage questions DNA 214 17.1 Practice cycles 198 menstrual Practice iv their ecosystems 192 hormones The 17 and Energy 184 reproductive Ante-natal 16.12 Unit 242 182 structure 16.11 16.14 Organisms 19.2 Unit 16.13 questions 19.1 180 Reproduction Sex 19 drugs questions 16.1 16.9 240 166 Unit 16.10 238 breeding 172 sport Practice 16 features selection 174 Drugs Unit 232 170 Drugs in selection 168 responses 15.1 15.4 temperature and 154 164 in Variation 156 Unit Practice 18 questions 216 Alternative 218 Glossary 298 220 Index 307 222 224 230 to practical paper 292 Introduction This book is designed specically for Cambridge ® IGCSE Biology involved in planning match all to 0610. Experienced aspects ensure possible to of that the the the teachers book, have including content gives been STUD Y the Expe rienc ed best you syllabus. to Using this book will ensure that you are for studies beyond the IGCSE level in avoid pure to sciences, in vocational below and are applied courses. sciences The designed effective as to make the learning book as you the at and end of the will should tnemelppuS Some be are able the only if supplement clearly start tell on or how ques tions . interesting KEY of you to each do will you the at the the as spread is are not questions you to test included your in every understanding topic of and the syllabus. At needed but the interest are goes in the covered end of in in are the each topic. unit there questions is a double written by page the of authors. the At throughout from any that KNOW? examination most learn QUESTIONS examination-style These the to spread. SUMMARY these work YOU things taking and allow beyond summarise important be are paper labelled, in POINTS These what These content your errors advi ce spread. outcomes needed DID give how outlined OUTCOMES are spread a of comm on useful tack le science-dependent on possible: These • in features LEARNING • or teach ers sugg estio ns well give prepared TIP… detailed the end of the book Alternative to practical you will also nd: found book to stimulate paper biology. A glossary of many Assessment important terms used in the book. structure PRACTICAL These show work. The you do End of at Unit opportunities results not studying the are actually included tackle the for to Paper 1: Multiple Choice (Core) Paper 2: Multiple Choice (Supplement) Paper 3: Theory (Core) Paper 4: Theory (Supplement) Paper 5: Practical Paper 6: Alternative practical help you experiment if or are home. answers are provided at Test to Practical www.oxfordsecondary.com/ essential-biology-answers 1 1 Characteristics of living 1.1 and classication organisms Characteristics of living organisms Biology LEARNING is classied • List the living study characteristics of animals, into ve Describe plants, the characteristics living things fungi, groups or living called organisms, which are protoctists kingdoms: and prokaryotes (bacteria) are seven characteristics of living organisms. These of characteristics living of major organisms There • the OUTCOMES are often described as life processes: organisms nutrition, and respiration, movement, growth, excretion, sensitivity reproduction. Nutrition Nutrition needed is the for growth, compounds proteins energy nutrition for from complex plants or taking in All Respi ratio n energy cells no t in is the from in the all relea se food the body . breath ing, the other food as gills in which that livin g It is living involves make to their is called and not to as make own gain used then substances are carbohydrates, ions). to turn convert cellulose and in which carbon these the dioxide simple proteins. They sugars need proteins. food like energy ingestion. then plants, and and The assimilated digested organisms chemical nutrients, needed such for respiration so they by nutrients. have food cells absorbed is is The to eat digested, for growth egested in process of absorbed and repair. faeces. respire reactions as glucose, respiration involving to because that to they occur release happen. all in need cells energy. This is the to energy. break Oxygen word Respiration down is usually equation for oxygen: whic h orga ns, + oxygen → carbon dioxide + water + energy released such Living or soil animals is blood glucose happ ens the mineral and Plants and Nutrients (like photosynthesis, absorbed such energy repair. complex (like involves sugars. provide and and simple compounds, cannot to Respiration TIP happ ens large or is simple from food bears. Food of into ions be plants sunlight into into STUD Y green water Animals provide in of development may vitamins) and mineral Salmon that and Nutrition obtaining things use this energy for movement, growth, repair and lung s. reproduction. Movement Organisms move areas change or Plants soil 2 move and move to to themselves slowly their face when leaves the or move parts of themselves into new position. and Sun so they stems they grow. move can Their up roots move towards absorb as the much down light. light as into Leaves the can possible. Most animals obtain their animals able to are able food remain move or to xed parts, to move avoid to one such their being place as the whole bodies. caught by on move predators. throughout tentacles They their a sea to Some lives, but they are anemone. Growth Growth is increase a in complex permanent cell increase number , chemicals, cell such as size in or size of both. proteins, an It organism. always which is This involves why the involves making dry mass an more increases. Sea Plants carry when they on growing reach a throughout certain their lives. Animals stop anemone. growing size. Excretion All living result of occur in organisms produce metabolism. an toxic (poisonous) Metabolism organism. Respiration is is a all the major waste substances chemical part of reactions as a STUD Y TIP that Excreti on is metabolism. meta bolic Excretion is the removal of these waste materials and substances of requirements from the body. Plants store waste food which their leaves, so the waste chemicals are removed when the off. Animals breathe out carbon dioxide; other waste substances the body in the gut digest ed. confu se leave the leaves being fall has substances throug h in remov al of wast e. Eges tion in is excess the the urine. passe d withou t Do two not term s. Sensitivity Living organisms external Sensitivity Plants light. is the respond The Animals touch, are able environments. ability to owers have to to detect change detect movement of some sensory pressure A and of and chemicals sense this these the plants cells or like in Sun the changes a stimuli open sense is by in and for air in internal (plural: their morning organs and their respond moving the in stimulus to leaves and detecting and stimuli). them. to close light, face at the KEY POINTS night. sound, food. The mnemonic, can help seven you ‘Mrs Gren’ remember characteristics of the living organisms: Reproduction Movement Organisms reproduce to make new individuals. Asexual to involves each one other organisms next parent and to the producing generation. each giving other or to The rise parent. to Sexual gametes offspring their offspring (sex are often reproduction cells) show that which variation. fuse They identical involves to give are not parent to the identical to parents. Respiration reactions in A visitor outer lands on Earth. The rst thing that is is a in to is a motor car passing Give two reasons why the b Give two reasons why you visitor thinks that the car is think that the visitor is wrong. waste cells out and ways a in animals then describe which feed, b are two how groups plants of living differ organisms. from animals the to detect permanent and grow, d use their of dry results new is the mass. in the individuals. removal chemicals during Nutrition food c able made of in the metabolism. Find in they: move, energy alive. Excretion and chemical by. a Plants place. it formation 2 or stimuli. size Reproduction sees organism release being respond Growth space involves that Sensitivity QUESTIONS from an position cells. increase 1 its to two rise change and SUMMARY causes reproduction for involves energy the and use of growth. senses. 3 1.2 Classication We LEARNING classify (see • Dene the term T opic kingdom binomial 1.1) tnemelppuS kingdom Describe the importance to rst groups. all is some plants smallest similar are subdivided The the largest grouping species. features. green into is and For carry groups The is the kingdom organisms example, out known within the photosynthesis. as phyla in a plant Each (singular: we must explain how organisms are phylum). named. evolution The binomial Meerkat, suricate that in lives confusion, system A and can within A is also the genus one other The Sun group a species binomial in is The as that to a names look give the system name type To of mongoose avoid using alike. the They offspring is are used by rst name name that should that Some case genus the trivial species other. is that names: the trivial of each species, scientic for Africa. binomial names’). together two name group with names southern live which in are the fertile together. given genus. is given ‘two are in individuals breed breed is are of angel Desert means and second interbreed only a species the and Kalahari organisms habitat Each and the system (binomial species same A into the of But classication and share kingdom, system • organisms OUTCOMES are with never closely genera is for the applies be to used related, (plural meerkats. of genus one on but do genus) This may species its own. not consist be of because extinct. biologists all over the world as it is meerkat. an international language for naming organisms. The table has some examples. Suricata human Homo cholera tree oyster white pelican, Pelecanus The sorting as They have whereas philippensis 4 along follow the a of of and sapiens digitata cholerae Plasmodium Pleurotus falciparum ostreatus classication the vast at the between same similar its is the have into groups looked at is the and anatomy appearance of of living an organism, structure. may instance, known organisms traditionally organisms. outward internal For pattern living between organisms lines. of morphology Morphology is array Scientists similarities anatomy Similarities Pelecanus out looked organisms. pelican, parasite classication. differences (grey) Vibrio mushroom importance known spot-billed suricatta onocrotalus The The name Adansonia bacterium malarial great scientic meerkat baobab The name as occur the the because limb bones they of pentadactyl have evolved mammals limb tnemelppuS common tnemelppuS Front Each and on limb has ve this bones one digits fossil record, bases in of limb species bone classication. also of study the mammal (blue), numbered scientists but their three (green, method relationships, of upper two 1–5). T o not structure the of shown limb However , obtain only are lower we evidence of proteins Figure cannot from anatomy their in bones always STUD Y the Rem embe r and nam e the sequence are DNA. methods (see now been involve T opic 4.1) Haemoglobin example, is coded for the the more studying and is a human by same the the bases, These that protein in so sequences to of of bases transports has classify 574 in oxygen amino are at compared any two The animals in 1722 in bases amino that more closely the a once bo th has then shor tened H. is nam e it like sapien s. For acid code sequences similarities If that species 4.3). animals. Each this: a used be These proteins T opic many with more the (see acids. are for least acids DNA there animals. organisms. amino sequences different are to sequences sequences protein between likely methods haemoglobin three protein. accurate of nam es. of can There TIP rely evolutionary organisms and 1.2.1. (yellow) for there related are SUMMARY QUESTIONS 1 complete they be. Copy and sentences using fertile the these genus words: shared humerus trivial 1 classication humerus radius binomial breed 2 ulna The system organisms of putting into groups is called 5 . The system is 4 used for naming Each organism organisms. 3 radius has two names. bat The (flying) rst is called the ulna name and the name. second A is species the is a humerus very similar that can group of individuals ulna together produce radius and offspring. We 1 classify living things on the 5 basis 4 2 of their features. 3 2 human a Explain the term binomial 1 (manipulating) system 2 3 4 5 b Find the scientic names seal of (swimming) Figure 1.2.1 The variations on a pentadactyl two two limb. plant animal mentioned and KEY write The binomial system uses two names for each species: A this topic alongside name species that is breed and a the group together trivial of to Classication 4 The is individuals, produce important In the living fertile in the same habitat means of of bases in 18th century, Linnaeus worked binomial system living offspring. in the study of DNA is used as things. life Carl and out of Find work the naming out and about then evolution. write sequence names. name. his 3 common the 3 genus 2 in them and not POINTS their 1 species species a more accurate your a brief own biography in words. classication. 5 1.3 Features The LEARNING cells of all State living • List the features of cells structures in enzymes organisms the organisms organisms are made up of a cell membrane, OUTCOMES cytoplasm • living of features organisms into used one to of place the ve kingdoms. There that you can and Biologists are large cell see are in the of carry cell. that as out processes Cells of There same are The synthesis simple do as to of small and structure have all a other eukaryotic. classify all because kingdoms, cell not cells example, kingdom ve a share For cytoplasm respiration. known organisms the the bacteria are kingdoms. as have cells. cells in protein such Bacteria these into structure. that present prokaryotic features known have 1.3.1. as and together cell also in Figure nuclei groups same types known have classied the stored involved main use They ribosomes are two organisms ve DNA. called that are nucleus and them into bacteria they including have the plant wall food kingdom and the animal kingdom. cell reser ve membrane Plant kingdom plants are Plants are multicellular organisms. The bodies of roots spread out ribosomes through flagellum not the compact soil to like gain those water of and animals. salts and Their their stems grow many plasmid leaves DNA of Figure 1.3.1 A typical to roots absorb and light. stems. Growth This occurs kingdom in special includes places mosses such and as ferns, the tips which bacterium. do not reproduce conifers out and the using photosynthesis, chloroplasts full seeds, owering of using and plants. light to chlorophyll, the All seed-bearing plants make have their cellulose cell plants, such chlorophyll own walls food. and a as and Plant large carry cells have sap-lled vacuole. Animal animals kingdom have throughout their not food have nervous Animals much the by more body. eating cell walls, systems are also compact Animals plants do which bodies not and/or chloroplasts multicellular or coordinate than organisms. plants. photosynthesise other animals. large their Growth and Animal vacuoles. All responses to Most occurs obtain cells animals stimuli do have and their Prokaryote you Staphylococcus, on the human a type skin of bacterium can see kingdom in Figure are rod-shaped. are a Bacteria 1.3.1. Many exist have Some in a simple bacteria short chains cell are of structure spherical cells. that and Most some bacteria found few micrometres in length and can only be seen with light (×4000). and electron microscopes. (One micrometre is one-thousandth of a millimetre.) Bacterial species There is Bacteria called from cells are no are also nucleus, often animal mould, Rhizopus nigricans, is a and 6 black structures contain spores. just a by by loop additional (see page plant Some cell of cells as of The they have The cells of some bacterial capsules. DNA loops 267). bacteria walls. slime within DNA the structure do not cytoplasm. inside of have extensions their cytoplasm bacteria differs chloroplasts called or agella fungus. (singular: The have plasmids mitochondria. Bread surrounded surrounded agellum) for moving through water or other uids. tnemelppuS movement. tnemelppuS Protoctists This are in classied four and some parasitic and are this kingdoms. are commonly All they vary in kingdom as is as size from plenty do light not cells they any are of many include ‘forests’ to in the are which other unicellular organisms which classied organisms can in organisms Plasmodium, Algae unicellular of nuclei; protoctists underwater so group belong with including malaria. tiny form of diverse Unicellular causes that a they have protozoans that seaweeds there contains protoctists multicellular . known organism giant where kingdom as the is kelps parts of the protoctists which the sea photosynthesise. Paramecium, a single-celled protoctist (×206). genetic Fungi kingdom Fungi are visible under a light microscope. Many are material also visible to the naked eye. Most fungi are multicellular although sur face yeasts are single-celled. Each cell has a nucleus and a cell wall which coat is made out chlorophyll The main its chitin, and body network food not cannot fungus branching of of source, of cellulose carry is out called threads releasing in plants. Fungi do not proteins have photosynthesis. the or as mycelium. hyphae enzymes It which which consists grow digest of over the a the food surface outside Figure the fungus. The digested food is then absorbed by the Viruses Fungi reproduce Most fungi are by making spores saprotrophs, that which can be means carried they feed by the on wind. dead matter, but some are are causes in or of decaying 1.3.2 Structure of a human virus. hyphae. inuenza size. a extremely (One is small. about nanometre micrometre.) 120 is Viruses This virus that nanometres one-thousandth are visible only parasites under an electron microscope. Viruses are or RNA) of a not cells. surrounded few genes that They by a are particles protein code for the made coat. The proteins up of genetic that genetic material material form the is coat (DNA composed and maybe KEY other cells proteins of that another help it organism reproduce. (the host) Viruses in order are to parasites multiply . that Viruses enter take over 1 the host cell and direct it to make new viruses. Viruses are not POINTS the The cells have in any in the of the kingdoms described here. All the organisms do not have of kingdoms have cells. Viruses cells in a different way. Their classication is based and so material and protein coat that they on the type There are Prokaryotes under The plant species with features kingdom that are animals. tnemelppuS Compare a Make a present in all cells. and familiar Y ou the to should animal us. kingdom Make include a table similarities contain to Why the table 6 How are Plant, Protoctist cells be without seen only microscope. organisms with as well eukaryoltic structure of bacterial cells with the to compare the features of the as cells ve viruses not classied in one of the ve plants 5 Fungi called differences. of a nanometres are there in a group many of features cells. are made hyphae. the food up of These supply, threads grow digest it plant. and then absorb it. kingdoms. kingdoms? Viruses an can electron are many a many compare 6 5 can light externally 4 have are over 3 They Protoctists of 2 kingdoms: QUESTIONS 4 the ve Prokaryote, Fungi. nuclei. State DNA. have. 3 1 and of and SUMMARY organisms cell are Animal, genetic a classied 2 classied living cytoplasm, membrane ve all classied tnemelppuS Viruses not be seen only microscope. cells but a few under They genes metre? inside a protein coat. 7 1.4 Vertebrates Animals LEARNING that have vertebrates. • Dene • Describe the term vertebrate bone or some of the ve vertebrates external main using visible, characteristic Describe how vertebrates All vertebral vertebrates column cartilage. They invertebrates all that have an or backbone belong share to internal are the common skeleton called phylum features made chordata with the of either which includes vertebrates. groups There are ve main groups of vertebrates: features sh, • a OUTCOMES amphibians, reptiles, birds and mammals. these are adapted to Fish their environment Most sh as the of time. Typically, This dace has ns, tail and a their – adaptations for have gills. herring, sh, sound and eyes They Their shark, the can and skin and a is there out of have lateral line and of for for with some for species, varying swimming detecting oxygen from scales. such lengths and for pressure the water Examples include cod. vertebrates although are water ns dissolved covered classes limbs, but survive breathe catsh other four permanently, that streamlined water. Unlike some have have ears evolved for into detecting legless forms streamlined like shape in water are They changes tuna, in skipper, sh balance. using live mud snakes and some lizards. swimming. Amphibians These vertebrates amphibians is external inside a hatch into On are have on the body). adult water, amphibians they sperm swimming in smooth, land, because female land, they live and eggs can frogs, is which amphibians skin. to are Development tadpoles they include moist return toads external: gills using through and to released have breathe breathe Although water most breed. into the for water fertilised (not eggs breathing. lungs, their Fertilisation the but skin. when Examples of salamanders. Reptiles The bright thought for the to red eyes startle frog to of this tree predators, frog giving are time Reptiles have dry, scaly skin to cut down water loss. They can live in escape. dry regions Fertilisation as takes development shells air . they which is not place them lizards, have inside external stop Crocodiles, do as the they from to return female’s lay eggs drying snakes, to out. turtles water body. with breed. However , leathery, Reptiles and to have tortoises waterproof lungs are all to breathe reptiles. Birds Birds of Birds with American 8 crocodile, Crocodylus acutus have them feathers are have able no different and to teeth types y but of their but front some, different food. limbs like are modied penguins species have and beaks as wings. ostriches, adapted Most cannot. to deal Fertilisation is eggs which are Birds are able to even internal protected homeothermic regulate though include and their the hawks, development by eagles, external temperature. temperature sparrows, as the females lay shells. (warm-blooded). body outside hard is This They can changes. parrots and means keep that it they are constant Examples of birds starlings. Mammals Mammals internal they are young ones Like are and born on like is vertebrates milk that development. already from whales birds, internal the so well mammals dolphins, are temperature. also or All lungs bats, Fertilisation in a mammals mammals, for is womb and suckle their even Grey Heron, long beak Ardea for are all maintaining dolphins, bears, a STUD Y constant lemurs learn ve this DID has hands and feet adapted to living in a and complete the sentences using these ve classes wings breed scaly y sh moist fur land water are different group in groups called and have skin have front skin limbs have and or feathers of vertebrate. Sharks 2 a the learn rare spend all their hair that are most and and lay return their modied are give and able birth to to time in species are . of their golden were an lmed Blood. frogs were for BBC After Sir TV the moved David series Life lming them from to a zoo disease, to habitat and pollution. Birds They Mammals in Panamanian . . . young extinction. . to on form to to water eggs with belong also have advanced KEY state you KNOW? amphibian Cold loss Amphibians have these to pic. protect Reptiles you of Mak ing help Attenborough’s the the help words: frogs to a QUESTIONS development There to featur es will YOU Some Copy table the threatened 1 with trees. Many SUMMARY bird TIP grou ps. table chimpanzee a and mammals. A – sh. aquatic Mak e wolves cinerea catching breathing. homeothermic, Leopards, fur. develop Female glands. use hair young developed. mammary and have The POINTS . State the features that are exhibited by all vertebrates. 1 Vertebrates have b Name c Give the ve groups of a are animals vertebral column that or vertebrates. backbone. an example of each group. 2 3 T o which group of vertebrates does each of the following The into a turtle b bat f hawk g shark c whale d salamander e vertebrates are divided belong? ve groups: snake sh, amphibians, birds and reptiles, mammals. 9 1.5 Invertebrates Invertebrates LEARNING are animals that do not have a vertebral column or OUTCOMES backbone. • Describe the external features Arthropods of contains • Describe of is the largest of the groups in the animal kingdom as it arthropods the insects, features segmented and myriapods used body, number an of external species. skeleton Each arthropod (exoskeleton) species and has jointed a legs. hard to classify them exoskeleton allows arthropods to live on dry land. When that they are largest crustaceans, The arachnids the grow too big for their exoskeleton, they moult and grow a new into one. Some moult all through their lives, others moult only during the groups early • Describe these their how groups the are animals adapted stages of their life. in Four to of the different types of arthropod are: environment crustaceans, myriapods, insects and arachnids Crustaceans Crustaceans and abdomen. hard two ve and crabs of Woodlouse detecting or slater. Notice its antennae of all are and so the made bodies the are. and crab, Grapsus feeding grapsus. and exoskeleton against in They they (also do crabs, eyes. breathe water. Some use shrimps, as They water have a very have between gills live on slaters) for craysh provides Crustaceans using crabs known not that predators. (head-thorax) land and breeding. and but some return land Examples lobsters. Notice centipedes up of many not divided Centipedes total number Centipedes paralyse have slow-moving two and into have of are millipedes. separate one legs pair They pairs regions of depends fast-moving their herbivores. the have long segments. legs upon such on how carnivores. as each the many They thorax segment segments have powerful prey. of legs You can on each often body nd segment. them They feeding in are leaf litter. defence. Millipede moving 10 as cephalothorax compound legs. live include are can Millipedes for and of Woodlice exceptions are that jaws claws pairs breed. abdomen. there lightfoot chalky a Myriapods Their large a into for stimuli. bodies its have crustaceans to divided protection antennae crustaceans These Sally body Many twenty water a effective pairs and Nearly to have – with its efciently. many legs for Centipede – a fast-moving carnivore. Insects Insects and On have bodies that are divided into three parts: head, thorax abdomen. the two thorax pairs of compound They eyes breathe called there wings. are three They that are through pairs have one made holes in of of legs pair of many the and tiny sides many antennae of species on individual the thorax the have head and components. and abdomen spiracles Monarch Insects have colonised most habitats in the world, although Notice are very few species that live in the sea. T wo reasons why they are on that them stops This is the beetles, bees is that losing largest ies, and land group locusts, they too are much within covered water, the cockroaches, by and a waterproof they arthropods. dragonies, can its wings Danaus for its plexippus. migration over so long successful buttery, there distances. cuticle y! Examples include butteries, moths, wasps. Arachnids These and arthropods have bodies divided into two parts, the cephalothorax abdomen. Arachnids antennae They have but paralyse silken webs four do their with pairs have prey their of legs several with and pairs poison spinnerets. no of wings. simple, fangs. They not Spiders Scorpions, have no compound, are ticks able and eyes. to mites weave are also T arantula classied as arachnids. paralyse SUMMARY QUESTIONS 1 four a Name b List c State the groups key of features ways in a large spider with venom to prey. arthropod. of insects. DID three – its which arachnids look different YOU KNOW? from There are over a million known insects. 2 3 Distinguish between a centipedes b crustaceans Describe the successfully 4 Copy and and the and basis of visible features: altogether , of insects that adapt them for of the knows. crustaceans insects arachnids KEY POINTS of Arthropods are segmented legs an regions number of one table: animals body no living 1 pairs but arachnids myriapods number the land. complete feature on millipedes features on following pairs 2 of with jointed legs and exoskeleton. Arthropods different are classied groups into including: antennae crustaceans, type of myriapods, eyes insects and arachnids wings 11 1.6 Ferns and owering plants tnemelppuS Like LEARNING • State that owering making • State and plants the owering • ferns non- reproduce by the between plants, ferns green in These chloroplasts absorbs made spores Describe all and owering plants are multicellular. They are OUTCOMES main features of plants Both of differences dicotyledons light of and mineral adapted monocotyledons for tubes. substances and because many contain of the their green photosynthesis. cells contain pigment Each cell is chloroplasts. chlorophyll, surrounded by which a cell wall cellulose. ferns tiny and colour owering These salts, such to live are and as on plants called have phloem sugars. transport xylem vessels, tubes, Both ferns which and systems which consisting carry transport owering water dissolved plants are well land. Ferns Ferns on a are land. waxy them to left. quite supports grow If fern Dryopteris lix-mas you will Ferns a look under Features Flowering by means inside the Shoots apical of and are helps the at leaves that carried by have true which within the tree stem ferns and the the of several ferns at a in do have a life have Most of photograph some thick metres. not that stem Many produce times of microscopic form loss. the for leaves that ferns rhizome. certain to Their including that called adapted water species habitats release wind well leaves. reduce ferns heights of make of plants, and to different owering the become roots those many leaves have underground owers ovary in owering plants of of and are which largest thick structures spores that stems, resembling live crown a plants strong cuticle) The conifers see These (the dry. of have leaves from Unlike The group layer have the are a Ferns new the seeds. year you spores. plants. plants stems, make roots and seeds. The leaves. seeds They are reproduce produced ower. roots bud The up shoot of a is stem the part bearing of the plant leaves, buds above and ground. owers. The The shoot apical is made bud is leaf stem side buds side main root Figure 1.6.1 root root cap Structure of a typical dicotyledonous plant. Magnolia 12 is a dicotyledon. Maize, Zea mays, is a monocotyledon. part where the stem grows new leaves. The stem supports the clusters structures receive The which stem food the roots are anchor blown from shoot, are the by soil to of in wind. Topic Dicotyledons of (see out to of owering the 6.6) also the the not It soil the up to such found contain they of flowers can owers the as in leaves the a below water it ground. from and and roots. chlorophyll. prevent absorb that holds plant, and so place. plants do ground Roots leaves take from parts they the Topic water since rmly (see air other parts the spaces pollination white plant over and transport leaves usually the the light and enables allows from Roots the adequate position The of tnemelppuS the Roots being mineral ions 8.2). and monocotyledons leaf Flowering plants dicotyledons can and be divided into two main groups: monocotyledons Figure 1.6.2 Structure of a typical monocotyledon Dicotyledons look like Their leaves are parts of ower, often the plant broad at with the a bottom network of of the opposite branching veins. The STUD Y are in the multiples cotyledons Grasses are of example four (seed and for or leaves) cereals, like ve in the the in a male each parts ower. known as Dicotyledons have two Be plant at the bottom of page and 12 of have most long, monocotyledons narrow leaves. have Other parallel veins. Grasses monocotyledons have a variety ower inside are in each of shapes, multiples such of as three. those of palm trees. Monocotyledons The have parts one of 1 complete and the parallel sentences two using these words: Flowering plants multicellular narrow network are with plants veins. They often have Dicotyledons wall; have that often have have with some inside a the names of ve inside dicotyledonous that grow key for the ten plants Make a table of differences between is leaves each plants where you in ferns and and have their one seeds and seed. you have contain Monocotyledons with parallel veins. ve live. Dicotyledons have two Construct and broad leaves identied. with 3 in stems cotyledons dichotomous cell cellulose the 3 plants a of leaves monocotyledonous by chloroplasts. cotyledon leaves cotyledons are each those cotyledon They – one 2 a 2.1) (from owering and Monocotyledons Find in POINTS cell broad 2 (T opic 16). surrounded veins. and differ ences cotyledon 1 seed. plan ts Note repro duct ion the KEY QUESTIONS leaves differ ences seed. SUMMARY Copy the and leaves Unit with the struct ure and cereals of owe ring anim als. learn monocotyledons. leaves awar e be tw een cell The TIP stamens, seed. maize plant. page. owering plants. a network of branching veins. 4 Ferns to life xylem are on plants land. and means of well They adapted have reproduce by spores. 13 1.7 Dichotomous Sorting LEARNING Construct and use identify dichotomous keys to • Identify in a name book of a until plant you or animal found the you right a lot of time and and for through that the would effort. features of start useful look However, animals external animals could one. identify take and the simple pictures plants out OUTCOMES To • things keys plants making a that here are key has it got yes no legs? has a it got shell? snail has it no 6 has it earthworm got yes legs? got yes no 2 pairs of wings? Figure 1.7.1 Scientists A use key and key has the you answer to Use out 1 2 3 4 Figure 14 1.7.2 Five invertebrates. numbered ‘yes’ to the means number nd another above at a a of key ‘no’ question identify numbered or steps on – this or and an rst to to 2 Has no Go to 4 Has 6 legs Go to 3 Has 8 legs Spider Has 1 pair Has 2 pairs Has a Has no shell shell wings see At things. or it Snail Earthworm step at the the in Use branching the the key branching beginning statement. the same works questions Wasp in This and takes branching you key left. but Housey them each Start identify the Go of the key, legs wings can question to living two. page. Has of identify identication. answer legs to you rst below the key. statement. the to into animals key from beginning to the keys dividing question or differently the dichotomous dichotomous Dichotomous A branching at in animals. the each same stage. It is way. set Start PRACTICAL STUD Y Making Now try a leaf making a key of your Whe n own. ‘size ’ 1 T ake six different leaves and label them A to Put the six leaves 3 Think of a 4 Write down 5 Now 6 Write 7 Carry question think the up these on out in front that will of you. divide into two Write out questions you your to divide each group into come to the last pair of as a branching key or as a numbered the are key. making a livin g muc h featu re thing s in size. TIP exam ination , usua lly rather key of these pond animals below. it than How ever , aske d is to easies t bran chin g damsel fly keys num bered if key are try key , leaves. keys . Now a good two. STUD Y key animals as so keys Pond a question. In 8 not groups. down. until use vary them mak ing is F . to 2 TIP key bran ched you mak e to a mak e key. Y ou key a may lar va also be freshwater aske d featur es shrimp for that mak ing to iden tify are suita ble keys . water beetle KEY 1 POINTS Dichotomous keys are used water to scorpion identify plants pond snail 2 A and organisms, such as animals. dichotomous key includes ramshorn a snail series or of paired questions identication. Figure 1.7.3 Pond 1 When She a made some laboratory. Give b Make 2 Write an Her each either a could down use an drawings drawings a a branching the features a pages to reptile, 8 and identify island and are 9 each discovered brought on an dividing into two. key to identify or as to of a would bird them the some back to insects. the right. name. key that a she shown suitable dichotomous as on visited insect amphibian, photos to QUESTIONS scientist a lead Dichotomous animals. means SUMMARY statements which and help a enable Present you mammal. you.) these them. numbered Now to classify (Y ou make vertebrate your key key. a a sh, can use key that the you groups. 15 PRACTICE 1 Which QUESTIONS process organisms is that carried live in a out by all the 6 forest? Which is not associated with excretion from a mammal? A moulting A exhaling B photosynthesis B release C pollination C removal D respiration carbon of heat of dioxide from toxic from the waste the lungs skin products of metabolism D (Paper 1) removal of water that the body does not [1] need 2 What are characteristics of all organisms? (Paper A excretion and respiration B ingestion and growth C photosynthesis D respiration 7 The 2) evolutionary species 3 (Paper 1) Which group and and [1] are relationships shown in the between ve diagram. egestion V photosynthesis [1] of animals includes those with W a X segmented body, an exoskeleton and jointed Y limbs? A amphibians B arthropods C reptiles D vertebrates Z (Paper 1) Which group time [1] An 4 of vertebrate includes those analysis DNA dry scaly skin and A amphibians four of base sequences from the with of these ve species was carried out. legs? Which two species will have the most similar sequences? B sh C mammals D reptiles (Paper 5 Each and 1) cell [1] is surrounded contains by a cell membrane table Which from A B C D ve shows organisms other the in all features features ve of shown cells. by B W W C X and Z D Y and Z and (Paper 2) Which is feature X [1] an example used in of a classifying morphological vertebrates? A egg laying B type of body C type of diet D pattern kingdoms? enzymes nucleus ✗ ✓ ✓ ✓ ✗ ✗ ✓ ✗ ✓ ✓ ✓ ✗ ✓ ✗ ✓ ✓ ✓ ✗ ✓ ✗ 2) and cells chloroplasts (Paper 16 shows row V cytoplasm. 8 The A DNA ribosomes [1] (Paper 2) of covering bones in the front limb [1] 9 The to drawings the same show ve arthropods (not drawn 11 (a) scale). Five of their the features denitions Match each denition of by of are the A movement B respiration D a things and below. features pairing C living listed with letter its and a number. sensitivity nutrition E growth Denitions A B 1 A permanent 2 The to increase chemical break release reactions down of in size that nutrient occur in molecules cells with the energy C 3 An action change 4 The by of an ability to environment 5 The taking Make a table to compare the features or detect and in environment (a) organism position of cause changes respond materials for to a place energy, to in the them from the growth and of development the ve arthropods that you see in [3] the (b) drawings. Explain what is meant by the term species [6] [2] (b) Use in the your features table arthropods. to that you make (The key a have key may to be used the (Paper ve either a 12 branching key or a numbered 3) key.) The drawings owering (Paper 10 Copy plant. leaves They are from not three drawn species to of scale. 3) and crosses show show [6] to the complete indicate features feature sh the table whether or using the ticks four and groups not. amphibian bird mammal backbone ns A C B wings (a) (i) Identify the group of owering plants fur to which each species belongs. homeothermic (ii) State the make (Paper 3) features your that you used to identications. [5] [5] (b) List ve would key to features be shown useful identify in by the devising species of a leaves that dichotomous owering plants. [5] (c) (i) State ferns three have structural in features common with that owering plants. (ii) Explain walls, [3] why are kingdom (Paper fungi, not with which classied plants. in have the cell same [3] 4) 17 2 Cells 2.1 Structure of cells Cells LEARNING OUTCOMES Cells • Describe the structures Very plant and under • a animal light Describe the cells are the small building blocks that as microscope differences small living things such as bacteria An insect for certain such as how a y many may contain cells there millions are in animal plant State between the functions of organisms. only one cell. a of cells. human No being one – knows estimates 10 × 12 10 and 50 × 10 seen under cells Plant cells the cell membrane the cell cell living of cells structures light all and Animal • up made in 12 between are seen vary structure make of microscope and in the in the animal wall plant cell nucleus cytoplasm cell membrane nucleolus Figure 2.1.1 A cheek cell (stained nucleolus with a blue dye). nucleus Figure 2.1.2 A palisade cell Differences Liver cells magnied by The differences this table. between between plant plant and and from animal animal cells are mesophyll a leaf. cells summarised in ×300. feature cellulose cell plant wall cell animal present cell absent present; cell STUD Y membrane present surrounded TIP permanent Whe n you have differ ence s plan t mak e state wall shape determined by the cell shapes be tw een shape wall; and sure of anim al you cells , write shapes can abou t bo th chloroplasts nearly spherical, like cylindrical or present in some vary as there be cell wall box- cells absent cell. large vacuole permanent vacuole in containing present nucleus side the cytoplasm 18 cell no some thin g type s to by of cell present cytoplasm cell (often the small cell wall) sap at the close to vacuoles cytoplasm; do in not contain cell present (found anywhere cell) present sap within the is Functions of cell structures STUD Y cell structure • forms a barrier between the cell and Mak e its liver surroundings • • cell TIP functions membrane keeps allows cell, • simple e.g. controls out • contents of often of cell oxygen, carbon movement the cell, e.g. described as of to enter dioxide other and and leave the the water substances into and can page the use of palis cells . struct ures write and each label func tions . your ade Labe l Y ou draw ings permeable to (see and unde rnea th glucose partially cells meso phyl l inside substances draw ings help your revisi on. 28) • controls all • controls how activities • place in the cell nucleus where cells many develop chemical reactions take place, cytoplasm e.g. respiration and making proteins for the cell chloroplast (plant • photosynthesis • stores • stops • gives • allows cells starch only) cell wall cells cells from shape to bursting when they ll with water cells (plant water and dissolved substances to pass only) through freely (often described as freely or fully permeable) sap vacuole (plant • cells full of water only) • stores salts SUMMARY QUESTIONS 1 complete Copy and indicate to maintain shape and ‘rmness’ of cell if the this structures and table are cell cheek structures (animal) by using present cell Cells sugars ticks or onion and crosses of onion magnied by ×250. to not. cell leaf cell KEY (plant) POINTS (plant) nucleus 1 A cell and cell epidermis a membrane, nucleus cytoplasm are found in wall both plant and animal cells. chloroplasts 2 large All plant cells have a vacuole cellulose cell wall; some have cytoplasm chloroplasts containing 2 State the functions a chloroplast e cytoplasm b cell of the following membrane c parts: cell wall d cells vacuoles cell not a vacuole sap. have Animal these parts. nucleus 3 f do and Refer for to the the table functions above of the cell structures. 19 Cell LEARNING OUTCOMES As you know, structures • State that the organelles all cells contains ribosomes endoplasmic on Identify rough ER in • State that occurs in Calculate and the a cell. number These of are small called include mitochondria, vesicles and cell ribosomes on reticulum diagrams of and The cells aerobic endoplasmic reticulum and endoplasmic membranes. respiration which reticulum They allow contain materials to (ER) is a complex uid-lled be spaces transported system of between throughout double the membranes the cell. the membranes mitochondria the actual specimens as contain of reticulum Where • cells cytoplasm rough mitochondria photographs and endoplasmic Rough • animal the vesicles rough and and in cytoplasm organelles of plant present magnication size of using are biological of micrometres ribosomes called rough rough ER is are present on endoplasmic to package their outer reticulum and surface, (ER). transport The proteins main function made by the ribosomes. units Cells that digestive rough Small small a lot in of the protein, for alimentary instance canal, those have large making amounts of ER. pieces of vesicles. rough Ribosomes produce enzymes ER rough In and this ER may way be pinched proteins transported around can the be off at the made cell in ends and the to stored small form in the vesicles. Ribosomes Ribosomes cells. cells Cisterna They but are are smaller cytoplasm, The Lamellae small not function organelles about in 20 prokaryotic attached of that are nanometres to ribosomes cells rough is to found (nm) where in in huge diameter they are numbers in in all eukaryotic found free in the ER. synthesise proteins, such as those of enzymes involved in respiration. reticulum made of up double Mitochondria membrane Mitochondria Figure 2.2.1 Structure of are relatively large organelles found in all eukaryotic rough cells. endoplasmic reticulum They are often visible under the electron microscope as sausage- (ER). shaped Each structures about mitochondrion controls many the folds entry on has and which 1 µm a exit wide double of some and the long. membrane, materials. of 5 µm The chemical the inner outer one membrane reactions of of which forms aerobic Folds respiration take Mitochondria they Inner Outer membrane Cells are the with vast 2.2.2 Structure of a mitochondrion. 20 are sites high often of described aerobic rates of as the ‘power plants’ of the cell since respiration. respiration have many mitochondria to provide membrane sufcient Figure place. energy . numbers of For example, insect mitochondria. ight muscle and liver cells contain tnemelppuS 2.2 Look of at 1000 cells the To work Now larger 1000 out magnied we specimens photograph times magnied and can than of in actual in size use size human life. of millimetres. this a This cell, Let’s formula image actual some real cheek means cells. that The they cells have are been times. the cell tnemelppuS Size to measure say that work out it the length measures actual of one 13 mm. size: size = Human cheek cells (×1000). magnication 13 So the actual size of our cell = = 0.013 mm 1000 There are answer We as can in 1000 to use this T o a similar of size actual using calculate the 1 2 Which a in a in the millimetre. by when goldsh. 1000 the This of you an image size actual size We can to give image size time photograph. formula magnication If will there you nd image we it convert has has been been calculate is the 13 µm. the 90 mm reorganise reduced, a sh’s long. the formula: = The image (×0.33) of this actual goldsh is one third size. QUESTIONS organelles manufacture b convert c control d carry e package the carry out the following functions? proteins light out and ( µm) multiplying same a Copy of size the magnication SUMMARY by technique photograph reduction actual micrometres micrometres energy into substances reactions and in the that pass aerobic transport complete chemical by into and out of a cell respiration proteins table energy around using ticks the and cell crosses. Figure 2.2.3 An of feature bacterial cell liver cell palisade electron a micrograph mitochondrion cell (×80 000). cell wall rough ER KEY POINTS chloroplast 1 mitochondrion Ribosomes the on cytoplasm rough make ER and in proteins. vesicle 2 Rough ER packages transports 3 a Measure the length of the mitochondrion in the electron 3 micrograph. It has been magnied 80 000 times and proteins. (x Aerobic respiration occurs in 80 000). mitochondria. Calculate the micrometres actual length of the mitochondrion in 4 ( µm). Cells with high respiration b Calculate the actual size of the liver cells and the rates have of many onion mitochondria. cells on pages 18 and 19. 21 2.3 Different T o LEARNING function Identify cell different from types diagrams of of cells In Relate cells the to features their the of to body organism and photographs • are Calculate and organisms have cell and topic certain divided we between from change look a to at functions. different fertilised become some This cells egg, groups new of of cells specialised examples means that for that are the cells. are functions an produced. certain specialised As These functions. cells. these functions cells magnication actual size of biological Ciliated specimens using cells are found in the air passages in the lungs (trachea and millimetres bronchi) as out develops grow this carry Specialised • many-celled of OUTCOMES specialised • efciently, types and in the oviducts in the female reproductive system. These units cells have current cilia in the on their uid surfaces. next to the Cilia cell beat back and forth to create a surfaces. cilia move ciliated these cells cells make mucus In the up to the area root 2.3.1 Ciliated cells line to hair to move and throat. the the mucus In the that traps oviducts, cilia dust and move pathogens the egg from uterus. cells absorb hair cilia nose ovary Root Figure airways, the have water long and extensions ions from that the give them a large surface soil. cells xylem vessels the airways. STUD Y Whe n a cell TIP explai ning Figure 2.3.2 Root and is adap ted hair to thin you tions give featur es each one carry , mak the say helps its the are long Figure how Xylem vessels columns of like cellulose water and tubes the help from are pipes. and ions Ner ve cells to the up soil. a cylindrical The cell and walls waterproof to move support cells are cytoplasm form Red empty. are from They thickened material the called roots of nerve blood the highly like and specialised wires. impulses cells stem are carry small water the stem. are arranged with bands lignin. These into or spirals to the rest of the cells plant. allow They They are around leaves. cells. able the protein that carries shaped This surface their Nerve cells carry like shape the oxygen. They thin extensions information in of the body. blood cells attened provides volume a discs. large compared which are with makes for Figure impulses body. have transmit haemoglobin area efcient around They to contain red the absorption of 2.3.5 Red blood cells have a substance oxygen. called haemoglobin oxygen. 22 vessels that func tion. Nerve 2.3.4 Xylem cell also Figure 2.3.3 absorb sure struct ural and out e to its water func cells how that carries Palisade These The cell. by plant cells have chloroplasts have cell mesophyll trap cell wall In the cytoplasm sap. numerous light a made Starch up of are and chloroplasts energy there grains photosynthesis cells tough is a a in in the cytoplasm. photosynthesis. cellulose large found are for which vacuole the which cytoplasm. temporary store of Palisade strengthens is lled These cells the with are formed energy. Figure Sperm the sperm female Egg of cells have carries parent. cells are energy . a tail genetic Genes much Genes and of adapted information from bigger the are the from father than mother are sperm are for the male present cells. found swimming. They inside in parent the head to yolk nucleus Leaf lots palisade of cells contain chloroplasts photosynthesis for (×500). nucleus. as of 2.3.6 of the sperm contain the The a the store egg. middle head Look real To of carefully life. work the This out cells at Figure means the in 2.3.6. that actual the size millimetres. The cells of cells have these Let’s are say been cells, it 500 times larger magnied measure measures the 500 than times. length 20 mm. Now of we one can a use a formula to work out the image actual size actual size of the tail piece in sperm cell: size = Figure 2.3.7 Sperm cells have a tail for magnication swimming So T o the actual calculate size the of actual cell is magnication magnication The our 20 of divided an image size actual size by object 500 we = (×2000). 0.04 mm reorganise the formula: membrane = diameter of an egg cell cytoplasm is 0.1 mm. To calculate its jelly magnication by 0.1 mm to in Figure give SUMMARY 2.3.8 we divided the diameter of the ×180. nucleus QUESTIONS Figure 2.3.8 Egg cells store 1 Draw its a table correct T ype of matching shape cell and the type of cell in the blood Shape cells rst hollow like with the air from passages dust water and wires ions KEY transmit root hair cells at energy tube transport cells an Function free ciliated column contain (×180). function: keep red coat drawing POINTS electrical discs 1 During development, cells impulses change nerve cells long and thin transport often absorb xylem vessels have cilia that their water from their the 2 Specialised structure Here the out are some functions their other of specialised these cells and cells. how Use they this are book to adapted functions. nd to out carry to carry muscle d pollen cell b goblet cell c white blood cells that out a function, e.g. have to cilia along a and shape. move soil 2 structure oxygen the have a enables them particular ciliated move cells mucus windpipe. cell cell 23 2.4 Levels Tissues LEARNING Dene the terms tissue, group organ Describe of same examples of and that occur in is work called a tissue. together to All carry the out a cells tissue and is made so the tissue: blocks similar up of muscle identical tissue muscle cells. in working the groups look These cells work system: same way of tissues a working group cells contract muscle tissue is made your heart is made of cardiac muscle cells that contract muscle and other pumps blood tissues; it 2.4.1 Levels of organisation relax in the together human An circulatory organ together The STUD Y heart Lear n these book . deni tions orga n and Mak e exam ples plan t as work system . orga n working your group of body your and your carries blood vessels circulator y blood system around body made up perform an of a specic example of different tissues that work functions. an organ. It is made up of different tissues TIP such tissu e, is organs system. is to around up which relax and heart make and of of together together your cardiac of a list of and orga ns system s together muscle, to nervous pump blood tissue, around brous the tissue and blood that body. of The anim al tissu es, cardiac stomach, lungs, brain and kidneys are all organs. orga n from and this Different systems blood are to other and a work digestive liver work of perform vessels some The organs consist together • body of as part organs as part of an with functions. together For of organ related example, the system. functions, the circulatory heart Organ working and system. Here systems: system is made up of the gullet, stomach, pancreas, intestines. The excretory • The nervous • The reproductive and vagina; and penis. the together group organ • All 24 tissue contracts. organ: cells together Figure a function. animals building muscle in shared plants cells: the cells they the together above similar and system Muscle • organs organ the and organisation OUTCOMES A • and of system system in different is is made made system males organ it is in up up of of the the females the systems is testes, make kidneys, brain, the a spinal ovaries, sperm up ureters ducts, living and cord bladder . and oviducts, prostate organism nerves. uterus gland Plant The tissues diagrams and show photosynthesis in organs the tissues leaves is in called a leaf. The tissue mesophyll. The that cells carries out making up DID layer of the mesophyll are called palisade cells. These cells word packed and full of chloroplasts so that they are well the absorb lots of light. The palisade cells make up the tissue. All the cells making up this tissue is are used close like the wooden stakes palisade used mesophyll cells adapted together to ‘palisade’ are because closely KNOW? the The upper YOU look alike to make walls known as and palisades. do A the leaf Other same is an function organ. structures, cells: the building – they Other such absorb plant as light organs owers and for are photosynthesis. roots fruits, are and stems. modied leaves. blocks organ: groups working tissue: leaf similar cells of tissues together working palisade together in the same way the leaf food for palisade mesophyll makes and gas allows exchange cells upper epidermis photosynthesis takes place cells in the mesophyll tissue organism: milkweed spongy mesophyll is cells made the plant up of organs lower Figure 2.4.2 Levels of organisation SUMMARY QUESTIONS 1 complete in a owering epidermis cells plant. STUD Y Mak Copy and the sentences using these e words: TIP sure explai n organ system cells tissues tissue An is organ made is An formed is several up a body of that from group of a group organs carry out of the same working working together to . adap ted together. to Copy out correct the organs system listin g the from listed those on the listed left. on Match the each with trachea digestive and blood vessels nervous brain and spinal cord gas KEY one Cells that oviducts and uterus stomach and intestines the bladder following with the are to grouped form tissues. Different tissues make up circulatory words smallest into and the ending correct with to sequence, the system tissue do a which work particular together function. largest: 3 organ same reproductive organs Arrange the excretory 2 and have exchange together organ and each POINTS function ovaries, starting how helps. the 1 3 by featur es right. heart kidneys out System and gullet, is functions. Organs lungs cell pho to synt hesis perform can palis ade carry explai ning 2 a function meso phyl l A you how organism cell Different together organs as work organ systems. 25 PRACTICE 1 Which QUESTIONS structure is found only in plant 6 cells? The diagram liver A cell B chloroplast C cytoplasm D nucleus (Paper shows a mitochondrion 1) Which [1] structure is not found in animal cell membrane B cell wall C cytoplasm D nucleus 3 Which the is [1] the correct and sequence, ending with starting the 7 tissue, B cell, C tissue, D cell, organ system, organ, organ system, ×4000 B ×400 D ×40 000 The (Paper tissue, organ, organ system A out, A CO in, specimen. drawing ×40. A The is is drawing length 140 What a mm. the of the The actual 5600 mm of CO out, and out of CO O 8 Cells in, nutrients in in, nutrients out 2 out, (Paper in 2 in, CO nutrients O out, nutrients out 2 2) of [1] organisms contain classied which of in the the prokaryote following? biological specimen of O 2 in magnication size B a in 2 2 [1] makes O 2 2 1) student move with kingdom 4 that are: D system [1] substances organ organ is: 2) mitochondria cell organ, diagram C largest? cell, the ×40 C tissue, of A B A magnication (Paper 1) smallest µm cells? The A (Paper a membrane 1.0 2 from cell. the A cell membrane, B cell wall, enzymes, nucleus, vesicles the is cell membrane, cytoplasm, ribosomes specimen? C 56 mm cytoplasm, DNA, endoplasmic DNA, enzymes, reticulum, ribosomes C 35 mm D 3.5 mm D (Paper 1) Which is cytoplasm, (Paper 5 not found in an animal 2) [1] cell? 9 A mitochondria [1] The palisade mesophyll cell is a type of plant nucleus B permanent C ribosomes D rough cell. A 2) cell and complete is a type of animal cell. Copy vacuole endoplasmic cells. Copy think reticulum you (Paper liver the think the the table table structure it is is to and compare put present a tick and a these (✓) if cross two you (✗) if absent. [1] palisade cell liver structure mesophyll cell wall cell membrane cell cell cytoplasm nucleus chloroplast large (Paper 26 vacuole 2) [6] 10 The diagram shows three animal (iii) cells. the organ system for transport in mammals; (iv) the plant [1] tissue that transports sugars. (b) Distinguish [1] between the following pairs of terms. B A (a) Identify the (b) State the (c) State where (i) Organs (ii) Cytoplasm (iii) Cell (iv) Organ A, functions B and of the C. [3] three cells. the body these cells 13 (a) Five cell magnication of cell A is system and and cell wall [2] organism [2] structures and their functions are its actual size in below. ×1000. Cell The membrane [3] Calculate 11 [2] 3) listed (Paper nucleus are found. The and [2] [3] (Paper (d) tissues C cells in and millimetres. structures [2] A nucleus B cell membrane C cell wall D large E ribosome F rough G mitochondrion 3) diagram shows three plant cells. D vacuole endoplasmic reticulum E Functions 1 controls into the and movement out 2 stores water 3 makes 4 withstands of the and of substances cell ions proteins pressure of water inside F the (a) Identify (b) State (c) For the each organ a (d) the cell, where actual Calculate D, functions different The cells D, it E is E of and the and F, found. F. three state In cells. a each the 5 carries [3] 6 transports 7 stores DNA of cell give organ. length [3] plant case [3] of cell D is magnication Match the out each function 0.05 mm. of cell by of (a) proteins and the within controls cell writing a the the activities structures letter and cell with a its number. [5] [2] (b) A student looked microscope. 12 respiration the drawing. (Paper aerobic She at a cell made a under a drawing light of 3) the cell the nucleus and showed the diameter of Name: (i) an animal cell which does not have nucleus; a [1] She (ii) a plant cell that does not have calculated drawing size of as the her the drawing 70 mm. magnication ×10 000. nucleus as in What is the of her actual micrometres? Show a your nucleus; in working. [2] [1] (Paper 4) 27 3 Movement 3.1 in out of cells Diffusion Molecules LEARNING Dene • Describe in the term liquid diffusion and do move the importance about in a random way. They bump into one of gases Describe the water a and as in a out well, gas to ll up although is faster as all it the takes the space available. longer molecules for are them more Molecules to ll the spread in a space. out. The of difference diffusion spread this Movement in speed between movement in gases and liquids is important solutes for as gases OUTCOMES another • • and importance organisms. This movement of molecules is called diffusion of solvent water molecules substance in before Figure diffusion after 3.1.1 Diffusion in a gas. a coloured gas spread the TIP you write molecules of them not as that place to they ano th er , that e difference in A entrat one you has a large so lu te given disso lved high is the ient. that are easily , of vo lu me in a of the where to there where are there low concentration). The difference between carry on in two places diffusing molecules so until keep is a they moving, diffusion has concentration are but spread there is out no evenly. longer stopped. movement to a of molecules region of lower or ions from a concentration region down a the substances also lose they some of need their by diffusion waste from substances their to their diffusion. These permeable as oxygen, larger substances as they carbon molecules. allow dioxide The have the and to water movement cross cell movement of to membranes of pass molecules small through by diffusion cell membranes is passive movement as cells do not need to use a to move the molecules. the energy for of diffusion molecules comes and from ions. the The kinetic more energy molecules of random present, the has their kinetic energy and therefore their rate of movement. so lu te given that affect diffusion so lven t. These factors • distance The are • The as 28 by not Factors of of They such but across in so lu tion mas s from of The disso lved (a molecules the net partially molecules greater smal l out concentration) gradient. some movement a of concentration gain energy dilu te spread high say so lven t. A them concentrations concentration so lu tion mas s vo lu me they (a the grad conc entrat ed diffuse volume alwa ys down ion liquid. abou t surroundings conc of happens this surroundings. mov a are from sure many When Cells mak e ions given Molecules of diffus ing or a concentration Diffusion mo lec ules in gradient. a Whe n in container . the STUD Y Diffusion water diffusion out are through 3.1.2 after solute Molecules lots of diffusion of through diffusion When Figure molecules dispersed tnemelppuS before soluble water very inuence the molecules efciency have to of travel diffusion: – note that cell membranes thin. concentration quickly as gradient possible, so – they cells use keep a the low substances that concentration diffuse inside the tnemelppuS cytoplasm. because This the means cell is that molecules maintaining a keep steep diffusing into concentration the cell red blood cells gradient. air • The surface give • The a area large some surface temperature temperature Gas – – to have allow many molecules move increases. versus cells Diffusion is cell membranes molecules faster faster to and at that cross collide warmer are by folded diffusion. more often as the temperatures. liquid There Animals with the and their gas plants page and all exchange surroundings exchange (see 131). at surface the gas is gases oxygen exchange formed Blood transports in body. of surfaces. the these and alveoli two carbon In in gases dioxide red a short cells Magnication mammals, the is blood distance and very thin opposite cells layer of the cells direction. into In the Breathing the alveoli, blood. Carbon constantly diffuses dioxide refreshes the blood constantly removes oxygen and brings air in in the concentration gradients are always steep. carbon There the TIP Alway s dioxide, refer are many give a very large surface area for gas dilu te plants, cells gas provide exchange a large spaces between this (see air the page occurs surface cells 64). in This 300 000 times faster Water as solvent a inside area a is than for plant the the to and efcient through ‘stro ng’ exchange. leaves. The exchange each cell because spongy of There are exchanges gases with through the air air is SUMMARY QUESTIONS 1 complete water. Copy and sentences A solution is made up of two parts, the solute and the solute dissolves in the solvent. If you dissolve sugar using in water a sugar solvent. can be The solution. solute solutes dissolves in a as is not they solvent The always can is sugar is a solid dissolve described the in as solute like sugar. solvents being and the water Liquids too. random is and gases Something is sometimes called the universal gas is which of soluble solvent. the molecules a About 75% is water and it is the main component of of from an blood, and xylem sap and phloem sap in transport plants. movement a or an area area of of of as a result of uids the like high net concentration cytoplasm diffusion the to Water words: you low make the these solvent. liquid The and so lu tions . mesophyll gases. diffusion so lu tions , alveoli ‘ weak ’ In to so lu tions so neve r to the alveoli. alveoli and the the a conc entrat ed and in lungs across diffuses the between air lungs between oxygen the ×1500. STUD Y the space to movement of Everything molecules. transported of the water KEY 1 is plants needed and reactions for animals that digestion has occur and to in dissolve cells excretion in happen to take water in and water. most Also, 2 place. Diffusion down of a is the high net movement concentration concentration Factors that surface area, affect to a molecules region of or ions low from diffusion gradient. are: and how the size of concentration molecule, steepness of distance, the into a distance b size c surface d concentration e temperature of factors cells: molecule area 3 What do the gradient terms concentration the following diffusion a gradient. temperature concentration of State affect POINTS region 2 in chemical 4 Explain why important and solution gradient water solvent is and mean? an for animals plants. 29 3.2 Osmosis Each LEARNING of • Dene the • Describe the term on and osmosis the Explain of the water cells surrounded effect animal and tissues the out term allows cell the by a cell small outside. membrane. The molecules membrane is cell It separates to described membrane pass as through being has the but tiny contents not partially holes large in it ones. permeable osmosis movement into using of from of Osmosis occurs is a when special two kind of solutions diffusion are involving separated by a water molecules. partially It permeable membrane water Osmosis is the diffusion of water from a dilute solution into a more potential concentrated The tiny solution holes membrane in through a partially permeable membrane. the allow Water small molecules solute diffuse water molecules to pass water through, solute too the but the molecules big to pass partially from a high molecule large to a concentration lower water concentration are through permeable fewer membrane. Water is water many diffusing from a place molecules water where there is a dilute molecules STUD Y TIP solution with a high concentration of water dilute If aske d to dene to a place where there is solution concentrated partially osmos is it, mak that of it or e is wate r write sure the abou t you say diffus ion mo lec ules. concentrated permeable with membrane a low concentration of Figure 3.2.1 Osmosis. water Water to potential move by available, water a in dilute water In the two solution of water A dialysis to are lot is a free a of on a of ability much of water water pressure accurate molecules) is exerted to say has (containing potential molecules high partially water a on that high fewer left since hand through potential gradient diffuse potential permeable through However, the molecules water the more water water move energy. is as solution water region to It the how water potential The through by such wall. a water present water the factors cell there about inuenced concentrated from kinetic of down Dialysis A potential by the membrane. molecules model by above, the thinking is other low molecules movement right, a gradient, directions water has of This (containing potential. potential way by cells diagram Water a also plant sides lower is osmosis. but molecules) 30 solution solution a the the to a this the water region of membrane. membrane there side, between down are there in many will membrane both more be from a net left to gradient. cell tubing tubing represent (Visking to the tubing) represent cytoplasm. the is partially cell permeable. membrane and We the can sugar use solution tnemelppuS tnemelppuS • is cell which The plant cell OUTCOMES PRACTICAL 1 Cut two pieces water diffuses of into ‘cell’ dialysis 12 cm tubing, long. each Tie one end sugar solution of each with cotton. dialysis tubing 2 Fill one model cell with a (partially dilute sugar solution permeable (cell membrane) A). Fill the other model water STUD Y cell with water (cell ‘cell 3 Tie the other end TIP B). of A ’ Y ou both may be given water diffuses model cells and resul ts weigh out of ‘cell’ them ‘cell on A ’ water a a balance. into and beaker a Put beaker put ‘cell B’ a demon stratio n and into the be resul ts. solution of 30 minutes to solution out the model Mak e the sure you den ition osmo sis and sugar permeable take osmo sis explai n dialysis tubing of After to a (partially sugar . of expec ted remem ber concentrated the pract ical water of containing of the resul ts cells apply you it can see. membrane) Alwa ys and weigh them again. ‘cell resul ts ‘Cell A ’ increases in mass explai n because are molec ules capillar y water has diffused into the ‘cell’ level by that B’ due to the water movin g by of osmo sis. tube sugar osmosis. ‘Cell B’ decreases in mass solution because water by has the cell An osmometer diffused out of osmosis. dialysis tubing containing Y ou can you set Fill the see up the this partially membrane effects of osmosis water if concentrated apparatus. sugar solution permeable with a very KEY concentrated solution of 1 Tie it to a capillary tube and stand it in POINTS sugar. Osmosis water Very quickly measure your you how ideas will fast about it see is the liquid moving osmosis to moving using explain a up ruler why is the diffusion of water. the and the a tube. Y ou stopwatch. liquid rises in of can their (dilute Use the molecules of tube. higher their lower through a a region concentration solution) (concentrated from to a region concentration solution) partially permeable membrane. SUMMARY QUESTIONS 2 A partially permeable membrane 1 Dene the following molecules diffusion 2 Describe osmosis practical osmosis how into you a can sugar partially nd out solution. permeable how fast water Remember to membrane diffuses include pass tnemelppuS Explain all details. in terms water potential, how water passes cells placed in distilled as but molecules. 3 Water molecules water a potential water not to large region of diffuse down gradient higher water into potential plant such through solute a of small by from 3 allows terms: to a region of lower water. water potential. 31 3.3 Osmosis animal LEARNING • Describe enter OUTCOMES how and water leave plant and cells PRACTICAL can plant in Osmosis cells in potato cells by 1 Cut nine cores from a potato so that they are exactly the same osmosis length. • Describe affect how animal osmosis Record this length. can 2 Feel 3 Set the cores to see how rm and ‘bendy’ they are. cells up the following test-tubes: B A STUD Y test-tube A test-tube B – distilled – dilute water distilled dilute water sugar sugar TIP solution solution Whe n cell desc ribin g mem bran e say that it is test-tube concentrated the sugar 4 partia no t – solution. alwa ys Place three cores of potato 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 lly into perm eable, C each test-tube and tissue swells up no change semileave perm eable. 5 them Remove for the measure 60 cores their minutes. C and concentrated sugar lengths. solution Calculate of cell the the cores average in each length test-tube. membrane Compared (partially to the start, cores permeable) will 0 be: 1 tissue water A cytoplasm – longer and 2 3 4 5 6 shrunken 7 8 9 10 and flaccid rmer passes into the B – about the C – shorter same length and rmness vacuole vacuole by and softer and ‘bendier’. osmosis cell wall (freely These results are explained in the text. permeable) the cell solution is less outside the concentrated Turgidity than in the vacuole The Figure 3.3.1 Osmosis in a plant cell sap inside cells are there STUD Y tnemelppuS Paper expec ted Y ou 4 to you use osmo sis may the As be wall wall in and refer plan t is plant a cell water, solution is partially the of water gradient salts permeable enters so and the that sugars. and cells. water When the cell This is plant because molecules diffuse enters osmosis. it makes water stops as the it a can cell the cell turgor hold. It’s bursting. swell up. pressure. like We a say The blown-up that water Eventually the pushes the cell balloon. cell is against contains The turgid. strong This is the as cell what or to happened to the cells in the potato cores in tube A. The cells have water , swollen and caused the core to get slightly longer . ‘ water T urgid cells plants upright. give the plant support. They keep the stems of many to This is because the cells within a stem are supported movem ent by out by tissu es. grad ients ’ water and tissu es. the potential developing absorbed also poten tial into in water cells water cell term has cells can explai n of vacuole placed a the much abou t anim al of cells turgor pressure. The water pressure within the cell acts against the and inelastic these and 32 is the TIP into In membrane cell. cell cells leaves walls, lose that keeping water, have they lost the are cells no water turgid longer wilt and rm rm. and However, turgid. when Plant stems tnemelppuS Plasmolysis the solution outside the cell is more concentrated When plant cells are placed into a concentrated sugar or salt solution than in the vacuole water passes vacuole limp. out starts We say of to the cells shrink. that they by These are osmosis. cells are accid. As As no water longer more passes rm, water out, and leaves the sap become the cells water out the by cytoplasm starts plasmolysed. cores core in is to test-tube shorter move This is C. than away what The at cells the from has the cell happened have wall. to the decreased in These cells cells in the volume so are passes of the cell osmosis now potato the whole as cytoplasm is pulled start. away from the cell The the cores in water water test-tube potential potential overall about of diffusion the did not change of the sugar the cell sap of same B water into in solution in the or out length was potato of the very about cells. cells much the There so because same has they as been have wall, the cell becomes plasmolysed the no Figure 3.3.2 Water cell stayed passes by out of a plant osmosis. length. a Osmosis Figure in 3.3.3 placed in animal shows different cell membrane The red blood Their The cytoplasm cells cells by them in D in a they so to picture have cells has the the blood blood salt been water. cells when solution. they E same of they are Remember passes not water no blood shrink into proteins, have red have when placed Water cells When (F), in red a solution animal burst. solution The of that permeable. distilled they salt in the in which are partially However, osmosis. solution how happens concentrated were swelling by is in a osmosis. concentrated cells is what concentrations the cells cells as into cells potential by and are put size as stop into out as the blood sugars. b to passes in liquids. the wall water surrounded salts cell changed different a of they cells. the are This is plasma. D These (a) Figure 3.3.3 This shows water as (D) they what and a appear happens when concentrated when red blood solution suspended in of cells salt blood are (F). E put into shows KEY distilled red blood epidermal turgid 1 plasma. Water passes osmosis. of what is turgid water meant turgor Some potato dilute sugar by each of pressure these mass and accid 2 plasmolysis If plant cores were solution. dried on a weighed After paper 2 and hours, towel then they and placed were weighed into taken of of the potato What does sugar solution? Explain tnemelppuS Explain, cells are passes turgid. cells that is T urgid cores remained this tell you about the your answer to part a in using the term water These cells are shrinks, unchanged. concentration terms potential, when they are placed into of what distilled for stems. of into a solution, out by osmosis. are no happens to for 60 accid. longer the cell away As the rm, vacuole membrane from the cell wall – the 3 osmosis. water placed sugar again. cell Animal cores is now cells into plasmolysed. burst water if they as are they of have potato cell support young water placed 3 plant the the b are a out moves a onion terms: they The red plant is concentrated solution, into A provide leaves 2 a QUESTIONS cells Explain from plasmolysed. POINTS full 1 cells (b) cells by SUMMARY and no cell wall to resist the minutes. increase in size. 33 3.4 Active Active LEARNING Dene the term Look tnemelppuS the Explain active the importance transport consuming • Describe of • ions the by villi in as an active plant glucose up molecules at the and ions concentration concentration of and keep them in high concentrations. of magnesium magnesium ions in ions the in soil the root hair cell and solution: of energy- process the in Describe take active transport • transport OUTCOMES Cells • transport vacuole of root hair cell transport roots active uptake epithelial cells of in soil and kidney tubes solution soil particle Key: = magnesium Figure The of 3.4.1 down high root hair ‘conc in of use entrat the activ e of ion deni ‘ Aga inst of cell ions to diffusion cells magnesium than it gradient. inside in out ions the of The the by active is far water the transport. greater in root hair magnesium root hair the cell cell ions by a inside soil. We into are the vacuole might the soil expect water maintained process called at a active the grad term ient’ a cell using transport through energy is the the cell released movement of membrane during ions against or a molecules in or concentration out of gradient, respiration. tion 4000 a conc entrat ion from to cell in 3000 water outside gm conc entrat ion md means 3– a conc entrat ion. / high is diffuse inside low ions tran sport. grad ient’ a absorb transport TIP the a hair concentration Active No tic e Root concentration the magnesium STUD Y ions noitartnecnoc 2000 1000 0 + + Na Figure The of a bar Ion chart against have a the plant been concentration due to in the into active water the gradient Ca magnesium concentrations and taken 2+ Mg potassium concentration shows freshwater cannot 34 3.4.2 2+ K sodium plant by Cl calcium chloride transport. of in by some which ions it lives. diffusion. active inside These They transport. the are cells ions taken in tnemelppuS Active The cell the with to membrane cell enter leave carrier change its membrane. and the a and cell by protein. shape The carrier needs contains membrane or a transport carrier provide active to carry protein proteins. means by transport. Energy molecule energy from the or reverts to First the respiration ion ion is or to original carrier ions and to the or the the proteins molecules molecule enables molecule released its These which ion combines carrier inside inside of of the span can protein the membrane shape. ions outside cell cell outside cell membrane + membrane energy inside 3.4.3 Carrier proteins in membranes carry out active transport. STUD Y Epithelial absorb rates cells lining glucose of by the villi active respiration to in the transport provide small (see energy intestine T opic for and 7.8). this the These active kidney cells TIP tubules have high Roo t hair transport against a upon concentration respiration oxygen relies will would also gradient. affect reduce respiration the Any rate respiration of to take factor active rate and up that ions or affects transport. active the So are molecules a rate lack up increase to The a in point, presence active temperature so of transport SUMMARY tnemelppuS 1 Explain 2 a 3 would have such stop as increase the the same cyanide man y transport. rate effect can their stop of on respiration, active to transport. respiration, Make a Make sure be is meant the table to State role to that and of active carrier of compare you have ‘active from think what transport, rate a lack proteins and respiration an c the respira tion energ y. in active transport diffusion with taking active place. KEY of three columns transport’. the cell’, some For headed features ‘concentration other features to transport. can gradient’. in your transport molecules include Y ou Active movement ‘features’, you use POINTS effect in each each case of the give following reasons for would your have answer: of is ions across the or the against concentration table. on of membrane, may from cell a gradient, using respiration. active 2 Active transport cells to enables take up root ions, and oxygen epithelial b of in and transport. hair a pro tei ns mem bran es provi de energy 4 havi ng altogether. by examples energy able villi activ e so 1 ‘needs high by carrier cell of for transport. two ‘diffusion’ and QUESTIONS Describe Give also poisons what active b would would cells adap ted trans port of of a An cells transport. epith elial Active cell tnemelppuS Figure cell increase in of the villi to temperature take presence cells of a poison, such as up glucose. cyanide 35 PRACTICE 1 Which A is cell QUESTIONS not partially membrane B cell membrane C cell wall D dialysis permeable? of of palisade red 5 mesophyll blood cell Which A the cell B 1) A is the best partially denition of solvent permeable concentration net of the net molecules D through membrane down random the of net from molecules down of molecules against diffusion a a a a movement of molecules in a molecules down solution a membrane of water molecules permeable with with through a a low high membrane water water potential potential 2) [1] Some fresh plant tissue salt was solution put for into 60 a minutes. Which explains why the tissue became softer? liquid hair cells are surrounded by soil water , water diffused gradient [1] dilute solution nitrate ions higher concentrations hair water gas 1) very down gradient partially solution water cells and absorb of mineral magnesium ions of ions. these from soil ions, such Plant cells ions. How active B diffusion do C diffused water D random into water to the potential their cells surroundings so that they out of the cells so that they plasmolysed water? the cells lost turgor pressure and became accid (Paper osmosis a cells turgid diffused became root transport C down the as have D A from which became is molecules a B Root a gradient A 3 through a best (Paper water of permeable concentrated a molecules gradient potential through a 6 or osmosis? gradient movement concentration D of membrane of diffusion water (Paper net water potential partially diffusion? gradient movement concentration C of permeable diffusion water to B net denition [1] movement a diffusion the a Which best tubing C 2 the partially a (Paper is 7 (a) 2) Explain [1] the importance to humans of the movement following: (Paper 4 A 1) [1] student cut up a potato into pieces (i) diffusion of oxygen in the alveoli (ii) diffusion of carbon dioxide in [2] the that alveoli looked pieces three like as chips. ‘fairly different results that the The rm’. student The liquids. pieces Which student described were row [2] these put shows (iii) into absorption the the small of glucose by diffusion in intestine. [2] obtained? (b) Explain the importance to plants of the following: very very dilute salt salt (i) fairly soft Osmosis osmosis rm (Paper swollen 36 soft fairly rm soft fairly rm and D of magnesium ions by cells. root [2] is a type of diffusion. Explain how and rm very 1) leaves rm fairly soft absorption hair (c) (Paper into [2] swollen soft very dioxide and rm very C carbon solution (ii) B of solution swollen A diffusion water concentrated rm [1] 3) differs from diffusion. [3] 8 A group They divided of of students began 10 the by peeled onions batch was and surface dried calculated The for table small onions into of salt two and the 50 into weighed placed concentrations immersion investigated peeling a hours reweighed. their The in B of was the was B mass. mean mass onions / set Some and up bubbled a oxygen A in gas gas cut three solution with from A; a solutions, ions. rich a in A each oxygen solution very solution mixture. ions through mixture oxygen; the of potassium mixture of were in bubbled through gas investigate uptake roots placed was solutions. to the containing gases concentration results. of C, of received no conc. roots. and was inuencing washed mixture After students change plant A, different batch factors plant, chloride). each experiment by batches of An the They Each solution percentage shows ve them. (sodium 9 osmosis. onions. C The low received roots were g left for 24 hours and then the rate of uptake percentage of of salt before after immersion immersion 2 hours change potassium ions was determined. in / −3 mass The rate of uptake of potassium ions was g dm highest 0 147 173 25 153 165 + in solution + 172 100 154 149 Explain how 149 142 −4.5 200 183 175 −4.5 The Journal (a) and data of in Biological Calculate used to vegetable compile Education the the pickling, (1993) percentage supply uptake table Ray 27 W (2), change was of of solution oxygen to C roots potassium repeated containing temperatures. gas osmosis the their experiment solutions 150 Practical in ions. [3] −2.0 The Information lowest 8.0 inuences 176 and 18.0 (a) 50 A mixture results They that are roots were had all been shown in with kept at different provided given the to with the solution A. table. from temperature rate of / ions uptake of potassium James. pages in °C / arbitrary units 90–91 5 3 10 5 20 10 30 20 40 15 mass −3 for the onions solution. (b) State why the percentage (c) Plot (d) Use a which (Paper of is the the to no 100 g dm salt working. students graph there in your change graph your kept Show in [2] calculated the mass. [1] results. nd the change [5] salt in solution mass. in (b) Draw a graph (c) Describe of the results. [6] [1] the results shown in your graph. [4] 4) (d) Explain uptake (Paper 10 the of effect Explain the (b) Explain why Some term resources and concentrations Describe absorb by the concentration of in is on the roots. [3] are their by or cells, often in as the ions. such very [2] as low surroundings. epithelial molecules gradient. [2] described molecules required ions, how contents. (Paper ions diffusion movement molecules (c) temperature 4) (a) net of potassium of cells glucose of the from villi the gut [5] 4) 37 4 Biological 4.1 molecules Biological Biological LEARNING List in the elements for present carbohydrates, fats Describe large the synthesis molecules from place energy of cells. Green smaller need how They of raw Describe are in different sequences give in plants from the Relate proteins chemicals of the that we body. protein are mean These synthesis, needed all the by reactions and living chemical the include growth organisms reactions the and release repair the raw for complex chemical materials. Carbon photosynthesis. compounds dioxide The simple wide range and that they water sugars are the produced in need are used minerals to to make make a some of these of other complex compounds. compounds. shapes the structure shape eat of plants and/or other animals that feed on plants. and protein molecules that animals require are present in their diet. The molecules different their carbohydrates, different Biological to like amino Animals • chemicals metabolism cells make simple materials Plants protein useful By respiration, photosynthesis acid complex of molecules • fats. metabolism. taking and proteins • are OUTCOMES and • molecules molecules biological molecules needed for a balanced diet in humans function are carbohydrates, proteins, fats, vitamins, minerals, bre and water. Carbohydrates These contain the Carbohydrates a simple Glucose sugar molecules, e.g. in is a b complex atoms sugar e.g. and sugar and which transported in (C), hydrogen (H) and oxygen (O). starches. is made the in blood. photosynthesis, It consists of six used carbon arranged simple made to is a double sugars by bonds. Plants catalyse It is stored Starch complex carbohydrate and Cellulose glucose Figure 4.1.1 Different types and glycogen, a units. unlike The of by two They together starch) is animals molecules a by have into another as mo lecules eaten to refer is also to by the used which an are made animal. bio logical to refer of carbohydrates together store. glucose animal store are chemical enzymes long chains. complex of energy. muscles. sugars, structural glucose up Complex molecules energy glucose and complex, an join called from liver sugar as that made bonds. units are insoluble carbohydrate are held and do made together by not up of bonds taste sweet. thousands forming bres, chains. which give These plant cellulose cells walls molecules their are strength linked and of long together rigidity . TIP Bio logical ions, simple starch made the molecule chemical reactions unbranched form when many (sometimes in is by of carbohydrate. STUDY ring. sugar store the carbohydrate – a joined joining Glycogen, starch into sucrose Sucrose 38 simple respiration carbon sugars glucose molecules, c elements include to by such need organisms. term mo lecules ions, organisms T he described as from nutrient nitrate their T hey (or in only T o pics ions, become nutrient 4 .1 sodium environment. food mo lecule) and ions 4 .2. and mo lecules is often Beware – used it magnesium to Proteins Proteins are complex oxygen, but they molecules also contain made up nitrogen of (N) carbon, and hydrogen many have STUD Y and sulfur Y ou (S). Proteins are long-chain molecules made up of smaller TIP may compa re called amino acids. After formation Topic 5.1) they are either folded shapes (see or become arranged into long of bres. to compa re peptide head ings bond of acid part molecules of a protein 4.1.2 How a protein is made from amino are about 20 different types of acids. amino this acid. and will Molecules of be table Whe n There are made into chains as you can see in the diagram. It is of the different amino acids in the chain usin g as ‘Nam e molec ules ‘Elem ents’. which able in to add T opic nam ing to 7 .2. the alwa ys use the full sequence table amino elem ents acids such a molecule Y ou Figure Mak e them biolog ical grou p’ amino to three biolog ical molec ules. different aske d these into grou ps different be molecules nam es, no t determines their their sym bo ls. the type the chain tnemelppuS The of by different molecules. to protein their that means of a sequences These function. is formed. chemical of amino different shapes Enzymes are Each bond acids of individual called give peptide different protein proteins a amino that a joins bond. shapes molecules provide acid can to be surface protein related fatty acid glycerol molecule for molecule reactions are to take proteins enables with them pathogens place to and a called structure bind with make the the ‘active that has chemicals pathogens site’ (see binding called stick page sites on antigens together 47). its on (see Antibodies surface. the page This surface of 120). Figure KEY Fats Fats and Each to fat this these oils made molecule are can energy are three form storage is up made fatty the up acids. different and of fats thermal of elements one There with carbon, molecule are different different insulation of in hydrogen glycerol types properties. the of and and fatty Fats oxygen. acid are 1 attached for body . A Carbohydrates up of hydrogen Proteins of the List the Give components of a balanced diet for a a fats are and are made elements plus sulfur. (e.g. one example of each of the simple sugar ii a complex are simple glucose), and human. carbohydrates such following: as i same and Carbohydrates complex b fat. QUESTIONS sugars a of elements oxygen. up 2 1 and the carbon, nitrogen SUMMARY molecule POINTS made and used 4.1.3 carbohydrate found in starch, glycogen and plants cellulose. iii a complex carbohydrate found in animals 3 2 a Which in elements are carbohydrates present and in proteins, but are not found Small fats? Name the small molecules that are joined together to Give d State three examples of proteins that are made in the the Name made and Amino function of each protein that you named in the molecules that are reacted together to into acids are part A molecule make of of a fat is made c combining three fatty acid a molecules molecule proteins. body. by a are glycogen chain make 4 3 joined long molecules. made c are make Sugars starch, cellulose. protein to molecules. into b molecules together with a molecule of fat. glycerol. b Give two uses of fats in the body. 39 4.2 Chemical tests biological Simple LEARNING how the following and are carried vitamin can be used to identify starch, sugars, proteins, it is important you iodine test • Benedict’s to carry out these tests on pure forms of these out: compounds. • C. chemical First, tests tests molecules OUTCOMES fat State chemical for for should For rst example, carry out if you the are testing chemical test a food on a for reducing glucose sugars, solution. starch Then test for keep the results to compare with your results from testing other reducing materials, such as foods or animal and plant tissues. Y ou should also sugars do • biuret test • ethanol for a emulsion test for test for water so that you can see the negative from the material result as well. vitamin will need to make an extract you are testing. fat This DCPIP with protein You • test C involves water The with eye so a pestle chemicals Safety: Safety: grinding will Some always of wear and be the eye up a small mortar in amount or solution chemicals of putting in the used the it material into a with some blender. extract. in these tests are corrosive, protection. protection T esting • Half ll • Add two Iodine • Figure 4.2.1 Test for A a tests If drops usually result the contain are for the of food iodine looks starch extract if wish to test for starch. solution yellow is you the or light iodine brown. extract remains a yellow or solution light turns brown blue– colour it does starch. • as they ‘food can any anim al be sugars Put a known mad e in a volume of the extract you wish to test for reducing test-tube. carried plan t • Place a beaker • Carefully half (or the on a heat-proof mat. and or up ll the beaker with boiling water from a kettle on in place beaker on a tripod and gauze and boil the water the with labo ra to ry. • Add a Bunsen the burner). same containing Safety: reducing tests’, mater ial so lu tions for of ten sugars on three with TIP know n but or positive T esting out test-tube starch. not T hese starch solution black. STUD Y for • Benedict’s • A positive volume the food solution test for of Benedict’s extract is and bright simple put solution it into the to the hot test-tube water. blue. sugars is when Benedict’s solution turns eye red or orange (if you look carefully you can see it turn green and protection then cool • d t you can present. B o You yellow t will use If of • Test for reducing colour If the a reducing lot colour of a orange). If you leave the test-tube to precipitate. test to changes sugars. sugars. reducing remains sugars. reducing 40 see Benedict’s the the contains 4.2.2 also turning tell to how much green, the simple extract sugar is contains only a o little Figure before blue If it turns a deep orange colour then sugars. then the extract does not contain any it T esting for protein Safety: • Half ll • Add ve copper a test-tube to six drops sulfate Safety: T ake • solution with of solution care as the extract biuret and sodium you wish solution sodium to (this solution for solution hydroxide hydroxide test protein. contains solution). is corrosive. S od h Biuret • A positive violet • If the or usually test for looks protein blue is if in the colour. biuret solution turns C um yd ro x s o ut e d s remains Fats will for not solution of is formed. • Chop (Do • Put up not the blue, then the extract does not contain protein. Figure 4.2.3 Test a Put • Add • Shake fat in water ethanol grind add in a small water extract is to into a but they added to amount make clean of the will dissolve water a material extract test-tube cloudy you this and in ethanol. white wish to If a 1 emulsion test for Describe in each what of stopper some the white over the distilled test-tube water contents emulsion positive test for starch b a positive test for protein c a positive test for a time.) add enough ethanol to to and make shake the up the test-tube of the test-tube once d a negative half e a positive test for that looks cloudy does not for Describe of is vitamin that loses C its happen, juices, can Put 2 Fill a the white extract or a milky colour is does not contain such as freshly-squeezed made from when it volume or vitamin comes into C lemon tablets. contact juice. DCPIP with is a A with test an blue vitamin for of DCPIP solution in a dropping pipette with a a juice, the e.g. liquid orange one drop demonstrating liquid 3 C. You the are each the colour If the blue of DCPIP solution of vitamin C a glucose given are a to carry sugar test solution four a of test-tubes different glucose. labelled you do A, not B, C know and the then of glucose in time. the the test test is is positive for vitamin tube. C. have been told to nd negative. which most is the solution concentrated least is the and which concentrated. POINTS Describe the procedures 1 Iodine 2 Benedict’s solution gives a blue–black colour when added to solution turns orange when boiled with simple to solution gives a purple or violet colour when you would and the observations sugars. you Biuret practical that starch. follow 3 how reducing containing and out KEY food juice. at disappears persists a sugar or You colour of test-tube. each If extract reducing concentration Add would the solution D 3 of procedures: making out be syringe C fat. They a vitamin a C colour known for you each concentration 1 starch. fats. vitamin in test how out using C for more. b T esting test full. to Vitamin sugar contents. a this see a following positive If would following: a carry • you the fats. 2 A protein. it. • • for QUESTIONS reducing cover on fats dissolve or fate ut corrosive SUMMARY T esting op p e u s o on purple, lilac. colour eye protection added would give expect. safety Remember precautions. to protein. 4 Describe the 4 A white emulsion forms when fat dissolved in ethanol is you to would use compare C content of the different water. fruit 5 test added vitamin to how DCPIP Vitamin C decolourises DCPIP juices. solutions. 41 4.3 DNA tnemelppuS The LEARNING Each • Describe structure the structure of two to form strands coiled chromosome double State that DNA chemicals Describe called up how in the the how for we eye the bases same place in we could DNA TIP DNA of unravel The so is the G, of DNA. show bases, A, each are Y ou C, remem ber a The no t need what colour we look and like. height. For instance, Some genes there code enzymes that control all the chemical reaction thread a chromosome, would the of long be acid). made it would A thread gene that up is of a form an chemical extremely made makes up up a of a called long short DNA length chromosome contains genes. belongs to acids. a complex called a Each DNA group of molecule biological nucleotide. A single is made up molecules nucleotide of known is thousands made up of of as units three phosphate • a sugar • a base sugar the and DNA phosphate strand. The molecules bases are join up attached and to form the the sugar backbone molecules. struct ure nucl eo tid e show n you look at Figure 4.3.1 you will see that DNA is made up of two in strands Figu re and hair to of the like information in If a arranged genetic T arrang ed do genes the molecules: • DNA. of block ’ diag rams and of carry a nucleic how that always hundreds nucl eo tid e T he thousands way of ‘build ing of genes cells. (deoxyribonucleic A up the grow colour, production take thread. STUD Y is bases If pair made It strands that • is necklace. affects genes for contain a helix are • in together that a DNA DNA beads as of OUTCOMES of nucleotides. It is rather like a ladder. The whole molecule 4 .3.2. is twisted bases as into the a double helix – a bit like a spiral staircase with the steps. phosphate base P sugar The DNA looks like Figure molecule a 4.3.2 A spiral single nucleotide. phosphates make The up the sugars and ‘uprights’ of staircase the ladder and the bases make up the ‘rungs’. Base A T So C G If how you Each T A G C on Figure 42 4.3.1 A DNA model. of bases the the the look pair at of The DNA don’t bases molecule Figure bases bases thymine (You pairs is different • form pairing in 4.3.3 held you together? can together see by that weak • have to adenine (A) remember pair up in • each the of same the • cytosine (A) (C) pairs pairs with with thymine guanine (T) (G) (C) names, way: steps adenine bases bonds. cytosine staircase • the join There together. are four DNA: (T) always is held • guanine just their (G) letters.) are the weak, double bonds there helix in are holding many of the two them. chains So of nucleotides altogether they tnemelppuS Although together keep the DNA shape. cytosine guanine adenine thymine A student shows (guanine) thymine examines the pairs is of yellow a model bases. and C In of DNA this that model (cytosine) is G red. adenine phosphate guanine cytosine sugar weak Figure 4.3.3 How SUMMARY 1 Figure 4.3.4 of bases pair up in DNA. QUESTIONS molecule. letters the bonds shows Copy the a and partially completed complete missing the section diagram by of the writing DNA in the bases. James the They G Figure 2 The table DNA below from four C A T Watson structure they are and of posing made in Francis DNA with by Crick worked building their Cambridge nal in the out models. model early that 1950s. 4.3.4 shows the different percentages of the four bases in KEY POINTS organisms. 1 percentage of each base The two DNA molecule strands coiled consists of together organism to A C G T human 31 19 19 31 locust 29 21 21 29 2 form Each a double strand chemicals and yeast 32 18 18 32 bacterium 15 35 35 15 3 A C a Explain b In A. c an the pattern organism What Explain shown 26% percentage how organisms it is such percentages of of the DNA be to humans bases. the table. bases would possible as in C? have and in 4 DNA Show two yeast are your very with found to very similar called always bonds bonds chromosome long bases bond with with is A, C, G together. T; G. made super-coiled up strand of of DNA. working. different contains which always A a be T , helix. 5 A gene that of a is a codes length for particular the of DNA production protein. 43 PRACTICE 1 What QUESTIONS are the chemical A carbon, hydrogen B carbon, hydrogen, elements and in Use proteins? the nitrogen and molecules molecules oxygen shows carbon, hydrogen, of nitrogen, oxygen a are known questions 6–8. small part of sub-unit nucleotides. of a DNA The diagram molecule. and B carbon, (Paper for composed as sulfur D DNA oxygen DNA C diagram nitrogen, oxygen and sulfur 1) [1] C A 2 The small proteins molecules that are built up into are: A amino B fatty acids acids (Paper 1) Which row C glucose D glycerol [1] D 3 four gives chemical the positive results for the tests? Benedict’s biuret iodine emulsion test test test test green violet yellow Adenine no A X suspension 6 Which of the labelled parts of DNA, A, B, C or D, no B blue blue indicates yellow a base pair? suspension (Paper 2) Which of [1] cloudy C yellow red blue suspension D orange 7 indicates blue- cloudy black suspension 4 Water 1) is because [1] an it important is molecule in 8 organisms a: A solute C solvent B solution D suspension What 9 5 1) Enzymes regions that form [1] and of bind antibodies these to parts of DNA, A, B, C or proteins other specic are proteins. have molecules. shapes A molecules of B molecules with because D, different [1] the structure labelled X? A adenine (A) C guanine (G) B cytosine (C) D thymine (T) The 2) [1] diagram molecule below increases shows in how specic a starch length. A Special Proteins they 2) is (Paper (Paper labelled nucleotide? violet (Paper (Paper the a shapes can have: lengths different numbers of amino (a) Name molecule (b) Name two A. [1] acids C molecules with different sequences places where starch is stored plants. amino [2] acids (c) D molecules with other molecules or Describe to plant would nd out whether tissue contained details of the starch. test in Include your the answer. [4] [1] (Paper 44 you them practical 2) how ions a attached (Paper in of 3) 10 The diagram shows a protein 5 molecule: Repeat steps 1 to 4 with the juices to be tested. The (a) Name the sub-unit molecules that results are shown in the table. are volume assembled into the protein. added to DCPIP [1] 3 test (b) Name two proteins found in the solution substance / cm human body. 1 2 3 mean 1.8 1.9 2.1 1.9 2.4 2.6 2.3 2.4 3.2 3.1 2.9 3.1 9.6 9.1 9.4 9.4 [2] −3 (c) (d) State two places many proteins Some seeds the are are chemical in the body in that 10 g dm where made. rich test human proteins. orange Describe would use juice to grapefruit determine whether different types of rich details in of proteins. the test Include in your the answer. [4] The Explain why readings 3) (b) 11 juice practical (a) (Paper juice seed apple are diagram shows a molecule of a Use the the for results (Paper 13 juices. Name the (a) components of the DNA of vitamin Show molecules X and Y. the your C in the three working. [3] two places are stored. State in the human body a double what this helix means. [2] the precise site of DNA in an cell. [2] where The sequence of bases in a small sample [2] of three have Explain [2] animal State calculate [3] molecule (b) labelled (c) substance. 4) structure. fats three Y X List to test took fat. fruit (b) student each concentration (a) C solution [2] you vitamin roles of fats in the DNA is: human ATAGATCCCGAA body. [3] (c) (d) Oils have the same molecular structure Write out opposite fats. Many seeds are rich in oils. chemical test to nd out whether different owering plant The oil or not. Include strand DNA of of the test in your A student the used vitamin the C is DCPIP test present in answer. to The concentration of nd out different the the DNA molecule. [1] determines of a a small protein. above to explain Use how determine the sequences base of [4] acids in a protein. [1] how In 2007, scientists compared the degree fruit of juices. in practical (e) much this structure sequence amino 12 in sequence the sequences details bases species the contain of seeds part from sequence Describe (d) a the as DCPIP similarity between some of the DNA solution taken from the nuclei of white blood cells −3 was 10 g dm . The student followed these of a domesticated cat and several other instructions. mammalian species. The results are below. 3 1 Put 2 Use 2 cm of DCPIP solution into a test tube. percentage a graduated pipette or burette to similarity between add domesticated cat and: −3 a 10 g dm vitamin C solution drop by wild drop to the DCPIP solution. Shake the tube human dog cow rat mouse 90 82 80 69 67 cat gently add of after the the adding vitamin DCPIP C each drop. solution solution Continue until the to colour 99 disappears. What 3 Record that 4 the was Repeat of vitamin C a (Paper procedure mean two more do you conclude from these results? [3] solution added. the calculate volume times 4) and volume. 45 5 Enzymes 5.1 Structure and action of enzymes A LEARNING catalyst end • Dene the substance term that catalyst speeds chemical reaction changed by the and as up is a of speed Dene enzymes the up act not How as as speed biological up the tnemelppuS Explain using rate how the an ‘lock enzyme and key’ works too catalyses many of in Breaking is 2 They take keep are different of 3 of storage are known place in organisms many as at organisms, biological organisms. alive different reaction. shows its (see we will Topics of 3D enzymes Most discuss 7.5 and up in nutrition the large cell the one when that they These unless types they of enzymes the that catalysts reactions are enzyme speeded as work each inside cells, here work outside cells, for 7.7). gut for as work of large to down small cells and types. and their are broken then food used. and we reason. joined inside starch, three molecules absorbed break from into ones food be same are divided ones together to speed structural to up make the large formation molecules such as plants. small chemical as be small the glucose, such can can enzymes enzymes walls into molecules such molecules, for so release into These catalyse molecules ones fungi Converting molecule reactions that into occur another inside cells involve small an changes right) that molecules, Many image that gut enzymes cellulose computer-generated those large and molecules. to molecules, such as adding or removing atoms or groups shape. of atoms. from For example, compounds Figure 5.1.1 breakdown shows of a there during the are enzymes that remove hydrogen respiration. way in which an enzyme catalyses the molecule. TIP writi ng enzy mes abou t alwa ys enzy mes reactio ns. say enzyme substrate substrate active cata lyse Figure Figure from 46 to There small Building Small that reactions important into release Whe n a the reactions Bacteria STUD Y unchanged by model down the remains produced work slowly enzymes. example This (on and reactions 1 enzyme reaction proteins, of The This reactions. enzymes chemical by but • chemical are catalysts one chemical chemical proteins up to a Enzymes reaction happen that up reaction. a Many • speeds OUTCOMES in enzyme products site released 5.1.1 5.1.2 two shows smaller how an enzyme molecules. is involved in building a molecule Enzymes are made All enzymes have 1 They are all 2 Each enzyme 3 They can 4 They are inuenced by temperature. 5 They are inuenced by pH. ve of protein important properties. proteins. be catalyses used one again reaction. and again. active site substrate Enzymes are made of protein molecules. These molecules can be enzyme folded a into shape many that explains different makes why there it shapes. suitable are many for Each type catalysing different of enzyme one enzymes type – one molecule of has reaction. enzyme for This each substrate in reaction. active Enzymes catalyse products. Look reactions at enzyme matches and substrate the together. Once Figure the t which 5.1.1. shape have they in of Notice the shapes substrates that together that substrate are the the are converted shape molecule. of part The complementary reaction can take site into of the enzyme so place. they t product Other released substrates involved have in the the wrong reaction shape catalysed to t by into this the enzyme enzyme. so When will the not be reaction is Figure 5.1.2 This shows enzyme over the product or products leave the enzyme and another tnemelppuS As you an join two substrate molecules molecule how can together. enters. can substrate(s) This way of key’ model. lock to see t in Figure and describing The form an 5.1.2 where the how enzyme the part reaction enzymes and of work substrate enzyme-substrate the takes is enzyme place is known combine like where the as a the active the key site. ‘lock substrate A substrate B and entering a complex enzyme Figure 5.1.3 Only the SUMMARY Copy and complete the sentences using these words: 1 Enzymes catalysts proteins are biological that up the rate . type Enzymes of are the meant 3 Use a terms by the why the ‘lock each all and each enzyme why an rate Enzymes catalyse in substrate reactions acts which complementary and key’ enzyme key’ model will and active model act to of site to enzyme explain what is only on molecules, action. explain: 3 one converted or breaking All enzymes molecules. substrate enzyme can be used to catalyse a large quantity to molecules the product either up where b the . ‘lock and increase reactions. by building down. are Part protein of the reaction enzyme occurs has of a complementary shape to substrate the c why high destroying the temperature active stops site the by heating enzyme from the enzyme working to substrate molecule(s). a 4 The of active the site enzyme substrate reaction ts is the part where and tnemelppuS tnemelppuS Use biological that chemical are 2 are of 2 chemical one t site. reactions of on will POINTS catalysts speed Enzymes A active QUESTIONS KEY 1 substrate enzyme’s the where the occurs. 47 5.2 Factors affecting action: The LEARNING activity Carry the out an effects enzyme investigation of into temperature on reaction measuring substrate the activity Describe enzyme the effects temperature on that how is e.g. the is determined enzyme much used reaction time, • an temperature by measuring the rate of OUTCOMES the • of enzyme product over a measured per catalyses. is period in This formed of time. quantity of may or by The done either measuring rate product be or is like how the substrate by much speed per of unit of minute. of enzyme Effect of temperature on enzymes activity Explain the effects activity of enzymes is inuenced of 6.0 by temperature on temperature. This graph shows enzyme effect of increasing temperature nim the 1– activity on the rate of an enzyme-catalysed tcudorp reaction. the can reaction: slow are use this some from the answ er . say the low temperatures, 10 °C desc ribin g • like at at increases as the increases to 40 °C etar alwa ys your of observe 4.0 3.0 2.0 fo you grap h take n rate and noitcaer is e.g. a graph TIP • Whe n the / that STUD Y at gm Look 5.0 temperature one, 1.0 gu res grap h Here • reaches a maximum • decreases at 0 40 °C in 10 at 5.6 mg min ute at high es greater t prod uct per • is zero the than be describ e the tempe rature enzy mes, 4 aske d 40 °C and effec t and but will explai n, enzyme. fungal • human • some which Here and plant are the some maximum 37 °C enzymes rate This examples enzymes: enzymes: of the temperature. of is 20 °C temperature produced by reaction best optimum approximately (body of the – bacteria for is for temperatures: (see see occurs temperature page T opics use in 250) 7.5 and industry: 7.7) 90 °C. be saw in the T opic 5.1, an enzyme substrate molecules. by between molecule The shape is of folded an into a enzyme’s shape active that site bonds different parts of the molecule. is Remember that the shape into the enzyme of the active site determines whether the substrate will t on for the reaction to occur . in aske d At rst, will increasing increase have the greater there are the rate. kinetic more temperature This is energy. chances of of because They them an enzyme-controlled enzyme move and around colliding, the substrate more reaction molecules quickly substrate tting and into remem ber the are tempe ratures of we of pH pH. active site and a reaction taking place. protei ns denat ured extrem es by and At higher together site, We so say temperatures start the to break substrate that catalyse 48 at optimum maintained only you enzy mes are the to inu ence enzy mes. Whe n high 5.2.1 60 °C. temperature accepts to exp lain ho w thes e fact ors that at • As you 60 °C TIP may Paper 50 / 40 °C . called Y ou 40 rate The STUD Y 30 temperature Figure is 20 temperatures you the the the no enzyme reaction. bonds down. This longer has holding the changes enzyme the shape molecule of the active no longer ts. been denatured and it can tnemelppuS tnemelppuS The • PRACTICAL Investigating Amylase is changes iodine iodine an the enzyme like not temperature breaks down blue-black. change starch When colour. on enzyme to starch Draw a action maltose. is broken table for Starch down, your this. temperature and will of that solution solution results effect starch at which was kept / amylase time °C taken fully for broken starch down / to be min Figure 5.2.2 T esting starch the in solution for iodine. 3 1 Put A, 5cm B, C, of starch and solution into each of four test tubes labelled D. 2 Put test tube A into the refrigerator 3 Put test tube B into a test 4 Put test tube C into a water tube and note the temperature. and note the temperature. rack bath at about 35°C and note the temperature. 5 Put test tube D into a water bath at about 80°C and note the temperature. 3 6 Collect 7 Put a of 10cm drop spotting of amylase iodine solution solution into in a clean each of boiling the wells tube. on a tile. 3 8 Add 2cm note 9 At the amylase test iodine When solution to each of the four tubes and KEY time. two-minute the 10 of intervals solution solution the from on each the amylase use a clean test tube spotting solution pipette and to remove add it to a some drop of 1 of has broken down all the Increasing of tile. POINTS an iodine solution will no longer turn blue-black. temperature reaction increases reaction up to a the rate of maximum, starch which the the enzyme-controlled They occurs at the optimum will temperature. brown. on What the does this tell you about the effects of amylase? This is because energy SUMMARY QUESTIONS is number enzyme 1 a Sketch a graph temperature to on show the rate the of effect a of increasing reaction catalysed enzyme, such as salivary Describe, in words, what is Suggest what each reaction catalysed of by the shown a following human At higher by your a temperature below b a temperature of c a temperature of temperatures the would do of reaction decreases graph. to the rate of it stops acting as a catalyst. enzyme: This a between substrate amylase. until 2 collisions and kinetic greater a rate b of a molecules. by 2 human greater causing tnemelppuS light temperature tnemelppuS stay 10 °C is shape 37 °C due of to the means the longer t. a change active site substrate The in can enzyme the which is no now 50 °C tnemelppuS denatured. 3 Use the ‘lock enzymes are and key’ model denatured at to high explain what happens when temperatures. 49 5.3 Enzymes The LEARNING Describe enzyme • Carry the effects of pH enzymes on i.e. action out the an at a that low of pH tnemelppuS Explain active in the is can be present affected stomach work in the by the best stomach, pH in acidic so of the conditions, pH. bile is that present are in active the rst here part work of best the in small alkaline intestine, so conditions, the i.e. at a activity the effects of pH pH. on Most enzyme enzymes work best inside cells where the conditions are neutral. action The optimum Enzymes Enzymes Many pH of and are these is therefore about pH 7.0. pH inuenced enzymes enzymes work by best the in pH of neutral their surroundings. conditions, but some work best substrate enzyme in Enzyme – the acidic conditions and some in alkaline conditions. denatured substrate fits Figure are acid on high • reaction Hydrochloric investigation effects enzymes enzyme enzyme-controlled surroundings. Alkaline into of pH OUTCOMES its • rate and no active longer site Look and at the graph in Figure 5.3.2 showing the action of enzymes X Y . 5.3.1 • Enzyme • The • Up X works optimum best pH for at pH 2.0 enzyme Y – is that pH is its optimum pH. 8.0. 6.0 to pH 2.0 the rate of reaction increases for enzyme X and then 5.0 between pH 2.0 and pH 5.5 it decreases. There is no reaction above 1– fo tcudorp noitcaer nim pH 5.5. 4.0 • 3.0 Between Y and pH then gm etar reaction 4.5 and between below pH pH pH 4.5 8.0 the 8.0 and rate and pH above of reaction 10.0 pH it increases decreases. for There enzyme is no 10.0. 2.0 enzyme X enzyme Y As we vital 0 0 1 2 3 4 5 6 7 8 9 10 11 pH if have it is structure seen, to of the three-dimensional function. the Many enzyme are of the weak shape chemical bonds. If of an bonds these enzyme holding bonds is the that acid Figure 5.3.2 STUD Y TIP hold the enzyme then the shape reaction is that substrate At is say kille d’. no t enzy me Enzy mes orga nism s. are pro te in T he co rrec t dena tured. 50 ‘the are T hey mo lec ules. wo rd to use is at the these can Never molecule of values affect the zero, the the of rate extremes denatures. the of in active shape of molecules pH of its shape site the will enzymes reaction pH are can be active no are an by altered. site longer has the changed Small denaturing enzyme changes When in pH, rate so of much t. denatured. without range broken changes the becomes in enzyme, unstable pH but and tnemelppuS / 1.0 PRACTICAL The effect Egg white egg pH on contains investigate in of the white. a lot effect You the of will action of protein. protease also of see a In this from how protease the pH experiment stomach affects the you on will the way protein the enzyme works. 1 Set up a water bath 2 Using syringe put 3 Add 2 cm 4 Add 2 cm at 40 °C and label three test tubes 1–3. 3 a of 5 cm egg white into each test tube. 3 of sodium of water carbonate (an alkali) to tube 1. This is a model of protease that breaks 3 to tube 2. down proteins intestine. It to amino works best acids at a in pH the of small about 8.5 3 5 Add 2 cm 6 Compare each of the tube to dilute hydrochloric pH each of dip into test the acid tube by solution to tube using and a then 3. and clean touch glass the rod pH at 37 °C. for test KEY POINTS paper. 7 Place all three 8 Add 9 Compare test tubes in the water bath at 40 °C for ve 1 minutes. Most one enzymes value of work best at pH. 3 of protease to each test tube. 2 the appearance of the tubes every minute until At either side optimum is no further the table pH value, enzyme At some shape white appearance + changes 5 plus: values of the of pH active the site after pH tube protease decreases. below. 3 egg their change. activity Complete of there tnemelppuS 1 cm so that substrate minutes molecules no longer t. 3 2 cm of sodium 1 carbonate solution 3 2 2 cm of water 3 2 cm of 3 hydrochloric SUMMARY 1 Sketch the a QUESTIONS graph optimum 2 Use 3 An the ‘lock to pH and investigation Eight The test acid tubes show is 7.0 key’ was were concentration of the and effect there model carried set up to reducing increasing no explain out at of is a into activity what the sugar pH. a Plot a b Explain of graph the reducing to show effects of sugar these pH produced of was the pH pH They (product) pH concentration on happens effects different pH below rate 4.0 when on were then of and an enzymes the action incubated estimated. 4.0 5.0 6.0 1 12 26 enzyme-catalysed none are of in above The enzyme water bath results are reaction, where 10.0. denatured the a pH at extremes amylase at 30 °C shown 6.5 7.0 8.0 9.0 32 33 27 13 on for in of pH. starch. 1 the hour . table. 10.0 5 results. on the action of amylase in this investigation. 51 PRACTICE QUESTIONS 1 the Which is correct statement about enzymes? 5 In an enzyme-catalysed binds A Enzymes are biological catalysts to B inside Enzymes only C are outside catalysts function Enzymes and are inside are used they catalyse. up of protein Enzymes only substances catalyse are made the by cells reactions reactions broken substrate down in into site B complementary as C reaction D substrate site site site 2) [1] which smaller 6 Albumen and in 1) is the at a protein blood. 75 °C A and found solution then in egg of added white protease to a was solution of [1] albumen. The the molecule the: active kept 2 enzyme that molecules. (Paper as A (Paper D reaction, the that cells. during of cells. made continually they part that known function the equation shows a reaction catalysed by No reaction occurred. an Which is the most likely explanation? enzyme. A 75 °C is below the optimum temperature lipase of fat + water → fatty acids + B The progress of the reaction the protease glycerol can be albumen cannot be broken down by followed proteases by detecting the decrease in pH. This is C the protease D there is denatured because: A fat is an acidic the B fatty acids they lower are one of the products the no D the reaction is a 1) Starch and kinetic energy for 2) [1] stops when the pH decreases 7 The diagram possible shows an enzyme and four substrates. reactant A (Paper enough pH further water not reaction and (Paper C was substance C B D [1] enzyme 3 together human at salivary different temperature will amylase were temperatures. give the fastest mixed Which rate of starch digestion? A 20 °C B 60 °C C 37 °C Which of substrate D (Paper 1) shown is the enzyme? pH 2) of enzyme-controlled reactions changed affect the from rate of pH the A always increases B always decreases C has effect D may the (Paper no change on the 7 to pH 8. How does The optimum reactions? the the the rate rate rate rate or have no temperature effect reaction is the for an enzyme- temperature at which: this on rate. 1) [1] may catalysed 52 substances this [1] 8 The be for 10 °C (Paper 4 the [1] A least B most C the D the (Paper substrate product rate of is broken is down formed reaction reaction 2) is is at completed its in fastest the longest time [1] 9 (a) Explain the following statements. A (i) Only small required (ii) Cells quantities inside make of enzymes cells. many B are [2] different types of 1 3 enzymes, The the table shows relative solution at not the activity pH just one. effect of an of [2] temperature enzyme kept in on C a 7. 2 relative temp / °C activity 5 4 15 8 (a) State (b) Use the the when 25 16 35 32 45 30 55 7 (c) (d) the when (b) Explain why kept the at all the same reaction mixtures were pH? Draw a graph (d) Describe of the results in the table. results Hydrogen shown in the graph. [4] (a) model to is what a happens reaction. known explain enzyme what molecule temperatures peroxide is produced metabolism. as [4] ‘lock or happens changes extremes of shape pH. [4] is a very toxic substance The by cells enzyme peroxide and as part of catalase is found their breaks in down organisms in 3) all 10 model [3] 4) hydrogen (Paper describe catalyses C. [6] which the and [2] 12 (c) the B [2] the high (Paper to enzyme why A, key’. Use in of diagram an Explain and names Explain the following kingdoms. statements. catalase (i) Amylase digests starch, but proteases Hydrogen do not. Human enzymes catalyse reactions student but not at 73 °C. table shows enzyme kept 35 °C. the in relative solutions activity of investigated in yeast by the activity measuring of the the enzyme volume of a different collected over time. The graph of shows the results. pH 3 human water [2] oxygen The + at catalase 37 °C, oxygen [1] A (ii) peroxide mc at 7 / relative 3 detcelloc pH activity 5 32 9 10 emulov 7 fo 14 negyxo 5 6 5 4 3 2 1 × 0 0 11 20 40 60 80 time (a) (b) Explain why all the reaction mixtures Use at 35 °C? Draw a graph Describe the results catalase of the results in the table. 140 on shown to hydrogen describe the [4] Explain results shown in the why catalyse catalase the is the breakdown only of enzyme hydrogen graph. [4] peroxide. (Paper 3) (c) Describe catalyses 11 The diagram reaction. effect peroxide. [6] to (d) 120 s [3] (b) (c) the / were of kept 100 4 shows an [2] what a happens reaction. when an enzyme [4] enzyme-catalysed (Paper 4) 53 Plant nutrition 6.1 Photosynthesis The LEARNING process When • • Dene State the the term Describe leaf tnemelppuS • for State photosynthesis word how equation for look round, green energy to into to test a green starch the you at cells Photosynthesis raw is called carbon sugars. This the materials dioxide process process using Describe the by can role of chlorophyll carbon be dioxide + balanced + equation This is full of not that TIP tnemelppuS this is there of the balanced write it out. are the atoms their see use many light surroundings photosynthesis plants make carbohydrates light. in of and this word equation: chlorophyll glucose equation 6H for photosynthesis and a case. H 6 There different photosynthesis are oxygen is: C that + chlorophyll O suggests the by energy transferred sure you plants many is one reactions in O 12 + 6O 6 simple 2 reaction. photosynthesis, each enzyme. chloroplasts. Light Make from 2 This catalysed STUDY from Green water 2 are called summarised chemical 6CO cells microscope water which energy light plant the photosynthesis The These and is light • under chloroplasts. chemical Photosynthesis for leaf structures convert simple from balanced equation some photosynthesis photosynthesis • of OUTCOMES equation when you Make same form the The becomes sure are the carbon, As by to a is a water used to are the bond Glucose as chemical from is result, starch chlorophyll. as ions chemical produced. converted energy hydrogen carbohydrate. number absorbed chlorophyll carbohydrates process oxygen. is by used to in simple store of energy to the energy in carbon simple that During leaves that produced; and and to chlorophyll sugars is ions dioxide by is reactions hydrogen absorbed sugar light the dioxide. into reduce from drive carbon water energy energy one and split light The energy other it is parts of plants. hydrogen and both of sides oxygen the on Photosynthesis arrow. that feed show that oxygen carbon dioxide on where in it provides plants oxygen its is is own used energy directly or produced respiration by other for plants indirectly as or it a and (see for by-product. may all page diffuse other 244). The out plant into organisms The equations may the use atmosphere organisms. Sun oxygen chlorophyll Investigating photosynthesis light traps light energy energy Green if too a very plants much make sugar simple is sugars dissolved in from the carbon cell sap of dioxide plant and cells water . it However , would make sugar cells to concentrated by osmosis make very together effect starch Figure 6.1.1 A simple overview photosynthesis. 54 of out on in to and thick form leaves. cause cell Y ou As you This the walls. larger osmosis. whether solution. will cells T o starch can to see iodine in has so this, water much glucose which solution Topic been make swell prevent molecules use photosynthesis would 6.2 are to we that in they insoluble for use or from the this not. other would molecules test can happening move are and need linked have presence test to no of nd tnemelppuS 6 PRACTICAL T esting a leaf for starch Safety: eye 1 Submerge This it kills easier a leaf in the leaf as to extract boiling it water destroys the for one wear At this boil 3 Put point, the the turn is ethanol ammable minute. membranes, making chlorophyll. boiling 2 Safety: protection off any Bunsen burners used water ethanol to water. leaf into chlorophyll is a test-tube extracted by of ethanol. dissolving The into the ethanol. 4 Stand the test-tube in a beaker of hot water for turn about 10 off Bunsen burner minutes. iodine 5 Wash the ethanol makes 6 some 7 If and it Spread leaf the leaf stays to leaf drops cold water. rehydrates easy the in of out there is SUMMARY QUESTIONS 1 complete and oxygen on plants chloroplasts for this made make the process in the are leaves white on softens surface is own leaves and present. and put If it Safety: using chlorophyll food traps these careful 2 To nd carry of this out out a if process is the by the are . Green Sun’s . . changed gas photosynthesis to burn yourself dioxide in Raw Simple to . the materials sugars The are waste KEY product not words: carbon and some be photosynthesis carbon and it starch. water their the it. sentences starch of which starch no the energy Green a solution blue-black, red/brown Copy leaf removes out. at iodine goes the spread This has POINTS . taken place in a leaf we can 1 test. Chlorophyll absorbs energy is that used light in photosynthesis. Copy out correct the stages reason on listed the on the left. Match each one with the right. 2 Photosynthesis by Stage in test which the leaf in cold water to test for to soften to remove raw the leaf add drops in ethanol iodine solution the ethanol the glucose leaf rehydrate using from light. Carbon the dioxide and water and are to materials it 3 of process starch energy boil the make Reason from wash is plants the raw materials for leaf photosynthesis. dip the leaf in boiling water to extract the chlorophyll 4 3 Write out the word equation for photosynthesis and The are the raw materials and Using only information in this topic, explain why plants to our of and photosynthesis oxygen. A leaf that has been exposed are to vital glucose products. 5 4 products identify light will give a positive survival. test for starch. 55 6.2 What is needed for photosynthesis? The LEARNING requirements Green • List the raw needed • for Describe materials that plants need for the following in order to carry out photosynthesis: • light, which provides • chlorophyll, energy for the process photosynthesis the that dioxide photosynthesis are experiments chlorophyll, and light are a green pigment that absorbs the energy from light. that Chlorophyll prove for OUTCOMES is in the chloroplasts of the leaf carbon • carbon • water, dioxide, which diffuses into the leaves from the air needed photosynthesis Water which and If a needed plant them To as be starch. certain leaves the dark is then that given we out If are cannot the no all the that plant’s raw roots from materials chlorophyll, the of as will investigation 48 at things (It the hours. is that plant is is for carbon make the soil. photosynthesis. dioxide it is to water do so a you sugars will not must and this, a and make make light plant that plant can for the water for so hardly store starch. sure is left de-starching. except show by it we called needs required is To simple then valid, start. This difcult water the it photosynthesise starch testing. most are the photosynthesis least photosynthesis, things; it that at by photosynthesis. have for dioxide demonstrate for carries the absorbed carbon Investigations are is that in The plant substance is needed many ‘take it for other away’.) PRACTICAL Showing T ake as a a that de-starched, leaves is important affect to understand photosynthesis in the order to factors that variegated needed plant for photosynthesis such are means white chlorophyll some because parts there of is the no there.) increase Place crop is geranium. (‘Variegated’ It chlorophyll the plant in sunlight for about 6 hours. yields. Draw one leaf to show the white and green parts. Now STUD Y TIP the test this starch variegated test described leaf in for starch T opic using 6.1. Variegated No te and that carb on wate r mater ials; sour ce no t a of are the ligh t dioxid e raw is energy , the and Y ou should The green that parts photosynthesis only contain to make the green parts chlorophyll of the which is leaf needed blue-black. for starch. white parts contain no chlorophyll, so no photosynthesis mater ial. occurs here. Therefore the starch the white parts of the leaf give a negative result with test. Safety: 56 go leaves. is The raw nd geranium wear eye protection STUD Y Showing for You that carbon dioxide and light are Y ou needed photosynthesis could own prove food except by that a carbon it dioxide. mus t explai n plant providing TIP needs with Then carbon everything test to see if dioxide it needs it has to for make in we to need these experim ents . photosynthesis made able why cont ro ls its be starch. PRACTICAL Showing 1 T ake a that de-starched absorbs 2 Leave carbon carbon the plant described in dioxide plant. dioxide. in the Topic needed Enclose (Soda light 6.1. is for The a leaf it in lime a for plastic absorbs few hours. should photosynthesis bag Test show with carbon a a a chemical that dioxide.) leaf negative for starch result for as the plastic starch bag test. Deprived make of carbon dioxide the leaf is unable to photosynthesise and starch. soda lime elastic band A control the soda carbon can This dioxide dioxide Y ou experiment lime. that also should means removed. caused show the that a be the Then lack we of plant set plant up in can starch, needs in exactly the be sure and light the control it not to same was the keeping carry way experiment out but does absence the plant without not of have carbon inside the plastic bag. photosynthesis. PRACTICAL Showing that light is needed for photosynthesis aluminium 1 T ake a de-starched plant. Cover part of the leaf with some foil aluminium 2 Leave 3 T est the the foil to plant leaf for of the test leaf of the leaf that prevent in the starch that light light as were for getting a few described left in through. hours. T opic uncovered 6.1. go Only the blue-black. parts The parts starch carry out covered photosynthesis SUMMARY 1 were did and so not receive could not light make and could no Describe b Explain how why show that c What is d Describe you it is would de-starch necessary plants need to light use to a a plant. de-starched carry out plant to photosynthesis. KEY a variegated how carbon you could dioxide POINTS leaf? carry out an investigation to show 1 is needed for Plants need in State whether the following light, chlorophyll, photosynthesis. carbon 2 starch starch. QUESTIONS a that present not statements are true or dioxide order to and carry water out false. photosynthesis. a Plants get all b Plants need their food from the soil. 2 chlorophyll to carry out We can light, c Water d Leaves for photosynthesis is are de-starched absorbed give a to see through the chlorophyll blue-black colour with are needed Explain what is by for not giving iodine. plants 3 carbon when photosynthesis tested that and leaves. dioxide that test photosynthesis. meant by a control experiment each testing of leaves these for and starch. 57 6.3 Products of photosynthesis The LEARNING products and • State the products in outline that how show they the are used procedures oxygen of the is such as glucose, of the glucose • Some of the glucose in • Some for of make use the cell Glucose plant needs for food are made in the leaves. is used for respiration in the leaf. in is the changed future, into e.g. at starch and stored in the night. is plant • Plants get • Glucose • Plants also to to make sucrose phloem be (see converted nitrogen and Sugars The these the need energy used cellulose, which is needed to by nitrate and Topic to other absorbing are used transported to to other parts of 8.4). substances: nitrate form ions amino from the acids, soil. which are built proteins enzymes • is converted in can into glucose walls. Glucose up in a that produced food which Some the makes sugars • • proteins and are in for growth and cell repair and for making hormones. converted to oils, which are an efcient way to store seeds. importance of photosynthesis wheat plants. Think what soya STUD Y sugars, in photosynthesis Photosynthesis simple and leaves Describe are are photosynthesis plants. • photosynthesis oxygen. Most formed of OUTCOMES TIP If about you beans you eat the eat food comes and meat you have from eaten plants like in the rice, last 24 maize, hours. wheat, A lot of potatoes, nuts. or sh then that comes from animals that have eaten plants. Mak e conc how a diag ram map plan ts simpl e to use a you learn mad e T his them Oxygen Some is 58 is is is a a by-product product used upon plants? so why are made from plants. of photosynthesis by the of photosynthesis. plant’s It respiration, is but not the usually main there product. is most it is diffuses called a out of the leaves into the more than atmosphere. by-product. products provide more about also timber depends is needed, Plants food margarine all. Plants this and will Plant of oil in That much cooking the is How like show Oxygen suga rs pho to synt hesis. help or Products ept and us with this on provide a cotton. including digitalis, extracted from the our food page range Many which rosy and of raw food materials medicines is also for our livestock. There 248. a heart periwinkle have drug, from for been and industry, such discovered two in anti-cancer Madagascar. as plants drugs Plants are the dominant organisms in almost all environments. As DID such they provide rainforests support make more habitats up than only half for 6% the animals of the and microorganisms. Earth’s world’s land species of surface, animals but and YOU Plants they plants. provide everything works The concentrations of gases in the atmosphere are kept constant Without green plants, the concentration of of in the air would increase and the concentration of art. Lignum The for of to that the grows in is the hardest wood used oxygen Fast-growing trees decrease. provide is PRACTICAL Oxygen 1 timber wood vitae commercially. would with construction carbon Jamaica dioxide us from by tree photosynthesis. KNOW? The Set the collect in of as fossil a biofuel form fuels of (see that energy, page 282). photosynthesis apparatus bubbles wood renewable unlike produced up a to gas gas rich in oxygen given off by the Canadian collecting pondweed (Elodea canadensis). light Canadian A lamp provides the light STUD Y pondweed energy that the plant Plasticine Carbon in the dioxide water. sodium is to to dioxide Rem embe r dissolved Add of some hydrogencarbonate powder This is the water make in the sure TIP needs. and that the in stir to there dissolve. is always by the respira tion. carbon that water. some produc ed If there is not enough carbon dioxide then produc ed the down. plan t T his is fo r its means oxyg en is no t photosynthesis into slows some pho to synt hesis used enough that oxyg en relea sed atmos phere or wate r . 2 Place gas 3 Test the to apparatus the gas Standing dioxide for the the oxygen funnel dissolved photosynthesis A in light and allow a few hours for the collect. water plant downward in on the does is with glowing plasticine water not used a slow because displacement of to splint. gives reach a gap the to allow pondweed carbon so down. it is easy to collect the gas by water. KEY SUMMARY 1 QUESTIONS POINTS Products include 1 What a are the glucose following b starch products c made cellulose in d plants used protein e to for? photosynthesis glucose, make amino oils of starch, acids which is used cellulose, (and then proteins). 2 a Describe as a how you by-product practical of would show that photosynthesis. plants produce Remember to oxygen include all 2 Photosynthesis it details. provides medicines; b How would you show that light is necessary for us it is important with helps food to as and keep oxygen constant concentrations of production? carbon 3 Plants are important because they provide us food Give three b fuels examples c of building plants materials that provide d us and oxygen in with: the a dioxide atmosphere. medicines with each of these. 59 6.4 Rate When LEARNING plants Describe how effect varying of temperature dioxide rate of to investigate light and the much by carbon concentration the products intensity , on photosynthesis describe carry photosynthesis out photosynthesis they produce oxygen. We can OUTCOMES determine • of the as by results that starch nding use. and how can are or out Instead, we or slow oxygen the an is dioxide in conditions be Starch as such as done but it oxygen by the light is is described measuring concentration occurs by an be in T opic rate of is 6.3. method much This oxygen is to easier done produced. temperature of the how measured easy produced volume the can not intensity, inuence measuring measuring production mass, much plant by can dry how aquatic or This made. change bubbles Environmental photosynthesis produced. measuring use counting carbon fast and photosynthesis. PRACTICAL Photosynthesis Y ou the can use rate 1 Cut 2 Put of a this and light apparatus intensity to measure the effects of light intensity Canadian on photosynthesis: piece of pondweed about 5 cm in length. stream a paperclip on the pondweed to stop it oating to the surface. of bubbles 3 Put a lamp close to the plant and measure the distance between the metre plant 4 and Count times 5 the and Repeat The less number this the of of bubbles lamp is close photosynthesis energy bubbles the for the released over 5 minutes. with the should to is plant the high. and lamp at decrease plant As the the the rate different as of sis ehtnysotohp of In the light lamp distance intensity is moved graph are dark very fo the rate as the the This away some plant. lamp gives the results intensity is no and the light the plant plant lots intensity etar investigating an the oxygen intensity increase energy on of of increases. energy decreases; experiment rate of photosynthesis. of light not the so the there is any available the effect At further . light The until the of different the plant for intensities rate at a Increasing to measure effect photosynthesis. low produced. increases to of photosynthesis certain the there light light intensity intensity photosynthesis. light intensities it is intensity important The effect light of increasing intensity on the to T emperature keep can the be other kept environmental constant by conditions putting a the same. thermometer into rate the beaker of water and adding hot or cold water if the temperature photosynthesis. changes. The by The lamp concentration adding dissolve. 60 high. bubbles the from decreases. light does increases of is there few increases 6.4.1 several between further shows increasing the When Figure distances photosynthesis The light Repeat average. procedure of rule lamp. calculate number When rate the sodium This may of give carbon off heat, dioxide so in hydrogencarbonate ensures that the plant the the to will temperature water the not can water run out be and of may kept increase. constant letting carbon it dioxide. PRACTICAL Photosynthesis and To of nd the of beakers of different lamp water kept at one The to similar into a range all the of time hydrogencarbonate make number of apparatus test-tubes temperatures. across distance Sodium test-tubes constant. placed different temperatures constant. the at are sure carbon bubbles of The 10 °C so is about the added dioxide be are used. put minimum to that oxygen can which ve 40 °C. light to is the The intensity water concentration produced inside at etar in temperature fo is is effect pondweed sis ehtnysotohp Pieces temperature is different temperature temperatures can be counted in the same Figure Figure 6.4.2 shows the results you might / ˚C way. expect. The 6.4.2 The effect of increasing maximum temperature rate of photosynthesis occurs at the optimum temperature. on photosynthesis. actual temperature depends on the plant that is used. Plants in lower temperate than those latitudes that grow have in optimum the temperatures The rate of rate that decreases grow the The that are because at chloroplasts tropics. high enzymes are temperatures in the denatured. PRACTICAL The same Adding water of carbon apparatus different increases dioxide can be the modied quantities the on of for sodium concentration of rate this of photosynthesis investigation. hydrogencarbonate carbon dioxide. At to least the ve deewdnop The effect fo sodium test-tubes You can intensity see that and the the light intensity. photosynthesis. If As is is a different mass of added. of the there the with temperature effect photosynthesis each must increasing same no carbon as carbon the carbon dioxide be effect dioxide kept constant. dioxide of on the etar the used increasing there can concentration be fo light of be hydrogencarbonate The rate can sisehtnysotohp different no carbon Figure there is an increase in the rate of photosynthesis. dioxide concentration increases Above a 6.4.3 The on concentration SUMMARY the rate remains List the the of rate carbon of dioxide photosynthesis. constant. QUESTIONS KEY 1 effect certain main environmental factors that inuence the rate POINTS of 1 The release of oxygen photosynthesis. from 2 A student used the distances 25, 30 cm the and and apparatus the 24, shown numbers 40 cm and of 18, opposite. bubbles 60 cm per and He wrote minute: 10, 20 cm 100 cm to down and Explain how the student kept other conditions Make a c Explain table of the results and plot them as a constant. line Light and intensity, the your graph does not look like Figure is used of temperature concentration dioxide are of three graph. environmental why rate 6. carbon b plants the photosynthesis. and 2 a aquatic measure 6.4.1. that inuence factors the rate of photosynthesis. 3 Describe carbon the effect dioxide on the rate concentration, of photosynthesis and b increasing of the a increasing temperature. 61 6.5 Glasshouse tnemelppuS We LEARNING • Dene • Identify the OUTCOMES the term and limiting environmental in of the enrichment, use light of • Temperature • Carbon carbon and in inuences dioxide These to three intensity, the rate determines concentration enzymes light inuence intensity is a use to raw temperature of activity there is and photosynthesis energy material make are the the increases factors available of for carbon in to enzymes photosynthesis. in the photosynthesis, more of it dioxide plants. available chloroplasts. so if for the chloroplast carbohydrates. limiting factors optimum Limiting temperature that Light conditions dioxide seen • different Explain optimum factor explain photosynthesis • limiting factors have concentration production factors glasshouse systems A limiting short Light dioxide sisehtnysotohp CO 2 is of In of fo CO etar 2 something it restricts does water and energy this case increases increases also see because that the warm rate environment of if in photosynthesis. the is the 6.5.1 of plant temperature intensity light rate rate matter Figure the the photosynthesis light In in such processes. the not a for present life influences it photosynthesis. intensity 0.04% Y l o w, and shortage high. is that intensity intensity 0.4% factor supply and can photosynthesis intensity becomes is the rate that constant for as however is very rate light The Yo u much a be the the f a c t o r. light carbon there increases. limiting the of cannot factor see If lots because the limiting you has rate can the light X light Figure 6.5.1 The is f a c t o r, must it dioxide intensity effect intensity of be on the photosynthesis concentrations of at carbon on page certain reactions move 61 grap h and you a the ruler from lines the rate a grap h alon g left The substrates and more can the rate see rate by as enzymes from of when longer the temperature the increase graph in photosynthesis the increases enzymes often at (see to higher are or limiting carbon with Figure 6.4.2 in rate reaches because the To p i c the The of and a and energy increase rate until maximum kinetic chloroplast 5.2). increases a of then the they photosynthesis Here on you because To p i c the enzymes in 5.3). Look at the graph in Figure 6.5.1. rate of photosynthesis at point X. rate of photosynthesis at point Y . Light intensity Another is factor limiting is the limiting This could be carbon the dioxide right or temperature. or H o w e v e r, can grap h cond ition s to (see the trend s the temperatures denatured to alwa ys concentration the starts cons tant . 62 use ques tion, follo w nd such no TIP patte rns. rule that decreases. chloroplasts a catalysed Yo u temperature decreases Whe n else now two collide answ er something is rate dioxide. STUD Y intensity increasing intensity temperature. of Light concentration. Chemical light increased. to carbon there is you can dioxide more see that the concentration of this raw rate is of photosynthesis increased material from available. This remai n factor at Y is carbon dioxide to means when limiting increases 0.04% concentration. 0.4% that if as the Growers best try to possible Conditions earlier • grow in • improve inside grow The production the conditions • in a yield for of their crops photosynthesis glasshouse the places following tnemelppuS Glasshouse allow to plants by giving take them the place. to: year where they conditions would inside not normally glasshouses are grow well. controlled. T emperature Sunlight The heats glass up stops a the lot inside of this of the heat glasshouse. from escaping. Glasshouses Electric heaters Ventilator • glass when and lets light in opened in sunlight. intensity shading cold to weather. cool dioxide Growers can gas pump dioxide which the too the as glasshouse of lighting low. Blinds temperature carbon dioxide concentration. provides temperature Articial gets lowers Carbon carbon • are used on hot can temperature, control light limiting intensity factors, and such humidity. days. Light The • aps are carbon They in cold used out also grow plants strong light countries. burn also to very glasshouses can and be keep tropical into dioxide glasshouses in can heat to increase butane to raise or natural the weather. Water Many and All glasshouses humidiers these factors concentration, process data which are automatic ensure monitored humidity, from SUMMARY have the light watering plants and sensors and always controlled intensity systems and control get by using enough all heating, Water so detect few staff changes ventilation, QUESTIONS are in lighting needed. these and Explain process 2 State what of is meant by the photosynthesis which factors term to would help be limiting explain limiting factor. your of shading Give your reasons in each glasshouse Use A for factors. in crop. the carbon dioxide Computers glasshouse. POINTS limiting factor is a factor the in the in such environment that is answer. photosynthesis in short supply that it the restricts following. a Sensors limiting KEY 1 1 misting water. computers temperature sprinklers a life process, such as case. photosynthesis. a Plants growing on a high mountainside early in the 2 Light intensity, temperature morning. and b Plants c A d The e A growing in a dense tropical forest at carbon dioxide midday. concentration eld of same maize eld early late on in a the very bright morning. factors plant in a photosynthesis. shaded position in a warm room. Carbon light dioxide intensity, temperature 3 Explain how each of the following can be controlled to give optimum conditions for carbon b light dioxide and controlled glasshouse in systems give optimum conditions. concentration This intensity humidity are growth: to a concentration, in modern glasshouses limiting afternoon. 3 house of are c ensures that the rate of temperature photosynthesis is plants maximum produce kept high so yield. 63 6.6 Leaves The LEARNING of • Identify a tnemelppuS • and label the parts of a and Leaves Explain how leaf of absorbing into leaf of shape a leaf makes it ideally adapted to carry out its functions OUTCOMES is the out light of for the photosynthesis leaf and allowing gases to diffuse tissues. have: structure adapted • a large • a thin • many surface area – to absorb light rays for shape – so gases can diffuse in and out easily photosynthesis place • veins the leaf – to nd – to absorb light for the reactions that take photosynthesis to leaf Inside To chloroplasts in support cells, all a and other the to leaf take parts of surface sucrose the and and to carry amino water acids and away ions from to the plant. leaf out how a leaf works we can look at the structure of a typical leaf. A leaf has an ideal shape for photosynthesis. upper layer epidermis: of cells with chloroplasts. cuticle: down waterproof the water layer lost by that also straight cuts lots of Most mesophyll: air spaces more rounded between cells vein: with and lower epidermis: no thick cuticle. Has here contains that ions tiny holes called stomata (singular: allow gases to diffuse in and the water leaf tubes that and take stoma) away These to xylem bring lots phloem of the contain chloroplasts. vessels them mesophyll: cells photosynthesis occurs of goes evaporation palisade lots Light through palisade spongy single no sucrose and amino out acids stoma guard 6.6.1 Leaf cell structure. Some of the internal features are adaptations for photosynthesis. PRACTICAL • Palisade upper Looking at a leaf surface Observe a transverse a leaf on a the are leaf to packed tightly maximise together absorption near of light the slide is where its highest. section • of of cells section intensity 1 mesophyll under There are many chloroplasts in the palisade mesophyll cells to the absorb as much light as possible. microscope. • Look for the tissues in Stomata dioxide 6.6.1 under low (usually in the lower epidermis) open to allow carbon Figure to diffuse into the leaf. Carbon dioxide is a raw material for power . photosynthesis. Now look tissue 64 at under each high type of power. • Leaves the are thin so atmosphere that to the carbon cells of dioxide the does palisade not and have to spongy diffuse far mesophyll. from tnemelppuS Figure There are large intercellular air spaces within the spongy tnemelppuS • mesophyll palisade layer. This makes mesophyll from cell cells. to it easy for Diffusion carbon through dioxide air is to diffuse much faster to all than cells the diffusion cell. spongy • Xylem in veins bring water and ions to the mesophyll cells. Water is cells CO a raw by material the cells to for photosynthesis make and magnesium ions are 2 needed chlorophyll. CO 2 • The sugar produced in photosynthesis is converted to sucrose lower and epidermis transported away from the leaf in the phloem in CO veins. guard cell 2 Figure 6.6.2 Carbon into Stomata the dioxide leaf diffuses for photosynthesis. Stomata to are diffuse small into epidermis, pores and but out some (holes) of the plants in the leaf. like epidermis Stomata water lilies are that allow usually have them in in gases the the lower upper closed stoma epidermis. guard pore In cells partly closed sunlight: • carbon dioxide • oxygen made • water diffuses in vapour in for photosynthesis photosynthesis diffuses diffuses out out. chloroplast Opening and closing pore Stomata are Stomata usually cells by opened open osmosis. Carbon dioxide diffuses out. and during This into vapour by the makes diffuses Water closed guard day. them the also Water bend leaf for so passes the into stoma the guard opens. photosynthesis diffuses and oxygen out. Figure At night osmosis the and stomata prevent stomata they pores. the SUMMARY Water straighten The plant close. stomata passes and move also close out closer in of the guard together hot, dry so cells closing weather to 6.6.3 Closed by Match function on the STUD Y the leaf See parts on the left with their open help wilting. of and the QUESTIONS each stoma stoma. TIP T opic your self 1 open cells which correct into right: is 3.2 to abou t how and remin d osmo sis, water out of moves guar d cells. stomata palisade spongy carry mesophyll water allow mesophyll up gases to from pass the into stem and out of leaf contain chloroplasts for photosynthesis cuticle contain chloroplasts for photosynthesis veins prevent too much water being lost KEY 2 a Which gas would pass b Which gas passes out into a leaf during 1 of a leaf during POINTS daylight? The diagram structure 3 Leaves Lay a have leaf area by Find out same a large onto graph counting if leaf leaves area. surface the area paper, to draw absorb around light. it different and work out have its carry squares. from Record the top your and results bottom and of the internal daylight? of a explain plant them. have the 2 a leaf important shows which each functions to out. Stomata of of tissues gases control into the and diffusion out of a leaf. 65 6.7 Mineral Plants LEARNING need Describe the nitrate ions ions plant in importance and Explain the They Nutrients of magnesium active are light, need absorbed transport effects of carbon in the mineral dioxide from roots salts and the soil (see (also water in Topic called for small plant healthy quantities nutrients). as ions by 3.4). nutrients nitrate Nutrients and also nutrition Plant • than OUTCOMES growth. • more requirements magnesium deciency are needed for healthy growth of plants. They are used for on a variety of purposes in plants. If these nutrients are lacking in the soil plants then Use do not grow well and show certain symptoms known as hydrogencarbonate solution to exchange kept in investigate of the an light aquatic and deciency symptoms. which are used plants decient Plants need nitrate ions to make amino acids gas in to make proteins. As proteins are required for growth, plant the in nitrate show poor growth. dark Magnesium Leaves as for the may ions plants chlorosis. and If of are absorbed decient Plants need in by plants chlorophyll phosphate for and look used to yellow, making a make chlorophyll. condition compounds known such as DNA respiration. soil does add more not as contain enough fertiliser to nutrients, replace the farmers missing and growers nutrients. tnemelppuS • plants PRACTICAL The effects Some of plants grown in culture nutrients on growth are water to show that cotton seedling plants need different wool nutrients. 1 Set up some normal test- culture tubes as shown solution here. This plant has magnesium deciency. Cover the tubes 1 with black black paper to to prevent growing YOU in 3 4 no distilled magnesium nitrates water keep algae out DID 2 no paper light the KNOW? water. Legume plants, such as peas and Each beans, have bacteria in their has that are able nitrogen plants (see can page clover back are into nitrogen 66 into to a use ‘x’ 252). that make Plants grown the soil content all of lacks a certain nutrient except test-tube 1 which them. atmospheric form to solution roots and to for the 3 Leave 4 After 5 Y ou the apparatus in good light for 6 weeks. proteins such ploughed increase crops. 6 weeks you could examine the colour and size of leaves. as the could growth. measure length of stems and roots to compare All exchange living in organisms, plants including plants, carry out respiration all the time. tin Plants they are need waste. At During In no a supply night, the bright different day, light, of from plants when other oxygen plants tnemelppuS Gas and exchange carry there out is organisms. a they T o produce these gases carry carbon with photosynthesis, high rate of out dioxide their as foil respiration as pond weed a surroundings. well as respiration. photosynthesis, some of hydrogen the oxygen aerobic of is the produced respiration. plant. used by The in The their rest carbon chloroplasts chloroplasts of the dioxide for is oxygen used is produced photosynthesis. not by by mitochondria required so mitochondria However , this is for diffuses in carbonate indicator out respiration not enough Test so carbon dioxide diffuses in from the tube Figure Gas exchange in aquatic plants is 1 Test carbon solution. dioxide This and solution investigated two pH contains with it dissolves in water indicators. it forms Carbon dioxide is an to Hydrogencarbonate carbonic atmospheric air through indicator it. This acid, solution gives which is acid a the is prepared indicator a by red Explain why in Set up three test tubes as shown colour . 2 3 plants in Figure Describe a the plant Add 3 Cut in hydrogencarbonate two each pieces of test of indicator pondweed tubes 1 and to in to each length test and tube. place plant at growth and Put test 5 Leave If carbon tube 1 in darkness test tubes near a ii is added hydrogencarbonate to by covering it in carbon dioxide is light the indicator taken up carbonate for water solution from indicator 2–3 In test tube dioxide 1, was the the by the will plant, turn water solution indicator released by the Plant from for the by the red to plant, roots will turned turn yellow pondweed In test tube 2, the indicator turned was taken up by the from red because during purple pondweed nutrients ions needed growth. Nitrate ions are to amino needed acids; to magnesium purple. are make carbon used by the plants to chlorophyll. respiration. because for nitrate healthy yellow. If mineral ions are lacking, carbon a dioxide absorb the 3 • i sunshine. hours. ions • surroundings bright POINTS make hydrogen its in foil. 2 If gas between 2. including dioxide the occurs one 1 the without explain that and night, KEY 4 appearance 6.7.1. solution 10 cm likely ions. Describe a 2 need ions. exchange 1 plants bubbling nitrate respiration QUESTIONS gas. of and 3 weak PRACTICAL Photosynthesis tube provide mineral acid. Test hydrogencarbonate hydrogencarbonate 1 When 2 6.7.1 SUMMARY indicator tube surroundings. plant develops deciency photosynthesis. symptoms. • The purpose of test tube 3 was to act as a control. 4 The indicator The colour the plant oxygen to solution changes in the light dissolves monitor the in only are or to absorbed water changes responds nothing it in does by not oxygen to do changes with the the plant change in carbon oxygen in the dark. and by pH. If you concentration you would have an oxygen probe and a data pond weed solution remains same. at is low red as kept light the in a test intensity, rates of carbon photosynthesis by oxygen. only At night carbon respiration. Hydrogencarbonate indicator logger . solution If up to 5 use in use produce dioxide wanted plants release plants When the light dioxide dioxide. released In tube the of hydrogencarbonate colour of photosynthesis the and solution indicator usually respiration are the changes is in used carbon concentrations of gas to as exchange detect dioxide a by result aquatic plants. 67 PRACTICE 1 Photosynthesis cells. out Which occurs in structure palisade inside mesophyll these cells light carbon intensity concentration A chloroplast B cytoplasm C nucleus D vacuole The 1) raw materials A carbon B light energy / A high low 30 B low high 20 C low low 30 D high high 35 for photosynthesis dioxide C light energy, D water and nitrate (Paper 2) (Paper and ions Which feature good and carbon carbon supply a dioxide and ions cellulose B chlorophyll large B many C thin are used by plants for D xylem internal air a cells spaces chloroplasts cuticle on in the and and palisade lower phloem mesophyll cells epidermis in veins 2) [1] Hydrogencarbonate atmospheric indicator air is solution bubbled is red through it. A oils placed a piece 1) [1] tube Y that contained T ube Y was covered was Which represents the movement of of pondweed inside test through the open stomata of a repeated leaf uncovered. indicator completely test tube Z, in but solution. foil. the This tube Both tubes were left in was bright during sunshine. the for this gases left After 60 minutes the colour of the day? indicator gas into leaf gas out of was leaf A A oxygen carbon in B water vapour carbon tube purple. pondweed carbon D oxygen dioxide Which does water vapour pondweed dioxide had the in and in tube reason absorbed for Z this? pondweed in carbon Z had dioxide Y had the produced pondweed in carbon Z had oxygen [1] not occur during pondweed dioxide, photosynthesis? A absorption of light by B conversion of glucose to carbon dioxide to of molecules using light 9 energy The see 2) Which row would provide in Y pondweed in carbon Z had dioxide had in Z produced had oxygen, absorbed but oxygen 2) [1] diagram transverse (Paper carbon pondweed (Paper water produced pondweed a carbohydrate splitting had sucrose the of Y the chlorophyll D reduction in but absorbed it in a on the section next page through a shows leaf as a you would microscope. [1] of the table the (top of conditions next for (a) Name photosynthesis of a the tropical the (b) Describe tissues labelled E, F, G and H. [4] column) the functions of the parts of the highest leaf of and correct oxygen C rate Y yellow the carbon produced 1) was is dioxide B (Paper in and produced C Y What dioxide dioxide labelled I and J. [3] plant? (c) Explain and 68 ensure the proteins (Paper 6 to to making: student D dioxide leaf? A when C adaptation dioxide 8 5 an carbon water (Paper 4 is of [1] A fats [1] water 1) Magnesium D °C are: inside C temperature [1] 7 3 dioxide carries photosynthesis? (Paper 2 QUESTIONS G how are cells in adapted the for tissues labelled photosynthesis. F [3] I (a) State how the student would: E (i) vary the light (ii) determine intensity; the rate of [2] photosynthesis; [2] F (iii) maintain constant a constant carbon throughout the temperature dioxide and concentration investigation. [4] G (b) J for 3) plants, several K and days. L, were They placed were then in the placed dark into carbon L was the student’s results. the light apparatus if shows etar T wo below fo 10 graph sisehtnysotohp H (Paper The shown dioxide provided below is in the required with for carbon K light to nd photosynthesis. Using dioxide. the L (Paper 12 the limiting shown in the factors, explain graph. [4] 4) groups that were M group term results T wo Group bag intensity out N of seedlings decient was was in grown grown were two grown ions without without that in solutions plants nitrate need. ions; magnesium ions. bag Group O received all the ions that plants require. soda lime The band results are shown in the table. band group of colour of growth seedlings (a) Explain why the plants were put in leaves reduced the growth yellow dark for several days. but [2] (especially M Explain why the plants were well watered lower kept in bright light. Describe how you did not carry would out any show that leaves – plant photosynthesis inside the bag, but plant L did. Explain why plant L was included. A student investigated intensity the effect of varying normal growth Explain the on the apparatus rate of shown the effects of the deciencies of the ions and magnesium ions as shown photosynthesis in using green green nitrate light reduced growth 3) (a) 11 – [2] O (Paper leaves [4] pale (d) severely N upper while N [2] yellow K in leaves) lower (c) much seedlings group and as the as (b) not the table. [4] below. (b) Why was seedlings (c) Many it in crops grown in (Paper group to achieve the yields. world Explain controlled high the [2] throughout are include O? glasshouses. conditions to necessary in are how glasshouses [6] 4) 69 7 Animal nutrition 7.1 A A LEARNING balanced balanced Dene what balanced • Describe and provides an adequate intake of the biological OUTCOMES molecules • diet diet is meant by a health and and energy needed to sustain the body and ensure good growth. diet how activity age, affect gender dietary needs • Describe the pregnancy on • the diet Describe effects and of the of breast-feeding the mother effects malnutrition on of heart disease Figure STUD Y A TIP 7.1.1 balanced Which diet carbohydrates, Rem embe r bala nced energy that die t as Each of well as • T o these carries provide and T o fats. diet proteins energy one released will keep from the brain T o (see The if you to energy in 8-year-old a the in are this or is used and more mainly for of three the energy role only development, repair source and bre basic functions. of of body amino if of repair cells acids for carbohydrates they are and and in excess replacement. tissues. cells of to Proteins make their in own 4.1). body’s very small aged 14 a used day / kJ 8 500 8 500 12 500 9 700 11 000 9 800 little Diet worker have manual worker woman breast-feeding mother 15 000 in The about you your still metabolism quantities have for a and in – vitamins the diet and repair, these varies per body from day. energy. on age, greater your chemical this basal completely beating, The 7000 kJ need higher bed heart BMR depends a in growth required (BMR). requires lying constant. involved Children 70 one growth, Topic keep energy rate pregnant water to and help minerals regulate our metabolism. active those adult minerals, hour. temperature office – are growth needed energy adult for provide regulate are one Even teenager, vitamins, KNOW? • for components: fats, out energy Proteins allow the peanut meal? provid es • The better-balanced these proteins, requirements YOU has the a nutr ients . DID is So sex energy metabolic inactive lungs reactions are functions even and if to your is the lie are and still but down body such require basal using your body, and person, you as energy. metabolic an and adult do very activity requirement rate working in occurring person you than adults because they (BMR). 12 500 10 000 11 500 A young BMR per child may kilogram weigh per day less than because an adult they are but still may have growing. a higher Y oung they children are people lower stay constantly generally BMR. men. tissue have has a Figure The Fat a they daily and a energy to of and eat relatively fat tissue, rate per need to to occupations body new mass cells. needs fat and diet if under so because Elderly have they content example muscle, than the make higher for of balanced a are to in their bodies the skin. Fat women generally men. requirements explain unit protein a than requirement try needs and need have in protein energy metabolic energy the lower stored lower 7.1.2 energy is more developing have Women lower Compare need However , healthy. than also of the people shown in differences. that involve physical activity pregnant are 10 000 greater who than take and high less part they months 9 MJ pregnancy can fat provides proteins. that The extra need us be with However , may for a protein extra about at a required during a desk. require 0.8 MJ more teenage day fat: saturated fat that in the that comes energy is a of the from sh be per the woman. gram aware comes and concentration from plants. chemical made cholesterol genes that that determine tend to high concentration High in increase the we the than that carbohydrates there animals Saturated risk concentrations cholesterol liver and produce our in of of found depends metabolism of the are two or main and male types manual girl, producing in fats in our the upon in the which more blood. blood. our we 8 500 developing types of of the high blood cholesterol (see in page pressure fat. diet diet The cholesterol per cholesterol. concentrations the blood 108), and an heart Monounsaturated Polyunsaturated which will 7.1.2 Typical energy a b What High and as fat the diets having a are linked increased to risk a disease.There fats have little of are thick, inner of sur face two effect Figure 7.1.3 A healthy and on help to fats may reduce help heart an artery artery to reduce State meant how following who the will does not by term protein differ take and from much balanced energy those of diet? 16-year-old of A balanced an iii a elderly person pregnant mother and minerals, the correct female the fat wall. diet provides proteins, fats, water and vitamins, bre in the quantities. exercise: 2 i (left) with POINTS carbohydrates, requirements a layer deposit cholesterol 1 the in rough fatty disease. QUESTIONS is needs. quantity well energy 1 day may KEY SUMMARY per day Cholesterol as inherit. kJ deposited blood years blood. arteries unsaturated 8 kJ unsaturated smooth narrowing years day three than Figure increase 14 per and last 15 000 fat kJ energy worker of boy, 12 500 muscle pregnancy woman per People high for woman us? energy should is example, non-pregnant more also nutrients For for sitting sports require bad we involve physical breast-feeding. recommended Why Fat of diets. Women are jobs vigorous protein development. when active in kJ ii a 2-year-old iv a male child Requirements depend gender athlete on a and of the diet person’s how age, active they are. 2 a What are b Explain the health risks associated with a diet high in fat? 3 how a person may reduce the fat content of Saturated fats cholesterol diet. (You may nd it useful to look at pages 73 and answering this blood which is linked to 74 narrowing before increase their of the arteries and question.) heart disease. 71 7.2 Sources Eating LEARNING • State of nutrients healthily OUTCOMES some good components of and the describe sources a of balanced Diets in different from each parts of the world vary. However, we should all eat the of the food groups shown in the food guide pyramid. diet importance of Carbohydrates them Carbohydrates • Describe the source symptoms due to lack mineral C sugars and starches, which provide us with a ready of energy and salts D, iron and and that is easily respired. Simple sugars are absorbed almost of immediately vitamins include deciency by the stomach into the blood to give an immediate result of respiration. source the of energy . of carbohydrates This energy is released as a Good sources calcium are rice, potatoes, bread, yams, sugar and honey . Proteins fats, oils, sweets In it order needs protein meat, poultr y, yogurt, beans, cheese your protein into body to to grow make amino new acids and and cells. then develop, You use digest these to fish, make milk, for eggs, your own proteins. There are 20 different nuts types of fruit of these Cell amino to acid make membranes and its your own and body protein cytoplasm must (see have Topic contain a all 4.1). great vegetables deal bread, or cereal, pasta, rice of protein. damaged your food growth daily Figure 7.2.1 exercise The food and guide weight energy. control for and Y our cells so this as repair Good it body you well. may sources may need If protein be are need to enough is respired meat, sh, replace protein not to old in used for provide milk and nuts. pyramid. Fats Fats are under the releases one STUD Y can now infor mation you each (e.g. in starte d featu re energy kJ) write mak e 0 add to in (e.g. provi de gram the Fats are Fats also a 4 .1. long-term around than twice the as carbohydrate energy heart much or store. and kidneys. energy protein. The than When One can we fat be are is stored gram of fat released short of from thick you uses also energy fat. good give layer the thermal buoyancy of blubber. to insulators, marine Good since animals, sources are they for cut down example butter, heat whales cheese, fat in loss. have meats For sh, nuts. inclu de sure and if Water you for Water when the you up drink two-thirds or of your body mass. You take in water eat. answ er vitam ins, water makes each do energy ). not You could in few to a take go without food days without water. place in water. in the that your in Waste urine, faeces, 72 of and a conten t bre , any table body and even min erals more T opic someth ing nutri ent is skin more as TIP our Y ou important solution. intake sweat water of and in water are our number is blood day of weeks, needed for transports passed sweat each breath. a Water The chemicals and for out of cools equals bodies down. your you substances our us but chemical loss It of in is would die reactions dissolved solution important water in urine, Vitamins We be of need and small, healthy. If minerals regular these deciency amounts are lacking of in vitamins the diet and we minerals can develop if we are to symptoms diseases: deciency rich symptoms food use name in body (deciency source disease) oranges, tissue lemons, resistance repair, bleeding vitamin C other gums to (scurvy) citrus sh fruits oil, butter vitamin disease milk, D made strengthens soft by bones bow the and outwards T angerines are a good source of vitamin C. (rickets) Sun) used in formation liver, legs skin teeth in bones, (also meat, of haemoglobin in tiredness, lack of DID YOU KNOW? iron cocoa, eggs red blood cells energy (anaemia) In for transport 1747, James Lind, a Scottish of ship’s surgeon, was able to oxygen show weak, milk, sh, strengthens green bones teeth The Fibre bre cabbage, the The or bulk gut muscles helps the plant part to of the the and our from comes cell of sweetcorn adds entire roughage from important Fibre disease preventing the citrus walls. diet. food. gut Although High-bre Since to wall of plants. it It is made cannot foods be up digested, include bran Fibre from diet it anus need food constipation bacteria lowers reduces the the in is not and digested, does something the not to alimentary it passes provide fruits provided C the push canal down any energy. against. by Fibre KEY (see Topic 7.3). Fibre POINTS peristalsis absorbs Carbohydrates in our gut. Many doctors believe concentration risk of heart of disease cholesterol and bowel in that the List the a each of an balanced diet and give a 2 good source one. 2 Explain why 3 Explain the quick of energy, energy while fats store. blood. cancer. Protein is needed repair Lack can a a high- QUESTIONS components are poisonous 3 SUMMARY of on vitamin it and 1 sailors years; cereals, are bre for mainly source wastes affected voyages celery. mouth movement from 1 so as successfully remedy. cellulose an lemons, cramps in is and (rickets), long of such weakness teeth and Dietary fruits, and muscle vegetables citrus bones oranges and calcium brittle that of of calcium cause lack of and lack and rickets iron of for growth tissues. vitamin (soft causes D bones); anaemia vitamin C causes scurvy. the diet must contain each component. 4 Roughage of term deciency food helps through the the passage gut. disease 73 7.3 Balancing Getting LEARNING the reasons why put • Describe on food as a result If health in a day should provide you with enough energy to day. risks happens if we eat too much? of malnutrition the eat that and What you eat more food than you need, your body stores the extra as fat. associated Your with you through weight obesity constipation • List right some get people balance needs OUTCOMES The • State the energy energy intake is the energy you get in your food in a day in obesity proteins, • Explain the role of Your (bre) in the carbohydrates and fats. roughage energy output is the energy your body uses in a day. If diet energy body intake and body overweight page. that or People become greater mass even with diet foods low or a energy increases. We Obesity basal obese contains with than obese. a overweight their rened is of may is run than the rate those foods, added then dened metabolic fattening lot output, risk in stored box high in the becoming are higher as is of the (BMR) with such fat on the more BMRs. fat next likely It is foods to likely and sugar. Obesity In rich, suffer if Many children do not eat this sort of meal a industrialised from person countries, overeating takes in than more like from energy Britain eating in and too food the little. than they USA, As more we use, have then people seen, the at excess is stored as fat. T aken to extremes, people can put on so much lunchtime! weight Major • high that of obesity intake of fatty • too • social People Exercise helps ght heart disease and 74 growing and rened foods containing a lot emotional are people 9.5), sugar stress, overweight to have high (see Topic and health blood leading obese and ‘comfort are problems pressure, 10.3) to eat • take of much such as diabetes arthritis eating’. more heart caused (worn likely than disease by high joints). could someone lose weight? could: • A a foods obesity. They is and Topic How Obesity include: exercise who thinner obese. sugar little blood become causes added (see they less high-energy more sensible exercise approach • a balanced • a gradual • having diet foods (increase to with increase (lower slimming a in their lower their energy energy should intake of intake) output). combine: energy exercise problem. an ideal, but achievable, target for weight reduction. DID YOU KNOW? Obesity STUD Y There are two ways in which people can identify being Y ou • being 20% above the recommended weight for his or TIP obese: her do no t remem ber • having a body mass index (BMI) greater than body mass index mass / inde x, kg be 2 / the but metres awar e person with a BMI of less than 20 is underweight; between is severely body overweight; obese. mass These same is If in your the calculations way for more BMI than is in acceptable are for children 30 the the obese; range of more 20 to than 24, 40 then or indigestible but is grea ter is The BMI is calculated interpretation important is bulk to our in the for a healthy, balanced diet. It TIP is food. This is important for moving down the alimentary canal. The muscles of the gut die ts that to squeeze the food along. Soft foods do not stimulate to contract as effectively as the harder, indigestible too little foods muc h that form roughage. If the movement of food is slow it will result making it difcult to defecate. or A diet containing fruit and vegetables contains lots of certai n far are the best foods to relieve complete Copy and the exercise sentences energy you take . long by in more than Eating periods eating of foods time can less lead foods using muc h is to the List four health problems that are A is stored added Calculate person can more as KEY lose weight 1 the the body BMI mass category index in for each linked the . to people their a man 1.70 m b a woman in 1.75 m height in is following people a man a State 1.85 m in height a body with a mass body of mass 110 kg of Obesity and a 50 kg with a body mass of two good sources of Explain the effects of a roughage lack output can lot intake rened of in the than (in their (in their exercise). be of roughage in of caused fatty by a foods added of too foods containing sugar little plus the exercise. A diet lacking in roughage diet. (bre) b greater weight 75 kg 3 4 on intake and effects c put energy case: with height roug hage . obesity. high a of die t POINTS Some if 2 name fo rm the over energy 3 as words: excess with . taking in a fatty use, foods lack ing food) 2 of obesity fat you and and these sugar high-energy If shor tage constipation. is 1 too compo nent s. malnu trition QUESTIONS or compo nent s Cons tipat ion SUMMARY a roughage; those these too there energy energy , in of constipation no t beca use the is muscles are wall bala nced contract refers keeping to food their 30. different. Malnu trition adds is your STUD Y bre if than is Constipation Roughage someo ne obese range. adults. but is as mas s shou ld 25 BMI 30 body you that classi ed and to to = height A how 30. calcul ate body have height the can lead to diet. constipation. 75 7.4 Starvation and nutrient deciency People can water. • Describe the effects upon of are starvation This its no tnemelppuS Describe • Discuss the effects of of many weeks causes vitamin without and in the The During body muscles wasting energy by to a lack the to are of the dietary food fat food, provided starvation, and protein starvation uses stored use as a the fat source the they for basal and body have energy, draws but metabolic then breaks there rate down of energy. This leads to In (swelling abdomen legs); hair; appearance. that and (PEM). energy or with shown lack on the In which of so its worst terms are food. in suggests, are These two In given have The protein form to is it caused can describe lead the ways conditions, However, adapted food. is this different both marasmus. marasmus when undernutrition term protein. more with better of the PEM. to though children are and marasmus, responds respond form As it better is to symptoms in children of lack of these left. of kwashiorkor: and emaciated common children body conditions the of underweight, thought oedema an most kwashiorkor which Symptoms and malnutrition appearance sparse, aky both cases, frequent causes children servings cells enzymes of are of the are small in pancreas secreted danger quantities and and the and of feeding food. intestine surface to area should This die, for is so involve because fewer absorption PEM digestive of digested skin; food is reduced. During starvation, there are deciencies of the accumulation protective in water. reduced. Worldwide, fat carbohydrate, of iron deciencies dry of periods and D of of during scurvy muscle effects for because stores is protein the is stores (BMR) • survive OUTCOMES vitamins; people are at risk of developing infectious communities in developing diseases. liver. Dietary shown of surveys that cells, with has these Children such as of with to poor be which used conditions who these other and are protein as are develop cassava content, Symptoms of protein, an the in foods. be energy suffering potato; protein, Staple used for source. from symptoms sweet low should a may while so This lack be fed need such on a have and that energy in be wheat repair children the tropical high to as nations growth shows of having they foods the diet. crops energy supplemented and rice will marasmus: satisfy very low mass; energy legs; muscle we also 76 is found seen, symptoms protein of two energy This can Vitamin protein malnutrition. C have calcium of needs a in oranges, deciency of lemons and vitamin C other leads citrus to the fruits. disease called face. gums. forms protein. old- scurvy. Typical enough fat; As 7.4.1 provide arms Vitamin wizened, Figure also little or looking and body thin Nutrient and intake by C helps bones used helps cause in to and make the bleeding bond teeth. skin, healing of in cells parts of together Vitamin tendons, wounds C is the body, and helps used ligaments and the to particularly in form and the an blood formation of use the of important vessels. scar It tissue. tnemelppuS LEARNING It is also D needed needed Deciency rickets is in children. children body. Rickets the of can Iron bones is found iron. It Foods needed in red is to rich in a of iron iron grow the the of by In bend carry oxygen day. liver, At is puberty, rich soft, weight in leads protein the of vitamin gives to a so the D like rise to softening which combined is with body. If occur. girls become the cells. causing haemoglobin a cocoa. can bone fractures. around meat, in bones deciency which protein anaemia in and foods of calcium. calcium with adults, chance blood of absorb calcium eating milk. to properly bones Haemoglobin called each to fail increased include disease lack and cells. to deposition osteomalacia, make blood needed diet, 16 mg an as intestine the prevented eggs known and the walking be small include Bones start butter, condition the the oil, the regulate symptoms when sh-liver to for there An need to is a adult make lack of needs sure iron in about they have An enough iron in their diet as they start to menstruate (have X-ray bowed The lack The main of iron shortness of breath, SUMMARY 1 a leads symptoms to of a reduction anaemia heart are in the number tiredness palpitations and a and pale of red lack of blood the main inadequate are causes the of symptoms kwashiorkor Explain why frequent starvation in terms of servings of of very below is mouth are these small two conditions / amounts of as a box containing breakfast Fat / / g per a result much energy would How c The to 3 Make the in a this table fat of How get diet. the much protein much mass to 2 Scurvy be in a 150 g serving of the is to body, in good with a cereal in a 75 g adult serving female would a of the needs female cereal? per have day to 3 iron, table dietary The fallen C in in a very of the eat vitamin C and and the vitamin about D their deciency in roles diseases 4 cause bones a parts iron in of of D by can the anaemia Vitamin plus a low fat and lack of a vitamin and in ability of infections. of diet transport information sources nutrient. Lack cause is protein? your each be young more of have vitamin lack caused bleeding the with wasting, deciency there there compare Include associated would enough results mass particularly mass 60 g. not resistance cereal? b scurvy. POINTS muscle 3 How of Starvation in a has teeth 100 g 83 g the cereal. 6 Carbohydrate who and food. 1800 g person diet. body Protein a involves 1 kJ of inamed marasmus? from Amount / and of: ii treatment information Energy bones rickets. an KEY The weakened with diet. the 2 the child complexion. out c a cells. gums i of energy, The What legs QUESTIONS Explain b showing periods). C cause of the body, gums. the diet which the tnemelppuS tnemelppuS Vitamin can affects blood to oxygen. deciency softening causing of can the rickets and osteomalacia. 77 7.5 Digestion During LEARNING the different • Dene mechanical Dene ingestion, Ingestion the and be along the alimentary canal, a number of identied. the taking and of lipase, amylase, Digestion into of substances (food and drink) into the mouth. is the and soluble breaking the molecules down so that of large they can insoluble pass molecules through the into gut wall blood. listing • substrates the egestion function protease the is through small State food absorption, • assimilation • of can digestion body • processes and • chemical passage OUTCOMES the Absorption is the movement of small food molecules and ions endthrough the wall of the intestine into the blood. products • Assimilation cells • of the Egestion is absorbed, The large gut, food which system the the as mechanically is body out are of with 2.4). food the This the digestive used, that has proteins happens liver and the food When food molecules becoming part not of been into the the cells. digested or anus. starch, chemically. Topic of are through molecules and they passing faeces together (see movement where in and the pancreas has fats. form been Digestion alimentary your occurs canal, or digestive digested, it is absorbed mouth through the molecules wall can of go the small through intestine the gut into wall the they blood. must be Before the dissolved. food Large food food molecules through the molecules wall of another digestive are the are wall insoluble; of the soluble. small body They intestine uid that they small will not intestine. will and dissolve enter absorbs the and dissolve, On so the therefore other they blood can and transports fat hand, get the cannot small through lymph, (see page get food the which is 114). enzymes gut Mechanical digested digestion food Mechanical smaller digestion pieces of food is the breakdown without changing of the large food pieces of food molecules. into This anus starts in pieces 7.5.1 Digestion in the alimentary canal. STUD Y that continue faeces Figure broken about n ‘diges deni tions tion’ dige stion’ prepar , ‘mec the hani ‘chem to e the betw een body Muscular small globules digestion can into use by in food small digestion into contractions intestine, large emulsication the next few by into of the globules bile. smaller stomach of There fat is are more topics. that has been eaten, the food must be molecules. is smaller the breakdown soluble of molecules the by large the insoluble action of food enzymes. be occurs in the mouth, stomach and small intestine. Mechanical distin guis h differ them . ence gives a larger surface area for the enzymes to work on. s) The three types carbohydrases specic to remind of enzymes and enzyme lipases. because yourself breakdown 78 the food ical digestion (giv In down digestion down molecules and swallowed. breaks cal This ed chewing of Chemical and be where process. smaller Chemical TIP stion’ can this into broken dige mouth mechanical Before Lear the about proteins, in the Each they the alimentary type have of food different reason carbohydrates for and canal are: molecule shapes. having fats. proteases, needs See different Topic a 5.1 enzymes to a protein many molecule different is amino made up amino of protease down a starch molecule acids acids is made up enzymes protein break molecules of glucose many glucose molecules amylase starch a fat fatty molecule acid and is made glycerol up to maltose break (a down sugar) of fatty molecules lipase fatty enzymes acid down enzymes fat acids break molecules glycerol glycerol Figure The 7.5.2 The chemical carbohydrase breakdown enzyme that of protein, breaks starch down and starch fat. is called amylase KEY SUMMARY POINTS QUESTIONS 1 Mechanical the 1 Name the enzymes and end-products involved in the particles starch b protein c surface a Explain why b Explain the digestion is necessary. of large, is difference between mechanical digestion chemical what happens to food after it has been graph into food smaller, molecules by water- the shows the activity of the enzymes of enzymes. digested. 2 The Chemical breakdown digestion. action Outline the and soluble 3 increase insoluble molecules c to area. fat digestion 2 of of: their a is breakdown chemical food digestion digestion physical amylase Amylase breaks down and starch molecules to glucose pepsin. molecules. a i At what ii How pH does pepsin work best? Protease does hydrochloric acid in the stomach breaks molecules pepsin to What are formed when pepsin breaks down i At what ii What is amino protein acids. pH does formed amylase when the work breaks down fats to proteins? fatty b to work? Lipase iii down help acids and glycerol. best? amylase breaks down starch? iii Why is it useful that saliva contains an alkali? emyzne pepsin fo ytivitca amylase 2 3 4 5 acid 6 7 pH 8 9 10 11 12 alkaline 79 7.6 T eeth The LEARNING teeth breaks The • Describe the structure in teeth and mechanical surface their State the decay care mechanical area into of smaller digestion food is pieces increased so when chewing so making making it food. it easier This easier to swallow. for enzymes catalyse the reactions needed for chemical digestion. digestion causes and of out food function Adult • down of to human carry OUTCOMES of describe tooth the They humans have have different 32 teeth, shapes but for not all of performing the teeth different are the same. functions: proper • incisors are chisel-shaped • canines are pointed • premolars • molars for biting and cutting teeth are Counting there 8 teeth During teeth, small. to be the uneven ‘cusps’ premolars number 4 in of and each and for are type tearing grinding for of and chewing tooth, chewing up you food. should nd that our are canines, lives back we small Between will 8 premolars, and 12 molars, which makes all. replaced teeth our like piercing are: incisors, 32 have for the by come have teeth two and ages our of or 6 of and when wisdom teeth. are only 12 permanent through molars sets there we 8 these teeth. are at The rst molars teeth The least set, as or our gradually last 18, of if our at milk jaws fall are out, permanent all! These are teeth enamel pulp A child usually has 20 milk cavity crown teeth. dentine canine molar gum premolar root STUD Y Mak e TIP sure iden tify type s from of you ner ves can the differ ent hum an tee th pho to grap hs their and Figure 7.6.1 Adult Figure teeth. 7.6.2 Vertical section through molar. and Enamel the tions part forms above the hard, the gum. outer layer Inside this of is the crown softer of the dentine, tooth, which is which more is like in bone in bony socket structure. A layer of cement xes the root of the tooth into a dige stion. The pulp blood Tooth to in the cavity jaw. is a The root space in is the the part tooth that is below containing the gum. nerves and vessels. Healthy 80 vessels socket incisor a can func mecha nica l and bony blood diag ram s state that teeth decay form is and caused plaque, by which gums bacteria is a layer in your that mouth. sticks to They your mix teeth with and saliva gums. decay enamel dentine DID pulp YOU KNOW? Periodontal abscess No pain Slight toothache Severe toothache the 7.6.3 Stages in tooth if space between get tooth to the forming base an of abscess can make The bacteria holding decay. and After a meal, Bacteria in respiring of a this be be this will your should plaque and acid will make the of very The starts attack red food the acid off the painful gums sugary changes anaerobically. tooth away, particles tooth and cause may sugar can dentine. and the between acid the the 7.6.4 on the degrees, your brush teeth with up-and-down at the 45 Clean gentle, of your short the gently movements. sure inside teeth back not surface moving to and your the The shows of Brush brush forwards. forget the also the is worn pulp acid how both Be with the teeth. short, and the make gums They can rot teeth them unhealthy. the in fall bres position out. STUD Y TIP cavity can our biting upper the are No te also surfaces lower scrubbing that uo rid e streng then s teeth of outside the can into surface brushed. clean get teeth. they the enamel reaches toothache. Figure your because enamel When cavity severe swollen. left into attack decay. If be a Holding bacteria Agony! bacteria Figure disease occur the tee th , hard the exterio r KEY POINTS KEY POINTS enam el giving them surf ace. of teeth strokes. 1 back Incisors are cutting, for biting canines for and piercing teeth. Figure 7.6.4 Make SUMMARY sure you clean all surfaces of your Copy tearing, and molars and complete the and chewing. sentences using these Tooth decay bacteria words: in changes dentine crown mechanical bite enamel chew are of is used to digestion. gum and the a hard, which is and Each which outer similar layer of to tooth is tted the your consists into tooth; a of food. a is above bony inside This this . is the a a Name b For c What the The softer 3 Tooth by each is type the permanent d Describe e State in part types a, difference of caused to by which acid that the of enamel the and tooth. decay good can be brushing toothbrush, foods and avoided with a avoiding visiting the regularly. teeth. describe between its the shape milk and teeth its function. and the teeth? the three main sugar regular sugary . four is plaque, type the dentist 2 grinding bone dentine teeth premolars for socket attacks root The and are QUESTIONS 2 1 and teeth. stages ways in of tooth which decay. tooth decay can be prevented. 81 7.7 Mouth, and stomach Chewing LEARNING Describe the events that during the and of chewing food, of Describe Describe in the the digestion of TIP rst our enzy me food amyl ase. what starch , they mou th smal l the are is Mak e and pieces. digestion the moistened into a ball molar It easier. food or salivary through and the canine mouth. teeth bite When it into is teeth grind important to these chew chunks your of food food well The tongue mixes the food with as saliva is chewed by the teeth. The food is then bolus mucus, to act a glands slimy down amylase, the pro te in pass to the saliva, that which contains: lubricates the passage of the food throat enzyme that catalyses the breakdown of starch to maltose. no te s nasal to and from end intest ine. wher e make substance the ball prod uced they body teeth saliv ary happ ens enzy mes them , premolar smaller makes bolus • as The much rolled food • on the stomach STUD Y on into incisor peristalsis The T he the saliva and • ingested mouth, including this • are the and into action drink enters chunks. swallowing the swallowing take food place and OUTCOMES Food • oesophagus the passage food fat the of The food soft palate pushes your the List that of act This stops going on up upwards. the food your hard nose! palate enzy mes Before and you swallow, what your tongue food into rolls the do. epiglottis opening So food the The covers to food your your doesn’t wrong the trachea. go and down a soft pushes back of it your ball to the mouth way! squeezes epiglottis oesophagus. into past trachea your Gulp! oesophagus Figure 7.7.1 Events during swallowing. muscle direction The oesophagus Food passes contracting food is moving stomach. ball longitudinal of down The the oesophagus oesophagus muscles in its (also from known as the the mouth gullet) to the has circular and wall. food The movement muscular of food contraction down called the oesophagus peristalsis. The occurs circular by a wave muscles of contract muscles and relaxing it the along. longitudinal In front longitudinal Figure 7.7.2 Peristalsis in contraction the 82 the muscles relax bolus, contract the to behind circular widen the food muscles the bolus relax oesophagus to and to push the allow the the bolus oesophagus of muscles is to stomach. a wave pass of food to move along. Movement of food in the small and of food to large intestines also occurs by peristalsis, though to a lesser extent. The oesophagus stomach liver stomach The stomach food but can stomach The a walls juice. tnemelppuS Gastric a muscular stretch number of This proteins is the smaller juices also the that usually accommodate things stomach contains to to of bag happen make a molecules contain more. to pepsin called about When 1 food litre of reaches the it. digestive protease holds juice which known starts as the gastric digestion of polypeptides. hydrochloric acid which carries out gall two bladder important functions due to its low pH. pyloric • It kills any bacteria in the food. The low pH denatures the sphincter enzymes pancreas in any harmful microorganisms in the food. bile duct pancreatic • The the acid pH action of of about the 1.5 to protease 2.0 gives enzyme the optimum conditions for small pepsin. duct intestine Figure 7.7.3 Upper part of the digestive system. The mixture chyme. making is a of The sure type of contents of food, gastric muscular that it is walls mixed mechanical the juice of and the well with digestion. stomach are like a hydrochloric stomach the After juices. 2–3 runny churn acid up This hours of is the called food muscular KEY POINTS action churning, 1 the Food by A ring of muscle called the pyloric sphincter, is teeth. liquid. opens to let the the a little at a time into the duodenum which is the rst is up then actions by the swallowed of the tongue, food saliva, pass chewed It part soft pallette and of epiglottis. the small intestine. 2 Peristalsis of that 3 In the the carrying oesophagus mouth a wave contractions squeeze bolus, salivary involves muscular it to food down the stomach, the stomach. food is churned gland up and and mixed with hydrochloric gastric acid. juice This oesophagus starts liver SUMMARY the digestion of proteins. QUESTIONS stomach 1 With reference events that to take the place following, when describe food is the chewed pancreas and swallowed: a saliva c the tongue b mucus d the epiglottis a Describe small 2 one function of the muscle layers in intestine the b i stomach Name wall. the type of protease produced large by the walls of the stomach. intestine ii Describe the function of this type of enzyme. c Explain briey why a different enzyme is rectum appendix required anus food Figure 7.7.4 The digestive for the digestion of each type of substance. system. 83 7.8 Small intestine and absorption The The • Describe small the digestion small in the small the emulsifying its role of bile Dene the The fats term Describe how intestine is efcient after the the absorption for of food • amylase • trypsin lipase Bile a globules emulsied globules to of of are to increase Bile is fo r TIP lipas e no t a incr eases of of as chan ged it is the about large 6 metres intestine. long; The rst duodenum that leads into the ileum to the down duodenum the duct to by meet the pancreatic food arriving duct. juice from contains: to protease starch that to breaks maltose down proteins and polypeptides do the enters the not also stomach. to the made fatty well in in an and acidic glycerol. environment, hydrogencarbonate. along the a liver neutralises This acids duodenum duodenum uid and to sodium enters the fats work alkali, which alkaline in down gives from tube and the the stored the in for bile the which pH so pancreatic neutralises the stomach. called acid best the This duct. gall was is bladder added enzymes Bile in to the the small work. emulsies Cells globules. over fat fats which into fatty lining the by breaking These the minute enzyme acids ileum and down large droplets lipase can globules have act to a much break of fats larger down into surface molecules glycerol. make enzymes that complete the digestion of food. fat • Proteases • Sucrase • Maltose which break down peptides to amino acids. act which breaks down sucrose to glucose and fructose. is chem ical the a down fats Emul sica tion dige stion no t area enzy mes type ows breaks food intestine of upon . as of area. area surf ace the connected breaks enzymes smaller Emul sica tion – – also food smaller fat surface fat – yellow-green Bile the is Pancreatic contains acidic STUD Y small that peptides juice their is juice stomach. These Large so than small adapted • 7.8.1 really less stomach, pancreas to Figure is absorption the • not in Pancreatic • is diameter intestine, part, including intestine of however food intestine OUTCOMES of the is broken epithelium down lining by maltase the small to glucose on the membranes intestine. is chem ically . Absorption Absorption the microvilli wall of the the movement intestine into of the digested blood or food the molecules lymph. through Digested food forming includes brush is simple sugars, amino acids, fatty acids and glycerol. These border molecules goblet diffusion cell The small pass or by through active intestine is the wall of the small intestine either by transport. adapted for efcient absorption of food as it has: nucleus • a very large • a thin lining surface area of about 9 square metres basement membrane the Figure 7.8.2 Detailed structure epithelial small 84 cells of lining intestine. the the wall into (only the one cell blood thick), and so lymph. digested food can easily cross tnemelppuS LEARNING It is possible because has villi a the such lining villus). called a large intestine inner (singular: cell t small folded projections the to is of the area long millions epithelial microvilli. membrane very with The surface cells These epithelial (at of least tiny, tnemelppuS wall cell is small metres in space an adult). projections the villi have the absorptive (see Figure acids It called microscopic area of 7.8.2). and sugar molecules only are one 6 a increase amino villus such nger-like lining vastly cells into absorbed through the thin villus thick wall into the blood capillar y Villi increase the surface area of the small intestine. blood capillar y fatty acids absorbed and into glycerol the are lacteal lacteal (lymph blood pick coming up lymph food to capillar y) villus blood to coming to takes away molecules to lymph villus fluid glycerol Figure The 7.8.3 digested capillaries) to the in liver lymph walled result, the lymph. slowly veins, the food portal through enter to the and molecules body carries away to vein. of Fatty the lymphatic enter lacteals molecules Movement eventually not capillaries Absorbed hepatic the does reaches villi. moves like fat the in of fatty rest of acids and body villus. food by transported the A food rest into acids gut blood too (lymph transported and glycerol empties vessels, the bloodstream are the which near quickly (see are lacteal are the quickly and thin- heart. page As a 115). KEY 1 SUMMARY POINTS Bile fat 1 Match with each its part correct of the emulsies duodenum. QUESTIONS digestive function in oesophagus makes bile stomach moves food the system second in the rst lipase column: 2 from the stomach to globules surface column the area can Enzymes intestine liver makes pancreatic in the smaller have a upon larger which act. produced pancreas ileum fats The and the by the small complete chemical juice digestion. gall bladder carries pancreas mixes duodenum food food stores to the with stomach gastric by peristalsis 3 juice bile Absorption is of food digested through 2 a State: i the components of bile, ii the organ where bile iii the organ where bile is wall movement molecules of the is intestine produced, the the into the blood and stored. lymph. b Describe two ways in which bile aids the digestion of fats. 4 3 a How are conditions conditions in the in the small stomach different from the The for small absorption long, intestine? lining b State the composition of: i gastric juice, ii pancreatic intestine having with a by is adapted being folded millions of very inner tiny villi. juice. 85 7.9 Large intestine intestinal The LEARNING Describe the large its Describe diarrhoea symptom intestine the is about appendix, 1.5 the metres colon long and and the can be divided into rectum. Explain as of cholera how cholera the time food gets to the colon there is not much useful food left. a It is now it has mainly been bre, absorbed dead in cells, the bacteria small and some water, as most of intestine. bacteria 3 cause diarrhoea The and small food dehydration intestine passes absorbs along the about colon, 5 – 10 dm more water of is water every absorbed into day. the As blood – 3 about The 0.3 – 0.5 dm solid faeces waste, are per or egested day. faeces, through are stored the anus. in the The rectum. passing Eventually out of the digestible stomach food liver through the anus, in the form of faeces, is called egestion Cholera Cholera is cholerae. a water-borne The dehydration. main Diarrhoea Some people suffer from infected the disease symptom is the with disease of loss the and caused cholera of the called bacterium diarrhoea watery cholera are by is faeces bacterium as a from may symptomless Vibrio result the not of body. actually carriers colon Transmission caecum small Cholera tends sanitation, anus The large that of the is people is transmitted Almost acidic seen in an on all the cholera and mucous as in reach lining by by occur food conditions survive cholerae can handling Effects where supply there or is a lack of contaminated proper food. Water when their infected people pass out large faeces. the by or drinking water or, containing contaminated utensils more the water , without rarely, food bacteria. by washing infected their hands. body the the the of material cooking bacteria in ingestion faecal ingested stomach. small wall of by However, intestine. the humans Here intestine some they and are killed pathogens burrow start by to the may through produce a the toxin. electron Molecules of this toxin enter the epithelial cells of the intestinal wall. (×13 000). Here they epithelial the from and disrupt cells. intestine lumen cells water functioning a ions intestinal water and from of the Chloride (the creates the symptoms 86 areas contaminated bacteria contaminated T ransmission microscope in water intestine. Cholera Vibrio occur unclean become numbers 7.9.1 an rectum supplies Figure to intestine appendix tnemelppuS tnemelppuS • large caecum, function By • intestine intestine the and disease OUTCOMES The • large and the blood cholera – of This cell surface the cells the into Water the lumen dehydration and membrane into the accumulation gradient. blood into the out lumen). potential from the pass of ows lumen. of the of space ions by diarrhoea. the inside in the osmosis Movement intestine of of cause ions the tnemelppuS Oral To rehydration treat diarrhoeal infected not people effective drinking being and An lost. because or to water to • sodium • glucose bottled is like is not water, treated This cholera possible. is by is important giving absorbed does not giving oral it Just by them the contain people a rehydration to rehydrate water is intestine, the ions solution therapy and that of are salts (ORT). contains: rehydrate ions as water drink. solution • soon Cholera glucose ORT diseases as water, therapy to the blood replace the and ions other lost tissues from blood and tissue uid Cholera to provide energy for the active uptake of sodium there from the other is a most lack easily of transmitted clean water and where sanitation is intestine poor • is ions ions such as potassium and chloride to replace ions lost or non-existent. in diarrhoea. and made a a cholera glucose into person until are a to solution water ions cells that with boiling and is with The a water. given powder contents This regularly of containing each takes and sachet little in salts are training large for volumes recover. these epithelial sachets available. administer people When outbreak, made are reabsorbed, decreases was lost in and the water water is potential absorbed to of make the up for the diarrhoea. A child during SUMMARY 1 a What QUESTIONS sort of receives the KEY organism causes 1 cholera? How does c What are the the organism symptoms enter of the Diarrhoea a What b How sort of conditions 2 cholera? encourage the spread of effective treatment of drinking water help control sewage the is the Why are these developing measures not put and the spread of is tnemelppuS Explain in how th e into place in a Diarrhoea be disease caused treated The diarrh o ea and loss bact eriu m of br in g s s a lts f rom caused by by by cholera using oral the a bacterium toxin that causes a bout blo od ions to pass into the in intestine. the watery therapy. cholera chloride dehydration, of some 4 cholera loss intestine. cholera? countries? detail 2010. chlorination produces 3 in bacterium. rehydration c the from Cholera can of therapy Haiti cholera? 3 can in body? a 2 rehydration epidemic POINTS faeces b oral cholera tnemelppuS During This causes water to intestine. pass out resulting the in by osmosis, diarrhoea dehydration the cells loss of and ions from blood. 87 PRACTICE 1 The QUESTIONS breakdown of large, insoluble food vitamin molecules into small, water-soluble molecules C vitamin D calcium gums bowing of bleed leg iron is: muscle A absorption B digestion C egestion D ingestion weakness A (Paper and 1) [1] tiredness bones cramps bowing muscle gums B 2 Which is a correct description of the action of leg tiredness of weakness bleed bones a and cramps protease? A breaks down fat into fatty B breaks down protein C breaks down starch D converts acids and C scurvy rickets D tiredness rickets anaemia soft gums glycerol muscle into amino acids bones bleed weakness amino into acids glucose into proteins (Paper (Paper 1) The an [1] [1] 6 3 2) drawing incisor shows a vertical section The drawing shows part of the digestive system. 1 through tooth. 1 2 2 3 3 4 What part is 1, the function stored in A to digest B to increase C to acidify D to digest of part proteins the the 2 liquid and to produced released amino surface into by part 3? acids area of fat droplets 4 Which parts row is shown the in correct the identication drawing of (Paper above? 2 3 fats contents to fatty of part acids 4 and glycerol the 7 1 the The 2) [1] following events occur during the passage 4 of A cement pulp enamel dentine B dentine enamel pulp cement 1 starch through Amylase is the alimentary secreted in saliva canal. from salivary glands. C enamel dentine pulp cement D pulp cement dentine enamel 2 4 1) A C is a anaemia rickets symptom B D Which to 4 Glucose enters 5 Glucose is into epithelial the surface of intestine. breakdown of glucose. the blood plasma. absorbed by active transport cholera the cell. scurvy 1) Amylase catalyses the breakdown of starch [1] row the the small of of the table (top of next deciency symptoms for maltose. column) Which gives onto the catalyses to 5 in maltose 6 (Paper secreted cells Maltase [1] Diarrhoea is epithelial 3 (Paper Maltase vitamin is the correct sequence for these C, events? vitamin D, calcium and iron? A 1,6,2,3,5,4 B 6,1,3,2,4,5 C 2,3,1,6,5,4 D 3,2,6,1,4,5 (Paper 88 2) [1] 8 Which area of a villus increases 12 surface The diagram alimentary capillaries B goblet C lacteal D microvilli Copy its absorption? A (Paper 9 feature for shows a villus from the canal. cells 2) [1] the diagram from question 6. A (a) On the diagram oesophagus, label the stomach, following: pancreas and (a) duodenum. Copy and (b) Draw arrows on the diagram to show taken by food as it passes the parts of the alimentary canal on (c) State the diagram use label lines and lacteal. the part villi F an letters site of Name three to the secretion of hydrochloric H the With that secretes molecules of place 13 with organ A State diet what provided It is is an that alkaline stores essential reference A meal in a an balanced State three increased that they that a increased components [4] (a) starch, Describe good should health. The be diet. [4] when woman’s quantity she is components and explain should be diet of the in bread diagram, the from A [3] explain alimentary and cheese. cheese starch canal. In that diagram is the canal. [6] Bread contains digested your and molecule where molecule you shows molecule in answer protein. the state where the to describe a small places 1 break place. [5] protein along proteases help take the and it 2 act on down. should 1 certain 2 1 breast-feeding. that why it should is be important increased. (b) [6] How many after the two fragments molecule will has be been produced digested by proteases? [1] 3) (c) The to villi and how changes the 11 of contains contains pH bile for components important include (Paper pass villus. 4) the (b) that the 3) balanced (a) into a the 10 canal [1] substances diagram alimentary (Paper alimentary acid protease a the located. show: (Paper organ G [2] of are signicance the capillaries the (d) following E the [2] on On label the diagram. (c) and through where the diagram the (b) direction the [4] liver performs important functions in Suggest protein digestion and assimilation of food. One why protease 2 cannot act on the the in the same places as protease 1. of [4] these is the production of an alkaline digestive (d) juice that breaks down large globules of State the where (a) (i) Name the digestive juice secreted liver. proteases Explain how The this digestive alimentary canal protein. [2] fragments produced by digestion by the food in the 1 and 2 are not absorbed into juice the reaches the [1] proteases (ii) in digest by (e) the organs fat. small blood. Explain why this is so. [2] intestine. (f) Describe what happens to these fragments [3] so (iii) Explain why this digestive juice that alkaline. down (b) Explain (Paper how large what is completely broken [2] [2] (Paper Outline protein is down. (iv) the is this digestive globules meant by of juice 4) breaks fat. assimilation. [4] [2] 4) 89 8 Plant transport 8.1 Transport Most LEARNING living organisms State and • the and functions of xylem the positions phloem sections of transport rely phloem Identify in of xylem stems on and such diffusion Vertebrates so transport system. tube. This blood systems: and have for throughout water root Only very from of transport regnans is the tallest in the so remove as food systems same and and move up to 90 two of a dioxide. have water, uids through within pump separate are plant body in in from upwards xylem, to Topic in and the the unlike These stems mineral soil. stem in composed 2.3). roots, water ions stem tissues (see each (the heart) transport the the in The enter phloem, is that are are found in roots the leaves, absorb xylem owers one in the the and fruits. direction only – leaves. Phloem xylem sucrose cells leaves. ions. These to of tissues and tissue transports phloem sucrose, owering acids and bud metres. hormones sunlight YOU have can ow leaf DID not they carbon amino growing do that direction consisting have worms, at, organisms such mass system or phloem plant the via large in plants some and transport called circulatory Flowering and are moves is and small, substances, These uid transports water of a so oxygen plants transport mineral roots uptake the are obtain carry transport travel Transport plant, small phloem the tissue and and of phloem specialised Xylem to vessels. and to bodies. of xylem Xylem Xylem all type Vertebrates and their protoctists bodies owering systems that bacteria, Their alone and throughout tubes as systems. transport transverse roots, leaves Eucalyptus a OUTCOMES organisms, • need systems the throughout plant. Sucrose is KNOW? energy a carbon The world’s redwood It is in 114 m tallest tree is a giant dioxide California. tall. simple made simple made sugars sugars from and the minerals soil sugar which made especially for transporting energy. It leaves is made with the from moves growing root growing bud down or up and to to in sugars photosynthesis from storage as water is by into sucrose complex photosynthesis sucrose water soluble, starch organs, swollen roots in such and and stems. minerals taken by up roots Figure 8.1.1 Substances from leaves buds; 90 also Transport are to in the transported roots from and storage xylem in the upwards organs to and phloem. phloem from new in two leaves stems to directions: owers, and leaves. downwards fruits and Hormones They also Inside control control the cell the nd the to give transverse root and growth root To and transport hairs for of growth owers of and the stem, fruits roots (see and page leaves. 170). stem tissues of roots and stems, we cut across them sections. absorb mineral division water ions cortex stores some food This as starch phloem amino transports acids from sucrose the are used to make at root as it Figure the root cap the through 8.1.2 transports ions up The root the root tip tip cells the grows internal structure of a make new red dye the for xylem with dye. water root as the cells divide vascular phloem, bundle is cambium made and up xylem new The and a are root. of xylem in strands soil a cambium lled standing red tip protects grows vessels left The new and cells was hours. leaves xylem which celery several and tissue in the centre of this root is phloem cortex as the plant xylem, grows which between the is stained xylem are red. The phloem green areas tissue. pith epidermis is a single layer phloem of cells on the outside amino the stem which the stem and acids See up xylem loss 8.1.3 Topic sucrose to the and roots to the flowers and fruits reduces transports mineral Figure down protects and water transports of The 6.6 for internal the structure positions of of a ions up water to the and leaves stem. xylem and phloem in the leaves. A transverse Note SUMMARY QUESTIONS 1 complete the KEY Copy and the sentences using these sucrose water amino ions fruits blood heart have a Flowering transport plants system have two Xylem vessels mineral made up transport of a the transports and up the , owers and . and acids Phloem the stem from the Phloem tissue from leaves to all parts Using the roots leaves. vessels made transport in the leaves photosynthesis and in transports of the organs, to other parts plant, the plant. organs. 3 2 to roots of as water the Xylem storage such from and systems. during to transport ions stem sucrose, tissue stem. storage 2 . young vessels up Vertebrates a POINTS and mineral through bundles. words: 1 leaves section vascular the diagrams above, state the functions of each of Xylem and phloem are these distributed in a central core issues: inside a phloem e root b xylem c cambium d f root cortex root. Inside a stem epidermis they cap a are vascular organised into bundles. 91 8.2 LEARNING Water uptake Water by The • Identify root hairs as the main microscope take their structure to hairs. Soil water such State the pathway taken through root, of and roots are mineral to anchor ions. Just the plant behind the in the root soil tip and are small Water passes into the root hairs by osmosis as is a dilute nitrate and solution of potassium. various Root solutes hairs including have thin, mineral permeable ions, cell by walls water water water uptake • functions up and root relate roots seen to under uptake OUTCOMES stem and provide a large surface area to absorb water . The cell sap and in the root hair cells is a more concentrated solution than soil water . leaf This is because solutes water particle soil as diffuses hair sugars. from cells The the water also cell soil cell then Most walls From the hair cells of here stem enters cortex water passes up in the by by the other permeable so osmosis. cortex of the the in water the moves spaces through between the the a from xylem water and to cell in the cell to the moves the Water centre up leaves cells. walls, cell. cells. the of the xylem where Much eventually of evaporates it through enters the to root. the water form water and then diffuses through stomata to xylem the water across mesophyll vapour stem of cells have the airspace Absorption of and the spongy 8.2.1 hair passes moves reaches Figure root partially and B Some root the is ions vessel root. A mineral membrane into Water xylem absorb atmosphere. root. We describe and into Water a hair movement xylem passes potential root the in vessel down the cell. potential lower water in in in the potential in cells soil the to a root hair, potential gradient, lower from cortex xylem a water passes of the of into potential the turn, in water terms water solution Water water a of the and (see from water root across a the Topic high potential hair cell eventually to to an cortex 3.2). water in a tnemelppuS soil such root the lower even vessel. PRACTICAL Look then with at Root hairs on as can a a 92 hairs of a germinating bean seed. a at a root are also section have of a hairs. long look germinating or a osmosis hairs microscope. the bean They by root closely Look You Root at a and at thin. root hairs seedling such radish. large and surface mineral area ions through are which absorbed by water active is absorbed transport. tnemelppuS Looking Xylem that vessels lls instead are them. it is like pipes Water pulled is by as not the they are pushed empty from evaporation of the except roots for up the to water the leaves, water. tnemelppuS STUD Y Transpiration pull Mak e T ranspiration cells in the vapour is leaves can the evaporation and diffuse TIP the out loss of the of of water water leaf from vapour when the the to surfaces the stomata of mesophyll atmosphere. are sure the correc t We say, leaves The is by This • is As from up the xylem transpiration water wilting. up ‘pulled’ used water the mass for is xylem ow cohesion – of the stem from the roots to the and the photosynthesis up vessels, lost rather up water or the and from like xylem molecules to stop the water relies tend being on to the leaves, plant more ‘ water vapo ur each of ‘ water the leaf’ goes out of leaf’. sucked up properties attract not out from is sucked two use Water pull used water the in you term inolog y. open. diffus es Water that a straw. of other, water: sticking together adhesion the So xylem there is a – the water molecules also tend to stick to the inside of vessel. continuous ow of water from the roots to the leaves. This STUDY movement of water up the xylem is called the transpiration When SUMMARY QUESTIONS 1 complete TIP stream you and the sentences using these in stomata osmosis large transpiration are for 2 into taken taking leaves of passes also up a . root A water by the Look up. cell root and This is hair hair cell mineral ions. controlled ions the . a water xylem, Mineral leaf water of that from with water pulls the in the roo ts. surface Water by the start evaporation area by has how words: always Water are explaining moves Copy tnemelppuS • the is lost from opening and the closing . at the diagram of the root hair in the soil: A B KEY 1 POINTS Water enters osmosis. the cells osmosis It a root then of the hair passes root before cell by across cortex passing by into the C xylem D F the and then up the stem to leaves. E 2 a Name the parts labelled A to Root the b Explain c Give how water gets into tnemelppuS 3 Explain, root using hair vessels other cells, and up the functions term across to the water the cells leaves, of a root root hair hair potential, of are well cell from the absorption the where cells. how cortex, it is lost to have have water into passes the the of adapted water for since soil. they two hairs F . into xylem atmosphere. 3 Loss a of ‘pulls’ stem thin large water more from cell walls surface from water the transpiration the up roots and area. leaves the in the stream. 93 8.3 Transpiration Plants absorb water • Dene • Describe the term transpiration passes where it is diagram how water is related to cell lost of are spaces Describe and how temperature, light from humidity can There and affect rate tnemelppuS how a the leaf atmosphere you will see through the soil. as that stems Much water there and of vapour. are many If enters this you air leaves look spaces at a by mesophyll cells which have damp cell inside. walls. from this huge internal surface so the air spaces Water become wilting with water vapour. in is usually the outside the air. more Describe water up stomata variations intensity transpiration • of moves surfaces, saturated • quantities roots, to lined evaporates air into vapour These loss large OUTCOMES The air, more so water water from water water lost the vapour vapour from the in the diffuses spongy air spaces through than the mesophyll there stomata cells is is in into replaced by xylem. occurs Transpiration evaporation the of diffusion is the loss water of at water of water the vapour surfaces vapour of through from the the plant mesophyll leaves cells, by the followed by stomata. Wilting More the T wo open transpiration stomata are open the Carbon during place during the dioxide the day is a during so raw day that the and day closed carbon material than at at night. dioxide for night can because The diffuse photosynthesis into and stomata. diffuses The STUD Y into stomata chloroplasts close as Whe n form s refer water evapor ates water vapo ur . to at night in mesophyll to reduce cells. the volume of water lost by TIP transpiration. xylem open stomata leaf. takes it as just Do air lost in may also close transpiration is in not hot, being dry conditions replaced by during water the from day the soil. it not ‘ water vessel water They ’. space The stomata enough so much are rm plant close water it water and that give becomes up will reduce they the soft. to start to are plant The transpiration. wilt no (see longer support. stem is above no If If the plant on the right). turgid the or cells longer full of become upright and still Its does cells water . T urgid accid the not then leaves get have lost cells the droop. water evaporates off cell wall stoma vapour Wilting is not a bad thing. The leaves move downwards so are diffuses out of the direct rays of the Sun so do not get as hot. When the out temperature Figure 8.3.1 Loss a 94 of leaf. water vapour decreases and they can absorb from by transpiration the leaves will recover. more water than is lost tnemelppuS LEARNING Factors As factors see the light intensity of In very humidity is a dry the is of the measure is of rate high. of the are air rate and the of the transpiration Figure the other Y ou 8.3.2. increases conditions, temperature. the air in transpiration by quantity when As environmental. factors determined conditions transpiration humid, that these of water humidity becomes is etar the Humidity air . increases, maximum as of etar such a transpiration two fo to of fo up affecting effects noitaripsnart can transpiration noitaripsnart Other affecting vapour low, more the and in the 25 rate more 50 75 humidity decreases. Figure 8.3.2 10 100 / 15 T wo 20 temperature % factors affecting the rate / 25 °C of transpiration. The rate of transpiration increases as the air temperature increases. KEY Transpiration evaporation Light causes stomata to open. As the light intensity increases, wider . As light intensity decreases when it is cloudy or stomata close so that less water is lost by transpiration. conditions, there may be nearly as much water vapour followed in water as concentration low. In dry vapour cell out rate the surfaces water air conditions the inside the gradient diffuses inuences cells in of leaf. have of inside for the water vapour the concentration the leaves of temperature more kinetic This so the the water rate and is that of from very enter the is steep so such molecules air 2 is inside as the not easy velocity the leaf the If water water rate of transpiration but you can use to water lost slightly roots. This and in is is measure less because keeping cells the rate than some the of of water volume the water uptake. of is water used The taken up in volume in by potometer shown, is making allowed bubble is is to a sure form in loss of by the in increasing the greater plants lack of of rate. than wilt and turgor in leaves. of photosynthesis the of submerging stem in the capillary the rate of it in water. stopper tube. The water is It is set air-tight. distance up An air moved cut by bubble 1 How you rate shoot of State a capillar y rate set measure how explain a the by it a cut works. how conditions of up uptake Explain and an to water these the reser voir would potometer the uptake. air QUESTIONS as of A rate the 2 8.3.3 the while is stems shoot? Figure Increasing wind turgid. lled measure and decreases SUMMARY The increases rate. uptake, opens a cells potometer diffusion intensity and transpiration, as transpiration measure the through increases humidity to the atmosphere. light stomata because is the temperature the on to transpiration 3 It by vapour Increased the water vapour . Measuring at mesophyll no T emperature surfaces, water there transpiration stomata. increases, energy means gradient through evaporation As leaves. water the stomata atmosphere of the In of humid of towards cells evening, the stomata surfaces open is tnemelppuS tnemelppuS 1 Explanations POINTS each affects transpiration: increase in light intensity tube bubble b a decrease c an in increase temperature in humidity potometer. 95 8.4 Translocation tnemelppuS Food LEARNING is made in include • Dene • State that the term acids move parts translocation sucrose, of the • to Explain plant a sink the sucrose a in at phloem from a The act as a parts a of Compare transport source times to growth a and during the take converted plant photosynthesis. in solution which and in means fatty the acids. The soluble These phloem. ‘from place to This are products carried transport is to all called place’. food regions place. in where of the takes of The leaves growth place storage simple into or from or to regions sugars sucrose. storage regions to is production where produced This occur of by respiration or photosynthesis transported provide (the to energy. parts are of Sucrose the is: plant • • by acids amino leaves) some different of and sink that may life leaves amino plant translocation source the OUTCOMES transpiration with broken down by an enzyme to give simple sugars that are used in respiration translocation • changed • used and • to Leaves in use make are also DID tissues. make where If the the the and can stylet sap so be of stylet collected above for 96 are crop on phloem their piercing pests. sap They by using mouthparts. the at the and photosynthesis cells are are cuticle for isotope of and in seeds growing root tip all over made stored on the and the in in attract nitrate plant shoot many upper animals. to and seeds surface ions make root as of tips. oils the and leaves. to some the and sap insert of maple tubes trees. through which buckets. feed the the study on the called stem into the sap stylets a phloem aphid aphid single tube with cut, the phloem which can phloem causes it be tube. to of plants. inserted The pass along food. transport is in the of sugars sugary sap in the will phloem. pass out time. sucrose aphid and in that inside phloem tree transport the feeding below from the collects provide used a from and cortex sweet needed mouthparts surface Isotopically-labelled feed into insects piercing of root walls them that waxy prepared holes small the stylet the of Aphids new phloem pressure cell from are acids and Aphids 8.4.1 These Aphids the Figure sugars fatty for is drill have the KNOW? syrup are in new make and through living acids. to ows They are for sap Aphids tubes simple needed Farmers Phloem fruits especially Maple the the YOU storage cellulose some also for tip amino proteins, Leaves starch make shoot stored to to stylets, leaf. the can be that The injected have been contents passage of the of into a leaf inserted the sucrose sap and into can traced. be samples the stem analysed In plant transport, journey Water empty relies a is called and owers and ions and upon tension The the in part of absorbed (the the The sinks). by plant part roots Xylem where where (the are of water in evaporation of water vapour xylem. stream. This pulls up T ranspiration xylem water is it a substance ends source) vessels movement the transpiration translocation source. are fruits cells. the a tnemelppuS Transpiration its and from from greatest travel columns vessels the the on is (or to leaves dry is to a its sink leaves, pipes) passive, roots hot, begins journey of dead, since it producing give and the windy days. Black Translocation is an active process which occurs in phloem. The food are the source of food substances and the sinks are the bean and tissues, regions of growth (root and shoot tips) cells active tubes the such that as the contain transport to build sinks. root some of up cortex sucrose a and cytoplasm. head Translocation at of is the the source. pressure most seeds. Movement Water that active Phloem in on the regions tubes forces sunny, the are phloem enters the days very spraying are producing increased levels of rapidly. sap Movem ent in sugar. is the way – roots. in the b What the term translocation substances are translocated in the T he What are the materials transported in the phloem both used and for? leave s 2 3 Draw a table Substances the xylem to are and compare transpiration transported in plants with from translocation. sources to sinks to grow th in sink of for substances substances substances in in in the from stem In it is leave s tips, and to from wher e and this of phloe m season fruits ques tion only from trans port occu rs, owe rs, is upwa rds answ ering source them and direct ions. Rem embe r phloem. water xylem upwa rds down ward s phloem? of grow ing roots c control to when QUESTIONS Dene Farmers TIP subs tanc es a of aphids insecticide. STUD Y the 1 plenty living one SUMMARY is requires ions plants there favourable, of phloem phloem warm are respiring and by storage When conditions reproduce plant aphids. leaves to seeds. when Sum mary 3b. transported transport in the plant the plant the KEY POINTS xylem 1 transport Translocation movement the is the in of sucrose and phloem amino acids from the leaves (translocation) to regions growth a Copy are in and complete transported each in the each table tissue by giving and one two substances source and one Explain 2 Regions called case. how a root tuber can be a source and a sink times of the Aphids feed on storage, How are b Suggest are are regions respiration called and sinks. Transpiration is a passive plants. they used to investigate movement in involving why farmers and growers control dead tissue. phloem? Translocation spraying and year. process a production at 3 4 of sources growth different respiration, storage. that sink of b of and aphids by process is an involving active living tissue. insecticides. 97 PRACTICE 1 In QUESTIONS which water conditions by would a plant lose of most environmental caused transpiration? A cool and dry C hot and dry B cool and humid D hot and humid it to conditions is likely to have wilt? air light 2 (Paper 1) Which row transported in describes the the phloem amino B amino D glucose (Paper 3 acids sucrose Which is and molecule A root leaf B and and and and of ions sucrose sucrose ions water and and amino sucrose correct water ions it taken moves xylem cell, mesophyll pathway as mesophyll, hair D low B low low high C high low high D low high low water acids and (Paper water and 7 Which water ions air cortex, root moves in by Which through root, root cortex, air spaces spaces hair root in leaf, xylem a phloem C xylem down in xylem, cortex, leaf D xylem from water potential a down a a water water low in 2) mesophyll, 8 Which statement xylem, mesophyll the from root water from B mesophyll D xylem of spaces best the to high which the water pathway is lost water vapour from stomata intercellular into the from of water and mesophyll diffusion cells of through soil? into the atmosphere. hairs Evaporation and vessel of diffusion into water of the from water mesophyll vapour cells through the atmosphere. [1] potato plant grows in a eld Evaporation sunlight. Which row shows the of carbohydrate in the source destination carbohydrate A glucose leaves tubers B glucose tubers leaves C sucrose leaves tubers D sucrose tubers leaves 9 The A diffusion of water stomata into 2) water for 6 days. vapour the from air spaces atmosphere. [1] diagrams root, B show stem and transverse C after being Which leaf. B [1] wilted cells 2) A has mesophyll of carbohydrate plant from phloem? (Paper of water correct through movement of in and left combination C 98 gradient potential describes by through Evaporation D without gradient leaves? air cell, 1) potted potential potential water mechanism cuticle A gradient [1] Diffusion C 6 potential atmosphere. root (Paper water [1] absorbs type down (Paper atmosphere C bright of leaf 1) sweet movement cells? stem, A cuticle A the leaf from: B stomata 5 into plant? cell A (Paper explains stem a water 4 the mesophyll B (Paper statement atmosphere cells, stoma, stoma, [1] A and xylem, 2) from Water water stoma C high [1] cortex, root xylem? 1) the high xylem acids C A substances phloem A humidity temperature [1] best intensity sections of (a) Copy that the diagrams represent phloem in A, the B and shade positions and the of 11 areas xylem and C. [3] A leafy into Copy and complete functions term sap of the refers xylem table to the and to was a balance. uptake two from and Topic The the a plant 8.3) table rate and which shows of placed was the rate transpiration the leafy shoot during a hot, dry day. The transported in rate these cut (see compare phloem. liquid on water by the shoot potometer placed of (b) a tissues. time / of water rate of water h –1 loss feature phloem composition direction of of the ow / g –1 h absorption / g h xylem midnight 4 7 0300 6 9 0600 12 12 0900 18 14 1200 24 17 1500 22 19 1800 18 20 2100 8 14 midnight 6 10 sap in the stem destinations [6] (c) Describe how pathway through above (Paper 10 A you taken the would by parts water of the discover as it the travels plant that are ground. [3] 3) potometer measure (see water Topic uptake 8.3) by a was used leafy to (a) Plot (b) Calculate rate shoot. a of 1200 time the Describe move A cool, humid air in B cool, dry / min (d) Explain daylight C warm, dry D warm, humid air, in daylight E warm, humid air, at night in air, the daylight in of percentage loss your the change between Show in 0600 table. in [5] the hours working. and [2] the changes over the in water 24-hour loss and water period. [4] the how stem water to the moves from atmosphere. the cut end [4] 4) 6 daylight rate data 2 (Paper air the 100 of Calculate hours. absorption mm (a) the water show water conditions to to taken (c) for graph 1 3 60 water movement in −1 mm min E, (b) and Draw the for each present a ve bar of your chart to conditions the conditions, answers show on the in the a table. effect rate of A From the of movement (d) State two shoot with (Paper a [5] results, conditions that state affect through ways would [3] water movement. (c) to be in three the the of water plant. which affected transparent environmental rate the if plastic it air [3] around was bag. the covered [2] 3) 99 9 Transport 9.1 Describe The circulatory Most animals the one-way ow around the Describe the of pump the ow heart of as a of valves blood to and circulatory system vessels. that consists Circulatory systems of in blood, some animals useful permit substances surface and such nutrients as oxygen from the absorbed part of the from gut a gas that is the for absorption. Circulatory systems also transport waste, only such one-way a blood pump adapted role and body exchange for have of transport • system OUTCOMES sort blood humans Circulation LEARNING • in as carbon dioxide, from all over the body to the gas exchange ow surface. • Describe of • a the single circulation sh Describe Blood the circulation double of a The mammal heart its the blood very ows body. close their The flow let the Valves towards blood close to stop heart from The wastes from blood delicate so helps to the they blood the through blood vessels. heart to the different organs the and a blood so heart to in veins a veins. are good can have The smallest capillaries. supply their of Cells oxygen carbon are and dioxide and efciently. allows to the receive one-way giving maintain capillaries, capillaries reduce to arteries removed pumps this back capillaries system heart getting arterioles ows these circulatory small pressure a but it ow pressure one-way high the blood so that ow. pressure muscular before of it This vessels blood enters ows is blood blood around inside good will the for damage known as capillaries (you flowing nd out more about arterioles on page 107). When blood leaves backwards capillaries Figure circulates away connect capillaries and can the that arteries the blood which arteries Blood to other body. to pump in vessels nutrients open a advantages of Valves is and Blood explain circulation 9.1.1 How semi-lunar permit one-way the blood pressure is even lower. valves ow of There are semi-lunar valves in veins to make sure blood does blood. not ow backwards happens, valve of gills has the back veins swell three blood to ll away of and these pushes the from the the blood pockets. against heart is The them, (see not circulated valves but Figure open they 9.1.1). when close If properly. when the this Each pressure blood ows pockets. arteries heart A semi-lunar the between heart the single Fish body 9.1.2 Fish have a circulation ows once the 100 are valves chambers chambers of in to the heart enter the at the arteries. heart (see places There page are where also blood valves 102). circulation veins organs Figure leaves single in in a body. the circuit a single during from the oxygen which through have once it a organs and circulation complete is ows called because circuit into the of the heart blood body from deoxygenated ows (see veins. blood. through Figure This The the 9.1.2). blood heart heart Blood has little pumps blood blood into blood ows an artery that takes it to the gills to be oxygenated. heart around on from the gills in arteries to the body organs. The tnemelppuS detanegyxo detanegyxoed doolb doolb chambered There tnemelppuS A double circulation lungs Mammals twice have during a one this by The mammalian is a circulation. complete following septum double the heart thick circuit pathway wall Blood around that blood ows the through body. takes is divided into two of muscle that separates You around halves: right the the can heart conrm Figure and two 9.1.3. left. halves The of the right heart that stops blood in the right side mixing with blood in the side left side left of heart of heart side. Blood circulation • right The and side back to has of the two the functions: heart heart pumps again. The deoxygenated pressure blood required to to the force lungs blood the to the the lungs lungs occurs as as absorbs returns is not they blood the are a ows oxygen to very and high spongy in a is little lled capillaries carbon vein. there tissue through loses heart since with in dioxide. This blood resistance the The is air. Gas lungs. to red heart in exchange Blood oxygenated bright ow in blood colour rest and of body is • shown The of left the red side body leaving is in the much of on the and left more diagrams heart back side to is the pumps the much resistance of to circulation. oxygenated heart again. greater ow than than blood The on there to pressure the is right through the of rest Figure 9.1.3 Mammals side the as exchange such and as occurs muscles, carbon capillaries the dioxide and as blood gut, liver enters. ows ows and The through through kidneys. capillaries Oxygen deoxygenated veins is dark blood red in in leaves that colour, shown as ows through twice in but may and be complete KEY 2 the sentences using these words body veins The heart right . The is Here of it gas blood it side of tissues left lungs deoxygenated the pumped to to mammalian absorbs is returns and carbon right dioxide 3 oxygen heart and removed from the the side the is of where pumps now blood the it to in complete circuit valves up lungs. and from its of ensure a a around system. single passes once the blood circulation, through during one the circuit body. Blood ows heart the twice during body in a th ro u gh one circuit m a mmal. the blood. the have blood the called heart gives blood ow circulatory Fish of The a body. POINTS heart (some twice): oxygenated the blue. QUESTIONS used blood heart is so Copy the blood leaves the 1 double organs the one-way SUMMARY a which lungs. 1 always in there of Gas have circulation blood 4 The heart pumps low pressure to blood the at lungs The and at rest of high pressure to the here and the body in a double is circulation. now the 2 3 called heart blood. in what double circulation Explain the Blood b Blood c Veins passes back to the side of . Explain a It is 5 meant following the terms statements on the right on the left contain by side side of of semi-lunar the the single about heart heart is circulation the is at low high ows in from the veins towards arteries heart. Blood away ows in and mammalian at Blood the heart. heart. pressure. pressure. valves. 101 9.2 The Heart LEARNING Describe the four human the heart and locate of blood vessels and • State that the with the place The page one heart consists of that away from blood the two pumps and the lying left side side of by the side. The heart is almost entirely of cardiac muscle tissue one to is aorta pumped heart body body vena cava (main into vein) pulmonary arteries heart • and in Explain of the returns to to right lung importance septum to left oxygenated deoxygenated lung in pulmonary separating artery the veins the right another events during from State of pump 24). heartbeat • consists is heart sequence take heart valves (see associated the the pump. major heart chambers side of structure OUTCOMES The • heart veins and blood from • Locate the and name the valves heart right atrium left • Explain why ventricles those of the are the walls thicker atria of left than ventricle than and the is why thicker valve right cava TIP left Whe n tendons valve* vena STUD Y atrium the atrioventricular the lungs in you look at ventricle a right diag ram the it hear t from or draw ing you of ventricle from are *Supplement septum the fron t of the Figure body the – so hear t side of the is the lef t on the side YOU 9.2.1 The septum right draw ing. KNOW? Al-Nas physician was the the the side On each are called have was He an of 13th the suggested puried in the show how the blood moves through the heart. (wall mixing of tissue) side of atria When much prevents the oxygenated heart (singular: the atria more they with deoxygenated there contract the are atrium). muscular pump blood blood out the into left empties pump than the chambers. Blood they walls two on blood on the blood atria. arteries side. The into into chambers from ventricles, When at upper them the higher which ventricles pressure. Arab person functions lungs. 102 of rst was arrows righ t contract Ibn The of veins. DID body view ing century. to He connect heart that lungs. and blood Between prevent right walls each the and blood left than further atrium owing ventricles the than and atria the ventricle back – into contract. because atria to a right to or left have pump lungs valve. and ventricles have the one-way the The they either is to The valves atrium more when the muscular the blood the tissues much of the body. The left ventricle because more it tnemelppuS contract, The at more pump to pumps the muscular blood around wall the than body the right and has ventricle to from from heart relaxation overcome ow. two sides same blood chamber chamber the a action heart each to resistance Heart The has has when gets contracts of the time. it heart The its smaller relaxes work the relaxation phase, During the contraction and so it contract. squeezes lls together. ventricles During muscles contract blood up the with The and ows When relax into the blood blood atria the out. the atria phase filling After again. contract at muscles and same from relax right left atrium atrium time. the veins. left phase: ventricle • The atria between against contract and force the and ventricles atria blood into open the due ventricles. to the The valves pressure of blood right them. ventricle heart • Then The The the valves right artery. aorta The ventricles close left (main phase They they prevent pumps ventricle to force blood blood owing to pumps blood the blood out into the arteries. back into the atria. lungs to the in the rest of of full blood to to lungs body pulmonary the body in the artery). semi-lunar arteries. to ventricle The contract valves act shut, like occur the at the ones preventing in base of Figure back ow the aorta 9.1.1. of and During blood into pulmonary the the relaxation ventricles. heart During the the lungs contraction and the phase they open allowing blood to leave to contraction body. Figure Deoxygenated blood returns to the right atrium in the vena 9.2.2 The cardiac changes cava heart (main vein). pulmonary phase pumping Oxygenated blood returns to the left atrium in cycle that during – the occur one in the heartbeat. the veins. KEY 1 POINTS The heart muscular consists pumps of two divided by a septum. SUMMARY QUESTIONS 2 1 a What are the two upper b What are the two lower chambers chambers of of the the heart heart called? Ventricles blood make called? one c What is the function of the Explain each The atria The left blood ows in The atria have less muscular statement. have less muscular walls than the ventricle has a much more than the ventricles, as ventricles. they b that force valves direction. walls a sure to arteries; septum? 3 2 contract into muscular wall than only force blood into the the ventricles. right ventricle. 4 3 In each of the following cases, which blood vessel The right blood a blood to the rest of the blood from the lungs c blood from the body to to to the forces lungs, then the body left b ventricle carries: the the left atrium right atrium as a ventricle it has to pressure greater is more pump that muscular, blood at overcomes resistances. 103 9.3 Heart There LEARNING • State can be to the activity in monitored pulse rate sounds of the by heart monitored. These listening the Investigate listening valves of The the state physical pulse Explain control activity variety the activity of the sounds of the heart valves (ECGs), heart pulse may rate be and closing. (ECG) of of the heart heartbeat disorders depends can upon produce electrical activity. irregularities in this activity. on electrocardiogram, or ECG, is a useful diagnostic tool that can rate the effect of on the these defects. Electrodes are taped at various positions on the physical body activity to electrocardiogram detect • which and The the by electrocardiograms closing A effect methods include ECG, and The • different exercise OUTCOMES that taking are and heart and the electrical activity of the heart is then displayed on a rate monitor. ECGs The its Figure for a 9.3.1 heart resultant trace characteristic contracting, the P , the ventricles, shows a normal ECG, while Figure 9.3.2 shows disorder. can be QRS QRS and compared and T ‘spike’ the T waves. with The immediately wave represents the P normal wave ECG shows precedes the ventricles with the atria contraction of relaxing. R egnahc lacirtcele A boy an using ECG to an exercise monitor his bicycle heart while T P P having Q function. S 0 0.1 0.2 0.3 0.4 0.5 0.6 time Figure Heart ECG A normal (ECG) the of the this example one heart 0.9 1.0 s beats takes 0.8 seconds. sounds The heart The noise of During fibrillation contractions In 0.8 trace sound ventricular 9.3.1 / 0.7 ventricles are extremely valves of the your the respond blood contraction to force blood pressure of blood pressure when heartbeat contract to – the changes valves open during and a close cardiac make cycle. the ‘lub-dub’. phase, out of the muscular the pulmonary walls of the artery and ventricles aorta. The irregular shut, rst complete heart the ventricles atria and part During block are preventing beating independently high of the 9.3.2 A normal ECG trace ECG traces disorders. for in the the going sound from back – phase, arteries blood atrioventricular into the valves atria. causes This them produces to the ‘lub’. the ventricles causes going the relax. The semi-lunar backwards into blood valves the to under shut, ventricles. produces the second part of the heart sound – ‘dub’. Doctors are heart able any 104 heart the and This two blood relaxation pressure preventing Figure the against to listen to irregularity these in the heart sounds heartbeat. with a stethoscope and identify tnemelppuS The heart During order exercise, to muscles These and your contract. dilate changes exercise muscles So the increase the an increase in supply • an increase in removal can time you can wrist. the detect the left same the You as the The resting The tter The same energy faster are, of of and carbon blood a and from respiration arteries in supplying muscles and result in: glucose through arteries passes pulse per to dioxide. wave your pulses heart ow oxygen nd of pulse you blood beats, can number of ow ventricle feel. The more beats (widen). • You need heart by minute along feeling is your as a the an ‘pulse’. arteries artery pulse at rate Each which your and this is rate. rate the A gives lower a good your indication resting pulse of a rate person’s (see person minute but with of blood fewer is being passed out of the heart and shows levels of the taken. POINTS per heartbeats. ECG traces, sounds table pulse tness. 1 The their table). KEY volume having general relationship between resting pulse rate used of to pulse valves monitor rate and closing heart the can be activity. tness. 2 pulse less rate than level 50 of tness Pulse rate and then resting pulse with decreases to rate. outstanding 3 50–59 Physical activity increases the excellent heart 60–69 good 70–79 fair ow 80 increases activity and over rate, to more muscles, oxygen removing poor increasing blood supplying and carbon glucose and dioxide. PRACTICAL Investigating the Sit a still and get effect partner of to exercise measure on your pulse pulse SUMMARY rate rate at rest. 1 Try doing step-ups for 1 minute (light QUESTIONS a State pulse exercise). what rate happens when a to person exercises. As soon as you have nished, sit down and count your pulse rate. b Wait until your pulse returns to the resting rate. Explain pulse how rate and why changes with exercise. Now do (heavy step-ups exercise). Remember have the exercise until that same each your as quickly Then to make person time, pulse as count this doing rest returns for to you your a valid the 5 its can pulse for 3 minutes rate. 2 investigation exercise, minutes resting do the between you should same each type can your also results repeat more the tests and Draw b Explain to of exercise T or calculate an average to make Pulse can explain how reliable. the results in terms the normal what heart ECG is at trace. happening P , QRS and waves. of supplying substances rate certain be You a rate. 3 You a is risk some the affected factors. of result these of a by Explain can person’s to lifestyle. your muscles and removing their wastes. 105 9.4 Blood Blood LEARNING ows them arteries Name to the and and arteries to all main from blood the in and veins. This table organs shows of you the body some of and the heart, organs vessel Describe the function of structure arteries, lungs liver kidneys and veins and vena cava right atrium; to hepatic artery; bringing blood renal pulmonary hepatic (see pulmonary the functions vein artery vein arterioles, venules page (see 146) of and artery portal to organ State away important veins. lungs kidney capillaries • ows most vessels heart • the OUTCOMES from • in vessels to left atrium page 144) shunt taking pulmonary blood artery away right from aorta organ ventricle vessels tnemelppuS from hepatic vein renal vein pulmonary • Explain how the structure of ventricle; (see page (see page vein arteries, are veins adapted and for capillaries their functions from left 144) head, and vena thick 146) neck arms cava outer layer lungs pulmonar y pulmonar y vein arter y aorta vena which blood thick and right left atrium atrium cava flows layer elastic of right left ventricle ventricle hepatic muscle vein fibres liver hepatic arter y Figure 9.4.2 An artery. hepatic portal vein renal gut vein renal kidneys body arter y and legs two are outer layers thinner outer layer Figure than 9.4.1 Main blood vessels of the body. arteries Structure large space When which and function of blood vessels through blood your heart muscles contract they force blood into at muscle and a high the pressure. blood to Arteries ow have along. quite They a have narrow thick space walls and 9.4.3 in made fibres 106 arteries the centre elastic for Figure the flows A vein. elastic bres to withstand the pressure of blood. of muscle Veins have thinner, veins is walls. that The a less There squeeze are in branch so tnemelppuS blood and than one it is less valves times very wall easy elastic at – the a do to substances adapted to such veins to (see cell can from to a and their inside thick ensure page branches blood are pressure heart pass and need along the made to The not smallest red is arteries walls. intervals capillary are than they back until a ow so narrow; of for vessels to arteries direction are The blood have in many Capillaries cells for semi-lunar through. thin How lower ows arteries capillaries. space muscular much blood very wider 100). form only single from just layer the of blood. functions red The like elastic a bres piece original of where it the elastic length. maintaining in The its walls when recoil enters an you of pressure. As organ is of the stretch elastic a arteries a and bres result only it the little stretch then helps less let to pressure than and then recoil it return to push blood along at the when end it left of is estimated that there are over 80 000 km of capillaries so heart. in 9.4.4 A capillary body. These tiny vessels provide a huge surface area magnied capillary between blood and cells. Blood ows through slowly (about substances cells the with diffusion This makes and to it the by pressure mm As to of from second) walls blood the oxygen dioxide in and the blood is for from and exchange one cells nutrients, other of time made and veins contraction giving are between supply carbon pressure per the distance easy remove As 1 cells. is layer very such as of surround the are other wastes. very body low, it is muscles squeezed and other along KEY POINTS organs Arteries in the circulatory system. elastic blood have much small subdivisions of arteries that carry blood blood networks. from ow blood pressure. hormones in Like They the arteries, transport, order through muscular receive to they have arterioles nerve regulate are muscle important impulses their in and diameter. their in withstand less tissue Blood Veins muscle and have pressure and thin in veins low. walls. regulating respond This to pressure. to is Apart thick walls high walls. capillary have veins. vessels the removed cells). short. elastic are blood glucose, Arterioles Arterioles section red of and There view thin 1 that actually capillaries to very is for cylindrical, exchange ×2500 the (the human cells capillar y artery Figure It a its an the blood inside to 2 are various regulates Capillaries one have cell substances blood and capillaries. out of walls thick can the so that that pass easily blood in in body tissues. Venules Venules are from the veins which small blood capillary beds. transport vessels These whose function thin-walled deoxygenated is vessels blood back to collect then to blood unite the to SUMMARY QUESTIONS form 1 heart. Make a table differences Shunt and vessels veins. columns: A shunt vein, allowing Shunt In vessel vessels is the can endotherms response and to a blood vessel to control thereby heat that bypass blood (warm-blooded cold, reducing blood links the ow off artery capillaries by directly in certain constriction animals), cutting an the shunt blood and vessels ow to areas. dilation. the show Include feature, the main arteries three artery, vein. a constrict to to between in extremities 2 In what well ways adapted materials and body are for the capillaries exchange between the of blood tissues? loss. 107 9.5 Coronary heart disease (CHD) You LEARNING need muscle • Describe the coronary State nature heart the of disease possible preventative coronary • Describe CHD (CHD) causes measures heart the may get then blocked to be in could the and heart heart cause in the blood heart to around keep coronary could it 7.2 arteries. die Slowing Healthy which the arteries However, people from each cause countries. death The become is for one starved have a smooth cholesterol, This can condition narrow is which the called lining, is letting made artery and in the slow blood liver, down death It rate in is with can from has the CHD There are these differences of atherosclerosis Fatty deposits break Fatty deposit of a – blood 9.5.1 The artery clot and the healthy Blood walls block 108 blocked formed with of is if can the the become vessel. artery gets or angina. rough, The coronary activity called flow arter y along stops. Atherosclerosis. coronary heart blockage artery partly emotion It is which is causes caused by cause called a serious blocked makes can it the not can blood to thrombosis problems. cause heart the work enough chest pains, harder. oxygen getting to by to fatty deposits. further the narrow healthy artery muscle. Angina should a attack. heart total act blockage and the unless as or a warning thrombosis supply the beating follow Compare arter y. artery. stop has the flow chest artery blocks them. happens, it. their blood. many A above to of is the artery. stick ow lowest This the easily. the especially clot and the If blood oxygen many Narrowing coronary are arteries in Figure A of ow the the A these ow 3 Cross-section If coronary year. country Japan rate. reasons diet of death Ukraine; Heart These attack 2 highest body. and treated million disease leading your contracting. KNOW? world heart the muscle a 1 Around pump oxygen of disease ways This This YOU heart glucose to walls. DID healthy needs transported die. • a OUTCOMES of affected oxygen part altogether the heart – of this starts to the can is cause cut the is sufferer off. heart called beating a It is because heart attack. causes a again The arrest. within may lead When severe damaged. cardiac it this pain heart Death minutes. to in the may will Risk These • factors are factors eating can less a diet increase page 71). fresh being • smoking People • These age • sex fruit – too increase much concentration diet – down and of eating on fried – but other inherited the from control chances men risk are parents the of more likely to getting the reduce little or fat, which blood sh, less CHD: red the no (see which meat are and risk. exercise stress risk cannot – CHD metabolism getting to taking these factors in and eating helps of (animal) poultry foods; • about chance cholesterol more vegetables something the saturated • genes – the good do life, genes • with to overweight can of CHD thought cutting • way A fatty; more for CHD get factors be avoided tends of fat to than changing such run and increase CHD by in their as: families. cholesterol with age women. tnemelppuS Figure Treatment of 9.5.2 Three you A coronary of CHD. the arm below A artery blood or the leg, bypass vessel and is narrowed is can taken attached or relieve from to blocked patients another the coronary area. with part of the the artery Depending on above the CHD, a number of separate grafts may be there is just one incidence of narrowing, or severity STUD Y angioplasty widen open. it. and A This tube Antiplatelet the arteries. people with angina, involves small metal is may be inating tube called a medicines, T aking CHD, attack, SUMMARY is then carried out. This is a less ao rta a small then balloon inserted to inside help like the keep artery the aspirin stroke coronary or prevent daily other stent and is blood part forms of of bypass clots the forming treatment heart Dene d a T hey a If the disease, tissu es in vent for of ricles blood the to atria the and . e.g. surgery. heart disease b thrombosis c angina 1 arrest heart POINTS Coronary caused is full of blood, then why does it need its heart by disease blockage arteries of that is the supply own the blood the tran sport coronary 2 of QUESTIONS coronary cardiac base abov e valv es. to artery oxyg enat ed aspirin, the just complex KEY 1 put a stent low-dose known heart can disease. arterie s from semi-l unar operation that heart TIP co rona ry the coronary of of needed. blockage, risk usually and bran ch If at symptoms body, T he the activities CHD heart with glucose and supply? oxygen. b How c Why is the heart muscle supplied with oxygenated blood? 2 does the heart muscle need this oxygenated Risk factors control 3 There are getting risk heart factors that can increase the of a person sex. disease. List some of the factors that cannot b List some of the factors that can c What advice would attack? are you give to a be be controlled. person recovering diet, exercise controlled. 3 from a genes, Avoidable include a heart chances which we cannot blood? CHD and may aspirin be and angioplasty risk age and factors stress, lack of smoking. treated surgery and by (stents, bypass). 109 9.6 Blood Blood LEARNING • List as the red components blood cells, of Y ou have and cell • platelets white Identify cells as red and and seen microscope, 5 litres fragments of blood suspended in in your a body. yellow Blood liquid is called made of plasma. cells The red blood of blood is due to the pigment haemoglobin in red blood cells. plasma white under in about blood colour cells, composition OUTCOMES blood the light plasma photographs – liquid part of blood (55% of blood volume). 3 Plasma 10 cm and • in consists of water with chemicals dissolved in it: diagrams Describe cells and that they the the role of red • nutrients, • wastes, • blood • hormones, and blood such mineral as ions, such as glucose, e.g. urea amino sodium and acids, and carbon lipids, chloride vitamins ions dioxide haemoglobin contain in proteins, such as albumen and antibodies oxygen such as insulin, glucagon, and adrenaline. transport 3 5 cm • State the roles of white blood and cells, platelets and red Figure 9.6.1 When it Blood There Red are they shows cells red with smear blood their seen cells nuclei with and a light two stained are white in in three no of a centrifuge (or left to stand for 24 hours), is full layers. have cell nuclei molecules a colourless shown the blood in bacteria process group as nuclei. they do the and of centrifuge in blood. have cytoplasm haemoglobin They (see not look Figure have for white that transporting when 9.6.1). separated Under haemoglobin of oxygen. or a by microscope see them, stain has to be added as in the any blood other of photograph. and is takes known white blood One them as group into white vacuoles phagocytosis cells of makes where (see protein blood cells smear they Figure are 9.7.1). molecules searches digested. Another called antibodies cells to protect that us invade Platelets example transport dioxide against the are as of and different types of disease-causing organisms body. tiny when substances fragments you cut listed ions, in of yourself. Figure nutrients, cells which The 9.6.1. such as cause plasma Among glucose blood contains its to functions and clot, many amino are for soluble the acids, carbon hormones. platelets Red Red and white and platelets. blood blood cells transport oxygen cells Red a blood large to 110 types have of cells blood To This 9.6.2 spun blood phagocyte Figure main cells pigment. out lymphocyte is into microscope blue. red three blood spinning blood cells blood separates thousands White blood cells blood many This platelets plasma cells surface absorb are disc-shaped area oxygen. compared with with the their middle pushed volume and in. this They helps have them Haemoglobin have red this enough blood is in (see more Haemoglobin special iron cells makes a type of protein diet to make your anaemia space for combines on page that contains enough 77). As iron. You haemoglobin the cells have for no must your nuclei haemoglobin. easily with oxygen in the lungs to form oxyhaemoglobin: haemoglobin Look at the + → oxygen diagram oxyhaemoglobin below: There are 5 million red blood cells like these 3 in molecules an of in the Oxygen the to diffuses blood. the The from oxygen haemoglobin in the alveoli attaches the red millimetre (mm ) of blood. in lung the 1 cubic alveolus capillaries oxygen every lungs into temporarily cells making red blood cell oxyhaemoglobin. 4 The cells for red blood return more to the lungs oxygen. haemoglobin cell membrane 2 The carr y the red the cells blood cells oxygen which to Figure need 9.6.3 Red blood cells magnied it. ×2500. red blood cells 3 The oxygen leaves oxyhaemoglobin out The of the blood and to just diffuses the oxyhaemoglobin now the cells. is haemoglobin again. SUMMARY capillaries body cells in body tissues 1 a List 9.6.4 Transport of oxygen from the lungs to body Notice that capillaries • oxyhaemoglobin in the alveoli Oxyhaemoglobin capillaries in gives body in forms the out while blood ows found as blood ows c through a a the is cell white white How ways blood Name of tissues. three red from lungs. oxygen plasma. Give a through 2 KEY chemicals tissues. b • four tisses in Figure QUESTIONS in which blood two main blood the in differs cell. types cell. red blood POINTS cell adapted for oxygen transport? 1 The main components of blood are plasma, red blood cells, b white visible blood under cells and the light platelets. Red and white blood cells i What microscope. ii Where with 2 Red blood cells contain haemoglobin which combines is haemoglobin? are does oxygen to form combine and what with molecule oxygen it is formed? oxyhaemoglobin. 111 9.7 Blood tnemelppuS White LEARNING how white such as blood lymphocytes them protect cells than the red defend blood us against cells. The disease. two There groups of are far white fewer blood cells and described phagocytes from cells blood of cells blood defence OUTCOMES White • Describe in in T opic 9.6 are phagocytes and lymphocytes body disease Phagocytes • State in • the role producing Describe of lymphocytes These antibodies the process of are white blood cells that ingest pathogens, such as bacteria. blood They surround the pathogens, ingest them and take them into food clotting vacuoles. The Then process is they called entrapment food digest them by using enzymes and this kills them. phagocytosis of formation particle food of vacuole within cell nucleus tiny vacuoles filld with food enzymes vacuole cell membrane cytoplasm bacteria This image was microscope computer blood The It image a and then program. cells shows taken and can white was phagocyte an with see in ingesting red cells. the a ingested a two blood taken being electron coloured Y ou three below with same yeast way. cell. digestion of enzymes added to bacteria the Figure When They Find 9.7.1 A white pathogens can out squeeze about blood invade the through tissue cell destroys body, on vacuole bacteria. phagocytes capillary rejection some food move towards them. walls. page 151. Lymphocytes Lymphocytes enters not Like 112 be the are body there. a type the white Lymphocytes enzymes, antibodies Enzymes have active Similarly, each type one of type of blood lymphocytes sites of then are make with combine has When that proteins proteins that antibody pathogen. cell. recognise a it a is called many with bacterium ‘foreign’ binding site virus should antibodies different their or and shapes. substrates. that combines with attack • they make • they dissolve • they neutralise some There After a you produce the have their Blood again. in together cell the a number of ways: (agglutinate) membranes toxins (poisons) that some pathogens, such as produce. had of pathogens stick different more body When them bacteria, is the tnemelppuS Antibodies type a antibody disease, the This of such appropriate makes you as for each measles, antibodies immune to type of pathogen. lymphocytes should that the are ready pathogen particular to enter disease. clotting you cut yourself you Like the two white white Before long, platelets help the thicken and the bleeding thickened clot. blood Without has clotting, formed blood lost and pathogens cell in this of smear is a is another way would that The skin the in blood of is a cells. are They small the the is cut are body. and blood blood However starts called come there like fragments made the in blood the The fibrinogen. in contact with a blood vessel is The of the fibrinogen threads make into a threads net over of Whe n they the white fibrin writi ng blood to plasma into sure you use ‘phag ocyt es’ are bres. which Red forms blood a these The threads cells clot to the get hardens to time keeps the the skin cut heals a clean. and no t blood their call cells ’. Red blood cells get caught in the net clot. scab and make cut. The the New With a blood clot skin dries clot to which make a seals the grows under the scab. POINTS scab. scab 1 Figure falls when of KEY which e trapped the make mak nam es and do ‘ white protein meshwork make – the 2 in , desc ribin g the in them brin, abou t cells platelets change insoluble cell When brinogen the white cut. func tions protein smaller bone cells. damaged, substances soluble larger blood When air you release a TIP protein ‘lym phoc ytes ’ a of leaking is scab marrow photograph phagocyte. disease. turn Platelets these The enter . platelets against 110, stained. lymphocyte. STUD Y defends page a out This on been would 1 be have stops. fibrin The smear cells blood threads to blood bleed. 9.7.2 Blood Phagocytes ingest pathogens clotting. off. and digest them using enzymes. 2 SUMMARY Lymphocytes that protect pathogens 1 a b State where Explain how white blood cells lymphocytes act are to defend the body from 3 After a how a disease, person can become immune to an the to like a b Explain, What has had a lymphocytes for that more pathogen measles. in detail, would exposed c body. infectious if 3 the produce antibodies disease in person remain Explain antibodies against made. pathogens. 2 make QUESTIONS Describe to role happen the the the air at process if a of a of platelets person’s in the blood cut? phagocytosis. clotting did not of clot disease again. blood. when the 4 This Platelets encountered called help brinogen blood is is to to immunity convert brin during clotting. 113 9.8 Lymph tnemelppuS Tissue LEARNING Describe the exchange between tissue blood Describe tissue the lymphatic functions of gaps. the vessels lymphatic and lymph uid the may protect uid. from our disease immune Experiments have all able to cells stable the cells. squeeze stay in the environment substances glucose and Most Fluid but know cut of is and waste to White out of blood. for diffuse the oxygen found is blood the cells, which capillaries Tissue uid through ‘bathes’ the and tissue of it uid like then owing drains from out of urea pass passes from into tissue cells. our the uid Useful out back of into plasma lymphatic into cells. cells the and into the blood back into system. system produced white not cells a the so stress, than is circulatory our heart system beating – we and videos. Not glucose, all taken amino vitamins, Our other But feel circulatory system the beneath glands – the fluid and tonsils lymphatic – these vessels. In are the Unit 7, lymph page lower nodes 85, leaves at the This is a thin-walled vessel that absorbs part of the lymphatic when veins system jaw, think you that saw are a fat from the lacteal gut system. of in the tissue one-tenth of capillaries. (e.g. acids, ions) oxygen, fatty acids, uid it returns enters Once a to plasma separate inside these, waste (e.g. the products carbon metabolites, in blood system of tissue given dioxide, excess capillaries. capillaries uid is called called lymph out unwanted ions) the venule arteriole capillary network back arteriole the rest enters lymph The blood our lymphatic your some 9.8.1 see see those nutrients the by another lymph of skin. obvious. adenoids villus. About end feel and non-humorous capillaries blood can signicantly and tissue our we humorous blood reduced about that in 114 the form them. into pass chemicals constantly some ourselves, connected Figure of to and about watching watching walls systems. – had a lymphatic through more constituents capillary our we videos the the KNOW? We people surrounds are blood helps like plasma, The boost Red dioxide capillaries. bodies of in nodes tissue Laughter some gaps system Carbon YOU that shape, providing substances DID tissues, small system Tissue as body through the cells Outline out uid change these • reaches move uid can • uid capillaries the and uid of plasma materials tissue OUTCOMES When • and formation of tissue uid and vessel lymph. of the the tissue lymph fluid capillaries tissue into fluid the passes capillaries but capillaries will lymph not the vessels. thin-walled ows let in and one have tiny lymph These valves pass have contain a that out allow again. structure semi-lunar the They similar valves to tissue join to uid up to veins; make sure to tnemelppuS Lymph enter form they are lymph direction. The lymphatic The contraction system of has no pump surrounding so the muscles ow helps of to lymph make it is slow. ow. STUD Y right into lymphatic the right duct empties subclavian left vein TIP subclavian vein Plas ma, lym ph that tissu e are are very compo sitio n, in the the thoracic duct out differ ent body . text uid three uids simila r but Read e they in occu r places in throug h carefu lly wher and to are nd and remem ber! lymphatic from of lymph Figure Lymph join 9.8.2 to subclavian the blood lymphatic from form the two veins, before lacteals small in villi intestine nodes The ows up vessels system. tissues large under joining to lymph the the the heart. vessels collar vena The which bones. cava smaller empty Here just the before lymph into lymph it vessels the mixes enters the with heart. KEY At intervals along the length of the lymph vessels are lymph 1 There are many lymphocytes in the nodes and during an POINTS nodes. When tissue lymph they multiply by cell division and make antibodies. Some uid enters the infection capillaries it is termed leave lymph lymph nodes patrolling an and for important circulate fresh part around invasions of the of body’s the body pathogens. immune in the The blood, constantly lymphatic system is 2 system. Lymph and has SUMMARY QUESTIONS a What is tissue uid no large 3 1 and what are its The consists white red What is lymph and what are its Explain, in as much detail as you slow and how the circulation can, is What main are lymph function? nodes, where are proteins. lymphatic why the ow of lymph system circulation has a which lymph to the blood. is Lymphocytes are in lymph maintained. nodes 3 but or functions? 4 so cells functions? returns 2 plasma cells, blood plasma separate b of blood they found and what is their during where an produce they multiply infection and antibodies. 115 PRACTICE 1 Which the QUESTIONS chamber of the heart pumps blood into 4 Which row shows components aorta? A left atrium B left ventricle of the the correct functions of the blood? red plasma blood platelets cells C right atrium D right ventricle antibody oxygen formation transport A (Paper 1) clotting [1] B 2 The plan system. diagram Which is shows the the human pulmonary antibody oxygen formation transport clotting circulatory transport artery? of oxygen C clotting ions transport A head and oxygen antibody fore-limbs D clotting transport (Paper formation 1) [1] D 5 In a single through circulation the circulation C leaves the heart of the of once body. a sh, the during What a blood ows complete type of blood heart? B lower and A deoxygenated blood at high B deoxygenated blood at low C oxygenated blood at high D oxygenated blood at low pressure pressure pressure pressure body hind limbs (Paper 2) [1] Key oxygenated deoxygenated 3 (Paper 1) Which is owing A B 6 blood blood blood the correct body → the vena pathway human cava taken ventricle → lungs left ventricle → aorta cava lungs → → atrium right body (Paper 1) arteries to veins B arteries to capillaries that transport C capillaries to veins left D capillaries to venules system? atrium → (Paper right → body 2) pulmonary → left ventricle → right artery ventricle → [1] → Blood capillaries are exchange vessels. They atrium aorta → → → the exchange of substances between: left A cells and lymph B plasma and lymph C plasma and tissue D lymph aorta lungs → uid atrium and tissue uid [1] (Paper 116 vessels A permit D blood blood circulatory → left by 7 C are from: [1] through vena Arterioles 2) [1] 8 Prevention of coronary heart disease may 11 The diagram shows the heart. involve: A A angioplasty B eating C putting D taking B (Paper 9 This saturated stents more into fats coronary arteries exercise C 2) is seen more a [1] drawing with a light made of a blood smear as microscope. E F H D (a) (i) Name (ii) Give A to the E. [5] letters from the diagram that G indicate (a) (i) Name (ii) State the the cells F, G functions and of H. the oxygenated [3] cells F to (b) H The magnication ×1100. (c) Calculate Show your Some blood separate of the the drawing diameter (c) is of cell was the in a components. centrifuge The to (Paper the why lower rest of vessels contain blood. happens capillaries blood [1] to in blood the owing pressure the that than as it ows lungs. to the blood [4] lungs owing body. is to [3] 3) (a) Copy and complete the table to compare results. arteries, (i) what the blood diagram 12 shows a the [2] spun Explain at H. working. Describe through [3] (b) the Identify the veins and capillaries. cells J that would found in feature be regions arteries veins capillaries K relative and L. Give reasons thickness for your answer. [3] of (ii) Name the uid at thin very thin some none K wall J muscle and describe its role tissue in the body. L [5] elastic some (Paper 10 3) tissue T aking the health of pulse is one way to monitor direction the heart the of heart. to arteries to blood organs veins ow (a) What is (b) Describe during the pulse? what and [2] happens after to the pulse exercise. rate [5] [4] (b) (c) State of two the other heart can ways be in which monitored the health helps 3) it how to the carry structure out its of an artery function. [3] [2] (c) (Paper Explain Describe muscle (Paper how cells substances by are capillaries. provided to [4] 4) 117 10 Diseases 10.1 and immunity Disease Pathogens LEARNING that • Dene and the terms Describe cause disease how pathogens are spread from person that The Outline the against disease body’s humans cause fungi, protoctists transmissible or are disease. transmitted, bacteria and diseases from one and Most of worms. because person viruses. the organisms The the to Other diseases that pathogens another. They they are are also infectious diseases. to person • are in can called be organisms disease pathogens pathogen transmissible cause passed, • are OUTCOMES table shows different ways in which diseases are transmitted. defences method examples of of description diseases transmission pathogens are in tiny droplets inuenza, of through the liquid from the airways and air tuberculosis, lungs of infected people (see common photo people not preparing wash contaminated are food human not their food hands; cooked do foods properly; cholera, and drink water direct contact faeces supplies; insect uninfected people people, infected people the e.g. droplets her of nose she is water and using a are bodies touch or items, have of an that athlete’s foot used feed infected malaria, dengue vectors and then feed on an fever person handkerchief, containing mouth transfer mosquitoes, blood uninfected though their infected person Even ies on insects, typhoid contaminate pathogens on cold opposite) pathogens entering the blood from air and from person an enters infected the blood of HIV/AIDS, may be inhaled by others. body uids an uninfected person, an unsterilised e.g. in hepatitis between drug pathogens sexual activity person blood, Defences We have prevents three These houseies may have picked up third their and bodies human them 118 to while wastes uncooked feeding and are meat. on bacteria now rubbish transferring that line pathogens. on different pathogens pathogens The against to break pass semen shared addicts from sexual or infected HIV/AIDS, partner in specic vaginal uid (NSU), non- urethritis chlamydia disease lines entering of defence the through produces needle body; the antibodies rst that against the line disease. second and defend line enters us The rst destroys the against line any blood. specic Barriers to infection STUD Y The defences chemical we have against entry of pathogens are mechanical barriers. Y ou Mechanical The • The dead barriers: outer layers of the skin form a barrier to entry (see T opic in the nose trap larger particles that you breathe are The • Topic Cells that small from The If dust is a Blood White enter and The are is and and know diseas es show n in How ever , you in the acid that kills pathogens in up (trachea and bronchi) microorganisms. to swallowed the and throat any by The cilia make mucus (see pathogens are mucus is Topic moved easier me th ods food that it you fo r traps of may learn the tran smis sion learn each to an exam ple one. away 11.3). destroyed by acid. get second through line of these barriers to enter the blood, then defence. defences blood the cells body’s viruses into process white during airways particles pathogens there hydrochloric if the lungs mucus any makes 7.7). line the stomach to barriers: stomach (see the tran smitt ed ways nd • have of in. table. Chemical no t 14.8) the hairs do exam ples that • TIP and of a line or vacuoles of the cells infection which by defence blood. where phagocytosis blood an form tissues they is against are digested described produce pathogens any Phagocytes in and T opic antibodies. they produce pathogens engulf that bacteria destroyed. 9.7. Lymphocytes When activated antibodies which are All proteins that have a variety of effects, such as stopping outdoor activities involve some risk of pathogens infection. moving engulf through them. antibodies the body Vaccination and give and is a making way long-term to it easier make protection for phagocytes lymphocytes against to produce certain KEY POINTS diseases. 1 A pathogen causing SUMMARY Copy and complete the Pathogens from following: one through Pathogens are that cause disease. Human diseases by bacteria, and . The airways have that make to trap kills . any pathogens form in The pathogens stomach that the a . barrier lining enter the Dead to cells makes on the Explain why you always b never c always d use e never wash share and your hands towel your surface of the 3 The are pathogens. before with hands handling skin and of Explain how dog the and vectors in the barriers nose to pathogens. Mucus in acid the in lick climber in airways stomach and are someone after when your the going to the barriers. toilet Phagocytes are white blood sneezing face that digest engulf them; antibodies 3 hairs mechanical cells a food animal food 5 handkerchief let by mosquitoes). chemical a droplets, in should: a wash in contact, which 4 a air transmitted another body entry 2 be to cells (e.g. people can host the direct water when disease- are by caused a QUESTIONS 2 1 is organism. the photograph is at risk of to pathogens lymphocytes attack and make pathogens infection. that enter the blood. 119 10.2 Defence tnemelppuS If LEARNING pathogens Explain has that each antigens, own specic pathogen each with Explain that specic is their provided antibodies shapes that to have by the our help the blood mechanical and chemical may and destroy in order antibodies to engulf defences, nd and produced by engulf them. Many are the shapes of these have are chemicals made lymphocytes respond the on Describe how antigens are help lymphocytes. the of by on their protein. making surface of surface When you antibodies, the called antigens. catch which a disease can ‘lock your on’ to pathogens. They active cause for Some This STUD Y • TIP no t becom e be tw een is a all begin Unit. helps Bacteria prod uce secre ted help are ‘anti-’ antibody molecules attack • such as group stick together to nd agella can them in a and to to group. engulf that This much them. that the to and blood. combine them move and stop Each have pro te ins that destro y If Antito xins that type shapes. a mak e a is walls. kill bacteria This causing the you of The 3 shape have that an and and healthy antigens diphtheria with cells the by cell the ‘punching’ to burst. its own walls so on bind receptors on ts a If again, to toxins through enters by you Lymphocytes week strain will are or which against antigen. have each The specic type of antibody antigen has a shape as the common symptoms. two you of the virus not get the responsible for will that same this You be cold, will back causes you then to the are be your to You will activated ill for feel normal, common symptoms. and will begin cold not be during an response virus are large 4 lymphocytes born with number of a very different lymphocytes are activated and types 5 divide active secrete of lymphocytes. lymphocytes antibodies These to 6 to antibodies virus are different the specic antigens surfaces of of bacteria, particles throughout particles bind cells the body viruses and other throughout pathogens. body pathogen When invades, lymphocytes antibodies person 10.2.1 so to virus the are antigen. such of antigens made the the variety a the are around infection, have within self. has that specific inhaled spread the moving. release holes water You particles virus them harmless. directly weakens pathogen antibodies complementary while better harm less. 2 through Antitoxins immune Figure it that ill. measles makes bacteria. tetanus into making use agella these cause antibodies and they the destroy substances) of them which attach those antibodies cells osmosis lym phoc ytes antib odies Some their lym phoc ytes to have (poisonous special invades particles pathogens. in antig en are by path ogen s. toxins which wo rd s antib odies . Antib odies that to phagocytes neutralising with chem ical a conf used the An stim ulates to in phagocytes Antibodies toxins this bacteria bacteria body. that ways immunity • Do several pathogens easier Dene 120 That antibodies • 1 However , pathogens. antigens destroy • need pathogens There • in shapes complementary of phagocytes phagocytes All • through disease OUTCOMES then • get against Active immunity – the body’s response to a measles infection. help recover divide to of same some respond make more the the a type. and cells of these lymphocytes become bigger and ll many ribosomes lymphocytes which are attached to a very extensive network of endoplasmic secreted into antigens and reticulum. The antibody molecules are blood and on release recognise bacteria specific lymph antibodies to be the distributed specic Other throughout antigens lymphocytes on are the the body. The pathogens activated to antibodies that have ‘lock invaded patrol the body infected cell they on’ the looking to body. for antibodies infected cells. When they nd an destroy it to stop attach to it antigens on bacteria molecules producing is that much The it more pathogens. destroys of our the body’s defence response to the The HIV lymphocytes against rst reason infectious infection is is such that are diseases very slow. a serious infection responsible (see This Topic is why for 16.14). you have phagocytes fallen is ill. much The response faster; so fast to the that second you are infection unlikely to by the have same any pathogen attracted bacteria symptoms. engulf This process of def en ce again st th e pa thog en by small a ntibo dy is catching a gain type this During an called active transmissible of immunity . disease an d Becoming being ill is a immune na tur a l enzymes a f ter way to bacteria within immu nity. immune response, many lymphocytes of the specic types Many of these cells develop into antibody-producing cells, do not. These other cells remain in the blood and the 10.2.2 circulating respond throughout whenever there the same antigens. the same way response to produced body antibodies. faster and are far The store in the more cells do more body , so to any These invasion not the next with a same memory of a ability cells of the infection easier secrete for ingest bacteria and destroy phagocytes them. in immune lymphocytes is it with antigen each pathogen to make which pathogen During these time the subsequent memory the brain. more that are by have in and lymphocytes response much body . memories antigens, remain the another Memory we specic to there that is Lymphocytes that lymphatic to system digested vacuoles but antibodies some are food are Figure produced. and them vacuoles contain production are towards are invades produce the therefore the right much greater . KEY 1 POINTS Antibodies ‘lock onto’ Vaccination antigens It is This possible is done to by promote injecting active a immunity vaccine that without contains having live to be ill. pathogens, or antigens taken from the surface of pathogens. Each pathogen stimulates immunity to a specic disease, such as and mumps. In some cases, the vaccine provides a vaccines. specic strain Vaccination is of an that disease articial as way is to the gain case with active which specic Explain 3 Active what is antigen active meant 4 by: a Memory b antibody c a immunity Outline how e memory someone transmissible b Explain Describe the rst shapes is a pathogen defence by antibody why how becomes naturally immune to a and response. body . remain lymph in after the response to an provide much faster to and greater subsequent infections. vaccination second the cells response disease. the in cells is a form of active immunity. 5 3 the antitoxin a 2 t immunity immune d own specic QUESTIONS blood a its have antibodies. production 1 has inuenza immunity. against SUMMARY which protection of against the measles, shapes rubella to pathogens. Each antigens vaccine of dead 2 pathogens leading destruction response to an antigen differs from Active after immunity an is infection pathogen or by gained by a vaccination. 121 tnemelppuS Many 10.3 Aspects tnemelppuS So LEARNING far we Dene • Explain passive during During immunity an stimulate that passive a short-term using another an defence immune the passive immunity importance of the to Type how a immune 1 to of immunity pathogen response follows that and vaccination. enters the body antigens of which involving the production secrete antibodies and of others many which cells. immunity protection is required in a hurry, then antibodies may be given by breast- This provides only temporary immunity, but should be sufcient give system leads Antibodies giving diabetes the symptoms of Type 1 a TIP not cross to lym phocyt es the the later milk . the antib odies mothe r . It baby imm une develo ped and to fe tus and the so is babies can which placenta against will baby’s rst are cause vaccination them. much immunity way and are diseases have body The safer usually deaths lasts is passive present that immunity treats the immunity than active immune of until against immunity are at wounds. as soon immunity are in in breast the against. milk, so environment This mother’s is also antibodies to these time gained without immunity. tetanus children. the is as The Amongst and they other measles, protection when exposure both gained should from receive their diseases. used when In tetanus people these cases, possible that can to bacteria are involved health workers neutralise cause entering muscle the the in will toxins body nasty accidents inject through tetanus produced by open antibodies these paralysis. venom from snakes and other animals, such as spiders and has acts far too quickly for active immunity to be of any use. own People can is of until The its risk as bacteria wait system before the destroys of scorpions, lym phocyt es this in ‘borr ow ’ from has in placen ta T he baby the mother as diseases, and breast his/her antigens, Passive pass across protection temporary passive mothe r ’s gained diabetes to T he pass baby which foreign STUD Y Immunity and only treatment protection. malfunction and Outline the type that of to or the or babies Describe do some memory injection. • immunity, infection from If • the an person Explain fed active of against antibodies Passive • at course immunity become disease the infection lymphocytes, is looked immunity OUTCOMES occurs • have of produ ce who injection of have been antivenom bitten by quickly. the venomous Antivenom animals contains need an antibodies to the antib odies . molecules these prompts the of an blood, people No in are at risk cells immunity is is in Sometimes are – of one many the antibodies infectious 122 advantages most to of important protect diseases. the is baby and made being the body but of by in it they the is collect horses to and to the from sheep. This collected in areas from where animals. instantaneous. antigens are immunity, available venom or hospitals venomous passive are into antibodies available bitten produced arrival active the and companies quantities response are the Malfunction There of Specialist small short-term, enter between there inject immune memory wait venom. and processed antibodies as the animals be so As this soon used. production type as the There of is no antibodies immunity. of the immune immune system does system not work perfectly. When this breast-feeding happens it prompts an detects our own antigens as something foreign and this providing immune response. As a result tissues mistake. against and destroys healthy by the immune system attacks are of collectively these and T ype 1 1 immune known diseases: Type the as system cause autoimmune examples are a variety diseases. rheumatoid arthritis, of diseases There are multiple tnemelppuS Malfunctions that many of sclerosis diabetes. diabetes This type and destroys happens of diabetes the rapidly is cells and caused of the often when the pancreas before immune that the age make of system insulin. attacks This usually 20. Milking Insulin helps to control the concentration of glucose in the The It is made in response to an increase in the glucose the concentration venom blood usually while a meal is being absorbed. Insulin liver This needed The • cells loss – due lowers tiredness One to of – to store glucose is release Type cells 1 use glucose not stored energy in diabetes protein as glycogen for times (see when Topic it to the its due provide increased water to antibodies will bites of this snake. antigen to give protection to species of against snake. respiration. are: and fat instead of glucose as sources of concentration of glucose in the blood of glycogen between diabetes is that can be converted to glucose meals. the presence of glucose in the urine. with diabetes are treated with regular injections of people drug is manufactured using techniques of genetic Topic diabetics 20.4) can SUMMARY What is and many control their different blood types glucose are with programmable insulin. diabetes pumps into to body use deliver fat insulin through a tube engineering known 2 an 14.7). continuously 1 dangerous be Many (see a as potential lack energy indicator People The from used energy thirst to muscles that symptoms that • by weight of • and means be stimulates the the will in produce the venom blood. available so concentrations as a catheter. that efciently. QUESTIONS meant a passive a Use b Explain an by the immunity example why b to your following Type explain terms? 1 the example is diabetes advantages only a of passive short-term immunity . form of immunity. 3 a Explain Type 1 the cause and describe the symptoms of diabetes. Figure b Suggest why insulin has to be injected or delivered 10.3.1 Human cells catheter KEY 1 not taken orally (by made mouth). genetically by make this modied human to protein. POINTS Passive immunity against another 2 and insulin by No is pathogens a short-term using defence antibodies 3 from milk. individual. memory immunity. cells are Antibodies its produced in passive 4 These mother T ype cross 1 release protect has had diabetes destroying the cells insulin is in to placenta a baby or the against been caused and by in the the blood against. immune that breast diseases vaccinated pancreas control are system make and glucose. 123 10.4 Controlling of • Explain good food spread of tnemelppuS Explain in in Personal hygiene infectious diseases. hygiene, and proper • sewage preventing the role controlling important in preventing the spread of some • of all urinate Hair ages or should should defecate be wash and washed also with their hands before after handling shampoos to going or to the eating prevent toilet food. dandruff and headlice. of the People to disease the is of preparation, disposal treatment • importance personal waste infection OUTCOMES the hygienic spread disease Preventing LEARNING the vaccination spread • Everyone • Dental should wash themselves frequently, especially in hot weather . of hygiene is most important in ghting dental caries disease (see • Topic Cuts and applied bruises to Hygienic • Food • Kitchen • Food as • should Water is important the hands spread that with of everyone soap and learns water to to Proper • Household • be keep ies cleaned plasters away. with thoroughly going to disinfectants make sure to any kill bacteria. bacteria, such be to be eaten cold should be kept separate meat. and/or water drinking purication should tablets if be it boiled comes or from contaminated. attract Toilet often by found bacteria, to be such • safe to eat if it a buried and may houses health in into and covered bins businesses hazard. properly tips ies also put and collected at contain should regulated where which It it is not spread harmful should be landll buried disease. sites. disposed Putting carefully The chemicals be recycled, means efuent that it from cause pollution. treatment is a serious drainage wastes pathogens pipes are works health to broken (see that a down Topic cause hazard sewage by if it is not treatment disposed properly works. microorganisms in sewage 21.8). typhoid and cholera are transmitted as faeces and transmitted is contaminated thoroughly. from not be weekly. rubbish rats tips through is is or waste Human The it onto treatment is should e.g. collected through • waste so Sewage 124 and disposal correctly rubbish cooked is might Garbage will It antiseptic killed. cooking intervals, garbage Salmonella. to especially waste incinerated meat an disease. regular contaminated cooked adding that with wash prevent • Chicken should that for by washed preparation are food, used be covered be food raw sources their be surfaces Cooked should wounds. food should sterilised It open Salmonella, from • 7.6). with raw sewage. to people who drink food or water • Thorough and sewage cholera so treatment these breaks diseases are the transmission unknown in of typhoid countries with proper sanitation. tnemelppuS The role of Vaccination protection children and Many e.g. it of the was programmes offered are were vaccination by these last declared interrupted. against for diseases case of the important are ill now in still of in polio exists in the used and rare of citizens. that Americas transmission part their health very the disease to diseases much polio that But an governments vaccinated responsible are many be and very common deaths. parts was in had been other Infants to many health 1991, of the and in world, 1994 successfully regions of the world Household and could be introduced into the Americas by travellers. In in there were countries can follow whole 93 because are small transmit people into vaccines DID of campaign online to for vaccination give active coming Careful all with 2015); vaccines, around infectious into them people infected in neighbouring and the is used in immunity they Kenya. polio to bins overowing from substance health and be as many enters to SUMMARY a health hazard. and can neighbourhood HIV , For some Ebola disease will limited who dengue not identies be diseases and Mass may there or have are no fever . as 100 million different lymphocytes that the destroy body, there will be a lymphocyte with the against teach it is Quetta, Pakistan right 1 important children POINTS The spread to wash to: waste into is personal their food hands covered of transmissible prevented hygiene, preparation, waste food in it. QUESTIONS why polio 2014. diseases Suggest put becoming protected the workers spread ways. KEY b kept before the in a be You Vaccination 1 should collected KNOW? may specicity and everyone. be with immunity their two can contact by and people. are in eradicate but have surveillance diseases examples to more Somalia covered ‘polioeradication’. of them with Africa, to people contact (as Pakistan West respond disease. have the attempt vaccinating YOU There not most the by do in of programmes chances who stopped come as of searching schemes the polio parts progress by people of Syria, eradication vaccination Some in the world During cases and garbage 2013, disposal by good hygienic proper and sewage bins c connect d cook toilets to the main drainage system 2 chicken Vaccination tnemelppuS used 2 The Americas children were declared throughout the free of Americas polio in receive 1994. polio Why do Why is offered it important by their that everyone country’s health receives service? the to prevent transmissible the are spread of diseases. vaccinations? 3 3 programmes thoroughly vaccinations Many diseases effectively by vaccination are controlled mass of children. 125 tnemelppuS treatment. PRACTICE 1 A QUESTIONS pathogen A feeds is on an organism dead B lives in an C lives inside and decaying organism 6 that: and A organisms causes During host organism harm make all lymphocytes spreads disease organisms specic phagocytes divide antibodies disease divide to produce cells that without C D response: and to make causing immune lymphocytes B a an from infected antibodies phagocytes engulf and completely digest to bacteria uninfected people D (Paper 1) specic that 2 Which is a transmissible cholera B coronary B rickets D scurvy 7 heart make Which Passive [1] immunity A being bitten B being treated barrier to cholera of B skin C stomach infection is most effective D phagocytosis is gained by: a venomous snake antibodies to the injecting snake The in a quantity of antivenom snake with venom antibodies horse 2) [1] second the rst A [1] immune measles invasion the response people long-term transmissible is virus many much concentration measles gives small to an invasion acid 1) hand venom spider D by A snake with a produced 8 against a by injecting bacteria? mucus Which to C (Paper 4 cells [1] A (Paper produce disease 1) against to 2) venom 3 divide antibodies disease? (Paper A (Paper lymphocytes [1] remains months faster of antibodies high after the because: from the specic rst to response protection B lymphocytes respond C lymphocytes specic faster with age diseases? to other viruses washing B garbage C sewage D vaccination respond as well memory cells collection D are present in the blood and treatment lymph (Paper (Paper 1) 9 5 An antigen 2) [1] [1] is: Some that A a disease-causing B a molecule and organism produced by a (a) lymphocyte microorganisms, cause cause State cholera, such enter as the the body bacteria in our food disease. the term given to a disease-causing organism. C any substance that stimulates an [1] immune (b) response State two ways contaminated D a which food can become microorganisms. [2] pathogen (c) (Paper 2) Explain how the stomach provides a [1] defence (d) (e) against microorganisms. Microorganisms may Explain body in the Some and how (Paper diseases water. 3) the enter the prevents [2] blood. their spread blood. infectious 126 in with [4] are State transmitted four diseases other can be in ways food in which transmitted. [4] 10 (a) Explain the importance maintaining (i) good personal of the following in 12 The diagram and health: an shows antibody four different antigens molecule. hygiene Y W (ii) sewage (iii) proper treatment Z (b) Rubella by a is virus. against 11 A disposal transmissible Many rubella. provides (Paper a waste disease children Explain protection [6] are how against X caused vaccinated vaccination disease. [3] 3) child received measles at booster at four a eight antibodies to rst vaccination months of months. measles is age The against and then (a) a concentration shown in the The the of graph. (i) Which (ii) Explain doolb There has antibody forms a complex with one of antigens. is no been one? [1] your vaccine for vaccinated eht including measles, answer. [1] chicken against tetanus pox. several and A child diseases rubella. ni noitartnecnoc The child catches symptoms (b) Use of the ydobitna explain many (c) 3 4 5 6 7 8 9 10 the it is diseases, Explain such how eradicate a pox and has the disease. information why disease, 0 chicken in the possible but as still be chicken be ill to immune with to another pox. vaccinations disease diagram to from [4] can a be used to country. [3] months (d) Suggest must (a) Explain why no antibodies were present blood for the rst vaccination to be against carried out diseases even if in there the why continue week. are no cases of the disease for many [3] years. (b) The response vaccine is to the different. the graph the booster to two Use describe infections the how of information the response (Paper in eight months differs 4) to 13 at (a) The lymphatic response to the rst injection at and Describe why the response to the the is different to the and response to The injection. Suggest why further boosters of how may be given. (i) lymphatic (ii) lymph nodes [4] system consists lymphocytes of and the immune antibodies. system this us against infection by bacterial [2] pathogens. (Paper of [4] defends vaccine functions immune Explain (d) lymphatic the phagocytes, rst of second (b) injection consists nodes. [4] vessels, Explain lymph four months. (c) system from vessels the [3] the [5] 4) (Paper 4) 127 11 Gas exchange 11.1 The in humans gas exchange system Structure LEARNING • Identify name on the bronchi, lungs, • diagrams larynx, associated capillaries the need We breathe to breathe air of The lungs form The lungs are surrounded and functions in We The the thorax the volume part into our of spongy and from of our lungs the gas organs protected is a the the intercostal enters larynx lungs to in get order rid of exchange found by sheet of the inside ribs brous abdomen. lungs to which the the enter Its move to get carbon oxygen. dioxide. system and the chest the sternum tissue and movement air exchange The lungs which appear tubes It throat or to which through deep nose then the lung. takes between during mouth each bronchioles, gas muscles especially (voice-box). connects healthy air of (thorax) muscle up and and are (breastbone). that down separates when you breathe out changes and in. trachea Air of system the breathing, X -ray out diaphragm The An exchange alveoli, ribs, muscles cartilage gas trachea, diaphragm, the the and bronchioles, intercostal State of OUTCOMES and the lungs. It in move air through trachea branches continue tiny ribs passes enters These end the the ribs during the throat breathing. to sacs (windpipe), to divide called form to two form alveoli. It to the which bronchi many is small here that place. which air moves are often called airways. black. nasal lar ynx (voice box) C -shaped cartilage trachea (windpipe) intercostal muscle right left bronchus left lung lung epiglottis (cut open) lar ynx bronchioles trachea rib oesophagus Figure 11.1.1 Entry and of air into the nose rib trachea. heart diaphragm Figure 128 11.1.2 The gas exchange system. tnemelppuS The larynx make This to sounds. is down You because cover The contains the your the cannot when you opening trachea trachea is vocal kept to (see cords. breathe by a larynx. page open and swallow, your When air passes swallow ap at called This stops over the the any these same time. epiglottis food trachea you from bronchiole moves going 82). C -shaped rings of cartilage. The ‘arms’ of left the C are joined by prevents the pressure decreases. Deeper There is surface trachea into a very area diffusion). capillaries muscle the back collapsing of as the you trachea. breathe The in lung cartilage when the air lungs number diffusion Each for the large for from at alveolus efcient of (see is gas alveoli page in 28 surrounded exchange the to remind by into lungs a to yourself network and give out of of a huge about blood the blood. bronchiole The alveoli short have distance thin for walls made diffusion. of They a are single moist layer so of cells, oxygen so there dissolves in is a alveoli (air capillar y watery uid before diffusing through the walls into the network blood. Figure SUMMARY sacs) this 11.1.3 Describe the route taken by inspired air (air we breathe the nasal cavity to the alveoli in the The lung. diagram shows the human TIP a simpl e lungs. of 2 a in) Draw from of QUESTIONS STUD Y 1 Structure breathing system: the gas syst em some diag ram exchan ge and no te s label to the A explai ning B of E C the By F are the this Add func tions differ ent doin g it. labels parts. you anno tatin g your diag ram . D G KEY a Name structures A to 1 G. POINTS The the b Match parts A to G with these inspired larynx, sheet ii one of muscle forming the oor of the these enters each contains iv exible v where the vocal Cartilage kept open by rings of slippery vii an of gases takes made of the trachea passes spongy Gas exchange air blood tissue it. occurs between place membranes organ air cartilage the vi alveoli. cords 3 exchange the keeps when through tube to lung open iii down bronchi, thorax 2 of passes descriptions: bronchioles i air trachea, and found in the chest in in the the alveoli and the surrounding capillaries. 129 11.2 Gas exchange Breathing LEARNING Carbon • Compare the composition and expired the dioxide features exchange of if dioxide it is builds a up waste in gas made in respiration. can become breathe out in order to get rid of the carbon dioxide. gas surfaces composition • Describe It cells. air We • List carbon of toxic inspired out OUTCOMES gas exchange at the gas inspired air / % expired air alveolus (breathing oxygen carbon dioxide page 28 to 16 0.04 4 78 78 abou t conc vapour variable saturated remin d The your self and out) TIP water See (breathing 21 nitrogen STUD Y in) table shows that we breathe out more carbon dioxide than we diffus ion entrat breathe in. We and air that breathe in more oxygen than the air we breathe out, ion the we breathe out has a lot more water vapour. grad ients . The following more carbon practical demonstration conrms that we breathe out dioxide. PRACTICAL Carbon mouthpiece limewater 1 Set 2 Then up the apparatus breathe gently as in you breathe in • When you breathe out • The limewater more limewater The carbon turns limewater in A and the will Figure of the comes air expired go in air air 11.2.1. mouthpiece in goes rst also expired in out air the in and shown cloudy dioxide through through B, cloudy in if times. A. B. showing than several that inspired you there is air. breathe through 11.2.1 apparatus long concentration Gas STUD Y Gas alveo li have We and walls cells , but have anim al can say that capilla ries mad e no t remem ber cells of exchange enough, carbon showing dioxide in there is a lower atmospheric (inspired) air. surfaces TIP Bewa re! cell only cell of exchange a human, exchange oxygen and as in the gills common carbon of a that sh and adapt alveoli them for (air sacs) efcient dioxide: • a very • moist • a large surface area for the diffusion of gases surfaces so that gases can dissolve before diffusion plan t walls do such features walls thin surface (only one cell thick in each alveolus) so the gases do , not cells of surfaces, have of have to diffuse very far no t. • a good and blood lots of supply carbon concentration 130 inspired When the – in • • Figure dioxide so that dioxide is gradients lots of oxygen supplied for these is quickly. gases removed This quickly maintains the • ventilation is of changed; between Gas the this air in lungs helps the exchange When inspired contains a alveolus. through lot It the diffusing at of oxygen. capillary and the diffuses through the that the gas in air in the air passages concentration the gradients blood. alveolus in) air reaches Oxygen into cells, the the the the dissolves through wall two that maintain alveoli (breathed then ensures wall blood. distance alveoli in the of the (air water very it lining alveolus Although is sacs) this each SUMMARY 1 involves List four alveoli small. them Each alveolus has a network of capillaries around it. combine oxygen from with to the alveolus diffuse haemoglobin. the body The into blood the cells is wall ver y of can then cells the film inside of of moisture the carbon O O O adapt exchange transport this 2 Look on at the apparatus used in experiment: the cells gauze making dioxide O O O O the that alveolus respiring using oxygen O efcient cricket cells of lungs gases. this alveolus for the and thin respiring O blood tissues. thin the red features of Oxygen of molecules QUESTIONS and O O O O O O O O O O lime O blood carries oxygen blood carries carbon water dioxide A from the Figure the lungs to from the cells to the B lungs cells 11.2.2 Gas exchange at an alveolus. After an hour the tubes were examined. There is a lot of carbon dioxide in the capillary. in the blood It has been carried a there from the respiring tissues plasma. It diffuses in What result would you the expect? opposite into the Alveoli direction, space are through inside the surrounded by the capillary alveolus. elastic From tissue. wall here This across it is the alveolar breathed stretches when wall b Explain your c Explain why answer. out. you tube B is breathe included. in and recoils when you breathe out to help remove air from the lungs. 3 The air we breathe out is saturated with water vapour that Give of evaporated from the moist walls of the an the When to There is a you cold droplets POINTS b 1 more carbon dioxide, less oxygen and more water Expired expired air than in inspired Gas area exchange and a surfaces good blood are Alveoli are well adapted moist, thin, have a large surface supply. for and are gas surrounded on form. air turns cloudy c Alveoli thin, exchange as they have inspired by many (air have quicker and air. sacs) a are large have very surface walls with these elastic features out water air . area 3 each vapour than 2 breathe surface, limewater in for following. alveoli. a KEY explanation has bres. capillaries. 131 11.3 Breathing tnemelppuS When LEARNING ribs • you Describe how pressure changes ventilation of volume your and lead the outwards. Explain cells, the dust role mucus protecting system it lungs to so inside lungs of and the from This diaphragm they the moves • breathe feels as if the lungs are expanding to push your OUTCOMES in is and to through so. When ribcage occupy lungs not a move larger below your the volume. the nose you chest This pressure and/or breathe of in, cavity movements and decreases pull the atmospheric on air air of the pressure so that air mouth. goblet cilia gas in When exchange pathogens relax and you and pressure particles is forced alone This when in out, causes the out. (try is breathe this lungs You ne you for quiet exercise diaphragm chest cavity increases can breathing the the do this without to the by moving but intercostal intercostal decrease above just breathing, and to in atmospheric movement your The pressure your air so air diaphragm ribs). during muscles of muscles volume. deep breathing contract to and move the ribs. PRACTICAL (Intercostal the A model of the external Obtain a model like the one diagram. The rubber the that are ribs.) closer There to the are two layers skin, and the of these: that are deeper into the chest wall (see Figure internal 11.3.3). diaphragm is made of tough brous tissue in the centre and sheet strong represents muscles the in The the between chest muscles 1 means muscles that connect to the backbone, the lower ribs and the diaphragm. sternum glass (breastbone). tube passage bell of air jar muscles contract balloon ribs lungs move up and out the volume the chest of ribcage rubber sheet cavity increases diaphragm diaphragm contracts and 2 Pull and the rubber then sheet push it front up. Figure 3 Do this watch a few what times moves down down view of chest side view of chest 11.3.1 and happens to the balloons. Inspiration This model shows • movement of the in the the the volume thorax bell jar . As the and the inate lungs increase in pressure the 132 in The external in as the intercostal muscles contract and the internal a result space relax, raising the ribs upwards and outwards. • At the • Both same time, the diaphragm contracts and attens. by the downwards, and muscles pressure diaphragm moves volume balloons. and represented contracts in) diaphragm intercostals changes (breathing how of an decrease around • of these pressure Since they actions inside atmospheric inate. increase the thorax pressure is the to volume inside the thorax, causing decrease greater, air moves into the lungs and (breathing passage of tnemelppuS Expiration out) clavicle air trachea external intercostal muscles relax breastbone internal ribs move down intercostal ribs lungs muscles and in ribcage the volume the chest of cavity external diaphragm decreases intercostal muscles relaxes and diaphragm bulges upwards front view Figure • The This • The chest side view of chest 11.3.2 internal muscles • of intercostal muscles contract and the external intercostal relax lowers the muscle pressure ribs downwards in the diaphragm from the organs and inwards. relaxes below, for and it bulges example the up due to liver and stomach, internal and • contraction Both of these of the actions abdominal decrease the volume external intercostal muscles. inside the muscles intercostal muscles thorax, cilia move dust ciliated causing the pressure inside the thorax to particles cells • Elastic recoil Cleaning of the As you by evaporation the air, The the breathe trachea, helps to force air out of the in through water particles bronchi your from and nose, the and air lining. some is warmed Hairs and inside moistened the nose lter goblet cells pathogens. bronchioles are lined with ciliated epithelial Figure 11.3.4 Goblet cells epithelial cells and goblet cells which secrete mucus. Dust particles become trapped in the slimy mucus. The cilia and cells ciliated keep the and lungs pathogens make mucus lungs. air of removing alveoli these cells increase beat free of dust and to pathogens. carry a stream particles and of mucus pathogens up to your which you nose then and throat, removing the swallow. KEY SUMMARY 1 QUESTIONS POINTS Inspiration occur 1 When a person breathes in, describe what happens due volume in: and to and expiration changes pressure of in the thorax. a the intercostal volume inside muscles the b thorax the e ribs the c the diaphragm pressure inside the d the thorax 2 The internal muscles, 2 Look at the model of the chest in the Practical, Which part of the model the lungs ii the and the diaphragm represents: control i intercostal opposite. muscles a intercostal external diaphragm iii the these changes during ribs? ventilation. b Make some criticisms of the model as a way of 3 representing the changes that occur during Goblet which 3 Explain free the from role dust of mucus particles and and cilia in keeping pathogens. cells produce mucus breathing. the air passages traps pathogens beat the to dust in the remove particles air and mucus and cilia from airways. 133 11.4 Rate and depth of breathing Breathing LEARNING At • Investigate and describe exercise rest effects of on rate physical and you probably take between 12 and 16 breaths per minute. the When the and OUTCOMES you exercise this breathing rate changes. exercise depth of breathing tnemelppuS PRACTICAL • Describe of how exercise dioxide the effects increase carbon concentration The You the blood and how effects the rate and exercise on breathing rate can measure your breathing rate by counting the number of this times affects of in depth that you breathe out in a minute. of breathing You could record your results in a table like this: –1 breathing at rate / breaths per min light heavy exercise exercise rest 1 2 3 average • Try • As = doing soon as you breathing rate. • Wait until your • Now try (heavy • Then • You for have 1 minute nished, breathing doing step-ups sit rate as (light exercise). down returns quickly as and to its you count your resting can for value. 3 minutes exercise). count will change Performing step-ups your notice after breathing that doing your rate when breathing you rate have and nished. depth of breathing exercise. step-ups. • Repeat this twice and calculate averages. plastic container breathe out The here are rate and working They also depth hard, of breathing your produce muscles more carbon increase need with more dioxide in exercise. oxygen for When they respiration. respiration. rubber tubing Increasing blood and continue a trough Figure 11.4.1 This apparatus used to capacity can measure (see top of vital heart 134 to rid respire Your of and of quite oxygen pulse beating depth more fast rate to of breathing carbon fast after and they remains deliver dioxide exercise still high plenty gets the nishes. have carbon after of more from They to this extra oxygen and have their carbon dioxide the need to because your into Muscles still dioxide exercise blood oxygen blood. be your muscles next gain page). is rate gets supply removed. be your good the removed. so they oxygen delivered muscles rate of respiration rate in and depth more to STUD Y quickly TIP of exercise muscles breathing increases See increases carbon page your self removed muscles 11.4.2 The effect of exercising on to diffus ion. quickly Com pare resu lts with you go t inve stigat ing (pag is adult their out can vital after 105) take in about capacity breathing in – 5 the as litres of air maximum much air as in their volume possible. deepest of air At breath. that rest, is This on breathed about half a effect s the the air is breathed in and out. During exercise approximately four litres of extra air can be taken in during a deep and body add tnemelppuS You don’t happens. exercise? you So exercise dioxide about what the more your makes brain which become Y ou some (see has lowers you a tissues respire pH They – breathe special the acidic). breathing part more in the may most faster for the and time deeper controlling quickly tissues also of and and make page brain gluc ose when of the more blood blood acid (i.e. which When STUDY they does TIP the this rise in carbon dioxide and the lowering of are reaching it. The brain sends nerve impulses to and to the increase dioxide turn and in this through more the has intercostal the rate rapidly, blood the them. muscles! muscles so they contract and depth of breathing. By and same This is you this effect an lower raises on the the example the concentration blood tissues of pH back because homeostasis the hard faster require work. the extra and and glucose and breathing of carbon to normal. the – organs the need deeper the the the oxygen to 14 . carbon T hey further and Unit 140). detects diaphragm in you doing pH able abou t just breathing. make the lactic it T hey Your and be more tempe ratu re Remember same hear t will breathing think The ise includ ing breath. blood of mar exerci se a body Control of rate litre to half Sum mus cles, lung s. of . breathing the An e when puls e tnemelppuS of the breathing. resu lts Depth remin d abou t from more your Figure 28 dioxide blood see page to taken In have away. answer ows the 166. in on wastes Start this changes the their that muscles any topic with occur during exercise. 1 When a 2 QUESTIONS you the exercise, rate Describe of what describe breathing happens what b to the happens the to: depth of concentration breathing of carbon KEY dioxide 1 in the blood when you POINTS Exercise rate tnemelppuS 3 a Explain how the brain monitors and controls the rate when you and depth Explain what happens An increase to the following when you the intercostal iii the heart the breathing. in the muscles ii the of carbon exercise: dioxide i both exercise. concentration b of of 2 breathing increases exercise. diaphragm the in brain changes the blood triggers in reaching these breathing. rate 135 tnemelppuS SUMMARY PRACTICE 1 Which QUESTIONS is a pathway that air takes from the tube atmosphere to the gas exchange surface in A tube B the A cloudy cloudy B cloudy no C no change cloudy D no change no lungs? A mouth larynx bronchiole B alveolus mouth nose alveoli C nose trachea bronchus larynx trachea (Paper bronchus trachea bronchiole bronchus What A 1) many lled a conical ask with lime put student water cross the a drawing then to test of a breathed nd out became after features of a gas exchange how The three beneath the long invisible. doing cross into it ask took thick-walled, C area, small surface area, capillaries thin-walled, many the repeated of surface The lime before student minutes it. of large capillaries water few and the thick-walled, [1] student are alveolus B 2 [1] surface? A (Paper 1) alveolus 4 nose change bronchiole bronchiole D change bronchus D large few area, capillaries thin-walled, strenuous surface small surface area, capillaries exercise. Which describes the time taken for the 5 to become invisible in the test after (Paper 1) Which is The cross became invisible in a the function of the cartilage in exercise? the A [1] cross trachea? shorter A cleans the B contracts C increases air as it moves to the lungs time. B The cross become took three times as long to move air into the lungs to resistance to air owing to the invisible. lungs C The cross took twice as long to become D prevents the trachea collapsing invisible. D The (Paper time was the same. (Paper 1) [1] 6 The act 3 The diagram shows apparatus to 2) [1] diaphragm together production of carbon dioxide the intercostal expiration at muscles the end of investigate strenuous the and during exercise. Which of the following during occurs? respiration to see in of insects. tubes A and What would B minutes ve you expect after intercostal setting up the apparatus? muscles diaphragm internal external relax contract relax contract contract relax contract relax moves A contracts down B contracts C relaxes moves up moves down limewater D relaxes moves up limewater (Paper potassium living hydroxide animals solution carbon 136 (absorbs dioxide) air flow 2) [1] 7 The gas photograph exchange shows some cells from the (b) (i) Calculate system. the (ii) (c) changed minute. per of of in same class. so What A is cell X? alveolar B ciliated C goblet D muscle cell 10 The the cell (a) cell (b) cell 2) 50 step- of exercise on the to on that between the two they they investigate boys features would could the the and have make boys of to the keep valid and girls. 3) [2] diagram thorax Name (i) shows from A to the the ribs and muscles of side. C. Describe the (Paper to the [2] State that comparisons (Paper rest in when [2] effect exercise investigation the from decided this the the change breath breathing. students effect girls each ups Describe The percentage of student rate X the volume [3] how structures [1] shown 8 The it percentage passes composition through the lungs of air changes bring as about breathing because: A movements A carbon dioxide and water vapour are C during absorbed from the air inspiration B carbon dioxide is absorbed and and oxygen expiration. [6] excreted (ii) C oxygen is absorbed and carbon Explain how dioxide B the movements excreted you D oxygen (Paper is absorbed and nitrogen excreted 2) air move into Some students investigated the effect Here on are the the rate results and for volume activity each depth one of of of the and lungs. [5] 3) breathing. the students. number breaths breath of of (Paper exercise to [1] out 9 describe cause 11 Look (a) of at the table Describe the student’s taken of results effect of in question exercise on 9. the breathing. [5] 3 / cm rest 20 minute 500 18 750 25 1200 34 (b) 50 Explain why changed (Paper step-ups per the during student’s exercise. breathing [6] 4) minute step-ups per (a) per minute (i) Calculate of each the change breath changed from when 20 to in the the 50 volume student step-ups minute. (ii) [1] Describe volume per the of effect each of exercise breath. on the [2] 137 12 Respiration 12.1 Aerobic Aerobic LEARNING Dene aerobic respiration we the word State that is respiration catalysing cell in State the uses human Investigate oxygen energy by of energy reactions in body is living in the released the uptake respiring of tnemelppuS State the that living petrol, gives off oxygen a lot of is used light up and and carbon heat. organism cells is needs called energy. glucose, A but fuel unlike used to burning very gradually in a series of small, petrol, enzyme- cells In aerobic balanced for break to Respiration down release involves nutrient a number molecules, such of as chemical glucose, energy. respiration oxygen is used in the breakdown of glucose: organisms + → oxygen carbon dioxide + water + energy released chemical Cells equation reactions. in glucose • as cells the • every energy controlled • such ame reactions the in fuel The involves provide enzymes a made. equation Every • burn and dioxide state respiration OUTCOMES When • respiration also respire fats and proteins to provide energy, but you only have aerobic to know about the respiration of glucose, which is a carbohydrate. respiration Using Your the energy body needs following • muscle • cell • absorption • sending • protein energy for many different things. Energy is used in processes: contraction division of nutrients impulses synthesis in along for the gut by active transport nerves making enzymes, some hormones and antibodies • computer generated mitochondrion. made in these Most cell image of the of ATP structures. in Each cells is during is new STUD Y keeping the no t a with C H 6 in proces s for O 12 Most in of lo ts structures like the nucleus temperature constant. Some of the energy place of in + heat. all by Wha t living no t energy cells → to all stay of the alive. time The because balanced cells chemical is: 6CO 2 + 6H 2 O + energy released 2 of the energy you breath e released Cells in that aerobic require a respiration lot of is energy released have For instance, insect ight muscle has many numerous each its located between the muscle bre. The mitochondria own the energy for the muscles to contract during ight. Liver cells do have you of respiration 6O 6 mitochondria. provide enzy me. supply aerobic mitochondria is form of reactio ns, cata lysed when the takes mitochondria. chem ical 138 cell Respi ratio n chem ical cons istin g out body constant equation conf use breath ing. a is Respiration respira tion one and TIP need is membranes long. released Do cell growth about • 0.002 mm making a in and respira tion! cells a of active high the metabolism small transport, and intestine so have have absorb large many mitochondria. glucose numbers and of other The epithelial molecules mitochondria. by tnemelppuS A tnemelppuS PRACTICAL PRACTICAL Investigating the uptake of oxygen by respiring seeds Investigating The apparatus how up quickly oxygen which is in Figure 12.1.1 germinating during seeds aerobic absorbed by is the a respirometer use up respiration soda lime. oxygen. and The and The release it can seeds carbon decrease in measure respiration take and causes the red liquid to move along the capillary tube. of movement can be measured by the scale – the faster of rate of germinating apparatus shown in Figure The 12.1.2 rate of effect the air The pressure the on seeds dioxide, volume temperature the is a more accurate rate respirometer. of respiration, to keep the the quicker apparatus at the a liquid will constant move. Why is it important 1 temperature? Place into 2 1 eye 2 3 4 5 6 7 Set soda Figure the germinating boiling rest of seeds tube. the apparatus 8 protection up is some the as shown. Be very careful lime corrosive 12.1.1 A simple not to it corrosive. is touch the soda lime as respirometer. 3 Close the much plastic clip the and nd coloured out liquid how rises in capillar y tubing the tube capillary tube in 30 minutes. clip eye is This protection soda water lime at corrosive a investigation works on the bath same known temperature one. principle It can number germinating of the previous repeated at temperatures a by seeds changing wire be as gauze the temperature of the coloured water and so compare the rate of water soda Figure 12.1.2 A respirometer for lime respiration investigating the effect of temperature of the seeds. on respiration. KEY SUMMARY 1 1 Copy POINTS QUESTIONS and complete the sentences using these In is words: aerobic broken energy aerobic glucose oxygen in carbon dioxide takes place in all living . A fuel is . It is broken down to release is water and the waste gas . and Respiration When it of These in the reactions structures 2 a presence Write take of place called down we in every call it living equation for Energy Make is a released list of ve during aerobic processes that cell, inside 3 tiny The word aerobic glucose respiration. a Describe b What how a simple equation + the function use respirometer of soda this 4 energy. The lime in the apparatus balanced H O 12 + 6 do the you think will happen to the rate of for or chemical aerobic is: 6O → 6CO + 6H 2 O 2 Respirometers germinating ii increases seeds to if the temperature i can be used to respiration decreases the rate of respiration to under 5 °C → water 2 measure of + 12.1.1? 5 What oxygen in 6 c aerobic works. C Figure for is: respiration. respiration is catalyse cells. dioxide equation 3 the to respiration. carbon b in respiration word involves takes . the water. enzymes reactions place of carbon Also action produced presence forming for 2 respiration glucose release cells dioxide Respiration the to mitochondria oxygen, energy respiration, down different conditions. 50 °C? 139 12.2 Anaerobic Muscles LEARNING Dene anaerobic for in the muscle exercise • word anaerobic State and that exercise equations in carry vigorous energy glucose much out tnemelppuS the is possible balanced for Describe lactic in an is the acid in oxygen release glucose strenuous build-up muscle and during the of to cause for energy in is the this from the get enough happens glucose release absence exercise, aerobic not of of oxygen your to muscles your start to a without little using energy oxygen. from each oxygen. enough respiration how it tissue respires enzyme-catalysed without dioxide oxygen. and to oxygen supply all may the reach energy the the body muscles As water, anaerobically reactions a result but to of the aerobic glucose lactic to acid is release energy. respiration not do broken Most not down of happen to carbon instead: recovery → lactic acid + energy released exercise tissues, respire the to make an electron microscope. beating lactic is alcohol and absent C → H O 12 if Some same in not the bacteria way, heart, release for do not enough also respire example normally energy to keep anaerobically those that we use energy and set is H + OH in respire their anaerobically surroundings, when to make carbon + in dioxide 2CO + + energy released energy released 2 water released alcohol yeast, anaerobically to broken alcohol as supply 5 with compared in such from so the land or of a is no molecule respiration. and form little each aerobic down when lot of ooded oxygen of This energy chemical bond is and glucose is soils available. in because remains energy. anaerobic glucose stored Y ou in can is lactic see alight. –1 energy aerobic respiration fermentation anaerobic Hurdlers 140 build up lactic acid in their muscles. to dioxide: 2C respire completely you muscle would short alcohol saturated respiration acid the in 2 roots less or 6 become not in carbon → Far this properly. acid glucose Plant cardiac as microorganisms, oxygen 6 as yoghurt. Other under such anaerobically heart make cells These vigorous respiration to Muscle Other Yeast cannot When During respiration. respiration of glucose from aerobically. system. yeast debt removed respire chemical need. • to blood anaerobic muscles respiration lungs your respiration During equation glucose by molecule molecule State and enough. anaerobic Anaerobic • and muscles less It aerobic heart quickly Anaerobic anaerobic releases than oxygen your yeast respiration per need to your muscles respiration during brought tnemelppuS State muscles respiration are • oxygen OUTCOMES Your • without respiration by (kJ 16.1 yeast respiration released 1.2 in muscle 0.8 / g glucose) this tnemelppuS Lactic Lactic be acid acid can removed and blood, Our oxygen ‘paid after After to by the build in up after we carry to lactic lactic up acid acid. to blood in the exercise on hard, more The of acid oxygen beat at a the and fast in muscles. They has for is in to to be deeper aerobic removed the rate muscles must muscles debt and debt acid it the it faster oxygen lactic so in oxygen breathing from their cramps, lactic causes respiration the cause of supply continues in and build exercise, order down acid muscles The We aerobic heart lactic up away. break exercise Sprinters builds exercise recovery transport body. vigorous straight vigorous during to debt poison the during back’ respiration slowly from liver. order the often liver. hold their 3 breath of during oxygen after The the 100 get race in metres rid of order enzyme-catalysed aerobic respiration function glucose acid to a is without is partly the to in supply from acid. that That of release oxygen. in end the is oxygen mitochondria. down the Afterwards their reactions broken produced lactic ‘repay occur a race. they need why they most These breathe of the cell deeply this and energy structures anaerobic cytoplasm of 7 dm debt’. During product about not respiration, alcohol partial in do or lactic breakdown. This SUMMARY 1 QUESTIONS a Dene the b Give c Compare term runner breathing anaerobic during examples the of energy aerobic and anaerobic Describe and explain released from anaerobic the in aerobic and her her oxygen debt by training. POINTS a molecule of glucose 1 respiration. Anaerobic chemical differences between the anaerobic respiration. respiration reaction break down in is the cells glucose to energy release released after respiration. that 2 repaying respiration KEY two is deeply (See the energy without using table oxygen. for some gures to use in your answer.) tnemelppuS 2 3 The table below shows the units of lactic acid produced in In anaerobic glucose leg muscles of an athlete during a of / minutes 0 10 20 30 40 50 60 70 80 0 1 7 12 9 6 3 1 1 in units of lactic acid b When a graph using the the lactic Explain why the Suggest why acid muscles the tissue, reach a end of the produced lactic Explain why session of we hard Far more muscles produced less lactic acid Explain how an alcohol, dioxide in yeast energy each is released molecule in aerobic of than in towards respiration. race. carry on breathing heavily after we nish a exercise. The oxygen debt build muscles develops and how it is has up of during produces that 5 acid acid. 4 4 or lactic maximum? anaerobic the to absence plants. glucose d down the forming carbon from c in data. 3 did energy muscle and Draw broken oxygen, plus a is race: release time respiration, the an to lactic hard oxygen be paid acid in exercise debt back by repaid. breathing in extra oxygen. 141 tnemelppuS opposite PRACTICE 1 Which QUESTIONS process does not require energy from 6 The of A equations change respiration? diffusion of oxygen across the alveolar that contraction C passage D synthesis of muscle during (Paper 2 When nerve of to enzyme-catalysed show glucose as reactions. the a overall result the role of glucose Which for the term rst exercise enzyme of respiration wall describes B for occurs in respiration? impulses protein A activator B active C product D substrate molecules 1) site [1] yeast respires without oxygen, the cells produce: (Paper A alcohol B carbon C lactic acid D lactic acid 7 dioxide and After [1] vigorous high. A carbon Which carbon 1) [1] B lactic During aerobic chemical respiration, reactions molecules to is enzymes breakdown be to glucose B produce lactic C produce oxygen D release student’s heart rate reason from for this? anaerobic from anaerobic removed the respiration muscles respiration from the muscles catalyse C nutrient oxygen to: produce a removed from be is required metabolism A not dioxide to acid needs 3 a dioxide needs (Paper exercise, alcohol is and 2) D waste of in lactic products of the liver for acid respiration need to be removed acid (Paper energy 8 The 2) oxygen oxygen (Paper 1) During vigorous without is the exercise, oxygen. release The carbon dioxide B carbon dioxide muscle D much result of oxygen this additional the lungs volume after of exercise. energy and from energy each molecule of A anaerobic B metabolism C removal D respiration from each molecule does respiration in muscle tissue of lactic acid in the liver of carbon of dioxide for muscle tissue to release contraction 2) [1] of (a) Write for Which for glucose 9 1) required water glucose (Paper is respiration (Paper out and aerobic complete the word equation respiration: [1] + 5 the by respires energy little is of A C debt absorbed [1] This 4 [1] not have oxygen → + + mitochondria? [4] A ciliated B liver epithelial cell A to C student muscle nd red the blood student apparatus. cell opened (Paper 2) the of for took After apparatus respiration several each several [1] sealed 142 up rate shown of opposite crickets. cell The D set cell again. readings reading minutes the before from clip the was being spring clip time / 0 5 10 15 20 25 30 35 0 0 0 31 65 95 130 162 minutes position of liquid / droplet mm (a) Explain why crickets wire soda lime carbon gauze (i) a water (ii) the apparatus before The calculate the direction in which the closing diameter 0.8 mm. State was used was left the clip. for ten minutes absorbs dioxide (b) (b) bath Use of the the the capillary results rate of [2] in tube the oxygen is table to uptake coloured 3 in drop will move apparatus. as the Explain crickets your respire in mm per hour. answer. (c) [4] Explain how the investigation (c) Explain why the clip is opened after (d) readings. State one constant 10 Copy factor during that the should be (Paper kept investigation. complete The rst (a) the row table has with been ticks an completed. sisehtnysotohp negyxo a series of catalysed reactions produces carbon noitpmusnoc ✗ / ✓ oxygen of graph athlete short shows who period of enzyme- all The of after rest. 0.0 5 10 15 dioxide time the time 20 / 25 30 35 minutes Describe the change in oxygen (night 3) over the 35 of shown the apparatus in effect respiration of was question of Pinto put 9 was temperature used on the Explain was the clip minutes taken. that [4] closed over and time. the The changes (i) 10 and (ii) 20 to in oxygen between 20 minutes [6] beans. into open. the consumption a water bath After ten position results of are minutes the as 30 minutes. [5] at (Paper with recorded were [5] apparatus 27 °C clip minutes day) determine rate consumption 10 0.5 (c) to for energy place (Paper The oxygen [1] 1.0 recordings 11 cells 1.5 consumption and the exercised animal respiration. 2.0 (b) takes inside aerobic 2.5 0 releases structures out md cells the carry 3 plant nim consists [4] 1– produces in the 3.0 noitaripser feature only if and 4) Name The and a occurs differ 17 °C [1] 3) crosses. at 50 °C. that and would repeated [2] 12 (Paper results was taking at the [3] the 4) the droplet follows. 143 13 Excretion 13.1 Excretion LEARNING OUTCOMES Excretion • Dene • Name the term is the metabolism, and • the Describe in excretory excretory the the removal from the body of the waste products of excretion The organs organs, products role of assimilation the of waste toxic materials substances which are are the and substances removed lungs, liver from and in the excess body kidneys of by (see requirements. the excretory Figure 13.1.1). liver amino Excretory products acids Humans • Dene have two main excretory products. deamination • Carbon dioxide transported of • the to blood page 130). Urea is is the into made in made lungs the the air liver in in in body the blood the from tissues plasma. alveoli excess during and is amino respiration. Here, it diffuses breathed acids. It is It out is out (see carried to lungs the excrete kidneys the plasma where it is ltered out and leaves the carbon body dioxide dissolved Excretion liver is substances processes materials a in vital like the form process carbon of in urine. the dioxide metabolism and urea of would the be body. Without allowed to it, build toxic up makes in in the tissues. These substances would reach a toxic level and and destroy them the tissues. harmless Do kidneys excrete not are 13.1.1 The excretory are egested canal with ‘egestion’. body cells in Substances metabolism. that are Substances have been without eaten being and have digested passed and through absorbed into the the organs. bloodstream. hepatic by salts alimentary Figure ‘excretion’ produced urea that and confuse excreted Fibre is an example. vein Assimilation stomach Assimilation now become means part of that the the cells food or molecules are used by that the have been absorbed cells. liver portal tnemelppuS hepatic vein The liver carries out a number of important functions as part of assimilation: • stores glucose glycogen. blood by This (see removing helps page to it from regulate the the blood and concentration storing of it as glucose in the 166) large intestine • uses amino brinogen, acids to make involved with proteins, blood such as plasma proteins, e.g. clotting small intestine appendix anus rectum • breaks • converts body, Figure 13.1.2 The position portal of the fatty e.g. excess acids under amino and the acids glycerol into fat which skin hepatic vein. • 144 down produces cholesterol from fats (see page 71). is stored around the tnemelppuS Roles The see of liver the carries from liver out Figure over 13.1.2, 200 all different the blood roles from in the the body. digestive As you system STUD Y can TIP ows Deam inat ion to the liver rst before going into the rest of the circulation. breakd own amino acids produced in the alimentary canal by the digestion cannot is are absorbed store broken the down into amino into the acids two blood that parts. it in the small cannot One of use these intestine. and parts so is Your each made of of amin o protein is The acid s body amm onia . molecule into to mak e Urea prod uctio n urea. the excess is a sepa rate proces s. Other it roles enters breaks and of the the liver small down harmful include intestine, hormones that substances, making and have such bile, emulsies as which fat circulated alcohol in and neutralises (see the page 84). blood drugs (see for acid The a page as liver while 178). cells protein gut some acids into digestion amino are built protein make new to excess cells taken amino to the changed acids liver into are and urea urea KEY 1 POINTS Excretion is the removal from liver the amino Figure acids 13.1.3 made This shows what happens to amino acids in the body. that acids are not cannot be required stored for so making the liver breaks proteins. Each down amino amino acid broken down into two by the process of is converted to carbohydrate or deamination. fat and used as carbon acids The other molecule is ammonia (NH ) which chemicals during products dioxide include and urea. The lungs, liver and kidneys One a source excretory combines organs. Carbon of dioxide energy. tissues Excretory are molecule waste molecule 3 is in of metabolism. 2 Amino body is excreted by the lungs. with 3 to in the dioxide kidneys urine (see contains to in form the page nitrogen the 146). is excretory blood where The known part as it of the product is ltered the urea. out amino amino acid group – This and is is carried molecule this is 4 is called deamination because this group is why liver liver breaks down toxins, for example drugs urea acids. excrete from The urea in urine. the The liver breaks down toxins removed. such The makes amino kidneys that 5 process The excess excreted such as alcohol as alcohol and drugs. and 6 The liver uses amino acids to paracetamol. make proteins proteins SUMMARY QUESTIONS 7 Deamination of 1 a Explain and i how then tnemelppuS Distinguish 3 Describe of removed carbon 2 each what from dioxide between these excretory the ii excretion happens during products body: are produced and excess liver is to into as plasma brinogen. is the amino form made such breakdown acids in ammonia, the which urea. urea and egestion. deamination. 145 tnemelppuS carbon 13.2 Kidney The LEARNING Describe kidneys OUTCOMES The • the structure of kidneys • Describe the in role of They also Describe Your control kidneys the internal of the of urinary urea system. and excess the units fat the water at the They that top are and ion of your content of abdominal protected surrounds chemicals STUD Y out TIP of the a body cons ists subst ance s water . becaus e It one pigm ent. plasm a of is the a in yello w in If by the been then the of are in blood urin e. At or the it a As to form tubule the lot cavity just underneath lower ribcage water day and back you the blood a ows water uid of are ltrate. are the ltering these urea, substances depends will much water. have on the water) exercise, as you of or as units forced As the (glucose If produce because you not body’s perhaps they can it and water because is so have been very you taken you hot, produce in sweating, dilute of and at each to the intervals, carries the tubule the bladder through blood with a urine where a shorter low is it released is stored. tube a lot the of kidneys urine. and concentration of the here into it the leaves urethra. waste The chemicals the renal away kidney. renal vein blood away kidneys and ows From called takes from ‘cleaned’ the remove other from the artery brings waste to kidneys the kidneys in the blood urea chemicals blood KNOW? kidney you as and through through and renal YOU blood network known useful the kidneys complex salts, (short conserve and a into blood. during take is the reabsorbed and cold the glucose, into a will urine is less end ureter from has are a million born, decreases but with tubules the age. ureters to the carry urethra out Figure of carries the 13.2.1 ring urine The of closed body urinary system. urine down bladder bladder 146 body. that vein number the blood. backbone, cells enters kidney dehydrated sweating concentrated reabsorb the water kidneys as from Blood each plasma along you diffuse tubules. reabsorbed have body, when the them. kidneys. such blood volume water, a water , are urea Inside kidney passes content. wast e compo und and The yello w Urea is colou rless disso lves wast e disso lved is subst ance s of salts) uid like the molecules, ltrate Urin e is to arteries. called small Each are from kidney renal DID They salts structure transported in are diaphragm. Waste that part excretion the and the up the excretion the of for system kidneys • make the responsible urinary structure stores urine muscle until you keeps the urinate bladder If you cut cortex and the – the kidneys open a a kidney brown pelvis – lengthways, outer a area, white the you can medulla – see a three reddish areas: inner the area, area. medulla cortex medulla pelvis renal artery brings to the renal takes A kidney with A kidney cut part of the ureter attached. vein blood away the blood kidney from kidney ureter one kidney collecting tubule cortex duct Figure 13.2.2 A vertical of Inside which each you the kidney can see section kidney are of (left a kidney hand thousands only with a (right hand side). Detailed view of part side). of tiny tubes microscope. called The kidney function of tubules the medulla, kidney tubules determine is how the cortex. the body The in to lter much water waste the urine the blood is remove excreted. chemicals which and and ows The excess from waste ltering water the is are kidneys chemicals carried out removed down the is stored in the with POINTS The urinary kidneys, structure of the artery in the functions stores ureter in urinary the system right in the left column 2 The internal kidney column. lters kidney urea carries bladder carries renal carries and other waste chemicals out of the blood 3 The vertical A cortex B blood with a high concentration of a Distinguish b What the is urine blood section medulla down to with low of C between the kidneys c Distinguish d Name the a the concentration kidney renal and artery D of not main and excretion nitrogenous where between is the substances found inner of a outer medulla. the it and renal vein E in in the urine of a take substances back into the and the product glucose, quantity the urine the urine. of and control water excrete The ureters bladder excreted by 5 The carry from volume the lost in urea in depends urethra. blood plasma on and urine to the kidneys. and concentration the health e.g. the ureter produced? found materials label: egestion. waste ureter lter blood, urea of the how urine intake much of water which has are an bladder water two of urea 4 3 an kidneys of blood, vein a bladder structure consists and useful Sketch ureters, of urine out 2 consists urethra. cortex renal system QUESTIONS each one cortex, bladder. and Match the from the 1 show ureter . ureter 1 SUMMARY to and in KEY and open pelvis and been lost in sweat during person. exercise and in hot weather. 147 tnemelppuS tnemelppuS Inside 13.3 Kidney tnemelppuS Structure LEARNING Describe the structure of containing Inside Describe the role of the in ltration, removal and excess water and of reabsorption of glucose Each of chemicals these capillaries the ows renal into artery the kidney branches in many the renal times to give arterioles called a supplies blood to a closely packed glomerulus ltration, blood ows out of the glomerulus into another the arteriole. Blood then ows into capillaries around the rest of the and tubule, some waste kidney, of After urea the kidney group tubule tubule tubule arterioles. • kidney a artery. kidney a OUTCOMES Blood • of function which joins to form the renal vein. The kidney tubule itself salts consists of the The of a Bowman’s tubule being glomerulus Figure 13.3.1 is capsule pushed found shows in like inside that the at one the the end. This nger of Bowman’s tubule forms a is a formed rubber by the end glove. capsule. loop which goes deeper Bowman’s into the medulla and back to the cortex (see page 147). The end of capsule branch renal of the kidney tubule the medulla drains into a collecting duct which goes through vein and empties urine in the pelvis and then ows into the ureter. DID YOU KNOW? collecting People on taught to survival courses are duct assess dehydration blood capillaries wrapped colour of yellow the by their their looking urine. urine, dehydrated level the the at The of the darker more person. round tubule Figure blood Kidney tubule. glomerulus with waste e.g. 13.3.1 Filtration Look filter reabsorption Filtration urea small and chemicals, at Figure 13.3.2 showing how a kidney tubule works. molecules through The kidneys renal are close artery is high. glomerulus is wider to You the heart can see so the blood pressure that the blood vessel in the entering the Bowman’s capsule blood entering pressure to situation). useful the than is this one glomerulus increase It the inside the pressure leaving than it. there glomerulus that causes is So leaving (it’s the there must it. rather blood to be This like be a more causes bottleneck ltered. substances reabsorbed into The lining of the capillaries is like a net with tiny holes in it. Blood blood cells and through filtrate (urea, some like large the urea, molecules, capillary glucose, like lining salts blood and and so water, proteins, stay pass in are the out too blood. of the big to Small pass molecules, glomerulus and ‘cleaned’ salts and water) blood Figure 148 13.3.2 Filtration and reabsorption. into the Bowman’s capsule. It is in this space that the ltrate collects. microvilli All of the the body. tubule. If you will • glucose, They This look see some are salts reabsorbed reabsorption at the of a back large of into active the associated provide much involves structure adaptations microvilli and cells with surface the the water blood transport in the active area wall are needed from (see of the page the mitochondrion by kidney 35). tubule, you transport: for Figure absorption. 13.3.3 An epithelial lining • numerous After the dissolved water enters and the The process in may the then mitochondria be reabsorption, As bladder. the leaving of uid if ducts ureter From concentration this reabsorbed collecting to blood of water. provide and here the it waste is It in the for active left is low in Urine through renal and the water. down vein The the a uid that and is at much duct stored STUD Y TIP in Reabs orptio n intervals. and lower salts diffus chemicals. ion and to diagram of the kidney tubule and by a glomerulus branch 2 Describe 3 The of b the what table body activ e is osmos is. explai n Bowman’s renal happens shows the capsule vein in e c branch kidney collecting of the tubules concentrations of to ve in label: kidn ey d by Wat er reabso rptio n a gluc ose QUESTIONS Expe ct Sketch of occu rs reabso rbed 1 the tubule. salts tran sport. SUMMARY from kidney some collecting urethra has excess tubule, collects the cell the transport. urea through ows bladder. expelled kidney is on body urine. the is what ows the is energy of duct renal form to artery these page s by the referr ing proces ses 30 and (see 34). urine. substances in three uids. –3 concentration substance blood in renal ltrate / g dm in urine artery kidney tubule urea 0.2 0.2 20.0 glucose 0.9 0.9 0.0 amino 0.05 0.05 0.0 KEY 1 acids POINTS Blood is ltered through salts 8.0 8.0 removing 16.5 and protein 82 0 a the information state the kidney in the substances table that to: pass The explain the blood into of the the into tubule, kidney c state the d how substances you have named pass into 3 substances kidney tubule the that and results are reabsorbed explain for why passes salts, glucose they into are the blood reabsorbed, materials some water the are blood the salts such and as most reabsorbed capillaries tubule. the tubule, the explain the urea, useful along b it water. glucose, from as glomerulus 0 2 Use the from Urine, some out consisting salts of the and of kidneys, ureters, to bladder until be urea, water passes along stored in the the protein. urination. 149 tnemelppuS Reabsorption 13.4 Kidney kidney tnemelppuS The LEARNING Describe the process and person explain how the concentration machine urea and can salt in or survive on damaged, one it kidney. can be However, fatal unless a if both kidneys medical become procedure as kidney dialysis is available. A common indicator that of the glucose, dialysis it known controls transplants of diseased dialysis and OUTCOMES A • kidney dialysis kidney is damaged is the presence of protein in the urine. This the happens when the glomeruli are damaged so that large molecules of blood protein • Describe how machine works a kidney pass out of blood plasma into the ltrate. dialysis ‘clean’ blood passes from the arter y machine • Describe and the to a vein advantages disadvantages of vein kidney dialysis transplants compared with dialysis fluid blood carr ying fluid blood in wastes dialysis dialysis fluid dissolved useful salt Dialysis This machine. cleaner blood fresh back body fluid to is what • A tube • The • Inside is vein has a in the sugar machine and salts it the diffuses Renal like sugar dialysis thin fluid membrane out partially blood and permeable separating from dialysis fluid blood into dialysis fluid dialysis. happens when connected to someone one of the has dialysis patient’s treatment. veins. dialysis flowing dialysis over blood ows along the tube and into the machine. membrane • • the machine dialysis membrane, dialysis uid. Urea into The no diffuses the out dialysis dialysis overall the urea 13.4.1 to from substances stay waste Figure in passes blood which of the is pumped separates blood, the across over the patient’s the surface blood dialysis of and a the membrane and uid. uid loss the of already has glucose glucose and salts and from salts the in it, blood so by there will diffusion be into uid. urea • Urea and other waste chemicals leave the machine in the dialysis uid. • dissolved The patient’s ‘cleaner’ blood passes back into the vein. protein The blood flow dialysis patient times from body has to use the dialysis machine for several hours, two or three fluid (dialysate) a week. This may involve attending a special ward in hospital or it to can be done at home. Between visits to the dialysis ward of the hospital, waste patients eat a restricted diet without too much protein and salt. If they dialysis membrane Figure 150 13.4.2 Dialysis. eat too toxic much and protein, would mean they will more produce frequent too much dialysis urea which treatment. becomes tnemelppuS Dialysis KEY Dialysis involves the separation of two solutions by a partially 1 membrane. This dialysis membrane has tiny pores in it POINTS permeable which A dialysis small water and small solutes to diffuse through, but not larger molecules proteins. In the case of kidney dialysis the blood is pumped over molecules of a dialysis membrane which contains a uid (the pores water has the normal potential as concentrations normal of salts and glucose and is the molecules dialysis, solute molecules 2 such as salts and During glucose the membrane. As the dialysis uid has the as normal blood plasma, the same concentrations of into as blood proteins, reach equilibrium and are the the Excess dialysis salts, membrane Kidney uid, urea into so and the they other diffuse toxic out of restored chemicals are the and blood person not is no net since failed 3 may have a kidney transplant. This the diseased kidney with a healthy one from a donor . the Kidney be Before type a a of close relative kidney donor or friend transplant and is recipient or someone carried (the out, person who the has just blood receiving typing Blood reduces typing the is the chances same that as the for blood attack the new kidney and recipient’s reject it. To A and kidney) immune the occuring, drugs are given to the patient transplants be there may nding a there suppress means those they the immune are more infections for system. likely to They catch remain certain on these infections the problems suitable is always donor the risk of rejection. must be QUESTIONS Tissue system Explain the why for and the presence of protein in the urine may operation indicate to avoid dialysis, donor chances after uid. but of rejection same blood tissue transfusion. reduce of involves 1 will the died. type the dialysis SUMMARY matched. in the of tissue may in inconvenience and replacing is the dialysate. kidneys diffusion it present across transplants with the to in A of uid. solutes, and in urea out dialysis concentration normal. pass water glucose, such dialysis, salts diffuse There potential kidney some blood through from through. same plasma. and During pass prevents dialysate) diffusing which to but the large surface allows such through as membrane allow life, to kidney damage. which 2 have Figure 13.4.3 version longer. of a shows kidney a simple dialysis machine. After recovering normal dialysis life, including treatment functions of a continuously They in a also bone a marrow. match a a operation normal not urea and there to have that it is at is patient and does home. some from However, the diet, or just hormone people kidney the hospital remove wealthy donate in kidney, make suitable Some from the of them blood always resorted to the to able not as with rather red nd danger paying to at cell healthy, all The uid production a is rejection. poor people by blood from a the partially Name the which urea the to permeable blood process by passes into from the dialysis them. Explain how concentrations dialysis fluid and Make the salts returned normal while on a table to advantages show and fluid disadvantages dialysis fluid partially waste of are dialysis. fluid 3 dialysis glucose in to dialysis and kept uid. b dialysis is dialysis membrane. intervals. that patient’s separate the Kidneys kidney tissue a have dialysis. donor of lead replace than blood a to need Transplants stimulates difcult is and of kidney kidney permeable out transplants. membrane Figure 13.4.3 Simple version of a kidney dialysis machine. 151 PRACTICE 1 Which QUESTIONS substances healthy are found in the urine of a 7 person? The conversion proteins, occurs A glucose and proteins B glucose and water C proteins D salts (Paper and and The water C B kidneys D (Paper [1] part A of it system from the liver lungs 8 As part makes urine, stores it the urinary body. Which organ [1] of an investigation, collected from a samples person of urine throughout a and is hour period. The urine sample collected not early in the than the morning was more concentrated system? kidney C liver D ureter (Paper 1) samples Which is the collected used to make less urea B less water C the the amino was later in the blood day. B excess fatty C excess glucose the D excess hormones 9 The is from day the urine night concentration decreased day concentration at of the blood plasma night 2) [1] diagram blood Which the this? acids (Paper 1) at for acids increased (Paper during reabsorbed tubules glucose the explanation produced was renal likely urea? D excess most A in [1] is during shows the urinary system and its supply. [1] (a) 4 plasma brinogen, bladder B A to and 2) Which 3 acids organ? heart 24 removes which amino albumen salts 1) urinary in of as A were 2 such the blood concentration of A aorta B renal artery C renal vein C vena vessel with the lowest (i) (ii) urea? Name State A to parts the A to D. functions [4] of structures D. [4] B 5 A cava (Paper 1) [1] Which process ltrate in the A active B cohesion C diffusion D osmosis reabsorbs renal glucose from the C tubules? transport D (b) (Paper 2) (i) The of 6 Which is following is a list of components [1] not an A breakdown B deamination excretory of function of the liver? the found alcohol blood blood. in the Identify urine proteins, platelets, red of those that healthy urea, blood are people. glucose, cells, salts, water C production D protein of (ii) State three 2) [1] (Paper 152 factors that affect the synthesis volume (Paper [1] urea 2) and concentration of urine. [3] 10 Ammonia waste is produced product of by their all animals as 11 a A man shows (a) Ammonia produced by humans to urea. Explain why how this blood table in shows the The concentration of regular graph over the 17 urea days in of and for 10 days his afterwards. the renal composition artery, of ltrate in blood 3.0 Bowman’s / g dm urine capsule artery aeru renal Bowman’s in eht plasma doolb in / ltrate blood substance 2.0 g −3 concentration 2.5 md noitartnecnoc urine. 3– and received days. [3] ni capsule 17 is necessary. plasma the failure for changed treatment The kidney treatment is his converted with dialysis metabolism. 1.5 1.0 0.5 urea 0.2 0.2 20.0 glucose 0.9 0.9 0.0 amino 0.05 0.05 0.0 8.0 8.0 0.0 0 5 10 15 time acids mineral ions 82 0.0 0.0 State Explain four of table the are protein (ii) glucose present (iii) the substances present is is shown the in ltrate, the amino the higher acids are not the in of the blood (i) [2] urea urine and than in the in the renal concentration in how the renal ltrate is artery of has urea (ii) times the give support person the your received evidence from answer. [2] vein. formed a (d) the of decrease urea dialysis in until in the day the concentration blood 27. from Show the your [2] Describe the the concentration urea in Explain Kidney organ [2] in the man’s changes the the that in occur the in blood graph. changes [4] that you have described. than of (e) [3] transplants transplants. having with kidney. [4] a kidney continuing Before living (Paper to shown mineral [3] blood higher Explain days working. (c) urine the start [2] ltrate (c) many treatment; graph Calculate of but not and in in concentration ions (iv) 30 why (b) (i) how dialysis the (b) 25 16.5 (a) protein / 20 a kidney donor, it are is most Describe the transplant with is the dialysis advantages compared treatment. transplanted important common from that the [3] a donor 4) and the types. is If used the a kidney then recipient why (Paper recipient these it is as have from also compatible a deceased tissue closely procedures as are typed blood person to possible. match Explain necessary. [3] 4) 153 14 Coordination 14.1 All LEARNING Describe living impulses signals nerve that as pass of Describe your the structure of that nervous tnemelppuS Distinguish are sensitive to cells are changes in their temperature, called that detect glands speed, environment; stimuli detect the chemicals and in muscles, movement, the (singular: stimuli; your that for food. bring availability stimulus). example, Effectors about cells are the responses. secrete useful substances and muscles contract to bring about system between involuntary the as wind detect buds such The actions they take as a result are called responses. voluntary Animals and they taste movement. • are daylight, the Glands human in Receptors in cells food organs, • organisms OUTCOMES nerve electrical control humans changes along response Nervous in • and have nervous systems which at their simplest are networks of actions specialised complex, human for nerve they brain. detecting cells, as in are organs T wo organ changes in jellysh with systems our and sea powerful are anemones. processing involved environment – and the the At skills, their such sensory nervous most as the system system for cranial coordinating brain ner ves central our responses and initiating actions. Here we discuss the peripheral nervous system. The nervous system is involved in the coordination ner vous ner vous spinal and spinal regulation sensory system Human The functions. Topic 14.4. The the spinal by You will nd information about the nerves brain and to spinal main parts nervous of the system. Each by a but also the nerve is you need information STUD Y in up passing Voluntary actions along link the and a nerve see nerve two by to system organs: the skull different side (PNS). the and legs. cells the with brain the impulses all or of the Cranial brain the Spinal Spinal the visible neurones. parts system. of brain are central column. between Nerves to of of only abdomen. and the nervous nervous either spaces lots microscopes electricity on abdomen of parts: protected connected thorax tube. form is of vertebral nerves the two up peripheral through brous the is pairs thorax, made in the of peripheral made brain the in the is by Cranial pairs protective up are some arms, in The system make nerves consists and system cord. nervous that cord system protected respectively. head human is spinal cord The spinal system (CNS) nervous cord central and 14.1.1 nervous system central and The nervous human nervous and nerves spinal organs nerves nerves body in the link leave the the vertebrae. neurones to the Neurones which are surrounded naked eye, transmit like pulses of wire. TIP Rem embe r: trans mit ner ve cells impu lses, ‘messa ges’. not decision or a she making. kicks voluntary the 154 body in ner ves cord Figure of system system brain. a are A ball. action. under conscious footballer T urning These carries over the actions control out a pages are and involve voluntary of under a the book the action is an conscious brain when he example control in of of We make having two to types think unconsciously . heart are time, but the four we ileum other the When does This can person it, not is to stimulus The effectors to is to a you have them very of on breathing are and in the in sharp the that are our (see we most we us occur of of of page can’t those that beating of Movement ureter studied without actions conscious occasionally . occur a not actions quick, automatically involuntary the the food 146) control choose in are by to make brains. object automatic such as a response pin that without the person about. a simple pin the happen urine Voluntary think the are we control of actions are blinking, down is Some These that and make sits example The 82) actions there need an choose them. decisions a actions page about realising action. them. Swallowing, such (see voluntary of about involuntary thinking and and and reex the muscles which receptors in the legs is are an involuntary pain that sensors cause the in action. the person skin. to get Front up view of the top part of the nervous system. quickly. The sequence of events is: STUD Y stimulus The → coordinator about the central body and Some for from page → the to brain pain part the system the reexes (see is stimulus nervous neurones eye receptor coordinator of effector. to allow to be the body This of connect brain as we effector that will other Inside neurones see in the inside parts the to Y ou the the the of spinal section TIP response information happens with stimuli. with → connects always connections aware receptors involve the → cont ro l the cord, on muscles. on can see 157 . throug h SUMMARY QUESTIONS 1 complete and cranial the sentences peripheral using spinal these brain neurones and nerves spinal of the cord body make up make the up nervous the are connected to the brain the connected to the spinal cord. The and nervous The human of many specialised cells known made up a Put the following coordinator words into stimulus the system as correct effector tnemelppuS 3 Dene a Explain each the voluntary of the above difference system spinal receptor (cranial involuntary Neurones action and a 3 Some (not Give two examples of involuntary c Give two examples of voluntary spinal or nerve nerve actions under control). b and nervous and transmit an (brain cord) the system nerves). response words. between system central . sequence: action. the is 2 b of nerves peripheral 2 nervous system. and composed CNS . POINTS nervous are All coordi nated system. nervous is nerves are CNS . central 1 the the words: KEY All arcs perip hera l and respon ses The are reex 160). ner ve s Copy reex es T hey into invo lving abou t that simpl e page arra nged the more neur ones cells impulses. are involuntary conscious Other actions actions. are voluntary and involve actions. conscious control by the brain. 155 tnemelppuS tnemelppuS Involuntary 14.2 Neurones and reex arcs Neurones LEARNING OUTCOMES Neurones • Describe and transmit between the three types found in a reex these the specialised cells. Their structure allows them to functioning neurones in a information contains the as nerve nucleus impulses and almost over all of long the distances. cytoplasm, The but cell there arc are • Describe highly of body neurone are distinguish thin long of extensions way through of cytoplasm the that may be quite short or extend a body. reex Sensory neurones transmit impulses from sense organs to the brain action and spinal cord. cytoplasm nucleus cell direction ner ve a ending sense of ner ve body impulse in organ axon myelin ner ve ending in central the sheath ner vous system (insulation) Figure 14.2.1 Motor cord A sensory neurones to effector neurone. transmit organs – impulses muscles away and from the brain and spinal glands. dendrites This neurone has a long axon. direction cell body central in of nerve impulse myelin the nervous axon sheath (insulation) system neurone effector (as Figure The by diagrams insulation. that Relay neurones bodies with in their the brain. Notice the cell nuclei. used The and a YOU axons KNOW? of motor metre neurones whales! neurones long. in Think giraffes neurones When may There be about or the over the great of and travel reaches a synapse impulse rst in one on by is brain one side through acting the at It meet, or a an a muscle gland the layer at 100 sensory in do not across Since synapse, surrounded by fat. separate This neurones, metres per which to are second. neurone. neurones cells insulation These motor cord. a the the it touch synapse ensures is and an released impulses drugs other . impulse triggers transmitter that Many 159). each When substance chemical system. page actually synapse. transmitter (see rich myelinated called nervous neurones formed (connector) from diffuses synapses a Some they motor myelin, impulses them the form spinal neurone. of and as relay and chemical second to quickly . between a known impulses neurone. the direction effects gap sensory is transmit neurones tiny the on the a from very neurone pass two the neurones reexes, inside any show the here) in either neurone. insulation is produced 156 above This fast type short motor around our neurones sensory A impulses in third are DID grow makes A 14.2.2 ends – is an only travel produce in their Reex ner ve pain arcs impulse from white sensor matter sensor y (axons neurone extend of myelinated the length of neurones the grey that spinal matter (neurone cord) cell bodies) spinal sensor y cell cord neurone body pain sensor motor neurone synapse inside forms muscle motor Figure If you and example about of the a hot object, you automatically a simple pain but reex. not remove without Y our until brain you your hand thinking. This receives have already very is stimulated an The impulses hand. If you relied on the brain to make sensory would travel be to burnt the in brain the and time it took for at the diagram impulse along above the the the grey across pathway is called stimulus receptor is in the the and trace the pathway a reex sensor SUMMARY QUESTIONS 1 complete the synapse a the the hot ame. skin. sentences grey reex cord The When using arc it the to a spinal relay cord the impulse (connector) relay to neurone a motor passes the impulse across a neurone in neurone impulses neurones. the arm. transmits The the muscle is impulse the to a effector This Inside to action remove is the the hand from the hot and it object. response is these reexes so are you do protective; not harm words: relay effectors nerve by of synapse arc is in sensory In The motor quickly, and a of Many Copy impulse. along neurones. example heat matter a synapse contracts The an cord impulses muscle This generates spinal back. The the the decision second Look sensor to neurone neurone. to heat travels moved a passes you the impulse Inside your neurone 14.2.3 touch quickly relay neurone muscle they happen very yourself. A B C motor transmitter are transmitted the to matter the of spinal the D spinal The go cord the impulses to leave . where the impulse impulses the There is are passed spinal a gap cord the next to neurones. along between chemical to on neurones two substances neurones are to called released to a pass KEY 1 2 Look a at the Name diagram the parts of the motor labelled A neurone to to the right: A Give the functions of parts B, arc and relay a Dene each of the sensory and ii chemical iii myelin Explain Make a of neurone, and an a motor effector . Reex actions are rapid, synapse transmitter iv substance relay a the function drawing of a of relay i – and neurone iv in the (connector) nervous and protective. often They coordinate responses 4 of following: automatic b up types D 2 i a made three neurone neurone 3 is and neurone: D C reex receptor , a b POINTS neurone. by interpret stimuli with effectors. system. neurone. 157 14.3 Synapses tnemelppuS LEARNING Dene the term The neurotransmitter Describe • Describe nerve how an how impulse many transmission passes drugs, at across e.g. a heroin, synapse and a affect but synapses is a junction between two the The binding in two neurones meet, they do a small The gap that gap is carries the presynaptic the between called impulse the them, not about synaptic impulse to neurone. away across the touch. from the The the 20 nm gap. The synapse neurone synapse is only the These to the receptor on sites the have neurotransmitter, temporary. neurotransmitter postsynaptic triggers neurone. Once is the neurotransmitter is broken enzyme in the synaptic an this has down by gap. wide. 5 called The mitochondria provide energy to reform the neurotransmitter. the carries called the axon postsynaptic synaptic sites There neurone that is of the shape receptor neurones. an is specic membrane. binding happened Where to complementary impulse synapse attaches postsynaptic 4 A diffuses synapse gap • drugs OUTCOMES 3 • and of presynaptic neurone neurone How does from one a nerve impulse neurone to the transfer next? across the Chemicals synapse known impulse as end neurotransmitters are released by the of axon presynaptic myelin neurone an and impulse diffuse in the across the postsynaptic synaptic gap to sheath trigger neurone. mitochondrion synaptic Structure of the synapse vesicle The axons of neurones end in swellings synaptic called containing bulb neuro- synaptic bulbs. The surface of the synaptic bulb is transmitter called the the presynaptic synaptic gap from membrane. the It is postsynaptic separated by substance membrane synaptic of the cell body or axon of the next gap presynaptic neurone. membrane If you the look at synaptic Figure bulb neurotransmitter 14.3.1 has you many will vesicles molecules. It also see that dendrite containing contains protein many mitochondria which suggests that energy is postsynaptic receptor membrane required in synaptic transmission. The postsynaptic postsynaptic neurone membrane on its has surface a which neurotransmitter Synaptic 1 When bulb it an number act of as large protein receptor sites molecules for Figure the 14.3.1 The structure of a synapse. substance. transmission impulse causes arrives vesicles at the synaptic containing the neuro- neurotransmitter to move towards neuro- the transmitter transmitter presynaptic binds membrane. released 2 The vesicles fuse with the presynaptic protein synaptic membrane, into the releasing synaptic the neurotransmitter gap gap. Figure 158 to receptor 14.3.2 Action of a neurotransmitter at a synapse. a reex direction happens arc i.e. synapses from because presynaptic bulb ensure presynaptic vesicles and the of that nerve neurone impulses to are only postsynaptic neurotransmitter receptors can only are only found on travel neurone. present the in in tnemelppuS In one This the postsynaptic membrane. The effect Most drugs synapses. by of that These inuencing with drugs affect drugs the receptors of of the synaptic the by are a nervous neurotransmitters nervous inuence release either Amphetamines activity on of system the of system. the have them or excitatory so of or by effects interacting that brain them. increases stimulate increasing at impulses by inhibiting drug Amphetamines brain, their transmission neurotransmitters stimulating type in transmission the the release activity In and is making a person more alert. They also have the effect of this image coloured The Heroin between and the beta-blockers effects of are examples neurotransmitters. of inhibitory Heroin acts on drugs and to reduce sensation of the pain. neurotransmitters heart You release of neurotransmitters Beta-blockers and are taken by are drugs people to that and block reduce can this reduces receptors blood at presynaptic neurone. the neurone What is meant by b the each of these terms? neurotransmitter function with a synaptic c protein c receptor of an of each impulse of the vesicles receptor b across of vesicles left of clustered the presynaptic following is meant excitatory in reach inhibitory in an is effect for of research d b the number far of greater: (0.15 × 10 ). mitochondria the following POINTS terms? A synapse of each different type of is a two junction neurones. An impulse i heroin nerve and ii amphetamines impulses across the into the effects that the have on of c a the neurotransmitter, the diffuses across the synapse? following receptor drugs gap to bind molecules postsynaptic transmission: ecstasy triggers drug. trigger caffeine each drug do synaptic the As 15 synaptic on human synapses neurones, quadrillion which some many of drug example transmission adult billion. therefore release What number the 2 Give the 86 has between ii the neurotransmitter molecules by for synapses: 1 i a (below). between molecules KEY What have space KNOW? other 0.15 transmission Do lots bottom YOU brain QUESTIONS synapse Explain c neurone for these b tiny pressure estimate a the (×14 000). neurone a is see the neurones 4 neurones rate. SUMMARY 3 a postsynaptic gap Estimates 2 the shows that DID 1 of image presynaptic together neurones a synaptic them. reduce and The appetite. (above) the cytoplasm suppressing synapse the the orange. an with on the the membrane and impulse. cocaine 3 In a reex ensure only 4 one Many arc, that travel in direction. drugs, their effects with the at synapses impulses e.g. by heroin, have interacting receptor molecules synapses. 159 14.4 Sense We LEARNING are Dene of sense receptor particular • organs cells as groups responding to the function of Explain structure the impulses the of and Some eye The pupil reex to and also light intensity light central are the have as receptor stimulated the receptors eye and have other and and use that our sense organs These impulses concentrated to specialised cells travel to to detect generate along nerve sensory system. receptors tissues are chemicals. these nervous found ear cells in groups arranged modify the in in certain special organs. tissues. information from the in before it reaches the receptors. In the eye there are and structures pupil surroundings have such when environment terms our We stimuli, neurones stimuli Describe stimuli. certain They • of OUTCOMES detect • aware organs for focusing light rays; in the ear there are structures for diameter amplifying Sense sound. organs are groups of receptor cells that respond to specic stimuli. • The eyes respond • The nose to responds light to rays and chemicals in give the us air our sense and gives food and of us sight. our sense of smell. • The us • tongue our The ears use a variety of their senses of The to chemicals in our drink and gives taste. respond hearing. Musicians responds sense ear to sound also vibrations detects and movement give and us our sense position of of the body, when so provides information about our balance. performing. • The It socket tear also responds detects to pain pressure and and gives temperature us (see our sense page of touch. 168). gland Eye tear skin structure ducts Your cornea pupil eye three sits pairs inside of eye a socket muscles in as the you skull can and see is in moved Figure about 14.4.1. by The eye iris is a complex brous to eye brain a function 14.4.1 The eye in its socket. At the the front the chan ges and our fo r in blood the also inside de tect ing thin gs tempe ratu re tens ion mus cles. info rm ation hom eostas is. 160 syst em recept ors body like is composed tissue, with the sensory of different tissue detection of and light. tissues, blood. Figure such Each 14.4.2 as tissue has shows in of the eye. of the eye Light the eye is and the then their transparent passes pigmented functions. cornea, through iris, the through through pupil, the lens which which to the is a light hole retina at in the TIP sens ory has the centre back T he help structures enters STUD Y to which muscle muscle the Figure organ tissue, in T his helps At of the tears eye. very provides front wash lysozyme, In humans, opposed views the an the to your shutting The of retina the protection. that called with the at your eyes the same is visual is set moist side a light-sensitive transparent the time tear you layer, glands blink. receptor which that Tears cells. make also the contain bacteria. by eyes side at What are from to by every rabbit. but alternately with delicate, kills the eld tissue a clean like As the kept that are side, eld. eyes eye eye enzyme visual your It is a a the front you few of in the front centimetres slightly experience see different this. The head of apart, angle. two as you Just elds is each of eye try view overlap to distances give accurately. tree-dwelling tigers, The it in off. lets which a When you simple judge and you light into such as which vision is monkeys, distances gives an and us the ability essential to judge adaptation predators, accurately to such as for lions and survive. reex mirror When less light must vision Stereoscopic animals, pupil Look stereoscopic into turn the the your the eyes reex. shine turn eyes light so bright on and off, you Receptor a light cells see in near pupils the retina eyes decrease retina increase clearly. the your pupils protects your can light your This is send and in from in size impulses turn This damage. to another then size. let more example along of a sensory When neurones pass in the impulses optic to the nerve. These muscles in connect the iris to motor stimulate ciliary neurones them to that contract. pupil a bright light constricts to is shone protect into the the retina eye the from damage. muscle changes lens with thickness when of the focusing retina inner rod light-sensitive cells that work layer in which dim light, contains and cornea cone refracts cells that detect colour and details light yellow most spot or sensitive fovea part of the retina pupil blind spot lens point can change its shape to focus light onto the where the optic nerve attaches to the eye; no light-sensitive cells here retina iris controls light the intensity entering of through optic the nerve pupil carries suspensory away hold Figure 14.4.2 A the horizontal lens in section of the Sense organs are groups of QUESTIONS specic the impulses brain POINTS receptor Give the eye. 1 1 to place KEY SUMMARY nerve ligaments name in each case for the part of the eye is sensitive b controls c holds d refracts to that stimuli: respond light, to sound, that: touch, a cells temperature and light chemicals. the intensity of light entering the eye 2 the lens in place within the The cornea, retina, the light after it has entered the transmits nerve impulses f controls the shape g secretes the enzyme h allows light to of pass the to the brain lysozyme 3 In Describe and explain the changes in iris pupil the diameter of the the surrounding light intensity of and the blind eye that described in light, the diameter decreases. intensity When decreases of the the pupils diameter when lens, 14.4.2. bright the light 2 nerve parts functions Figure the optic are have lens through pupil, eye spot e iris, eye of the pupil widens changes. to let in more controlled by light. a This simple is reex. 161 14.5 The eye tnemelppuS Control LEARNING The • Explain the pupil reex of light size intensity the antagonistic action Explain on in the how near the and State are that light the The pupil is controlled circular muscles by a are pair of antagonistic arranged around muscles the pupil. The muscles muscles run are outwards described from as the pupil antagonistic like the because spokes they in have a wheel. opposite iris far eye focuses while rods the the circular radial muscles muscles contract contract to to reduce increase the the size size of of the the pupils pupils. objects The • reex of effects: • pupil and These muscles of iris. radial the the in in terms of OUTCOMES and sensitive cones cells in the diagrams intensity is potential show low to and what in damage happens bright the light in dim when light it is when much the light higher and has the retina. retina In dim light In bright light circular • • Describe the distribution rods and they function State the cones and position the of of circular muscles relax, circular radial muscles contract, radial pupil dilates pupil muscles muscles contract, muscles relax, way constricts the fovea radial muscles STUD Y Here is a way remem ber Cs: Figure TIP cons tr the three cont ract, Figure 14.5.2 through on (upside top control the diameter of the pupil. how light the transparent is focused retina. Notice because bottom of Information cornea, in the of the object about this that way passes the eye. the image the enter light the inverted through Light eye on rays and image the the enters lens retina reected cross goes to the be inverted from over the is to the behind brain the where TIP it Unit T he shows the down) and lens. STUD Y and muscles aint . focused cells , iris Focusing eye In The to this: circul ar , 14.5.1 2 we dealt tissu es, is few interpreted months eye is right way up. We learn how to do this in the rst with syst ems. a the life. orga ns light orga n of very from rays reflected object good retina exam ple wher e you tissu es tissu e) rod eye an can (e.g. and and is of syst em : cells of the iden tify mus cle cone part orga n (e.g. cells ). an T he Figure 14.5.2 This shows light rays refracted by the cornea and the lens. orga n sens ory Rods and cones syst em . Rods Rod and cells when night 162 it cones are is dark, vision. are the sensitive for Cone light-sensitive to light example cells are of at low night. only receptor intensity They sensitive are to cells and in the send responsible light of retina. impulses high for only our intensity. are three wavelengths cells to give contains brain so This The light. The our cones image. area gives horizontal of as in the eye enters the image clearly. the eye cornea it in blind is the when must About and Each our retina has spot. the its which The of own is in from of cone the neurone gives rods us and not the fovea different centre eld contains centre to impulses in visual vision the the fovea cone of the is sensitive as retina your a retina to the very few cones. detailed. on right the same eye is to the spot. Accommodation occur The peripheral fovea the blind of each interprets vision. middle rest our cell, brain rods. the The the level your no in us of cone colour and area position right of of us this detailed types tnemelppuS There term used focusing be on refracted 60% of the rest is which can be the done to far describe and (bent) so refraction by the the near that of lens. changes objects. we the The can light lens As see rays is that light the is the done surrounded by and ring the of tissue lens controlled is If you • the • the (or are looking ciliary are retina. If you • the so at a distant the lens is as distant looking ciliary and can recoil. The shape of the at muscles suspensory 14.5.3 tissue spherical when eye pulls pulled they the into pass is a object: near in suspensory an elliptical through object contract ligaments around (fatter). looking at the ligaments (thin) A distant lens and focused on the focus. to counteract the pressure inside the ring the are Light the lens not pulled recoils rays distant are so and the become refracted object. The lens slack becomes so more near than object the in ciliary lens muscle becomes When the 14.5.4 A near KEY POINTS The pupil reex the eye views a distant object, explain what happens ciliary muscles ii the suspensory circular the Explain shape what of the views a lens happens near to to the each of these a State what muscles control structures when entering the the muscles size of to each of the following in bright The the light: of the iris ii radial muscles of the State what the ciliary muscles, lens ligaments are all involved to c Explain d Suggest why each of the above in dim In the pupil they unconscious. reex is retina, doctors shine a Describe the distribution of light in people’s eyes when of low and cones in the retina their cells are the respond to detect high Cone light colour . to light cells intensity The fovea is and made explain and intensity. respond rods rod around controlled. and 3 in light. periphery are in (focusing) eye. distributed the and pupil happens how of through iris 3 b eye the the iii the object. happens circular in intensity the accommodation i the muscles pupil. suspensory 2 radial ligaments 2 eye of to: light b involves QUESTIONS the iii object. were focus. iris i contracts rounder more they is of eye, and a object. Light coordination 1 shape tight shape. 1 SUMMARY thin object: Figure elastic a muscles and • relaxes into the the ciliary muscle pulled relax, inside the refracted The are the muscles pressure taut) rays by stretched is by Figure elastic ciliary lens entirely of cones. functions. 163 14.6 Hormones The LEARNING A • endocrine Identify on adrenal glands, a diagram hormone • testes State by the each and the the these Describe the adrenaline released four the and than a glands into certain it. duct. organs These produced by an endocrine in that the are blood. Endocrine secreted into the means that the bloodstream gland rather are of Hormones or tissues referred its target to travel throughout recognise as target each the hormone organs. Each body and but only respond hormone to alters the organs. of heart, lungs coordinate the activities of the body but in a different way pupils to tnemelppuS • transported hormones Hormones and substance ovaries effects on chemical produces activity • a pancreas, hormone of is the gland the system OUTCOMES Explain that increases and oxygen that adrenaline supply to of the nervous they system. secrete and The the main actions endocrine are show glands, in the Figure hormones 14.6.1. glucose muscles during activity Pituitary It • Compare the endocrine makes a gland at the hormones base and of the controls brain. things and like nervous is many growth, and sperm and egg production. systems stomach lungs STUD Y TIP heart T he term Pancreas ‘secr e tion’ blood means a that cells subs tanc e mak e Adrenal glands adrenaline that makes glucagon. make glucose Glucagon insulin Insulin lowers and the concentration. increases it. when you is are frightened or angry . usef ul relea se fo r it the into body and Adrenaline helps your body cope with an the blood emergency or some body , o ther e.g. conf use the part gut. secre tion ‘excr e tion’ , of whic h the Do no t with Testes This is make wast e of (see me ta bo page development in males. of Ovaries make females. These oestrogen control the and progesterone menstrual cycle in and the secondar y remov al testosterone stimulates features during puberty. stimulate lic during 144). Figure 14.6.1 The organs of the development of secondar y sexual features puberty. endocrine system. Adrenaline Adrenaline are will The are Adrenaline is excitement, 164 released fear or during stress. times of in a is secreted situation immediately responses that by puts become necessary coordinated by the you much to increasing the breathing • increasing the heart • widening pupils risk more in which glands. of If you injury, aware these gets or and ‘ght you realise even ready or that for rate more light enters the take ight’ ready that death, to rate (pulse) so at survive adrenaline, • the adrenal eyes. you you action. situations action by: levels of stimulates within activity, the an body. To adrenaline increase provide in the rate enough stimulates cells of chemical energy in the for liver STUD Y increased to convert T he glycogen to glucose, which diffuses into the blood. This increases table of glucose in the blood, so that there is more the for muscles sudden as a source of energy for muscle contractions needed action. coordinates the increased uptake of oxygen and the distribution of blood so that oxygen and glucose Setti ng this way • The more that air air oxygen need them passages into that the can for reach be in bronchi the and lungs. bronchioles) This increases widen the to The breathing carbon the Arterioles more in rate increases dioxide glucose the and Arterioles to divert in the blood to at a to increase faster the uptake of oxygen and Hormones are brain and oxygen muscles for gut the and dilate respiration other too much in (become these wider) to deliver by organs. organs constrict (become is in as a result of the of anxiety, constant high blood pressure prolonged and heart They Beta-blockers also act adrenaline blood on and pressure endocrine coordinate the drugs surface reduce and Comparing The cell so are effects. the and activities the of at the synapses to block disease rate and nervous (see (see the Beta-blockers heart endocrine system act membranes its decrease the that Topic nervous system act to Topic to nervous structures nerves forms for 3 reduce 14.3). pulse control of and the ight’ oxygen stimulates pupils in situations. increases and supply glucose during SUMMARY and system endocrine system cells in impulses hormones neurones in the What glands to activity. QUESTIONS meant by the terms? a endocrine b hormone c target system (chemicals) organ blood State each fast is following of information rates breathing systems 2 speed or muscles of along organs. increases Adrenaline of information pathways the body. secretory electrical alter may 1 feature and to 14.3). receptors help secreted stress ‘ght result. blood target Adrenaline widening and/or are glands narrower) 2 released, that endocrine travel muscles. adrenaline chemical rate. and If system s. POINTS activity • two of substances • you absorbed. 1 excrete tables allow volume KEY • system s out compa rison s the respiration. (trachea, alveoli the ner vo us ensu res direc t betw een muscles the changes mak e in which horm onal work . in Adrenaline in available and to compa res the ways concentration TIP tnemelppuS reactions also the of gland the which secretes following: slow a testosterone c oestrogen b insulin transfer short-lived, longevity e.g. of usually muscle contracts slow and longer 3 lasting a short Suggest four in which the only the area at whole of a tissue or organ 4 neurone Explain how prepares e.g. muscle of contraction response conversion by of glucose adrenaline the body for action. to or glycogen, secretion increases. the area end secretion time adrenaline target situations for action protein synthesis, 5 State four ways in which the glands rate of respiration endocrine the system nervous differs from system. 165 tnemelppuS tnemelppuS Adrenaline 14.7 Controlling in the Controlling LEARNING the term tnemelppuS Explain the metabolism, concept cells, some Describe glucose down, the control of work see concentration how STUD Y The maint aini ng cond ition s is do In the chan ge to It say hom eostas is the and body. some are Enzymes are and the such kept pH control these temperature, suitable inuence conditions working. as reactions in and in the constant. enzyme the body, so is and See Unit 5 to activity. body Homeostasis pH can the that slow down maintenance enzymes or of control overall is control an of our example body of processes. The control of homeostasis. humans, the normal temperature of the blood is 37 °C. When body , reaching the brain is warmer than this temperature it sends sligh tly is more our along sweat nerves glands to the produce skin sweat to promote and this heat helps us loss. to For cool example, down, that body temperature to normal. maint ains When we brain or keep s feel cold our blood temperature falls below 37 °C. Then the will se t stimulate and by production increasing the of rate more of heat in respiration the in muscles the liver. It by also limits . stimulates sweat by The This gets control is falls acts the to body to conserve heat by decreasing the production of glands. feedback of body same temperature temperature thermostat the sweat Negative hot the them shivering too inside proteins, cons tant cond ition s oven occur as efciently. has returning with in glycogen. conditions temperature impulses near ly such cons tant in time. in from internal brain body blood the reactions up, say hom eostas is precis e built conditions, water, change metabolism we of enzymes constant TIP Alth ough all as when temperature slight stop they such best concentration blood Any that chemical are feedback and • molecules of broken negative many homeostasis In • conditions temperature sort of constant ensure that control at the the is an system pre-set actual example as in an of oven temperature. temperature is negative as to keep Negative close to the feedback the feedback pre-set switches temperature heater possible. In our body , if the temperature increases above off or required as required oven oven temperature temperature below bring be it close glucose oxygen thermostat the back to normal to it, 37 °C, normal. within set concentration, and carbon It then may limits. the dioxide it responds not be There water by exactly are also content of concentrations taking 37 °C control the of actions all the systems blood, the that time, for blood will but will blood pH and the blood. switches oven gets temperature heater too Figure on cold 14.7.1 rises Controlling the Controlling an oven is an example need glucose the energy and therefore need a constant supply blood. feedback. When you eat concentration stay high insulin a high can because concentration 166 for of from negative glucose temperature Cells of blood into in the carbohydrate increase cells the in the blood. blood. by a meal factor pancreas These Insulin cells your of 20. blood detect secrete stimulates glucose However, liver the the cells it high does hormone to not glucose convert called glucose tnemelppuS Dene body OUTCOMES During • conditions tnemelppuS glucose concentration glucose increases concentration STUD Y TIP insulin causes (food decreases intake) Insu lin glucose in the liver to change to glycogen normal blood glucose normal level blood glucose and gluc agon are horm ones. not enzy mes. say that T hey So insu lin are alwa ys and level gluc agon chan ges stim ulate th e to gluc ose. Do glucagon causes say that ‘insu lin glycogen in the liver glucose gluc ose glucose to change to glucose concentration concentration decreases to enzy mes such as 14.7.2 mus cle the the storage liver cells When you muscles you a race up Y our the cells blood Blood lots so blood glucose the instruct of and out glucose cells the cells to from to other the the so of • liver is an makes makes blood. this by the and it into the normal. pancreas, releases molecules not and stimulates diffuses to does decrease Glucagon which increases controlled but energy which hormones from the blood or example insulin to of negative stimulate a feedback decrease because in blood the tissue in the centre secretes make photo of the glucagon sure the decrease too to stimulate an increase in blood 1 glucose POINTS Homeostasis concentration stays within limits and does not much (see treatment of T ype 1 diabetes in T opic as 10.3). Homeostasis It involves operates constant negative to conditions of QUESTIONS and Dene the term Explain why is it water , oxygen in important that conditions in cells are its tnemelppuS the as 3 term an The pancreas negative feedback using controlling example. blood in the the blood controls the roles of the pancreas and the liver of by hormones glucagon Explain as well pH. concentration glucose dioxide blood kept constant. Explain carbon the homeostasis as b such temperature. glucose, a constant increase maintain b the of conditions, feedback. a is maintenance 2 SUMMARY glucagon. glucose body 2 this and or internal 1 of insulin pancreas: concentration, or and your the KEY to cells cells. more. concentration, • by cells, the pancreas This inside stimulates exercise, provide decreases, glucose, glucose to detect concentration remove This blood type blood concentration is the 38). The add T he normal. pancreas into glycogen glucose page concentration in concentration liver (see to some from glucagon glucose blood glucose returns carry down blood glycogen glucose Other break the lots or of hormone to monitors to absorb decreases decreasing. secrete liver run take need. keep compound to concentration done the glucose producing insulin which and stimulate the in liver. maintaining a constant blood glucose concentration. 167 tnemelppuS into is increases (exercise) Figure conv erts glyc ogen ’. conv ersion not 14.8 Controlling body temperature Birds LEARNING and mammals successful • Identify on • a different diagram Describe of how temperature ones structures the and ways skin to animals be as active adjust they a at the can constant night body as live in body well cold temperature. as temperature environments during in the day . different as They The well skin as are very hot provides conditions. body is kept The constant The STUD Y maintain OUTCOMES skin skin is the largest the body organ in the body and has several important TIP functions: We produ ce respi ratio n shiveri ng; to our e.g. we and we by lose heat evapor ation swea t; e.g. bene ath • protects from damage • stops • prevents • detects changes in • detects pressure (touch) • loses in surrou ndin gs, by heat, heat when pathogens too from much entering water loss temperature and pain we cons er ve by the havin g heat by conduction, convection, radiation and evaporation. fat skin . oil gland hair erector muscle hair sweat sense – receptors detect pore blood sweat capillar y gland pain, pressure, cold arteriole and heat sensor y neurones Figure Polar to bears conserve have their a thick body layer of insulating fat heat. Many fat 14.8.1 of the structure structures temperature. by The radiation. We We lose use of in the and our human skin. diagram absorb skin for layer help heat heat in controlling through loss our when skin we are body – mostly hot and to hot conserve weather hairs lie heat Mammals is hair when we are cold. flat a poor have fur or conductor hair , of which heat. So traps air a layer pockets in of air the close fur or to hair the skin. reduce Air the muscles loss of heat to the atmosphere by keeping convection currents of air away relax from the contract warm so that surface hairs of the stand skin. erect When to trap it a is cold, thick hair layer of erector air so muscles reducing cold heat hairs weather stand loss. up When is hair muscles it is trapped currents hot, hair close ow to erector the closer skin to the muscles relax so so heat can more surface of the that be hairs lost lie as at. Less air convection skin. contract Mammals Figure 14.8.2 Hairs are involved maintaining body temperature. 168 also have a layer of fatty tissue beneath their skin, which is in a good in cold insulator as it environments does have not very conduct thick heat layers well. of fat. Mammals that live Controlling body temperature blood gets blood temperature brain too hot falls switches No matter what the weather is like, your body temperature stays on very close to 37 °C unless you have a fever. There are receptors in cooling the mechanisms brain that detect changes in the temperature of the blood. When the normal brain detects action of any change effectors to in the restore blood the temperature, blood it temperature coordinates to the body normal temperature body temperature normal. brain switches In the heat, the brain detects an increase in the blood temperature. on blood The brain sends impulses to the skin to increase the rate of warming gets blood temperature sweating mechanisms too so that more heat is lost by evaporation from the skin cold Figure In the The cold, sweat the brain glands stop detects a decrease producing sweat in the and blood the rises surface. hair 14.8.3 temperature. erector sweat muscles contract to raise the hairs. The body starts to shiver as evaporating hot some of the body muscles contract spontaneously and release cools heat heat weather from by tnemelppuS A respiration. this very much the Blood ows through the muscles and is lost skin by radiation warmed heat. effective blood skin. way ows to regulate through Arterioles supply the body temperature capillaries these near capillaries to with is to the change surface blood. The change the how of muscle arterioles sweat around the arterioles can contract and relax to blood dilate gland ow. The To lose vessels heat, widen these and muscles there is in an the walls increase in of the blood arterioles ow relax. through the Figure capillaries. the In This is surroundings the cold, the known by as vasodilation. convection muscles in the and More heat is now lost 14.8.4 to radiation. walls of the arterioles contract so the cold little weather vessels become narrower. This reduces the blood ow through lost the heat by sweating radiation capillaries the The skin. and This control the is of blood known body is as diverted to stay beneath the fat layer stops in vasoconstriction temperature is by negative feedback as shown arterioles sweat in Figure 14.8.3. The brain coordinates the responses by effector constrict gland to lose, temperature conserve that stays or gain within heat set in order to maintain a body limits. Figure SUMMARY QUESTIONS KEY 1 Explain 2 Describe 14.8.5 how the brain controls body temperature. 1 what happens a to lose heat b to conserve when heat in we the are when skin: are The brain cold. 2 How do we produce heat in the body if we are Explain how fur and control fat in tissue cold beneath the skin Insulation conserves loses tnemelppuS Explain how maintaining vasodilation body many skin. heat help generates heat, and heat. in Vasoconstriction and environments. vasodilation 5 the the cold? 3 temperature body using in shivering 4 by structures sweating 3 controls temperature hot, we POINTS and vasoconstriction temperature. are involved in heat the is lost control from the how much blood in skin. 169 tnemelppuS organs 14.9 Tropic responses Tropisms LEARNING OUTCOMES Plants • Dene the terms the and respond plant the chemical such as towards light or and away gravity. from the Different different parts stimuli. of These plant Explain plant growth the by effect hormones responses are much slower than the responses coordinated by control the • stimuli grow nervous systems in animals. They are called tropisms auxins of synthetic used Gravitropism as Whichever way a seed is planted, the root always grows downwards weedkillers in the the shoot grows A direction direction growth of of gravity. The shoot always grows upwards against gravity. response to gravity is called a gravitropism. upwards Roots are direction to absorb Shoots, root positively as the water on the gravitropic stimulus, and gravity. mineral other hand, because They they grow grow in the downwards same into the soil ions. are negatively gravitropic. They will grows always grow in the opposite direction to the direction of gravity. This downwards ensures Figure 14.9.1 Which way is that shoots grow upwards getting the leaves into sunlight. up? Auxin STUD Y TIP A A seed plant stimulates germ inat es. roo t and then Gravi tro pi c ensu re the seedlin g itself o ther a Whi ch in If is a of growth seedling the side of causing the cells this to growth. elongate, Auxin but in in shoots by slowing down cell roots auxin elongation. shoot is put and and on its root. side stimulates In the the the auxin cells shoot builds there the to auxin up on builds the elongate and up lower on the side therefore lower to grow the more on the lower side. This causes the shoot to bend upwards. establ ishes compe tition plan ts by controls up? respon ses it growth auxin shoo t way sur vi val as called A inhibits appe ar . hormone with In the down near by. on root the side upper so auxin the growth the made auxin in side root by a root also root of the bends builds by up on inhibiting root the cell elongate lower side. elongation. more than But As a those auxin slows result, on the cells lower downwards. tip auxin builds lower up on auxin side causes elongate gravity lower less cells to on side gravity Figure 14.9.2 Auxin controls the positive gravitropism of roots. Phototropism The cress time These the cress light. 170 seedlings have grown towards This and sort shoots seedlings their of growth grow in shoots the photo have response towards the have grown is light been towards called they a are put the in a window for some light. phototropism. positively Because phototropic. tnemelppuS tnemelppuS Explain of either phototropism growth • to gravitropism advantage maximum efciently of this surface for tropic area to response the is that tnemelppuS light. They auxin made the can leaves then expose absorb the light more STUDY Cells This TIP photosynthesis. response is controlled by in the shoot tip. become moves away from the shoot tip down the stem. When a light only from one side the auxin is unequally distributed cells in is on found the direct towards on the shaded light. the The light. shaded side to shoot side the elongate grows Roots of are more more not stem. on than the sensitive The to auxin the cells shaded made shoot by on side the cells and pressure bends which osmosis. the turgor inside causes stretch. the the cell cell Auxins wall work makes by elongate more on shaded auxin by swells, increasing side light. auxin tip water vacuole stimulates to auxin they so T he most when shoot absorb receives or The elongate, auxin longer , tnemelppuS The making the walls to it easier for stretch. side passes down shaded side shoot bends towards 14.9.3 Synthetic Synthetic Auxin plant auxins Important controls are cereal them for water , Herbicides leaves of like the crops effective like 2,4-D wheat whereas nutrients cereal positive phototropism of shoots. hormones very (monocotyledonous) the light are and selective and most light sprayed plants as the are on because barley of are the narrow weeds broad they weedkillers. leaved crop are that but thin with (dicotyledonous). tend and leaved compete to run point off the upwards. The This weedkillers are more likely to be absorbed by the broad-leaved weeds. plant weedkiller fashion, The auxins increasing food from increase the rate the of growth cell rate division. photosynthesis to of The the affected weeds maintain this weeds, cannot rate of possibly provide growth Dene of the it soon die. KEY a tropic A b to c State what growth response will happen in each of the Some seedlings are placed in a window, in sunlight for 6 A Some horizontally for a seeds few are placed with their roots tnemelppuS the observed Auxins the growth responses in question 2 in action of Explain how growth of positively shoots are is the a growth the stimulus are and of positively grow light. are plant hormones growth. Synthetic terms are used as weedkillers auxin. by 4 to control auxins of twisted hours. that Explain a gravitropic. Shoots towards lying 3 3 are and phototropic germinating a stimulus phototropism light. hours. b hormone in following. response a a gravitropism 2 2 is the Roots gravitropic phototropism with grow die. gravitropism response following: response to it POINTS negatively a sprayed made enough and QUESTIONS each has causing gravity. 1 been that by 1 SUMMARY has synthetic auxins are able to act as weedkillers. making too the weeds grow fast. 171 tnemelppuS Figure the PRACTICE 1 In QUESTIONS which spinal A pathway do nerve impulses travel in a 6 reex? effector diagram shoot → neurone The sensory → neurone sensory cell → → to shows receiving the light response from of one a plant side only. relay light motor light neurone B motor C neurone → sensory neurone sensory cell effector → → relay → sensory relay neurone → effector neurone neurone → → motor neurone D sensory relay cell → neurone sensory → neurone motor → neurone → effector (Paper 1) [1] Which 2 Where are relay neurones statement explains how this response is situated? controlled? A effector C B spinal D (Paper 3 A cord spinal nerve 1) Auxins stimulate a gravitropic impulse cord metres. in The travels 0.02 s. speed from This of the is a a ngertip distance impulse B Auxins stimulate a phototropic to C Auxins stimulate cells of the 1.4 C light the opposite Auxins from 70 m s on −1 7 m s D to grow on faster the than side the closest cells to on side. stimulate (Paper 1) Which shows the the light cells to on opposite grow the faster side away than the cells side. 170 m s (Paper 2) [1] Which are [1] 7 4 the −1 0.7 m s −1 B response. is: D −1 A response. [1] nerve spinal A receptor hormone the and A adrenaline B insulin – its – correct match between effect? decrease increase in in heart blood symptoms of Type 1 diabetes? the rate glucose A bleeding gums B constant alertness C thirst D tiredness and and poor and wound healing insomnia unexplained weight loss concentration C oestrogen – decrease in the volume and unexplained weight gain. of (Paper 2) [1] urine 8 D testosterone – stimulates development A man injures his arm in an accident. of Afterwards, he can feel objects touching his sperm hand, (Paper 1) Which occur when in a hot A environment? them. all in sweat hair skin glands muscles are A constrict active relax B constrict not contract C dilate active relax D dilate active contract C 172 his hand away active cause of between this could his hand his spinal be and that: the spinal damaged all nerves effectors 2) move erector B (Paper cannot The nerves cord arterioles the he [1] from 5 but all nerves hand D all (Paper [1] between in and the 2) his arm between his are the spinal receptors in receptors cord his cord and the cut are hand in his cut are damaged [1] 9 The the diagram shows a horizontal section of 11 eye. A scientist and investigated cones shown in across the distribution the diagram. of cones the distribution retina The in the of a of mammal graph shows rods as the retina. D C B B A E X Y X Y A sllec the (b) Explain (c) A parts labelled A to E. [5] fo Name enoc (a) person brightly (i) the walks lit eye is from a a sense dark organ. room into rebmuN why [2] a place. Describe the change that you would A see happening to the person’s B pupils. [1] (a) (ii) Suggest the advantage of the Name Give you described in (i). parts reasons (a) the retina X and Y . for your answers. [4] Copy the graph and show on it the 3) distribution 10 of [1] (b) (Paper the change Copy that and complete shows part concentration of of the the ow chart control glucose in of the (c) (i) the State the of an rods involuntary blood glucose retina. action [3] involving eye. [1] Explain how involuntary in the blood. (ii) increase in the control action of differs an from the concentration control of a voluntary action. [3] ↓ (d) Explain having detected by the two advantages to coordination an animal systems: of the … nervous system and the endocrine system. [3] ↓ insulin secreted (Paper ↓ 12 (a) 4) Describe when liver cells respond by [2] (b) sensory There spinal Write out a similar ow chart to show response glucose to a decrease in Explain using concentration. as (Paper an the the principle control example. of of that impulse occur arrives at at a synapse the end are neurone. of huge cord and [4] numbers the of brain. synapses Explain in why the this so. [3] blood [3] (Paper (c) events the is body’s the nerve … a (b) a negative glucose in 4) feedback, the blood [5] 4) 173 15 Drugs 15.1 Drugs What LEARNING A • Dene • Describe are the term drug is any the use of antibiotics treatment of bacterial There the substance that is taken into the body that alters or drug inuences in drugs? OUTCOMES are chemical several ingredients of reactions different medicines in types and the of are body. drug. used Some to treat are the and active cure people of infection disease. • State that some bacteria makes to antibiotics them less State that paracetamol, designed to antibiotics but do which alter sensory perception. suppress morphine muscular pain pain, and antibiotics counteract the are medical symptoms of drugs ‘u’, soothe useful are not or kill socially pathogenic acceptable bacteria. drugs Alcohol, that people nicotine take for and their kill pleasurable bacteria mood-enhancing which caffeine • are are Aspirin, resistant Others effects, to help them relax or concentrate. affect viruses Drugs tnemelppuS are • Explain the strategies that be used to reduce of Explain why Acid user. Diethylamide Stimulants, mood-enhancing antibiotics well-being of their drugs. more severe effects Hallucinogens, or LSD, cause psychedelic like visions like cocaine, ecstasy and for amphetamines the are but do not and drugs energy. which Heroin, give the user although it a short-lived affects the feeling body in a kill different bacteria because bacteria of • illegal recreational antibiotic- all resistant be the drug development to called that Lysergic can tend sometimes way, also gives a feeling of well-being. affect Drugs act upon the human body in various ways. Some drugs, such viruses as nicotine system and works heroin, and mood-enhancing STUD Y TIP in the nervous impulses. T here are den e the term ways to cell the top of this the liver page , types can we write describ e, it the abused heroin change the combining way by and way with that the people. Many nicotine, in which protein nervous act of at the synapses neurones molecules send on the neurones. from is are the site broken of the down breakdown in the body of by alcohol and enzymes other and the toxins. products which excreted. The breakdown products can be detected in the urine, of and drug s of by as the at are all this often such and with ‘drug ’. den ition Drugs covers are drugs, do membranes The Lear n the man y these system They interfere so you this taking mem ory. who have Many rely it drugs why the in have drug, regularly. are urine tests Athletes been drugs on take is drugs. illegal accidents the a In are taking many and are potential person carried part can in out routinely to be possession or see tested addictive. become countries to if competitions addicted some or dealing all in of people and for If the them been drivers drugs. the and have car body feel comes the need to to non-medicinal results in severe punishment. The body’s produce to Many in an on medical drugs uncontrolled prescription 174 are way from a dangerous and are doctor. if taken available only metabolism more increase to may enzymes have the to become break effect it that used down the to so user the that rst drug. the The dose liver of experienced. may the drug has Antibiotics (bacteria growth. cure are and a group fungi) Antibiotics human Antibiotics and can antibiotics has be to was the Penicillin acts on a breakdown Some are be over the stop by cell made to kill by be by and and the wall cell to and their treat and fungi. Usually of a course of time. and mass-produced. formation, leakage crossing stop vets mouth. period cell or bacteria discovered inhibiting wall by certain substances microorganisms doctors taken to by pathogens caused a antibiotic bacteria of or taken rst used diseases injected be antibiotics chemicals are prescribed animal Penicillin to of that of cell leading contents. membranes and others MRSA prevent enzymes proteins. taking A big Antibiotics antibiotics problem resistant to to tnemelppuS Viruses are rely viruses for viral but be have no treat viral on and than They the that is such there are is that viruses. many vets not of use not differently on such There as is making no point are in and being antibacterial need bacteria to have know resistance carry their host. antibiotics possible. diseases as to out AZT their This that This antibiotics the development MRSA. This has of in which is by why viruses. used There that our to are such has hospitals. deaths as number recent only years when of as cases a of result in those necessary MRSA of and are antibiotic bacterial treatment been caused Overuse resistance. See anti-viral was by overuse responsible prescribing, test patients have had with organ in the USA and strategies. ensuring that UK taking more all on their pills use aureus or suppressed has decreased antibiotic a to against patient. contain nd the The out white the for a hospital discs on would be has this agar Here, effective to infected plate four ways resistance bacteria, whereas because two they would have not. their courses to on POINTS control page 239. A drug is the a substance body, which chemical taken alters or reactions QUESTIONS a Dene b Name two drugs c Name two mood-enhancing the term drug d Name two drugs that 2 are used as body. Antibiotics by medicines. the can cell pathogens wall inhibiting protein drugs. synthesis that destroy disrupting formation, be harmful, but are not illegal and metabolism in in the pathogen cell. countries. 3 Explain a in in 2 ask in antibiotic that antibiotics. inuences many may out which pathogen different into 1 doctor carried antibiotics complete are a be transplants. Prescribing people to of for 1 SUMMARY of using. HIV/AIDS, fewer Staphylococcus hospital who specic by is anti- KEY of doctor control killed The this bacteria use antibiotics There treat far to Before methicillin-resistant caused systems, which by own antibiotics immune hospitals metabolism, means inhibit explains caused antibiotics. own antibiotics. to especially gels in antibiotic laboratory antibiotics, antibiotic-resistant become which sensitivity Bacterial other controlled disease. cells to reactions, diseases. and do control available, work doctors have to effect antibiotics so cells. used important particular would drugs they drugs a not metabolism cannot with entirely we to them, prescribe but catalysing how antibiotics act to kill pathogens like bacteria Antibiotics cannot kill viruses and since they have no cell fungi. tnemelppuS wall host 3 Explain why antibiotics can kill bacteria but not but rather cells, live taking inside over their viruses. metabolic processes. 175 tnemelppuS Antibiotics 15.2 Heroin LEARNING Describe of heroin the effects of Morphine and codeine poppies abuse of and State that injecting heroin • infections Describe the addiction such as problems to withdrawal heroin, is Heroin has as a a tnemelppuS how nervous effect a opium compound so is Heroin rarely has only limited medical uses as it is used. depressant structure that that slows is down similar to the nervous endorphins, system. a that are found in the brain. Endorphins are made group naturally the brain and provide relief when the body experiences pain or stress. and heroin work by ooding system, on the limited function transmitting relief. affects to of When a the synapses in the brain and preventing neurons blocking nerve for and alcoho l depres sant s. shou ld when use this writi ng effect s more rst and on time This mimics synapses they intense post-synaptic in usually the T opic feel happiness. a This so producing molecules bind membrane function 14.3). warm state When rush is of of pain to the the synapse, natural people and known a take feeling as of euphoria on the term abou t their body . shou ld apply be these to ler ance depend ence addict Addiction TIP ideas and to alcoho l. injecting to heroin into a vein. heroin becomes part of the body’s metabolism and the body quickly able gets and the heroin are Heroin Y ou on receptors, the Y ou An STUD Y sites pain heroin, transmission. (see the from takes TIP Heroi n bo th impulses person endorphin-receptor endorphins synapses STUD Y heroin used effect. to the to to the More take The tolerance People in who dependent three the to on weeks are of reduce the order but This body feeling to start experienced, to But heroin quantities drug. painkillers brain. painkillers. a 176 and chemical contentment of from is and crime heroin to morphine. powerful chemicals from the Heroin infection Explain its extracted medicine. severe symptoms such from addictive Heroin They the compounds in of in problems • two painkillers HIV of HIV as can highly cause used heroin modied • are the feel taking they needed does pain the drug, to includes it heroin drug. This of misuse of produce This has to or want get can nerve prevent becomes euphoria quickly the to not pain. and the them more how be the taken just to of happen or its and body in the ever a has its impulses own natural addicts have develops greater the pain. feelings addicted within it sending deaden repeat ‘hooked’ heroin. where unbearable is to cells as matter they they of rst are just two tnemelppuS • Biology OUTCOMES is taken Injecting is highly surrounding known places The as to by smoking, dangerous injection gangrene. inject danger it. page as virus can die, it into a collapse and tissues giving can the run needles and is the transmission and the virus that vein. condition out share this (HIV) to injecting addicts addicts with or veins start Long-term associated of suitable syringes. of the causes human hepatitis 211). Social problems Heroin addiction often points Some immunodeciency (see snifng is dominates a the serious lives problem of addicts for and many they countries. think only The drug about how Heroin addiction addiction, they can get their next ‘x’. The drug can be expensive, which at many often people to become turn to difcult crime to in keep order a job, to fund and their habit. addiction often It risk from and breakdown families, and homelessness. preferring the Addicts company of tend other to shun addicts, isolated from a nicotine is produced in and so heroin in the and America smuggle the Afghanistan, and It elsewhere. drugs Heroin which is the largest is a highly dealers who into sell in the Golden Triangle (Laos, Heroin is then trafcked Networks of developed illegally criminal countries into gangs and it on the streets. Most of Europe, help to have harsh penalty, to penalties, stop such trafcking. A as life user drugs their next have resulted include happening A great to go centre. which to deal overcome is very unpleasant sleeplessness of addiction. countries some of the cramps, and stops and taking This addicts same the from only may are effects symptoms. (imagining sweating, support Often rehabilitation. some gives withdrawal hallucinations muscle willpower heroin into In them), and way involve given as to is These the hepatitis and and needed staying in a drug, who HIV inject Heroin the interacts nervous with nausea. to the habit SUMMARY QUESTIONS treatment methadone, 1 Dene in heroin. each relation of to the drug b dependence c addiction d rehabilitation a Why a is heroin highly If a heroin taking what Heroin to crime, viral the drug addicts who want to many give up people their becoming habit is involved available in with crime. rehabilitation Support for addict drug, happens social and how stops describe to them. can and the lead family spread of these consequences of drug? diseases. Explain cause described addictive, addiction problems the use: tolerance b 3 following a depressant often synapses system. are as are amongst heroin. can 2 Drugs needles spread drug things overcome another Shared in the the terrible vomiting others dose. to in experiences to for heroin-producing imprisonment who turn money and 3 death may obtain North process distribute the addicts Vietnam, addicts countries addictive drug. producer of drug lives society. world, Thailand). and their addiction. POINTS crime Burma of put they 2 of form people to depressant Heroin serious more friends 1 become is far can leads KEY family but drives society in a can affect negative way. centres. 177 tnemelppuS Heroin 15.3 Alcohol of drugs Biology LEARNING Describe the effects of sport alcohol a socially its supply acceptable and drug in consumption many are countries very tightly in the world. regulated and in consumption Describe the long-term alcohol on the body it is banned entirely. effects When of is some, others • misuse excessive In alcohol of in the OUTCOMES Alcohol • and and alcohol is consumed, it is absorbed into the blood very quickly on since it is a small molecule that does not need to be digested. It is society tnemelppuS also • Discuss in the use of hormones sport soluble the wall the stomach Alcohol type of volume alcohol of in cell the membranes, stomach slows gets and down distributed its so it small is absorbed intestine. very The quickly presence through of food in absorption. throughout the body in the blood. Some units is lost through the lungs and the kidneys. It is absorbed by liver 3 drink / cm by cells and broken down by enzymes so that its concentration in the volume blood / men alcopop extra decreases gradually. This breakdown happens more quickly in % 400 5 500 2 8 4 than their and in women enzymes less fat in concentration strong because tend to their bodies of be alcohol men more active. than in have the more They women, blood to of also which these have more tends decrease enzymes to more and water cause the quickly. lager Like cider 500 4 2 (glass) heroin, down the 125 40 5 wine 175 12.5 2.2 spirit 35 40 1.4 (vodka) of others. of is removing With depressant. of loss • slower reaction • loss self-control. nerve coordination, It affects impulses. inhibitions larger • of a transmission effect with cocktail the alcohol so quantities judgment In people this and lack the brain small nd of control by quantities, it easier to inhibitions of slowing ne this has socialise leads to movements times and Unlike heroin, alcohol does not lead to addiction as quickly if at mixer all. Many their The content one extra strong cider drink throughout alcohol 8 grams alcopop people of hour. lives alcohol; The drink more page 200 UK than for alcohol in without of drinks this is to advice 4 units about moderate in day drinking units. broken recommends per quantities addicted. measured quantity government 3 to becoming is the small and that in men women during One down 2 unit the is liver should to 3 (but in not see pregnancy). Addiction lager Some people referred to as metabolise greater irritable and aggressive wine spirit and mixer Figure 178 15.3.1 Some alcoholic drinks. dependent alcoholics. alcohol quantities Alcoholics cocktail become nd can are of it after alcohol hard cause They made to their drinking develop in to the get cope alcohol a the spend a They same and lot of are as effect. sometimes more therefore everyday pain and tolerance liver . with families and upon enzymes need They problems misery. They money on to feel tense without can drink. that take a and drink. become Social problems DID The misuse of alcohol is a factor in crime, family disputes, YOU KNOW? marital Researchers breakdown, child neglect and abuse, absenteeism from discovered vandalism, assault and violent crime including murder. In the damage done by alcohol is considerable and is three for governments to has and adverse making to other effects them drink drugs feel alcohol on involved people’s more and are drive in many road concentration, condent. then to four of times the more in people who abuse measure. alcohol Alcohol have cirrhosis often frequent difcult Finland that some liver countries in work, a In some vehicle accidents. while at countries or operate the it is type Alcohol same against machinery. of and time defence the that In law most who protein system. some have in the This people susceptible to a specic cells of their suggests are genetically cirrhosis if they 3 Europe There are the Long-term Drinking serious and large builds liver on is The of the blood with alcohol It can liver more is condition is the to is 50 than part a mg the in the of the per 100 legal so fatty by of cm . abuse that liver. brous If fat is this scar have disease breaks quantities that can heart of alcohol stored and continues the tissue. Alcohol the If heavy is drinking able the continues to This condition then carry out condition drinking. with in tnemelppuS misuse Anabolic increased of They hormone. of The strength as the liver becomes alcohol drugs are and by result is the is The full and in liver toxins fatal consumption of also the the less to reaction respond use of a number anabolic increased of similar mimicking the to the male sex male the features, facial In of and protein-building growth, which gives effects the to times stimuli, Armstrong side-effects men, use of resulting these baldness, drugs kidney from can and the breasts. body In hair women, and there irregular is a life for was banned doping from offences competitive in 2012. development POINTS of periods. Alcohol is if in taken a depressant excess, it reaction and can times and QUESTIONS a Describe b What how effects Explain alcohol does reaches alcohol the have brain on the after it is about why a person who has drunk 2 brain? alcohol should a What are the b Summarise long-term effects of alcohol on the not effects of alcohol on society and Long-term of its use of lack effects include and discuss of self- of alcohol cirrhosis brain of the damage. Performance enhancing drugs the anabolic steroids can have use. serious the a person. body? like banning a drive. 3 the in drunk. liver Discuss to lights. and abuse 3 longer trafc about damage control 2 takes as excessive bring liver for bring c it of lengthen 1 so such athlete 1 SUMMARY be endurance. impotence, development to Alcohol hormone KEY even thought sport muscle harmful steroids. aggression, are accidents. damage, cycling are road stops brain Lance There drugs many blood. person leads other nodules. becomes from unless of behaviour. substances work and cirrhosis. removing reversible personality steroids testosterone. this job not Long-term changes The its is known and cause slows This alcohol. limit. years ulcers, body large liver as replaced number stomach Drinking known and over lead toxins. metabolism damaged in driving alcohol other the This tissue of alcohol for health. and with up. of quantities damage. alcohol interferes limit penalties effects effects brain down legal severe hormones to improve performance in side effects. sports. 179 tnemelppuS of 15.4 Smoking Tobacco LEARNING plants It is structure the Describe gas the effects exchange carbon and tar system monoxide, in on State can that cause lung chronic tnemelppuS • link and the lung obstructive at of for smoking the T ar and is It the the smok e have hear t syst em gas Y ou this effect s and as in be as in on to are the as abou t it for a a against smoke smaller and It – Bogart by have nervous died smoking. at 57 from more stop bacteria insect a molecular system and so ts particularly to the the which enter the nerve cells depressant. arterioles, stickiness more as move of these lining mucus. help to are smoke the narrowing There Some lungs irritates normally in material tar. a the the T ar produce cough’. gas. volume an added in and is to of the about can This remove the back of 4000 cause cancer with hot there is less supply may not Due sometimes heart can that At a heart be to may by the the If it blood a oxygen baby (see by already when muscle. enough this, with carry time delivered premature it disease tobacco the they are keep but means in may page not where the on the lungs the mucus removed This to on is the 200). clean. the stimulates the particles the places settle to Tobacco the dust, air dirt lungs. the of is cells lining where out given and airways cells and from term bronchitis Mucus-secreting cilia that multiply. (COPD) chronic smoke airways. phagocytes bronchi to the permanently blood nicotine. there properly. response, bacteria send to including which of This to on that smoking diseases lining combines strain arteries develop of It oxygen response pulmonary in of respiration, by stick and in resulting this not increases to with clotting. to cilia in pregnancy to effect mucus system the alveoli narrows collects them make the its beating. that and bloodstream. coronary lung the the interacts stimulant, also poisonous weight efciency accumulates immune for the caused The It that the faster obstructive the passages a fetus of to a ‘smoker’s puts and birth irritates produce on to carcinogenic. during the collection reduce Humphrey our that blood smoking, to is This is faster compounds as oxygen for by cough through smokes blood into because rise harder emphysema. 180 protect happens through drug it material reduces 10%. more ows woman hum ans. as a beat stimulates monoxide so is promote pass and giving beating needs as on sticky not chemical Chronic brought with quickly it pressure. that described much be blood Smokers Diseases actor to smoke heroin heart damaged haemoglobin have cancer way drug. very unlike accumulate throat and the The interact heroin, the black are Carbon syst em . aske d ques tions tran sport on circul atory well exchan ge may tobacc o But airways different in Like does airways. the to term absorbed platelets the mucus TIP is increases cools. of chem icals the it tobacco makes blood tends T he of synapses. which coronary cancer STUD Y of bloodstream. Nicotine (COPD), evidence between allows denition Biology disease Discuss a Nicotine of smoking disease cancer heart as pesticide. smoke tobacco pulmonary natural the nicotine tobacco a that Nicotine • nicotine health OUTCOMES attack. • make and body’s this the happens air. Large amounts bacteria and of phlegm white blood (a mixture cells) are of 200 mucus, produced, which 175 attempt their Chronic nd lungs as it means difcult the up. to bronchi This long term. move are condition air partly is chronic People into and with out this of 000 condition cough blocked. 001 bacteria the Eventually much the lining this that of cells the weakens they surface blood break area for reach alveoli the alveoli. digest a to walls down gas the and pathway reach of the burst, exchange. 100 of them. alveoli the lung bronchitis 50 lung so cancer 25 reducing This tuberculosis 75 shtaed through white tar / Phagocytic and 125 rep Particles, 150 rep bronchitis. to raey people condition 0 is emphysema, which leaves people gasping for 1920 breath as remove lung have the control. form this a is area of discovered, the still, lung a and part of cells is block in of out eventually a occupy Deaths from lung tnemelppuS From that to the other a smoking and twentieth low, but lung these cigarette In contrast, you deaths increased smoking deaths tuberculosis In see the the from blood break the link early lung more other falling, a and small sort of care and better cancerous smoke deposit part of as the were the habit diseases, result of such improved showing in the increases the wa lls chan ce the of ch ance s arteries. tha t disease the (see of heart As 1 risk page oxygen in X-ray the on right page lung. 128. th a t blood will of developing 108) . to th e B lo cked h eart c lo t, Dene a rter ies th is the following words: there cor o na r y and QUESTIONS nicotine b tar c carbon monoxide hear t r edu c e the 2 da ma g es Explain how increased cigarette risk of smoking is linked to an developing: muscle. a lung cancer a What b Describe is the b bronchitis function of the c heart alveolus disease (air sac)? POINTS T obacco smoke monoxide and consists smoke of nicotine, tar , alveolus carbon particles. c Smoking is bronchitis, lung associated with emphysema, cancer. diseases heart such disease two is Describe who 2 cancer the nicotin e 3 KEY with fat a increased supply a housing. 1 increases an in data SUMMARY is alveoli disease Tobacco will between between Compare Heart tumour lungs. X-ray medical 1920–60. widespread. lung as Wales vessels. off cancer dramatically became from were can establish and If the cancer. century, of as above, scientists England large organs. graph helped in of A spread diseases may tumour. and may 1960 cells divide to airways tumour 1950 cause as grow 1940 These DNA but 1930 or long-term The tar. and known may the Many the slow cells it in grow very oxygen conditions. carcinogens The group enough efciently. these changes growth small of the airways. not Worse is of promote This absorb dioxide both cancer substances lining cannot carbon smokers of they ways adapted what develop in to which carry happens to a healthy out its alveoli function. in people emphysema. as and d Explain how functioning emphysema of the affects the lungs. 181 PRACTICE QUESTIONS 1 denition The A best any substance inuences of the taken chemical substance that term into drug the body reactions B any affects C substances that are D substances that may the in 6 is: Which statement on nervous the (Paper to body nervous treat become system A blocks B combines The effect of heroin the activity with of all sensory receptors information on about neurones nerves that pain disease C prevents the D stimulates release of neurotransmitters addictive 1) neurones to send impulses [1] about 2 the that the transmit taken describes system? drug in tobacco smoke is: (Paper A carbon dioxide B carbon monoxide 7 Why and C nicotine D tar pain A 2) is it [1] necessary develop all new viruses for drug types have of companies to nd antibiotics? become resistant to antibiotics 3 (Paper 1) Which statement of A [1] is not related to the taking B antibiotics have become C antibiotics have been 60 heroin? The drug is a D stimulant. in drugs use of for misuse over years many bacteria are resistant to some antibiotics B The drug is C Not taking addictive. the drug may withdrawal symptoms. The a lead to (Paper severe 8 D drug is depressant. Tobacco What the (Paper 1) Which component is [1] smoke the contains effect of carbon carbon monoxide. monoxide on body? [1] A 4 2) in tobacco smoke is causes mutations in the epithelium of the the bronchi cause of lung cancer? B A carbon dioxide B carbon monoxide C nicotine D tar reduces the oxygen-carrying capacity of haemoglobin C 5 1) Which drug muscle goblet [1] increases protein synthesis in adrenaline B antibiotics C insulin stops (Paper 9 tissue? A Drugs the movement make more of cilia may [1] be classied as useful and harmful drugs. (a) Explain (i) (b) (i) why drugs, antibiotics and Name (ii) one are useful drug classied as drugs. that is [4] classied drug. as a [1] testosterone (ii) (Paper 2) Explain briey named is why the drug you have [1] (Paper 182 to 2) harmful D cells mucus D (Paper stimulates 3) classied as a harmful drug. [2] 10 The graph the UK in between shown and 1991 as per shows which the number alcohol and number 100 000 was 2006. of of deaths the The deaths major death per in 12 cause rates 100 000 The graph smoked are 1910 men to number women. over shows by men 1980. of the the The deaths same number each year in dotted of men of the line cigarettes UK from shows from lung the cancer period. deaths per year 20 from lung cancer noitalupop 18 16 males 14 000 001 4000 12 number 10 of cigarettes 20 000 females smoked 8 rep 3000 6 shtaed 4 2000 2 deaths from 0 per lung year 10 000 cancer 5 3 1 9 7 5 3 1 1000 0 0 0 9 9 9 9 9 0 0 0 9 9 9 9 9 2 2 2 1 1 1 1 1 year Source: is Ofce of reproduced National with the Statistics. permission Crown of Public (a) Use the deaths graph in to which describe alcohol the Copyright Controller, Sector the was material Ofce Information trends the Calculate rates (c) for Cirrhosis the of cirrhosis among between the consumption of percentage men liver of has young is increase 1991 often alcohol. (a) cause. State (i) people. in by number the Explain UK, how (ii) [2] heavy of the the year of nd out if the cases of cirrhosis increase in alcohol increase is likely to in the Explain why inuence (Paper 11 In (a) countries prescription Explain these to (b) alcohol car is under 1980 which there was: highest number of cigarettes, (b) Describe of deaths from cancer. what [2] happened to: (i) cigarette (ii) deaths consumption, and from lung cancer over the you shown by the graph. [5] number due to (c) an [2] Discuss whether evidence to lung the support cancer. graph the provides idea that any smoking [3] the dangerous. [3] (Paper 4) 3) many on of a 1970 cases consumption. driving in consumption lung causes (d) 1960 especially the be 1950 highest period would 1940 and death 2006. caused The increased in and 1930 year [3] (b) 1920 (OPSI) in major 1910 of antibiotics from why a antibiotics countries are available rather are prescribed than freely buy. Explain only doctor. in available [2] why antibiotics do not kill viruses. [3] (c) Discuss the antibiotics. (Paper dangers of overusing [4] 4) 183 16 Reproduction 16.1 Asexual and sexual reproduction Reproduction LEARNING plants • Dene means producing new living organisms. Animals and OUTCOMES asexual and are sexual reproduce two types of to make new reproduction: individuals asexual of the and same sexual species. There reproduction reproduction Asexual • Identify asexual In from descriptions, asexual tnemelppuS • reproduction there is only one parent. All the offspring diagrams are and reproduction reproduction identical to the parent as they inherit exactly the same genetic photographs Discuss the advantages disadvantages sexual of information. They means there is due the are genetically identical to the parent, which and asexual little variation amongst the offspring. Any variation is and to effect of the environment, for example the availability of reproduction nutrients fungi Bacteria not and and are have a asexually water plants determine reproduce microscopic nucleus, the DNA but loop how organisms a loop is well organisms grow. Bacteria, asexually. of copied made DNA. so up of When that one cell. bacteria there is They do reproduce some for each new cell cell. membrane You can nd some information about how DNA is copied on DNA page cell 218. wall. parent This because cell duplication of the mould is reproduces specks a of the of damp cell asexual parent cell a fungus asexually dust, and surface, hypha, grows called produce divides into reproduction splits it which by into two is by making called a binary new cell ssion two. grows making they splits of over a spore hundreds oat open on bread spores. through and a (see These the air . thread pages are When grows 6 small a and and spore out. This 7). It light, like lands on the surface mycelium. cases new or of bread Eventually , sporangia spores are at formed forming short their a dense thread or network hyphae of tips. asexually grow Inside by upwards each division of and sporangium the nuclei. into Each two of growth cell threads division bacterial type DNA Pin continued The wall nucleus gains a small quantity of cytoplasm and a protective daughter spore cells case. When ready , the sporangia break open and the spores are dispersed. Potatoes Figure Each 16.1.1 new identical Binary bacterial to each cell other ssion is in bacteria. genetically and to the are reproduce swollen Sucrose is asexually underground transported in by stems the means that of stem grow phloem from tubers, from the the which parent leaves into plant. these parent underground stems that swell as they convert the sucrose into cell. starch. leaving The the However, ‘seed’ from one the farmers sexual organs. 184 to parent new potato Sexual In tubers potatoes regrowing, of parent plant in dig plant the are shoots as at the ground them plant known dies the up and next end to sell year. genetically and roots of survive the them. All growing over the Some from are kept as produced When the season winter. tubers identical. emerge the they start growing points ‘eyes’. reproduction reproduction The sex there organs are make two sex parents. cells or The parents gametes. In have animals sex the male gametes are nuclei are egg inside cells. structures fuse At an contain one which half comes the from set of In grains. During may animals the The A the female into a egg new comes The zygote or are the from a inside zygote the in gametes gametes individual nuclei has male gametes gametes reproduction gamete. chromosomes. the fertilised material female plants female sexual grow genetic the owering In plants fertilisation. embryo half cells. owering ovules. at fertilisation, and sperm pollen In called together form are nucleus to plant. male the divides gamete gametes that underground stem contains developing two sets of chromosomes – one from each gamete. tuber Unlike asexual genetically reproduction, identical to the the offspring parents. Each produced zygote are ‘eyes’ not receives half its genes young old from its male parent and half from its female parent. This means tuber tuber that swelling sexual reproduction brings about variation in the with offspring. stored Advantages and reproduction An advantage can plants If left grow. in place Plants There in may is very little, reproduction. affected none by may a more be if of rapidly tubers any, is much for from grow with asexual growth be a disease. resistance to into each are so as a Since Figure new than plants for could spread which all the potato plant. are of if and the same to new areas many seeds wasted. asexual these all in parent seeds. methods individuals genetically they may all are identical, very quickly through a crop be killed. plants plants are genetically identical. reproduce asexually by monoculture, producing in The resources. However, are the from Potato Disease 16.1.2 Organisms where dispersed result disease fast. other many they is areas tubers disadvantage the it competition. variation can that colonise reproduction as places This and compete sexual certain have spread potato but not unsuitable reproduction to grow parent, there in asexual ground, the disadvantages plants rapidly produced where land the as Seeds of of reproduce in If tubers, as well as sexually with environmental owers. conditions features rise to change, adapted variation. adapted to adapted if species the the are it to In is unlikely the the new wild, existing able to there conditions. many conditions environment better that as and their If be Sexual individuals changes. survive will individuals reproduction may not parents, there is with be but plenty as may of gives SUMMARY be well 1 Explain each Asexual Sexual nuclei reproduction offspring to form Binary in in one involves zygote, different ssion formation a results from reproduction genetically 3 a gamete b fertilisation c zygote d embryo Describe each the bacteria, the each spore are all production of of th ese fusion of male offspring other and of that their production examples in and female are a binary b spore production c tuber formation parents. fungi asexual and asexu a l reproduction: genetically parent. producing from potatoes in of ssion Asexual does reproduction not result in may variation produce of many tuber 3 reproduction. offspring as individuals in sexual in bacteria in fungi in potatoes Make the a table to advantages disadvantages 4 following: POINTS identical 2 the evolve. examples 1 of variation, 2 KEY QUESTIONS well rapidly, but tnemelppuS tnemelppuS starch compare and of asexual it reproduction and reproduction in sexual reproduction. plants. 185 16.2 Flower Flowering LEARNING the structure insect-pollinated of to an the grains ower functions of have carry part • State petals, is and • Describe and out sexual female reproduction gametes pollination. and pollen to parts. the female Female grains grow The parts. gametes a tube male by producing to parts The are transfer deep reach make owers, inside them. pollen of the Each grains pollen female pollen tube the a male gamete so it can fuse with the female gamete to form anthers, a stigmas male male delivers sepals, carry OUTCOMES which • Describe plants structure zygote. Fusion of male and female gametes is fertilisation ovaries the structure of a petals wind-pollinated • Compare the ower adaptations of anther stamen different types of pollen grain filament stigma sepal carpel style ovar y ovule nectar y Figure 16.2.1 Flowers vary A in half ower structure Insect-pollinated The spiky pollen pollinated from grains owers and wind-pollinated are the from smooth grains are Flower parts swollen owers. • Sepals • Petals • stalk in ies a smell jump in, of rotting slide esh down the of covered the out to 186 plant visit in pollen; change, another after a to attract sticky few allowing ower of days the the upon their ower. method of pollination. owers sepals rings form attached the outer to ring the end and the of a carpels that coloured and on the full the style are sugary protect the scented. nectar. ower Many Visiting when have a insects it is a bud. nectary land on at the nectar. male sex where the organs. the Each pollen anther. In is this one is made, ower made up of two and the lament, there are four a stamens ower). female and an inside sex organs. Each carpel is made up of a ovary. the ovary. Each ovule has a female gamete – cell. pollen in The in structures holds the arranged makes anther, ovules grains the ies walls are of insect-pollinated photograph, above left. owers They are are often also spiky often like sticky. ies the to same adapted to attach to hairs on the surfaces of insect The bodies. – grains become dislodged onto a stigma when an insect enters and another are depending insect-pollinated Indonesia The the are the egg grains produces feed a those Sumatra to are The stalk. brightly stigma, The from an ring. which Carpels the arum are in often leaf-like which (eight • are Stamens parts: • inner base, petals are ower the the Titan of insect- form The drawing ower of the same species. The ower in Figure 16.2.1 has walls climb species. stigma its way in the centre towards the of the ower nectary. which an insect will push past on a Wind-pollinated owers STUD Y inflorescence inside spikelet (group a single T here single of TIP flower flower are type s of feather y flowers) some stigma long man y ow er . with a differ ent Look hand filament and mak e sure anther you can stamen iden tify filament style anther parts ovar y hinge desc ribed differ ent 16.2.2 Grasses and perenne, The are so anthers that chances on a small, the are hang The feathery positioned They large act like a surface pollen grains that get wind. that the Rye grass, wind-pollinated inconspicuous no wind-pollinated scent are wind. small, These no Lolium ower. compared and ower. with nectar. smooth owers and light make huge The ower the are ower . providing for the a a catching blown into T wo them. Wind-pollination can owers lot of pollen, anthers which produce so is why that and cereals another plants much. such grow means be close that likely to were separated as by and showing feathery large, loosely stigmas. But the POINTS grasses to one pollen transferred Bromus, anthers the KEY fact of waste attached a in the stigmas area a of here ow ers. away outside net, on example by of main landing the blow an have grains as small. outside can and They carried grains very is typical green grains grass pollinated pollen easily pollen wind pollen. also of are rye all owers. pollen stigma anthers so of of features produce they numbers are many insect-pollinated The species cereals has owers This four with mobile Figure the at lens is than large 1 more if Insect-pollinated have they sepals ower distances. Long anthers hanging out of rye grass petals in to to the owers protect bud attract and the bright insects. The owers. stamens SUMMARY consist laments. up 1 Copy use and some of complete more the than sentences using these words (you of a Each stigma, carpel style 2 once): carpels pollen Wind-pollinated ovary parts of a ower are called the . Each is of an and a lament. the . The female The parts grains are Each is made up of Make a owers table and of a to compare the wind-pollinated , pollen a ower are called Compare the structure of an style and of that insect-pollinated large carried owers quantities pollen with on the Insect-pollinated produce ower ower. that of is . owers. insect-pollinated the smooth smaller and spiky wind. owers quantities pollen of that a attach wind-pollinated are feathery the sticky 3 anthers Wind-pollinated easily 2 owers with made light, . and outside produce inside ovary. made 3 up and stamens hang male and made stigma stigmas anther is may inconspicuous, The anthers QUESTIONS to insects. ower. 187 16.3 Pollination Pollination LEARNING • Dene the the term pollination agents transfer Pollination owers are different adaptations insect-pollinated pollinated adapted agents When the structural may of of to be pollen carried grains one pollination; of out these there are by from the insects methods. others or anther by Insects such as the to a wind, and birds wind and and are bats. of pollination • Compare the stigma. two • Name is OUTCOMES and of wind- an its pollen to bring gamete anther so that the so is it splits pollination male that ripe, gamete open can occur. (inside fertilisation along a can its length Pollination pollen grain) is and releases needed near to the in order female occur. owers tnemelppuS • Distinguish between self- pollination and cross- pollination and discuss Insect Look at pollination the diagram of the ower below. It has a number of their adaptations for insect pollination. signicance The ower tongues is and pollinated are able anthers brushing – by to ripe onto bees, reach with the which the land nectaries on at petals. base of Bees the have long petals. stigma pollen insect’s the the back insect’s back stigma and closed style ring of hairs stop anthers ovar y small ovule the insects reaching petals nectar form landing – dead pad nectar y Figure Honey bee with pollen on its legs. The 16.3.1 bees anthers brush STUD Y of TIP Whe n you po lli nated a hand how to insect s. able you do at owe rs lens, their them look shou ld for no t bee’s When against such back the the sugary in bee ripe pollination Look the at one nectar a as way it to made that pushes enters stigma ower in the sticky its another and another of from down ower, pollination same nectaries. pollen head the it is to species. The them the brushes will base some of achieved. a of outside wind the pollination ower so that on the they next release page. their The pollen by owe r seen diagram hang the wind blows them. be The stigmas they act as are a feathery net to and catch are pollen also found grains in outside the air. the ower, where Wind-pollinated before . owers by the grains the 188 the from helps po lli nated this the Wind when have upon pollen iden tify anthers Y ou transfers positioned petals. pollen bee insect - with struct ure be feed are against the the A have wind so same light, to that smooth another some, species. by Most pollen ower. chance, of the grains The which anthers will land pollen can easily produce on the produced stigma will be many be of carried pollen a lost. ower of The structural features of insect- and wind-pollinated owers are pollen compared in the feature caught table. insect-pollinated owers wind-pollinated owers pollen present – colourful and absent or very small and carried petals scented present nectaries which food to – is make a for attract insects difcult to by see nectar sugary liquid pollinating absent insects lots present – usually with long laments so of pollen stamens laments; attached rmly laments; for to hang to inside insects small anthers quantities anthers the rub outside ower the against of easily pollen grains light easily to blown attached so Wind pollination. pollen to is away quantities of smooth, that pollen stick loosely 16.3.2 ower; sticky, large spiky the laments made anthers Figure short wind pollen that can easily insects’ be carried by the wind bodies sticky, carpels small usually for stigmas inside insects to the rub large, ower catch against air feathery pollen stigmas grains in to the tnemelppuS Hazel Pollination and the Self-pollination a stigma of the catkins release pollen to be carried by variation occurs same when ower pollen or to a is transferred different from ower but the on anther the wind. to same KEY POINTS plant. 1 occurs when pollen is transferred to a stigma Pollination pollen another benet plant to material a of the species between same of species. plant, different since plants Cross-pollination it ensures and is of exchange results in a of which natural selection can operate greater (see Unit results in much less variation, since of the male to the stigma exchanged with different is advantage plants but with the part an if there are no plants growing in isolation from others of genetic same material one. pollinating the of the petals, same Give is b two ways Write to down pollinated in the three and pollen pollen other from from insect-pollinated wind-pollinated differences wind-pollinated between owers owers. tnemelppuS a What is the difference between owers with are feathery anthers anthers same of to the ower on involves pollen the self-pollination and of from stigma or a hang the the of the different same Cross-pollination owers. that ower . Self-pollination ower insect- and the transfer 2 have nectar . species. 3 which and and QUESTIONS different owers scent However , insects, transfer a ower female ower. Insect-pollinated outside 1 the the is stigmas SUMMARY of anther variation inconspicuous for of of Wind-pollinated self-pollination the 18). bright not transfer from genetic 2 Self-pollination the grains greater part upon is of plant. involves pollen tnemelppuS Cross-pollination from the the crossanthers of one ower to the pollination? stigma b State the advantages of cross-pollination over self-pollination. a of another different plant ower of the on same species. 189 16.4 Fertilisation and seed formation LEARNING OUTCOMES Fertilisation State that fertilisation owering a pollen nucleus plants occurs nucleus in an in fuses when with a Pollination the starts ovule to tnemelppuS nucleus. • Describe the events that • complete part grow of a a when ower. pollen Fertilisation the If tube a to pollen pollen take grains grain the land lands male occurs when the male occurs inside the ovule. on on nucleus nucleus the a stigma ripe to the fuses of stigma it female with the lead female to is female nucleus. This fertilisation State the requirements germination of Each for the seeds of pollen ovule. the style carries the The the ovary. male grain As it and carries male It grows grows, enters fertilisation in the a pollen ovule tube tube from nucleus nucleus which pollen nutrition gamete gamete a the with through then zygote fuses is to take gains the it. a tissues The formed male the – egg fusion the style the cell of nucleus from pollen hole the by of rst small with the nutrition and tube reaches micropyle. nucleus. the to tissues two This is nuclei. germinating pollen A pollen (left) grain with its and a pollen germinated tube and pollen male grain pollen down gamete grain tube grows style nuclei. ovule STUD Y TIP Rem embe r male the po lle n deliv ered gam e te tube . no t that gam e te the the to and gamete fuse with nucleus egg cell about nucleus is femal e pollen tube penetrates micropyle po lle n po lle n male male inside grai n to by T he the is the grai n is Figure 16.4.1 Fertilisation occurs within the ovule. gam e te. PRACTICAL Growing Find pollen some owers particularly Cut some transfer sucrose. anthers dish of Scanning grains 190 electron and pollen micrograph tubes of lily, of pollen Lilium sp. for small Use to squares to a the 24 forceps, with anthers covered in pollen. Lily owers are suitable. them to tubes lter of paintbrush squares 48 put of hours. on a damp paper to Visking soaked in transfer dialysis Remove microscope a (dialysis) nutrient some tubing. the pollen Leave squares slide and tubing and solution in grains a covered carefully observe. rich from with in the Petri a pair tnemelppuS • Seed formation KEY After fertilisation, the zygote divides and grows into the embryo. 1 The ovule forms the seed with the embryo inside POINTS Fertilisation male The of ovary the forms ower sepals, the are petals fruit not and with needed stamens the seeds when wither inside it. fertilisation and fall off. Many has of the occured, They have parts so gamete pollen when the fuses gamete nucleus the with nucleus the from the female inside an ovule. completed 2 their occurs it. A fertilised egg grows into functions. an ovary the embryo which becomes inside now an forms ovule the seed. fruit seed thin with The ovary forms the fruit testa containing 3 many Germinating seeds. seeds require stone water, warm oxygen and a temperature suitably for growth skin and the becomes seed 4 Figure 16.4.2 How a plum ower grows into a plum Pollen that Each fertilised ovule grows to form a seed. Each seed is made up the The embryo ovary forms Conditions Three • • the for is energy store • a seed coat or grows are needed of some down an ovule in SUMMARY needed for seeds for to seeds swell. to Cell from seeds. Cells expansion the absorb This swelling water, breaks develop the vacuoles seed. made these a makes Water is the also radicle needed (embryonic to dissolve root) the Oxygen is State what happens by enzymes from the food stores. occurs when in grow Water plants. Describe the role of the also tube. enzymes. needed for aerobic respiration to provide the What happens to each embryo of with to soluble c • style ovary. seed pollen activates the and b products the the tube germinate: owering out on pollen QUESTIONS fertilisation expand. land fruit 1 coats a testa. germination conditions Water an that produce of: reach • grains stigma fruit. the following after energy. fertilisation? • A suitably warm temperature is needed so that enzymes can work efciently. i petals ii ovule iii ovary PRACTICAL Conditions for germination 2 a State the three environmental Y ou can investigate the A conditions necessary B C conditions D that germination germination Set up and the leave checking with tubes them them mung as for a b to germination has In each explain week, day affects see damp if of the seeds. beans. shown every affect for started. case how in part the a, condition germination. cotton warm warm warm cold wool c Explain why the seeds in oxygen Only the seeds in A have all tubes B, C and D in the absorber the conditions germination. needed for temperature Practical box (left) did not germinate. 191 tnemelppuS ovule development. 16.5 The male reproductive system The LEARNING or • Identify of the on diagrams male system testes are the male sex organs. They produce the male gametes OUTCOMES and the parts sperm This reproductive state spermatozoa cells. stimulates during their The – a word testes also changes puberty. This that in is make a the boy’s happens usually abbreviated male body between as hormone he about to or testosterone. develops 10 sperm and into 16 an years adult of age. functions tnemelppuS The • Compare male and female testes outside gametes sperm and are the cells be need stored. cells which they mature. these located body. uids sac the puberty, much to in a keeps temperature stored A tubules secrete a After are inside This the in urethra. which the tubules cells to outside the can hangs gland develop produce the sperm swim. which temperature 37 ˚C prostate sperm scrotum cooler constantly just called The a than testes tube the at cooler the small wider called testes and The sperm testes duct as properly where connects other glands prostate seminal vesicle secretes as a mucus source together of and other energy form for semen, glands their also secrete sugars respiration. known as which Sperm seminal cells sperm and cells the use uid uid. prostate gland The of two the time. any sperm penis. A ring urine ducts Urine of join and muscle from the with the semen around bladder urethra, never the pass urethra during sexual which down runs the contracts down urethra to the at centre the prevent the sperm and same loss of intercourse. urethra spongy tissue Male and female gametes penis Gametes testis the are female specialised sex cells. gamete cell that is is The male called the adapted gamete ovum for is or called egg. swimming the The by sperm having a cell is a agellum that foreskin lashes male from side parent to to side. the egg Sperm of the cells carry female genetic parent. The information nucleus from contains the the scrotum father’s Figure 16.5.1 Male reproductive chromosomes. provides front An egg is much bigger than a sperm because system: the food store that supports the embryo after fertilisation. view. bone rectum acrosome middle the piece like head the containing flagellum a whip sperm (tail) and beats drives for ward enzymes a sperm cell nucleus membrane containing chromosome membrane anus cytoplasm sperm an egg tube jelly a coat sperm same this nucleus sperm tubules in on scale the as egg containing testis chromosomes Figure 16.5.2 Male reproductive system: Figure side 192 view. 16.5.3 Structure of a human sperm (top) and an egg (bottom). it Its nucleus half the haploid are contains number cells. of Body described as the mother’s chromosomes. chromosomes cells have the as body normal cells. Gametes They number of are contain described chromosomes as STUD Y Egg diploid. cells An egg is fertilised by a sperm cell. The head of the sperm to membrane The the sperm two help of it the reach sperm nucleus nuclei fertilisation, cell moves fuse the the coat fuses to of the with through together jelly surface the form changes, the cell. egg zygote that no The cell cytoplasm a so egg cell func membrane. of the egg (fertilised more cells are egg). sperm you and can adap ted tions can featur es After these enter. and sperm specia lised contains cells enzymes TIP and . fo r Mak state and adap t their e sure their key explai n them fo r how their tnemelppuS func tions . Comparing male and feature sperm size small female gametes cell egg cell much swims using agellum (or that lashes from not store very sugar for number move along itself the – is oviduct and by peristalsis side has energy cell side cilia to sperm tail) moved (mobility) than its does movement larger little in – uses seminal protein uid and cytoplasm respiration until fat – in enough implantation to in last uterus of 23 (haploid number) 23 (haploid number) chromosomes constantly produced produced puberty) sperm swimming pathway cell by has the through the The jelly SUMMARY QUESTIONS 1 complete Copy and semen urethra sperm The male the cells gametes which pregnant releases contains surrounding sentences testes penis are after contraceptive acrosome coat month menopause, when life mitochondria, tail. a until often throughout Each one (after using energy called these duct and taking a to that power digest a egg. words: ejaculation sperm or pill enzymes the puberty except are prostate Human made in the organs the . from to or each tnemelppuS a tube testis. form . and 2 A which Give out three called an adds the erect differences within carries gland During the contained the The of are the uid semen to a sac sperm the passes cells and away sperm along 1 The male consist cells sperm the egg cells. 2 The Explain how sperm cells and egg cells are adapted for of fertilising reproductive the ducts, and sperm smaller b sperm an POINTS urethra sperm and called . between (top) male KEY sex sperm egg. scrotum testes, organs scrotum, prostate gland, penis. cells than are the tnemelppuS millions number much female egg their cell. They are produced in functions. huge to numbers swim using and a are able tail. 193 16.6 The female reproductive Ovaries LEARNING Identify of the on diagrams female system female sex organs that produce the female gametes OUTCOMES called • are system and the parts or oestrogen between reproductive state ova eggs. and 10 The ovaries also progesterone, and 15 years of make which age the starts during female to hormones happen with girls puberty. their Oestrogen stimulates the development of the sex organs and functions secondary • State the the parts functions of the reproductive of develop female ready sexual into to an characteristics adult. receive an in a Progesterone embryo in the girl’s body prepares case of a as the she starts uterus so to that it is pregnancy. system The ovaries kidneys. oviduct 28 The ovaries months. The egg moves lining attached puberty, days. openings uterus are After of the slowly If sperm If the cells egg is are not tend passes the the egg to out oviduct down to an in a inside is release of the present in fertilised it an eggs) into just ovary the uterus egg about will a below about on the every alternate funnel-shaped ovulation. the the after an (or and called oviduct die abdomen from egg towards the will the ovary process oviduct of released The egg (womb). be day. If fertilised. the egg is ovar y fertilised uterus of will divide to form an embryo it develops which may attach itself to wall the cer vix it lining of the uterus where into a fetus. (neck uterus) vagina oviduct uterus opening of Figure vagina 16.6.1 Female rectum reproductive system: front view. bone STUD Y TIP urethra T he are testes the and sex gona ds – ovar ies orga ns the or orga ns clitoris that or fo rm gam e tes. secre te – the the T hey sex testos terone , and that their sex can also ho rm ones oestro gen prog estero ne. you cells Be anus sure compa re Figure func tions The It lower leads to outside of the Above vagina birth 194 16.6.2 Female reproductive system: side view. . of end a of the body. urethra the is the as tube is the it is the has a called Above through urethra called canal, uterus muscular the which The through of urine of from clitoris. vagina here muscle vagina opening sensitive vulva. ring the that is a the the called that vagina bladder The outer sometimes baby the opens passes is cervix. to the the opening passes opening known at as birth. out. of the the Sexual During is intercourse sexual pumped The erect made by penis the the vagina. the sperm towards As they are the to the vagina movement move to secretions form females in the vagina cells stimulate penis during lubricates stimulates sperm seminal and against from semen uid at orgasm. or into and tissue the so each that sexual penis the and other . of the around erect. Fluid penis contractions tubules Blood becomes intercourse. movements from it within begin the in testes penis. ow, an clitoris of males spongy placed walls ejaculation called is This the the special ducts added move intercourse into or the through this time vagina the the Repeated the glands seminal including uid. penis man into the experiences movements walls may the prostate Contractions of also the of vagina. This feelings erect produce the of penis gland urethra is an pleasure against orgasms for the the 3 woman. up to Each 500 ejaculation million SUMMARY 1 Copy out correct contains sperm between 2 to 5 cm of semen with cells. QUESTIONS the list function of organs from ovary carries vagina a oviduct receives cervix carries uterus produces ring the urine of list out muscle the on on of left the the at penis the the and match each with its right. body opening during sexual of the uterus intercourse An the egg eggs from and the ovary female If egg the hormones cell sexual time of fertilisation urethra 2 Look a the at the Name place where diagram the of the a fetus female b Where reproductive system to G A there is ovulation. at a around chance that occur. POINTS B the do each The female following reproductive of system the at below: 1 diagram ovulation will ovary happens parts A on the develops KEY labelled leaves intercourse consists of the ovaries, take oviducts, uterus, cervix and place? vagina. i the production 2 G of The ovaries which C ii fertilisation iii development are oviducts F of an 3 The the released eggs at into ovulation. oviduct is the organ embryo where iv produce oestrogen passage D The fertilisation uterus is the occurs. organ in E of the baby which during Some women’s oviducts can get blocked. Explain why with blocked oviducts would be unable to fetus have able whereas to have a later a woman with only one blocked develops. The oviduct cervix is a ring of muscle a that baby, and a 4 woman embryo birth the 3 the may separates the uterus be from the vagina, birth canal. which is the baby. 195 16.7 Fertilisation and implantation Human LEARNING There • Describe fertilisation in Describe the are millions an egg muscular of the a ball of cells that sperm swim in a man’s from the semen. vagina to If one the of them oviduct – is to the into the tube that links the ovary to the uterus. uterus intercourse, sperm cells swim through the mucus in the cervix into is the implanted must zygote After form it early development to of humans meet • fertilisation OUTCOMES uterus and then all the way to the oviduct. Many sperm cells do wall not survive produced this – to difcult increase journey , the which chance of is why some so of many them a sperm reaching fertilisation cells the are oviduct. forms sperm head of one penetrates sperm egg membrane jelly coat changes nucleus of other sperm stop fuses sperm with entering egg to successful the egg b nucleus at ovulation an egg into tail ovar y sperm Figure 16.7.2 STUD Y Events at 16.7.1 If TIP the time nucle us rst . T he divisi on durin g T his of divide nucle ar is there the that the same chrom osom es See page abou t this. sperm After is an 218 the in a in fertilisation. egg nucleus contains readiness oviduct, is 46 for through has fuses with as and it rst the the egg division the succeed the egg to sets start which the in head surrounding father. these on is left form of the of the membrane agellum nucleus two the and may coat with and from cell acrosome jelly contains one cell the fused chromosomes the sperm by cytoplasm diploid mother a released membrane the which the the pathway sperm from now the outside. zygote chromosomes The zygote being occurs the egg. – nucleus copied shortly after fertilisation. This to So stops fertilise can take if other the sperm egg. place. an egg If cells there However, intercourse fertilise 196 and Enzymes enters sperm nucleus one egg it. digest nucleus The mito sis. gene tical ly iden tical . more divide s occu rs sure have num ber for that of grow th all are cell mus t type mak es cells and a Ovulation fertilisation. penetrating Every released oviduct of successful Figure is the if the happened it is from is no entering egg sperm just released in can before during so the only stay alive ovulation, this one oviduct, time. sperm no for the 2 is able fertilisation or 3 sperm days. can Implantation Fertilisation zygote Then while to it this a place to continues divide After takes begins cycle while few oviduct, beating of to of to give or along ciliated by four slow embryo is a to less this, form cells the a and hollow the of lining the at of cells which cells. contractions cells eight, Some rate ball fertilised two-celled then regular . down peristaltic epithelial After once becomes stop the oviduct. divides divisions hours the the It divide others pushed in divide. It egg but after a continue they moves the or embryo. divide. down oviduct and the the oviduct. cell divisions form an embryo a ball of cells forms zygote divides zygote oviduct implantation of muscular of uterus lining of Figure 16.7.3 Implantation of the embryo wall developing ovary placenta uterus embryo. DID It may The take a embryo number embeds implantation. contains oxygen these wastes days into the uterus numerous from chemical The of blood blood diffuse for the soft lining lining has vessels. vessels out in embryo the the embryo diffusion. opposite reach the uterus. thickened The by of to in This is called preparation obtains Carbon YOU and nutrients dioxide and and Eggs cell than a to QUESTIONS 1 complete and zygote sperm Sperm cells The through the one of cells and these the swim then words: implants fertilisation the sperm using ovaries vagina enter made sentences sexual cells intercourse. the weeks female through of the enter about the every eggs ostrich into the present. oviduct The where which lining 2 a of the How fertilised the cervix An four passes down or to and egg . take were the uterus up KEY cells are needed where to Why does a membrane form around to State the following a an human egg b a of chromosomes in it fertilise the the sperm cell c a long equivalent Fertilisation of the in the 2 For an egg nuclei occurs a and of seven when sperm nucleus fertilisation place egg? and must a cell of to an the fuses egg cell. occur, have sperm reached the taken cell must oviduct. after of the The a zygote ball of embryo, cells: Aepyornis bigger . an 3 number 60 cm the if form fertilisation? 3 bird, of POINTS have b eggs even bigger weighs eggs. ovulation sperm times and egg uterus. many largest the is The place divides the were is during oviduct. may egg 24 The elephant with are is egg 1.36 kg. nucleus passes It The today embryo 1 in egg. weighed uterus cells. world hen’s maximus, Its Copy single the ostrich up direction. are in extinct SUMMARY KNOW? uterus. divides cells which the oviduct the lining to called form the passes and down implants in zygote of the uterus. 197 16.8 Pregnancy Pregnancy LEARNING OUTCOMES Pregnancy • Outline the growth humans development of the State the functions of cord, sac the and tnemelppuS Describe the placenta and embryo its functions of umbilical that some support toxins can and cross affect The its The so has and orga ns the featur es is know n have embr yo that The The the hum an, a One is It • are it as the the food area and a a fetal there and supp lies is why featu res large are the These site the to lining gain projections cord of other cord grows sac of the or attaches makes the attach which of to the and grow fetus surrounds oxygen they fetus blood to amniotic mechanical it oxygen into to the the it. and diffuse nutrients between fetal for blood to and uid damage, for the placenta from to the surround example and contains placenta. and when protect the the mother movements. in the development are after into summarised fertilisation, tadpole. where months toes The Three are a as human embryo a baby ready to be born at follows. does embryo not yet looks have a bit arms like or a legs, sh but months the the mother Seven the It the is The heart embryo now has has called a a started face, fetus. and other to beat. limbs, Most ngers of the and for carries fertilisation the nerves and muscles fertilisation, has perfectly body the hair. last after carbon wastes of the fetus rapidly. after months arter y human. after fetus ngerprints • develop. formed. months length, will fertilisation looks developing Five these after and Its although formed only about eyebrows, movements may 180 from mm in ngernails, have been felt by month. fertilisation development is almost complete. dioxide the dioxide and wastes fetus smal l diffuse into from the the fetal mother ’s blood blood distan ce the betw een blood blood maint ain grad ients vein from the brings oxygen placenta to and the food fetus 28). oxygen direction of blood oxygenated into Figure 16.8.1 blood blood The role the food diffuse mother ’s blood mother ’s blood deoxygenated and flow from 198 in period uterus, nutrients continue to exchange wastes; transport pregnancy month T wo the page into tissue surfa ce Sinc e good conc entra tion (see soft carbon the matern al to • the subst ance s short are tw o gas for where and diffus ion. exchan ges the T his same lung intes tine: for also absorb ed. has is surfa ce is the amniotic and to stages of clear are fetus. which fe tus. TIP disso lved birth, gestation blood. sudden organs placen ta the sac against main and T he and the it • exchan ge is vessels amnion end it STUD Y lls dioxide embryo as called are • recogn isably it umbilical makes the implanted into umbilical maternal fetus TIP all is fetus • Once has growth. An placenta blood fo rm ed fertilisation time the the • STUD Y of and and placenta between the carbon pathogens time period cord • State of This uid placenta • period projections placenta. • the months. placenta, to amniotic 9 the grows umbilical is fetus After • is and of the placenta. the fetal blood placenta dissolved features a short and is food as fetus amino excreted an some umbilical placenta and Amniotic similar sac into to the should Young be the HIV with can fetus returns from from to and the the has also the surface are to including water. where same area between supplies and fetal maintain glucose, The mother’s it. placenta. blood oxygenated ltered the have blood fetus’ skin developed the The barrier a uid fetus blood The from and are the uid to has shed fetus to be The fetus at 26 days. a The fetus at 8 weeks. The fetus at 5 months. contains fetus the to the fetus. composition into the carries lungs. does cord the blood the into amniotic and disease. that be causes positive if management to a child the is The not amnion out some fetus provide may during who the This before vaccinated mother pathogens. since cross is is the carry a why they urinates any is However, still virus all can young act with a the mother the virus. even susceptible that become placenta, infected not by they pregnancy does fetus caused fetus. rubella AIDS the and environment, harm also toxins measles) against for the to sterile (German should birth into deoxygenated taking a is placenta careful give as vaccinated HIV mother, it is fetus. acts virus born why large blood vitamins diffuses the that drinks womb men its organs Rubella infection The be the disease. across of for from is a It kidneys. Cells the This fetus. exchanges good food formed and placenta though is two the 28). joins vein Since ions, the intestine: page which her movements uid nutrients The a when the urea for absorbed. small are mineral plasma. breathing its surface (see transports uid to and all cord that there gradients fats, are the diffusion. blood through artery exchange and for obtains acids, produces The lung distance maternal gas substances the concentration The the can get women pregnant. as so a a baby virus. who reservoir may However, is HIV+ Nicotine can SUMMARY also pass across the placenta (see Topic 1 a How to b is the List two in 1 The fetus size and grows and develops inside the uterus. It increases all the major The umbilical the site of the amnion cord attaches exchange of the fetus substances amniotic the What is to the between placenta, fetus which and is in tnemelppuS The uid to protect the fetus the has diffusion of mother’s blood. What a large surface area for gas exchange long does it last are the and functions amniotic of the uid? Describe nutrients and waste between fetal blood structure and pathogens cross the placenta into efcient the acts as a barrier to many in the which placenta fetal diffusion blood and fetus; mother’s placenta ways of and between toxins two and helps the gestation How damage. placenta Some pass direction. from the 4 opposite and that mother; 4 3 fetus humans? amnion mechanical the that mother’s organs. 3 makes to the substances period? 2 connected in 2 develops fetus substances from blood POINTS the placenta? two pass KEY QUESTIONS 16.9). blood. others. 199 tnemelppuS tnemelppuS The 16.9 Ante-natal care and birth Ante-natal LEARNING Ante-natal • Describe the ante-natal pregnant Describe the while in labour and tnemelppuS Describe the she advantages disadvantages provides of the is breast important so iron the and • calcium, • iron, so carry blood that right the nutrition mother obtains all Particularly calcium. vital and has the for also the health needs protection a balanced nutrients important as the that • to of the make sure for the fetus it diet needs during for this growth are vitamins and and minerals, • her protein, new They to preparation therefore amnion at 7 to 8 weeks that provide for need body in are the Her the the the birth. will need to ensure such that she growing extra growing extra red iron blood pregnant red blood fetus in is the cells mother diet that has cells also needed making to make carries enough red more oxygen energy to around amino mother making fetus make substance so The the fetus. both the heavier tissues. of can the woman of: body to carbohydrate, move pregnant bones her oxygen cells. A quantities haemoglobin, the the fetus adequate to inside is mother milk gets fetus birth, The milk as A before womb. pregnancy. development. formula care the and time and or in birth It • is processes during involved it women that • care, care fetus of care OUTCOMES The many acids makes fetus new that muscle is also they tissue both in growing the and need to uterus make in developing and cells. of The mother should not smoke since nicotine and carbon monoxide pregnancy. cross the babies. also placenta She crosses birth should the defects placenta so and can drink no placenta and in premature alcohol, and mental some result can or retardation. babies are very cause born a small variety Drugs, with or an underweight quantities, of such effects as addiction heroin, to as alcohol including cross the heroin. Birth A placenta the born pregnancy prematurely, takes about perhaps 9 months. because there In has some been a cases babies problem are during amniotic cavity the normal pregnancy. An early fetus most breaking of the membrane (amnion) around the fills uterus A is few the weeks common before This positions and the its birth, head build-up of reason. the above fetus the pressure in usually cervix. the turns over Hormones uterus inside released stimulate the by hormonal uterus. the fetus changes in fetus (50 cm) the mother . A hormone, oxytocin, is released from her pituitary gland that uterus stimulates cer vix small 16.9.1 Position before 200 of the birth. baby just muscles contractions These Figure the of contractions contractions breaks, slowly allowing of the the uterus become stretch the uterus to wall. This stronger the amniotic contract. and opening uid is to the The beginning more of mother the escape. of frequent. cervix starts and to feel labour Stronger the amnion The to muscles push the the baby’s takes the and The baby It umbilical attaches navel. wall. The to After It is a for of is contract cervix. through As tied baby. few the now soon that The the as it the very cervix widens vagina. is born baby strongly This the has and or part baby airways start dilates of the breathes clear of and birth for mucus easily. pushed process painful the important cord the wall pushed quickly. is breathe uterus towards is quite time. can the head place rst of and The minutes out labour of the the with mother . cut just remains above the placenta vagina the She of as help the point heal comes the muscular can the cord to away where form from it the the baby’s uterus afterbirth contractions process by A of the gentle uterus newborn body before Pain-killing may the be drugs given space labour by can an between and also by be epidural. the spine breathing given This and to in ease involves the a special the pain inserting spinal cord. way during during a of impulses from pain receptors to The the drugs umbilical cord. of These (tube) prevent 1 into POINTS During the labour uterus the wall muscles in contract. the 2 transmission its labour . birth. catheter with is exercises KEY the baby At birth, the baby passes out brain. of the breath. and The takes its umbilical cord Breast-feeding is This is her so Breast pregnancy that milk soon the after contains glands birth in she the is mother’s able antibodies which the that to breasts produce pass to the will enlarge. detaches milk. baby passes and give immunity to diseases the mother has had immunity (see Topic 10.3) means that the child antibodies in the blood, but is unable to The antibodies remain in the child’s blood has produce while it for a short time afterwards. Breast-feeding also to form between mother and baby that is is a research has shown that breast-feeding is to and develop mothers. certain Mothers are Children diseases less likely such to who as are benecial breast-fed childhood develop cancers cancers of breast, are less and iron, protein it women difcult Formula or milk convenient, comes it in needs with to to may but be water do not be In to breast-feed They their therefore rely to avoid Breast milk likely not with be the that it contains Formula and that protect or they it form SUMMARY 1 Describe places each able the risk milk milk QUESTIONS of what the birth happens following of a to during baby: of the muscles b in the the uterus cervix or the amnion and amniotic also d the placenta whereas does not. sometimes Make a table simply to show the Of and disadvantages breast- of feeding from nd advantages course, baby infections. bottle-feeding. 2 milk the ovaries. uid money, notably antibodies infections non-sterile breast advantages milk, to c costs drugs more sterile some getting bottles. smoking, has formula wall from She both a babies diet. diabetes. womb babies on her mixed under may this, able since powdered conditions. women are embarrassing. in alcohol. common Some enough carbohydrate both. over children involves having close 4 Medical and breast-fed enables benecial uterus afterbirth. them and bond placenta the should and the the care mother and itself. as Ante-natal calcium, mother’s from out The recently. the Passive cut. it 3 passive and tnemelppuS During tied isn’t breast-feeding and bottle- an feeding. option at all! 201 tnemelppuS tnemelppuS rst vagina 16.10 Sex hormones Puberty LEARNING You • Describe the testosterone developing roles and oestrogen secondary characteristics are at the only ovary testes start time uterus the lining from the Whe n Paper you 4 , mak e no te s they 10 become and 14, the follicles your life start is to called develop in the ovaries. puberty than person. boys. The The actual changes that age take of puberty place by hormones. At the beginning of puberty the are all pituitary the base the testes of the make the sex which in testes brain the starts to make hormones that organs develop ovaries. active. our The sex organs secondary sexual start to produce sex characteristics. boys start • the growth • the testes • growth • the • development making of to of the hair on in of of testosterone, male make deepening ovaries and sex sperm the the which stimulates: organs cells face voice muscles in the body. girls start making oestrogen, which stimulates: • the growth the ho rm ones T o pic to a table ro les here 16.1 1. referr ing • the start • growth of • growth and • widening of all and Keep your A person nishes read and the rst sex organs menstrual cycle and the rst period intera ct to men strual mood parts of development the of body breasts of the hips. becomes you can changes an adolescent stop be and an growing emotional increased when at puberty about time. sexual 18 starts. years of Hormones Adolescence age. can bring about urges. table 3 how you they cont ro l cycl e so the them cont racept ion A cycles are complete hormones This to which the changes receive an cycle lasts coordinate coordination is for that occur the important embryo so that 28 activity so it about in the that can of the start days ovary the ovary lining its and of is and the controlled and the the by uterus. uterus is ready development. and Girls use on T o pics 16.1 unde rstand treatin g female hair Adolescence uterus. we of when Menstrual you 2 of your fo r includ e lists when start to have periods between the ages of about 10 to 15 years in and infert ility . old. During and cells this a period, pass happens menstrual 202 But about TIP revisi on fo r of adolescents. STUD Y how and in earlier to at The 16.1 sperm develop person stimulate Puberty the organs. the The in sex ages cycle Puberty that of the of hormones of make development usually These group set Between in gland A complete life. puberty during menstrual to of controlled the a in sexual changes and with later in varies the born active Girls Describe adolescence of This • and OUTCOMES out for cycle. of the the the rst lining of vagina. time, it the This uterus is shows breaks called that a down and menstruation. girl has had her blood When rst Stages Girls are ovaries. in the born They potential menstrual with do egg is a not very large produce surrounded cycle number any by a of more small potential during group egg their of cells in lifetime. cells and their Each together they ovulation form At a follicle. puberty, involves some the egg chromosomes food. Each follicle as in by the starts uid the to and follicle the thousands follicles by or a develop moves bursts, start by in As to by the The the ovary This to at the of number lls with develop. gland it the (see ovary. is page of the and After cells of stored This enlarges follicle ovary . development beginning grows some each the cytoplasm pituitary edge egg, in reduces start follicle the the follicles develop. follicles the towards releasing these which half. few released nishes. of meiosis nucleus one hormones menstruation with of are dividing month stimulated A There 2 and 164). cycle lls weeks, the uid uterus ready into the oviduct. This is called ovulation. The follicle cells left for behind implantation in the ovary weeks. If implantation While to If form 2 the egg thicken. In vessels and form ball the a the yellow implantation occurs is week glands. woman cells If not remains developing the of it body does in after active the becomes it it the has occurs, implants remains will during ovary ovulation fertilisation which which occur, into the the for then the next decrease in size. pregnancy. lining a of thick the fertilised thick uterus lining of egg uterus starts blood divides lining to and pregnant. menstruation If fertilisation vagina of the now If a and does the uterus begins not yellow breaks occur, body down the in egg the and is dies ovary lost and passes breaks during out down. of The the thick menstruation. The lining cycle again. pregnancy does occur, the embryo releases a hormone that Figure stimulates the yellow body to remain active which in turn 16.10.1 During cycle the lining of the uterus to continue to thicken. This supplies the with ensures that Between the menstrual food and oxygen menstruation ages cycles of 45 have will and as it not 55 stopped. continues its development. It also are years This a is woman’s called the Explain periods stop as her KEY role development of and the testes regulation and of the ovaries secondary in Testosterone males the sexual males and females at in a List at b the effects that stimulates the Oestrogen testosterone has on the body of a that oestrogen has on the body of a girl at puberty. 3 During follicle ovary 3 Explain the meaning of the following menstruation b ovulation c Draw and a in timeline the to uterus show during the a in stimulates the secondary that during a and the in puberty. menstrual develops sexual occur cycle inside lining a the thickens. If of the implantation implantation does 4 in terms: uterus a occur puberty. characteristics boy females effects that the sexual puberty. puberty. List synchronised. secondary during changes 2 the characteristics 2 in of uterus POINTS changes QUESTIONS the the menopause characteristics 1 and occur. 1 SUMMARY menstrual activities the ovaries embryo the stimulates changes menstrual that occur cycle. in the ovary the not occur , uterus down. and This is the lining vagina of break menstruation. 203 16.11 tnemelppuS LEARNING The There OUTCOMES The • Describe the production sites of progesterone cycle and in pituitary the Explain the hormones and gland at that the control base of the the menstrual brain cycle. secretes: and • Follicle Stimulating • Luteinising Hormone (FSH) Hormone (LH) pregnancy role FSH, of the ovary secretes: the LH, progesterone controlling hormones menstrual The • four cycle of oestrogen in are menstrual • oestrogen in oestrogen Each menstrual cycle cycle pituitary it starts gland. stimulates follicle there beginning FSH and progesterone with This the secretion hormone the development is cell of a the stimulates that cycle other has each cells is of in one the of into carried or more cells follicle blood the potential these the the in to FSH to follicles. grow starts to of blood to into the ovary Inside grow secrete from the an egg. and where each At the divide. oestrogen into the bloodstream. Oestrogen • In the centre enlarges in is the a yellow second body half of It has stimulates three the main repair effects. and thickening of release cycle to produce lining of the uterus. which the LH menstrual the released; and yellow progesterone. body forms ovary relative concentration luteinising in the blood hormones the pituitary hormone (LH) of follicle from stimulating hormone gland (FSH) relative progesterone oestrogen concentration in the blood hormones the of from ovary Lining shed Oestrogen (menstruation) by ovary; uterus released lining starts Progesterone yellow of uterus to body; released lining continues Lining by down of to pregnancy thicken does thicken lining breaks if not of uterus 0 days 7 days 14 days time Figure 204 16.11.1 Control of the menstrual cycle by 21 / hormones days 28 days days from the pituitary gland. occur It stops the secretion • It stimulates the of FSH pituitary from gland the to pituitary secrete DID gland. LH. YOU Nobody The lining of the uterus thickens in preparation to receive an you are can the cycle see from important from increases day in 0 size the graphs hormones to day within 14. the in Figure during During the this 16.11.1, rst half time the FSH of and the egg oestrogen menstrual develops and follicle. of of stimulates around day the 14 follicle of the to burst release its egg. This happens is is certain about of of In top the part of follicle the Figure second half of the the shows yellow cycle, that body after which ovulation secretes progesterone the by the ovary have these stimulate • maintain further growth lining in its 20%, has stop the of secretion shows the eventually As the cycle. it of that This stops for together with the FSH the of the lining state and LH of and from concentration secreting the of the the then begins. this the gradually this role. the it If secreted by They menstrual of it of progesterone of the around may LH pituitary decreases of and the the yellow also stop cycle the and middle in the in the there is second body in early body the part the hormone the uterus. This prevents occurring of the cycle and lining so This and tests. use and SUMMARY the egg If pregnancy there body is excreted a that the lining of occurring uterus and no in woman to LH the the embryo continue stop from the urine misses a secretes secreting pituitary and this period is she to QUESTIONS Name four a a pregnancy testing kit to nd coordinating 2 cycle each Describe is The pituitary the hormone ovary Oestrogen the roles in menstrual cycle. 3 Explain that Some of why the thick state of these controlling the at it is lining the important of time the of uterus is ovulation. pregnant. State what happens as a out. of the decrease of in oestrogen and progesterone end of and FSH the stimulates secretion of the development of a follicle 5 oestrogen. stimulates the thickening of the that uterus inhibits FSH production and causes and the the pituitary towards from the ovulation remains of the follicle. formation The of to yellow the body release the which maintains the lining of the why it is important progesterone pregnancy cycle. is occurs, secreted but FSH yellow not. LH. Suggest why nd what it difcult to proportion is of body out secretes a progesterone menstrual lining, 6 stimulates the Explain is LH and secreted. hormones if 3 the hormone basis be hormones in remains the gland. the a be progesterone. may as pregnancy continue the known is again. yellow as is of so menstruation is POINTS inside 2 during happen occurs. that oestrogen does concentration 1 of size. result KEY continues lining miscarriage. 4 can takes so less menstruation uterine progesterone starting important pregnancy She placenta Progesterone gland. yellow decreases decreases uterus the implant happens, stimulates this oestrogen, breaking where is yellow secrete placenta maintain menstrual This an not. uterus, prevent the stimulation progesterone lining occurs fertilised, that or the to but involved During no oestrogen 1 intercourse thick. is effects: thickened reduces concentration stimulation If one and graph half that whether pregnancy, sometimes The out continues pregnancy. • no there implanted menstruation down, but because and the the estimated progesterone to they the group remains from • in One progesterone. over secreted uterus. nding During 16.11.1 become many implant at cycle. body The the it way and how not researchers embryo LH do embryo. lining As KNOW? knows embryos tnemelppuS • woman’s embryos never uterus. implant in the uterus. 205 16.12 Methods of birth control Birth LEARNING if • Describe the methods natural, control lets couples decide whether or not to have children and OUTCOMES of how should following birth so, many. To prevent pregnancy, the method of birth control either: control: chemical, barrier • stop the sperm • stop the eggs • stop from reaching the egg, and from being made, or surgical the Barrier fertilised egg from implanting and developing in the uterus. methods IUD The uterus cap cervix or diaphragm before uterus. It is intercourse. should be used a It rubber dome. prevents with the The man’s sperm-killing woman sperm cream or places from it over entering her the foam. strings The condom is a thin rubber tube. It is rolled over the man’s erect penis vagina before It also intercourse. gives common Figure 16.12.1 Intra-uterine It stops protection form of the against birth control sperm from sexually and is entering transmitted easy to the woman’s diseases. It is body . the most use. device A femidom is the female equivalent of a condom and is inserted uterus into the vagina. vagina Chemical The IUD methods (Intra-Uterine wrapped in woman’s copper uterus or and Device) contains it is is a small hormones. thought to work plastic It is by device tted that inside preventing is the sperm rectum passing cap for Figure folded cap insertion 16.12.2 through the uterus. It may also prevent an embryo from fitted over cer vix implanting in the uterus should conception occur. Cap IUS is penis (Intra-uterine placed slowly and making The in it pill’ different the causes unlikely is an types system) uterus. the is a in sperm available. T-shaped progesterone the will contraceptive pill small contains mucus that oral of It cervix swim as They it is to plastic that is become device that released thick and sticky, through. taken contain by the mouth. There hormones are oestrogen and condom progesterone pills. by These Figure 16.12.3 to the be by concentrations. preventing production released by of the the There ovary FSH by ovaries are releasing the and also eggs. pituitary .) so progesterone-only As pregnancy (They a do result, cannot this no eggs occur . Condom The For woman many has vagina result uterus in a heart In and take the and a a pill pill is Drawbacks pregnancy. depression effects. to couples contraception. applicator varying work inhibiting mature in The painful very small circulation every a day . very are reliable that side failure effects periods number – of each are and to sore pill has women, convenient take the the pill breasts, its own pill weight set can method regularly be of of can gain, side the cause problems. spermicide rectum A contraceptive under Figure 16.12.4 the of implant the upper is a small arm. It exible releases rod ovulation and works for up to 3 that is placed progesterone Spermicide prevents 206 skin years. just which of Contraceptive different types Spermicides cream or should be they To avoid also woman with contain between chemicals The that puts are kill the not another 8 progesterone. and 13 sperm. cream very They into such are weeks. effective method There as are her on sold vagina their the as cap foam, before own or and the condom. methods couples may work Spermicides used Natural Some that are jelly. intercourse. injections may have not be religious becoming able or to moral pregnant use the methods objections they may to described using abstain here or Figure 16.12.5 from having sex Calendar for rhythm method contraception. at sperm times when rhythm likely after and is to fertilisation method. occur that then about date. A This most relies weeks each after especially in likely on abstaining woman predicts 2 method, and is month having women happen. determining from keeps to a sex record when her in days when ovulation period. who when the of do This not They may ovulation just she is not a very regular cut tube and ends tied most and her occur. the is before has should have use just periods This reliable sperm periods. tube testis A better method ovulation. For is to follow example, changes checking for in the symptoms increase associated in body with temperature Figure and changes just before It useful in cervical ovulation. mucus This which becomes symptoms-based wetter method and is less more for people who do not have access to family top and the Surgical other methods of contraception is described end of cut oviduct planning and clinics Vasectomy effective. oviduct is 16.12.6 sticky blocked here. ovar y methods vagina A sperm them is tubes must a are be duct also known vasectomy cut sure ejaculate is but and tied. that he there Sterilisation is a and The does are no minor as is a a vas minor operation not deferens. want sperm in is operation not any the operation The a a man. reversible, children. semen, for for usually more operation just woman. The to His so cut the man uterus sperm man can still rectum uid. Her oviducts are cut Figure and sure blocked. that she The operation does not want is not any reversible, more so the woman must POINTS QUESTIONS 1 Barrier methods condom, 1 Sterilisation children. KEY SUMMARY 16.12.7 be a What is b Under meant by the term include femidom, IUD the and contraception? IUS. what circumstances would a couple choose to use 2 birth control Chemical methods contraceptive 2 Explain how the following birth control methods cap or d vasectomy diaphragm b condom c Methods can be rhythm a Explain how oral contraceptives pill, and implants, spermicides. spermicides 3 3 the work: injections a include methods? (‘the pill’) act to of birth natural control (abstinence, method). prevent pregnancy. 4 b What birth are the control? disadvantages associated with this form of Surgical methods vasectomy and involve female sterilisation. 207 16.13 tnemelppuS LEARNING Control Outline in the use of contraception hormones and fertility drugs Some had Describe vitro the process fertilisation of Discuss of the is regular, social implications and fertility the release cause of to in you n read mak func tion a cannot sexual as because being intercourse for the infertile 12 if months man they or have without pregnant. infertility may be for in due this fertility women to a type drug is lack of that of FSH infertility containing the do production may FSH. ovaries involve The FSH not by the regular stimulates the eggs. treatments involve Remember if the effect then the pituitary of Unfortunately, of reasons tablets that that make oestrogen the inhibits pituitary the insensitive production of to FSH. oestrogen continues on to the pituitary release FSH is blocked and by ovulation the drug, occurs. fertility that may treatment not be easy does for not always doctors to work for discover. a On variety the other how hand, it can work too well; too many eggs may be released, resulting cycl e in twins, triplets, quadruplets or even more! and of FSH stim ulatin g the but regarded this sure men strual deve lo pm ent in e unde rstand cont ro lle d the children are TIP So is This release oestrogen. the of Treatment injections Other you unprotected becoming eggs. pituitary. ovaries Befo re have in treatments sectio to Couples (IVF) contraception STUD Y want infertile. woman Often • drugs couples woman the • fertility OUTCOMES Fertility • of of Articial the fo lli cles ovary. Some may couples be the uterus. If the are man man remains vitro does the placed is not then a child’s It via called is possible a ne donor donor father is the man sperm semen tube sperm lead a to for there the this, or of father be This are collected woman’s (AI). if the semen problems biological infertile. may into sample is or insemination provide can not that plastic enough may the enough articial produce by because produce later who sperm for in AI. life probably unknown. fertilisation fertilisation ‘in parents children not ejaculation. and infertility means have does insemination vitro treat he process defective, because In with The Articial In cannot because problems from insemination glass’. and (IVF) when Eggs mixed is other another technique methods and sperm together in a have are that been collected laboratory can be used unsuccessful. from dish the where to In vitro potential fertilisation occurs. To increase FSH to eggs can body A couple with treatment. 208 triplets resulting from fertility be wall follicles that the chances stimulate the contains a ne of success, development collected and on the from plastic surface nutrients of her woman several ovaries. tube the and the of A inserted ovaries. oxygen. The small to is often follicles incision collect eggs so are the kept injected that is made eggs in a with several in from the the solution and to is mixed the the the A with solution woman’s is into also inject it from the and If left to days the (or that started few uterus. a is used for up from to 24 fertilisation divide and into then procedure a is a sperm hours has for fertilisation occurred embryos. doctor donor) places successful, and These the are them kept into embryo will fetus. possible into a man checks have for the eggs technician zygotes develop It collected occur. that in is tnemelppuS Semen an to take egg. the The nucleus zygote is from then a defective cultured for sperm several cell and days so it A grows into an embryo and is then transferred into the woman in technician with hope that it The social fertility The implants for the a sperm also not had to implications of couples It a IVF clinic also a to safe plan gave great put of contraception their and contraceptive their families pill and in 1960 decide made when it to been of the of 7 The women effect on health infants ability at at more control women’s risk by over health, their giving pregnancy and around the is an IVF countries have per plan to and sexually often be a in and has the and time 1970s of to 30% are to own them birth. much fertility. the TIP It opportunity Death birth have falling rates T he use of ho rm ones in is not can available national receives in make an treatments they may have if the parts of the world childless couples choices changed a all. steep Success of service, and proves are not how age. rates In decisions KEY POINTS many unsuccessful. Infertile able to afford A problem is what to do with ‘spare’ embryos that implanted. Some people maintain that it is not drugs of them or use them for medical acceptable to to stimulate eggs and a QUESTIONS Explain how pregnancy b Explain fertility in If the of male couples how drugs infertile articial can increase the chance of a sperm women. when the insemination man is is are can help bring about Explain a nutrients why and eggs to oxygen, be used before and implanting b them Discuss that what are possible not should happen implanted. in why into future use or to Should used for for where used to articial donor fertilise a eggs. a IVF is a IVF are kept embryos are in a solution kept for a of a the Petri technique in which place inside few Oral contraceptives allow uterus. embryos they takes dish. women 3 opt infertile. 4 days infertile, fertile fertilisation 2 the pregnancy. may woman’s 3 pregnancy release research. insemination 1 the increase just 2 SUMMARY take are chances dispose can containing this of not females In FSH treatment. 16.1 2. parts fertility many T o pic 16.14). years health rst is average 1 repeat in control many also with to 35 treatment birth from has Topic under pills 2013. promiscuity (see in for decreased of steeply fallen 1.6 women women funded have just infections and Methods Contraception greater for who pill. they that careers. procedure about the rates means led publically of example, transmitted about made birth for families education with that woman expensive are introduction Thailand, behaviour in the successful In to their increase for so children sexual IVF since world. about egg have desc ribed considerably have an and cont racept ive mothers injects uterus. STUD Y children. an nucleus. treatments introduction easier in at the be from IVF destroyed, treatments frozen for they to wish pregnant decide to or whether become not. research? 209 16.14 Sexually transmitted infections A LEARNING sexually Dene sexually infection body uids gonorrhoea transmitted State • Describe that HIV is an amongst sexual (STI) is the contact. a disease major STIs that include is infections that HIV , transmitted can be syphillis and transmitted. the methods of HIV and its spread (HIV) human immunodeciency virus (HIV) is a human pathogen that can rst identied in the early 1980s. Like all viruses it is composed of ways a which virus of was transmission immunodeciency STI The in during (STI) Human • infection OUTCOMES via • transmitted (STIs) few genes and a protein coat. It enters human cells and uses each be cell to make more viruses which then enter even more cells. The main prevented type State lead that to HIV infection cell that it infects tnemelppuS Describe how HIV HIV infection affects with virus who (TB) HIV is may lead is a HIV is no t a negative and infection whic h number of of If Acquired someone they are described as being HIV has positive been (HIV+). the be body’s infected immune by People other who system. diseases, do not It is easier such have HIV as for a person tuberculosis are described as and destroys an important type of lymphocyte that the the of Eventually syst em . wo rd Of te n is T his immune system. lymphocytes number of T to During produce lymphocytes an infection antibodies. decreases these T During and so lymphocytes an HIV fewer every time there is another infection. By reducing antibodies the T lymphocytes, the person HIV infected weakens with HIV the will body’s ability succumb to to ght any disease. number of is infections because of their weakened immune system. ‘synd rome’ the term used . a The (acquired a patient with AIDS weight of with HIV immune diseases virus (yellow) deciency brought (×5000). syndrome) on by the is the name weakening of given the to body’s system. early glands treating infected collection immune worker the the AIDS health to other Lymphocyte in AIDS. resu lt weak enin g HIV/A IDS A or (HIV–). produced other what development of are imm une means . the lymphocytes attacks stimulate diseas e; co lle ction a lymphocyte. TIP diseas es from to Syndrome pneumonia. coordinates it HIV weakens HIV+ and HIV AIDS of system The STUD Y type the infected immune a may AIDS Immunodeciency • is symptoms and a loss, high of AIDS are temperature. various types of very much Later, cancer like u, symptoms and a with might decrease in swollen include brain function. Cambodia. Not all HIV+ without 210 any people develop symptoms at all. AIDS. Some people remain HIV+, but tnemelppuS • of How HIV is is one HIV transmitted? transmitted person to in the another blood during and semen. unprotected The virus sexual can pass from STUD Y T here Either partner may infect the other. The virus can also be passed are needles contaminated with infected blood. In this has spread very quickly amongst drug addicts who share needles. T hey Unborn babies are also at risk from HIV . This is because the virus can the placenta to the fetus. Even more likely is its passage from blood to the baby’s blood at birth when the two into for close contact. transfusions is HIV can another also way be in transmitted which HIV in has HIV only breast been milk. For not can There are is no trying that the drugs, HIV/AIDS cure to viruses, fungal Since may inside but that infection the (AZT), body with and that damage the people infections HIV drugs zidovudine multiplying prevented? HIV/AIDS develop drugs e.g. for be they will by yet no vaccine inactivate host and cells. AIDS as take HIV , some of them to these do the There are work the Scientists problem prevent not treat HIV . but lymphocytes. Antibiotics for is be cups of the virus. the cured, it is important tracing is bacterial to of the spread of HIV in the UK. person Any in positive either as people a are antibodies several is asked result then in of identify offered their weeks to sexual an blood. after the people intercourse HIV test has by which However, person who or diagnosed these been they may sharing reveals have the A sexually antibodies at be passed of appear during 2 The spread controlled HIV condoms, only sharing methods to reduce its spread on via sexual infected. of by body contact. STIs the can use be of preventing of needles, Other infection risk, These presence will transmitted with put needles. the them . the uids HIV food, with POINTS can control glasse s who and prevent important someo ne sharin g virus KEY Contact or or against 1 transmission touchi ng HIV+ by insect s, anti-viral have. cannot is HIV trans mitt ed bloodsuck ing How throug h exam ple, Blood transmitted. AIDS . infec ted describ ed bloodstreams is used becom e meth ods here. come may AIDS . catch the the mother’s and cann ot myt hs pass with across HIV way, Peopl e HIV man y via abou t hypodermic TIP intercourse. the hypodermic and education include: programmes. the use of condoms to provide a physical barrier to the transmission 3 of the virus during sexual HIV in • setting inject free drugs; shared • up this needles screening education the exchange reduces and donated contaminated • needle blood of risk of for those transmission people from the the to HIV used antibodies for make HIV the a virus transmitted use or of in a What the known AIDS. What c Why a State exactly is and aware how it of can the be methods of 4 as The spread reduced prevented. between AIDS and use an the HIV ways infection not be treated by State the a is by be sexual reducing shared drug can needles users of and by donated in which HIV is measures that can be in transfusions. HIV destroys lymphocytes transmitted. taken to reduce the spread to a weakening of the of system. This makes infection. tnemelppuS Describe the effect of HIV on the immune system and susceptible HIV infection leads to the development of to many explain diseases, how to which using during used people 3 HIV men screening immune HIV lead antibiotics? leading b time, HIV? 5 2 With diseases of by of between HIV? blood can is semen may of intercourse, difference the blood. infection careful b cells It eliminating QUESTIONS is in collection the 1 infects system. transfusion. people virus and the condoms SUMMARY that immune who HIV for being programmes transmission the schemes syringes blood is intercourse such as TB. AIDS. 211 tnemelppuS • PRACTICE 1 The the QUESTIONS drawing correct shows a half identication ower. of the Which labels 1 row to is 3 4? The diagram system. the shows Which events row the female identies reproductive the places where occur? 1 2 3 2 1 3 4 1 1 2 3 2 3 4 A anther stigma petal sepal B petal stigma sepal anther C sepal petal anther stigma D stigma anther sepal petal A fertilisation implantation ovulation B implantation ovulation fertilisation C ovulation production fertilisation of production D fertilisation of 2 (Paper 1) Which row eggs implantation eggs [1] shows the correct functions of 4 insect-pollinated (Paper 1) [1] Which organ an secretes testosterone? ower? A ovary B pituitary C placenta D testis sepals anthers gland carpels provide A produce contain landing pollen grains ovules for sepals site insects anthers carpels produce contain pollen ovules (Paper B 5 insects grains The stigmas ovaries anthers receive contain produce ovules pollen pollen [1] following sexual C 1) attract grains four processes reproduction 1 Pollen 2 The grains male in lands gamete occur owering on the fuses during plants. stigma. with the female grains gamete. petals stigmas protect D are ower 3 anthers The male gamete travels down the pollen a in site of tube. produce the pollination ovules 4 The pollen tube grows out from the pollen bud grain. (Paper 1) [1] In which A 3, 4, 1, 2 B 4, 3, 2, 1 C 1, 4, 3, 2 D 4, 2, 1, 3 (Paper 212 order 2) do these processes occur? [1] 6 Which in the hormone second is half A follicle B luteinising C oestrogen D progesterone secreted of the stimulating by the hormone hormone yellow menstrual body 9 The diagram before cycle? shows a fetus in the womb just birth. (FSH) A (LH) B C (Paper 2) [1] D 7 The diagram occur to the below uterus shows the changes that during the menstrual cycle. E day 2 2 lining of 1 8 2 3 7 4 6 2 (a) Name body (b) Describe parts A to E. [5] 5 uterus 4 2 the 2 7 3 structures 8 22 use the changes to letters E that during rather happen birth. than the You to the may names in answer. [5] 0 of uterus (Paper 0 2 lining 1 2 9 1 your A thicker 3) 1 1 1 9 gets 10 8 1 (a) Dene the (b) Explain term sexual reproduction. [3] 1 2 7 1 6 3 1 51 4 1 1 the following ovary, Which row events during shows the times (in days) when difference pairs and (ii) of between terms: pollination (i) the ovule and and fertilisation. the [4] the cycle occur? (c) State likely factors germination ovulation is three menstruation uterus occurs gets of required for the seeds. [3] lining to (Paper thicker 3) occur 11 A 10–27 25–28 Clomiphene infertility B 13–15 1–4 6–25 C 22–25 1–4 7–14 D 10–27 13–15 25–28 an in increase pituitary (a) 2) in Explain Outline fertility Potato and plants stem variation A drug that It is works used production of by to treat causing FSH from the how to a be deciency in FSH causes infertile. a [2] [1] (b) 8 a women. gland. woman (Paper is 4–10 reproduce tubers. among Which by results offspring cross-pollinating means in plants in of the potato of the social issues involved with treatment. [4] owers least (c) plants? Describe the roles progesterone in of oestrogen pregnancy. and [3] different (Paper 4) varieties B cross-pollinating C production D self-pollination (Paper 2) of plants stem of the same variety tubers [1] 213 17 Inheritance 17.1 Chromosomes, and People LEARNING Dene • State who capabilities meaning of to the chromosome, at closely; same or traits such in the family such things case often as as of resemble identical each physical sport and twins, appearance, music, often very other – closely. personality run in and families. the We terms belong quite Characteristics inheritance the DNA OUTCOMES sometimes • genes gene say that someone has inherited features from their parents. and DNA The transfer the next genes Unit as 16 are in zygote are we the next its of these inheritance. like looked coded at produced. the which individual transmission The features from characteristics instructions. The one are study of generation controlled to by inheritance is genetics humans from or called which known In is contains from parent new Genes gametes. grows male how At the the and generations from one fertilisation, genetic zygote half of generation the from half its of are gametes information – owering from to both genetic female parent. and transmitted fuse its plants form to a parents. A new information comes but see Chromosomes We cannot see genes chromosomes. The to rst look step at in The cell There is are called shapes and and shape. sorted into inherited DID YOU Chromosome a lot. is numbers Humans chromosomes but in chimpanzees have body have 46 cells, muntjac deer can fruit held ies by – have the some the of 8. The adder’s plants fern we can information that we inherit is that in they the number. can pairs. the In be each male a microscope can into human pair, a during human counted of a one and one pairs the and are based male’s of cell blood analysed. cell. This different on their size chromosomes chromosomes from division. white human chromosomes sorted parent be nucleus The a of the are has been female. of have in each but two of They not the always. strands chromosomes have of two Figure one strands 17.1.1 in the joined at chromosome the in photo on together top two of the the left usually next different at page colours. could unravel That a thread is chromosome, made up of it a would long form chain an extremely molecule called long DNA stands for deoxyribonucleic acid. The DNA is wound around tongue of protein. During cell division the DNA and protein are this over each that record very tightly together and the chromosomes are coiled up. 1400 At chromosomes other times cell! the 214 we chromosomes. only packed species containing chromosomes photograph, stranded. molecules fern genetic through the so They the 23 microscope, nuclei 48, have which is sizes. see centre, shows thread. 6, the chromosomes from double the If Indian visible shows diploid In light KNOW? You vary are prepared 46 the a have chromosomes. photograph specially cells visualising these Chromosomes through Most DNA. they are uncoiled so the cell can use the information in What Genes Each is a are gene? lengths of chromosome actual number chromosomes large the has many depends are numbers of DNA on much that you genes its along length. longer can than see its You in the length, can others; see these diagram although that some below. the of our chromosomes have Figure genes. 17.1.1 A double-stranded chromosome. Each It is gene a is a unit chemical of code inheritance that the cell in that it codes interprets as an for a specic instruction protein. to make STUD Y a protein amylase molecule. and proteins lipase and many Y ou for know about example. more. several There Humans is have a proteins gene for between – each 20 000 of to these ‘Diplo id’ genes. The proteins produced by cells inuence means how are two se ts works and what it looks like. Some features that genes inuenced by the environment. Y our height is determined by inhe rited and you how inherit much and your exercise environment you take. Other – for example genes are not by your environment. environment has Y our no blood affect group on this is at determined by a gene and diet affected inhe rited by A the and se t the each all. strand of cons ists The arrangement of DNA in a and of and complete the sentences using these pro tei n. DNA genes genetic gametes nuclei This in their the (sex information called is that threads are parents made cells) because from contained are of inside in of which the the they passed of and . on use to developed. thread-like the proteins 2 in small a Dene b Name the units called terms gene cells. human Write the a few and the DNA tight ly the What b State is 1 to explain the relationship chromosome, the diploid is pack ed cells can in gene s. POINTS Inheritance genetic is the transfer information gene, to from the diploid numbers of generation. between 2 by so proteins. sentences meant other inform ation A chromosome DNA is carrying a thread genetic protein. information a very At is chromosome following: nucleus, pack ed . of 3 cell and toge th er . generation c is These information of three DNA DNA structures most The the KEY found mad e resemble less Offspring is information times them Durin g are words: tight ly chromosomes of molec ules QUESTIONS pro tei n Copy pro tei n. arou nd divisi on, 1 one chrom osom e. (deoxy ribon uclei c chromosome. woun d SUMMARY of se t fath er . TIP DNA acid) 17.1.2 o ther the chrom osom e protein of Figure of the DNA Each of the from type STUD Y core one from both mo th er genes – control se t are of the chrom osom es body that 25 000 there different TIP haemoglobin, number? three non-human in the form of genes. species. 3 A gene that is a codes length for a of DNA protein. 215 17.2 Protein tnemelppuS Each LEARNING chromosome Explain bases that in a the gene sequence code for of order of amino Each called genes. a length up of A gene divided a long, is a into super-coiled small thousands part of the of molecule DNA shorter of sections strand. to of DNA, make a making up particular a particular protein. gene, Remember carries that the inside information every cell protein there • made is acids needed in molecule the The correct is OUTCOMES DNA. • synthesis Explain how a protein is are thousands of different chemical reactions taking place. made Enzymes that all control enzymes determines which all are which chemical these chemical proteins. enzymes reactions reactions. Because are take DNA produced place in inside You codes each should for cell remember proteins, and it therefore cells. DNA gene 1 gene 2 nucleus Figure mRNA The 17.2.1 A structure gene of is DNA a short (see section Unit 4) of DNA. contains bases. The information nuclear is pore found in the sequence of bases along the length of DNA. nuclear These membrane also determine controls the the sequence production of of amino other acids in important the protein. proteins, DNA including mRNA antibodies + and receptors for neurotransmitters. ribosomes cytoplasm DNA carries information information ribosomes protein is Figure 17.2.2 The vital role of given the ribosomes. code to the a kind name of build the proteins DNA to ’messenger messenger the from site molecule’. RNA amino of (mRNA). acids. protein This The molecule role The synthesis of is in RNA mRNA is the and to a copy of the base sequence on DNA out of the nucleus to the the ribosomes The are letters three and A, of copies on four T , is the instance A the the C C different G. bases code will will on – bases Each on for protein by G, this code for a it does G so will replaced U on in acid There different and is found amino DNA. DNA copy T where synthesis occurs. code coded base DNA cytoplasm and these each have in genetic There 216 by to from mRNA carry carrying moves is are coded C. ‘rule on of by base to a them DNA. base U by sequence different However , another mRNA. refer for , 20 triplet the copy We about base by by DNA. amino When pairing’, mRNA does (uracil). their of acids mRNA so for not Therefore, double strand DNA mRNA tnemelppuS DNA DNA unwinds makes mRNA amino methionine acid Figure 17.2.3 How DNA alanine base triplets code tyrosine for amino nucleus arginine acids. mRNA The coded information on mRNA is used to assemble amino acids in ribosome the correct sequence for each protein. nuclear pore • The mRNA arrives • The mRNA strand amino • The acid mRNA assembles in at the from base the triplets nucleus. for each particular protein. passes amino ribosomes contains the then the acids through into the protein ribosomes and each ribosome mRNA molecules. ribosome • The amino • The specic bases in acids bond order the of mRNA together amino and forming acids each is a long chain determined amino acid is by joined – the to the protein. sequence the next of amino one acid passed by a peptide to bond. ribosome All a body cells particular in an cell organism many genes contain may not the be same genes. expressed However, because the in cell amino makes only the specic proteins it needs. acid added to growing protein Figure SUMMARY 17.2.4 How DNA controls protein QUESTIONS synthesis. 1 2 What is the function a DNA b mRNA c ribosomes Look at the part of of a each of the molecule of following in messenger protein RNA synthesis? here: AUGACGCAUGCAGUCCGA. a How many b What is base the triplets role of are each of shown these in this base section triplets in of mRNA? protein KEY synthesis? c Write down the DNA base triplets that coded for this mRNA. 1 3 Indicate if these statements are true or The DNA is a b DNA has sequence codes false. of a POINTS amino DNA d The the a double contains acids 2 helix The role four bases: A, G, C and of code bases in shape between of DNA is a on DNA sequence protein. base is carry to it copy to the the U maintained complementary mRNA and ribosomes molecular bonds of correct protein DNA c for pairs. by in the cytoplasm. hydrogen 3 The ribosomes acids into assemble protein amino molecules. 217 17.3 Mitosis New cells below • Dene its mitosis roles in • Dene role in and of into state growth, replacement asexual As repair, cells In and reproduction meiosis and gamete state tnemelppuS State that before are Outline what Describe the the nucleus cell cells into are is a during role of to that is the rise stem cells The a cell DNA of in the The new urchin You can has see just that divided each old ones. new is In into two, wall nuclei the divides, between cell in the photograph is the the the process of nucleus cytoplasm two formed nuclei dividing must divides. to between divide. divide the nuclei. divide. of nuclear The division daughter that cells occurs are during genetically growth and identical. organs to cells form that gametes. are not It is the genetically nuclear division identical. divide, new copies chromosomes exact is see mitosis copies divides. uncoiled are of DNA of begins, thicker. They staining in is is the This going nuclei coils visible up This is the is so a very in this is attached that the in the each in reliable process DNA loosely when under information copying on, very chromosome DNA become technique it genetic made. arranged each the the be made. While and chromosomes mitosis of must occurs the nucleus. going to on. the original chromosome microscope when a used. in cell has During a a cell division which sex of can the copy As suitable sea of urchin the occurs daughter nucleus cannot becomes a in to which You copy. of in type process chromosomes mitosis. its plants ways sea mitosis before by In a Before nishing occurs gives process zygote cells. reproduction. Meiosis the two division of constriction two. two Mitosis Before A the egg mitosis happens chromosomes • by fertilised daughter asexual • • produced the production chromosomes duplicated two There its left, animal the • • are OUTCOMES mitosis the two copies separate so each new cell gets a copy nucleus. of each chromosome. The diagram shows what happens to one chromosome. As a a result of mitosis, each daughter cell has the same chromosome chromosome number copied two the a original reliable parent system, cell. they As are the chromosomes genetically identical have to been each identical other copies a as by of and to the parent cell. If they were genetically different they the would chromosome be rejected by the body’s immune system. chromosome after is it copied The nucleus to two starts copies of chromosome divide separate pulled and signicance are Mitosis produces daughter cells following • • daughter chromosome of this cell has 17.3.1 This is each cells 218 that the are same an exact number copy of of the parent chromosomes cell. and These are growth repair identical – in in of damaged a to the parent cell. Mitosis is important for the animals special wounds tissues this happens growing – your and areas skin all over such cells as the the divide body, tips by of in plants stems mitosis to it and roots repair wounds type • Figure cells have processes: happens divides–each mitosis apart genetically cell of the what happens chromosome divide by to when mitosis. replacement which only of live cells for a that short wear time out and die, such as red blood cells tnemelppuS LEARNING reproduction – this occurs in fungi and in plants, but is KEY rare in the animal reproduction on kingdom. page There are some examples of POINTS asexual 184. 1 Mitosis cells Growth: As multicellular organisms grow, the number of produces that up their tissues increases. The new cells must be the existing ones. Growth by mitosis takes place over the in animals. In plants, group is conned to certain areas 2 parent Stem cells and replacement of cells: Damaged cells identical new cells. Your skin cells and the cells must be dying and being replaced by identical lining cells. your Red cells gut need live to Asexual are only be reproduce, tnemelppuS Some a short by to the such as time will wear away and die. of the cells produce blood become keep dividing They do cells. and Asexual parent. yeast reproduction Mitosis and occurs potato results when tubers in offspring unicellular die. cells. (see T opic 16.1). that not form by develop from mitosis into an to any embryo type provide the of remain as specialised unspecialised body with a cell. These These cells are needed to replace cells constant that get QUESTIONS cells supply a Which type There is a layer of stem cells just under the These stem cells continually divide to outer make toughened for protection. They get rubbed off constantly replaced. When skin is wounded, cells and these in as the more bone cells to marrow repair to the produce damage. new red There blood are and cell division that to the are parent cell? that Give two examples of need stem many cells cells layer mitosis occurs i in cells plants produce of worn when be for that b become to cells organisms identical skin daughter specialised functions. produces of mitosis. also 1 out by cells SUMMARY They new unspecialised cells cells. of are mitosis. reproduction: identical Stem for replaced as are specic which same replaced that constantly the cell. produced They by have chromosomes called meristems Repair of whole the body and identical number to daughter genetically cells identical making are tnemelppuS asexual stem and ii in animals. cells phagocytes 2 Describe the role of stem cells. replacements. Each time a specialised remains cells in Mitosis stem for cell some divides, specic unspecialised meristems takes place in in the to go plants one daughter function through have meristem the behind and the starts other process same the cell the root role tip. as of to become daughter mitosis stem cells cell again. in Cells The animals. at various stages of mitosis. 219 tnemelppuS • 17.4 Meiosis Meiosis LEARNING OUTCOMES Meiosis • Dene meiosis as a is a type reproduction. division in which number resulting formation in is known Explain how meiosis variation by forming human of of paternal essential the the with haploid number, sperm the sort of This type 46 which half the normal number. is would of after the (As and results chromosome opposed diploid cells both would in to the number. full number). had have generation every father, nuclear the have in owering In meiosis different raw to eggs result contain of the material changing 23 23 46 92 chromosomes chromosomes. the number generation. in for In a of This This is of If the this chromosomes does reduction not happen. selection humans are to and in in – the the not the allows called egg a different and has 23 from number of generation. ovaries anthers gametes. meiosis cells and the to and and They variation organisms is zygote egg, identical. genetic there producing The generation occurs cells so reproduction from in in division each. mother, sexual contributes because involved chromosomes the organs meiosis daughter this is constant sex 46. life-cycle chromosomes from sperm. stays at the number plants and in division only the occurs In remains division halves cells Meiosis a egg double number nuclear chromosomes as and fertilisation chromosomes, the in are that to testes. the ovules. genetically provides evolve in the response environments. 23 meiosis. Figure 17.4.2 meiosis. four As cells. been shows you Each halved to can of what see these give a happens there cells are has haploid to one two one pair of divisions chromosomes of chromosome, the so cell the during resulting number in has gamete. cell 46 46 from with in sexual chromosomes sperm and cells at generation nuclei Meiosis diploid for organs new Instead, chromosomes is reproductive maternal in sperms gametes as formed continued combinations Human that the produces zygote and in cells If • division place genetically chromosome different cell takes is This halved, It the the chromosome of reduction the one testis pair of chromosomes cell diploid ovar y in cell testis first of division the cell 23 fertilisation 23 haploid second division sperm haploid of the cell egg 46 diploid zygote Figure 17.4.1 chromosomes haploid the 220 in number. diploid The number gametes is The number in number. four of the called a the zygote is Figure 17.4.2 This There one haploid shows are what two cells which happens divisions chromosome so of the become to the one cell number sperm pair to of give has cells chromosomes four been cells. halved. during Each of meiosis. these has 17.4.2 meiosis. In inherited mother . of each what pair , one from the father , When the 23 meiosis, and shows the maternal produced in happens and Differences are one of cells chromosomes. meiosis one chromosome pairs daughter to is is pair gain different is genetically between one as in it origin was separate different in in which from the and the one as it of during was inherited combinations way mitosis chromosomes paternal maternal chromosomes This of rst from the division paternal haploid cells another . meiosis A The differences between mitosis and meiosis are summarised in the fertilised of and in Figure 17.4.3. One The to sperm give division T wo number the of chromosomes The same daughter cells number of chromosomes a are genetically The daughter cells from the are cell STUD Y genetically parent cells are formed Four daughter cells are Meiosis 46 the of the chromosomes. Mitosis diploid shou ld haploid haploid Meiosis SUMMARY and mitosis diploid a compared. many pairs of body chromosomes are there in the an iii a the egg number POINTS nucleus Meiosis of chromosomes cell in ii a sperm iv a red these human cells: which number to cell blood three tnemelppuS b Explain ways in which meiosis are differs from Meiosis meiosis produces the advantage of is halved from resulting genetically in diploid cells different. produces variation by new combinations variation. of Explain division chromosome mitosis. forming how reduction cell 2 State a the haploid that zygote a is cell? in i spell co rrec tly. QUESTIONS human State to you haploid 1 of how diploid KEY How learn are and diploid haploid 17.4.3 T hey conf used duplication diploid haploid you mito sis diploid DNA haploid when wo rd s meio sis. them c nuleus TIP carefu l easily 2 The nucleus formed and b with the cells write a zygote. is Be 1 or with divisions different daughter Figure egg fusing halved identical T wo is Meiosis remains The the egg Mitosis human table genetic variation among gametes. maternal and paternal chromosomes. 221 tnemelppuS tnemelppuS Figure 17.5 Inheritance Cat LEARNING breeders Use to pedigree show cats diagrams how features the are terminology hair, bred all the if they kittens features kittens together short-haired haired the Use long some are inherited • that breed genes together two cats which both OUTCOMES have • know and at kittens all. that then have there in the Breeders appear will within may litter, can long be or make a hair. some there If short-haired long-haired may pedigree family two be no long- diagrams of cats as in looks very like and to Figure show 17.5.1. of You will see that a pedigree diagram a family tree, but inheritance symbols • Distinguish and between are used to indicate the gender of individuals. genes alleles I 1 Symbols 2 for II pedigree square = diagrams: male; circle = female III shaded circle individual or with square the = condition shading = long hair no shading = short 1 hair studied Figure 17.5.1 A pedigree family unshaded individual circle not or square showing of diagram showing the inheritance of hair length in a cats. = the Genes and alleles condition A individuals may be identied gene is a molecule. generation and I – 2, II – 5 Each of gene DNA is that always is the and III – the chromosomes. genes from vary versions of of a gene In Figure the Each same between each (see species gene 17.5.2, you You species individuals are below), chromosomes. has known but can can has from as usually see also of Nancy the gene the three see the father for Mary all disease, a Soto disease in who these the early from 1800s. descendants Maracaibo in different be two more. pair are of and d/d different, heterozygous The dominant expressed in the allele phenotype. two alleles individual is are the same, homozygous d These live two alleles individual is are the same, homozygous of recessive and d expressed the recessive allele the will be in the phenotype. Many from around of mother Venezuela. Figure 222 gene. be is may B/B alleles However, The serious by egg Lake one every dominant. chromosome of one A/a two this will the descendants died many individual These of for disorder , the on B B Wexler position There on alleles the studying protein and genes. species. are genes the a d neurological a place genes same alleles. A responsible Huntington’s making same own each there KNOW? discovered its These sperm A Professor for the the within chromosome YOU in 1. individual DID code located number, of e.g. length by 17.5.2 This shows three genes that are on the same chromosome. alleles Sometimes is only one an organism type metabolism. of But gains instruction many two to copies use organisms of during contain the same growth: two allele so there development different alleles. If STUD Y or an Notic e is expressed and affects the appearance of the individual, it is said to dominant allele. If it is not, then it is said to be a recessive the the 1850s, Gregor Mendel investigated inheritance in pea noticed that amongst garden pea plants one variety grew to while another remained short, or dwarf. He used pea plants bred true – from generation to generation they were a plants or dwarf capita l recess ive smal l letter . differ ent letter allel e allel es of the plants. Never letter s either the tall the that use always a be as tall as alwa ys plants. and He we dom inan t allele allel e In that be show a TIP allele for sam e gene . When tall. he plants of been tall give Using T these were plants on about letters This A for it and has the had allele the is all when He he there he a the a generation generation next that his gene that pea consisted dwarfness He did knowledge ‘factors’ were of generation generation. used called is next new reasoned ‘skipped’ but the this seeds, dwarf. what two letter But DNA, terminology capital letter some represent gene varieties, produced although represent dwarf. and two dwarf. and genes to modern plants. case them passed anything Let of self-pollinated many to cross-bred None that had not of controlled controls know algebra height height. in pea alleles. for tall, used recessive and for the let t represent dominant the allele allele and a for lower allele. Mendel The a genotype pea tt, plant the (TT) or they The of an could plant is be organism TT, two or alleles phenotype is the are way If They recessive that the tt. homozygous. homozygous have Tt is alleles the alleles be has. alleles for are So the are genotype the homozygous Individuals different, the two can (tt). it are example expressed same, of TT refers to all the aspects of an organism’s biology shape the of will apply the term to one feature of an organism, for round of seven including and the wrinkled. POINTS individual. its Pedigree diagrams show genes. how We – plants if KEY an seeds pea dominant heterozygous in inheritance in or Tt except the features 1 It studied different features are inherited in example families. height in pea plants. The genotypes TT and Tt result in plants with 2 the tall phenotype, whereas the genotype tt results in dwarf An allele is a Most 3 The genes of of an is an phenotype QUESTIONS have genotype makeup SUMMARY version of a gene. plants. is many the alleles. genetic organism; all organism the the features other than its genotype. 1 Chromosomes occur in pairs in all cells except the gametes. 4 Explain why they are not in pairs in A dominant expressed 2 a What are b Explain 5 3 Explain is meant by the terms dominant allele and of the following genetic terms: a homozygous b heterozygous c genotype d phenotype A recessive only allele each 6 seed how shape you is would dominant nd or out whether is always phenotype. allele for wrinkled allele no homozygous identical a is expressed dominant A two the when present. has Explain the is and 4 in alleles? what recessive allele gametes. individual alleles heterozygous two allele different of a has gene individual alleles of a gene. recessive. 223 17.6 Monohybrid inheritance Monohybrid LEARNING inheritance characteristic, • Dene • Explain concerns the inheritance of a single OUTCOMES monohybrid inheritance It involves the such as plant inheritance height of or ower the parental examples alleles of of one gene. We will colour tall × dwar f use phenotype monohybrid the crosses example of Mendel’s peas. parental There pea is one plants. gene The for height gene for in TT tt T t genotype plant genotypes height has two alleles: tall, T, of and dwarf, gametes t. gametes There are three genotypes for t possible plant height: T TT = homozygous Tt tall F generation: genotype – all heterozygous (Tt) 1 Tt tt = = The STUD Y The TIP tall Whe n you gene tic the on them this simpl e hom ozyg ous only one mak e write this As – so once parental result plants of phenotype dwarf. Figure a above shows homozygous plants that a all tall plants 17.6.1 cross dwarf Mendel used between plant, in his tt. a homozygous These crosses. represent This is the called cross. of meiosis, allele, all T, recessive the and allele, t. receive one dominant and all because the have allele, T, gametes all heterozygous tall, – cross and dominant the tall diagram T T, breeding contain only in parental genetic a the orga nism s gam e tes geno type the like page , homozygous plant, pure out diag ram s ones mak e write heterozygous the When allele the is from gametes the tall from fertilisation and one genotype, dominant to plant the occurs, recessive Tt. Their the contain dwarf the allele plant new so phenotype recessive allele, will be will be t the diag ram . The rst generation is known as the F generation, and in this particular 1 genetic cross, all the plants in the F generation are heterozygous tall (Tt). 1 Crossing F tall × the F tall generation (3:1 ratio) 1 1 phenotype The F plants are allowed to self-pollinate (see genetic diagram, 1 F Tt left). Tt 1 When meiosis occurs, half of the gametes of each plant will genotype have genotypes t T T allele, T, and half will have the recessive allele, t time when fertilisation occurs, there are three possible gametes combinations gametes T t TT the F , or second generation: (homozygous tall) (heterozygous tall) Tt tt genotypes in 2 Tt generation: alleles tt Tt T of t TT F dominant t This of the (homozygous dwarf). phenotypes 2 Amongst 25% homozygous dominant 75% 50% heterozygous tall homozygous generation ¼ (or 25%) will be homozygous ½ recessive (tt) 25% (or 50%) be will be heterozygous homozygous dwarf. and Since the therefore tall; phenotypes are the same, ¾ of the F plants will be tall and 2 224 17.6.2 75% : 25% is a 3:1 ratio. of ¼ (or TT 25%) and dwarf Tt Figure tall; (Tt) will 25% this (TT) dwarf. This can also be written as 3 tall : 1 dwarf. ¼ will be tnemelppuS A If test you allele cross look is at not the last two expressed in crosses, the F you will generation see but that is the recessive expressed in the F 1 generation. plant have just the plant This by means looking same because that at it can only do because phenotype. it We be STUD Y 2 we not know plants do know the with the genotype genotypes genotype of of TT a a and G en e tic Tt shou ld dwarf test cross whether If our plant it tall is is used gives heterozygous half tall determine homozygous plant (tt) to is tall plants then (Tt) and the genotype heterozygous homozygous all (Tt), plants or (T T), (Tt). crossing half If, it (see then an individual genetic crossing however, with dwarf of a plants our dwarf (tt) in it diagrams with tall a the unknown tall phenotype plant is (tt) ratio of nd out the below). squa re possib le be tw een includ e the to a show fusi ons gam e tes. is will give 1:1. the unknown tall plant is heterozygous: homozygous: × tall phenotype tall ‘unknown’ Tt dwarf × dwarf tt genotype TT ‘unknown’ alwa ys dwarf plant plant a to if if diag ram s Punn e tt tt all A TIP tall tt genotype genotypes T of genotypes t t gametes T t of gametes t gametes t gametes T Tt genotypes test cross Figure offspring: 17.6.3 100% diagrams SUMMARY QUESTIONS 1 Complete these inside brackets. the (Tt) like 100% these by test tall show the ratios expected cross in the offspring: offspring, 50% heterozygous 50% homozygous not the actual choosing the correct word from 1 A pea plant with a tall (genotype/phenotype) TT or could A tall pea plant with genotype A tall pea tall 50% dwarf offspring. the inheritance inheritance characteristic height TT is of such a as or ower colour. Crossing a homozygous tall (homozygous/ with a homozygous dominant. dwarf c 50% have plant heterozygous) ( tt) Tt. 2 b of Monohybrid involves (genotype/phenotype) (Tt) recessive POINTS plant the phenotypes numbers single a Tt genotypes KEY sentences tt T phenotypes heterozygous Genetic t plant with genotype Tt is plant produces all (homozygous/ heterozygous tall plants. heterozygous). 3 d A dwarf pea plant heterozygous) 2 Fruit a ies have Using the a with genotype tt is gene that symbols State for the this Give W determines = long the wing length and w = of their short wings. gives tall plants to (3:1 genotype of a fruit y which is genotypes heterozygous Crossing plant its tall A fruit which to y is heterozygous homozygous predict the ratio of 3 for for wing short proportions of plant a heterozygous with a plant plant tall homozygous gives to 1 a ratio dwarf of plant gametes. (1:1 b a dwarf ratio). dwarf of 1 wing: characteristic. the heterozygous plants 1 ii two tall recessive. 4 i Crossing (homozygous/ length wing. each is Use wing mated a with genetic type in ratio). one diagram their offspring. 225 17.7 Codominance tnemelppuS Codominance LEARNING OUTCOMES Up • Explain the term to either • Describe the now the inheritance dominant blood or we have recessive. looked The at recessive involve allele is alleles not that are expressed in the of phenotype ABO examples codominance of individuals with the heterozygous genotype. Sometimes, groups however , both So alleles the are expressed phenotype is a and neither mixture of the is dominant. effects of each allele. × parental This condition is known as codominance and the alleles phenotype are called can R parental C R W C C have codominant red owers alleles. or The white four owers. o’clock Flower plant colour is W C determined by one gene. However, if you cross homozygous genotype red-owered F plants with homozygous white-owered phenotype 1 × all pink plants, the offspring are all pink. The two parents produce flowers heterozygous offspring (the F generation) in which both 1 alleles R F genotype C 1 W R C C are R W pink – an intermediate colour. can see are in Figure pollinated 17.7.1 what amongst happens themselves. when There the are pink red-, W C C give W plants R to C You C expressed C pink- and white-owered plants in the F generation in a 2 ratio the the Notice R W C : 50% phenotypes when C C C 25% is : 25% the or same 1:2:1. as the Notice ratio W W C C of alleles also that are R C R R C C genotypes generation: of genotypes each allele is represented as a capital letter, W red ower neither W = allele is C W and white recessive and ower that = they C . This both shows exert an that equal C effect F ratio codominant. R C the the C so R that W R gametes of on the phenotype. phenotypes 2 R 25% homozygous C R C R 50% heterozygous 25% homozygous C W C 25% red 50% pink 25% white W C Multiple So Figure alleles W C far, we have looked at examples where a gene has only 17.7.1 two alternative may The four have groups of alleles. three the or There more are examples where blood group determined human by system one gene, I, A different alleles: I B I O and I I A O I B A I A B I B I B O I B A A The alleles I B and I I are B I O I codominant slightly and different code group A I A three Blood are I with gene alleles. Genotype ABO a AB O I O for molecules on O the surface A I and the four different groups I at group. of and anti-sera anti-sera clump the A 226 A A together or B (blue), and if B the molecules anti-sera (white). anti-sera on their B Red blood reacts cells with surfaces. blood does table. Remember tested (yellow) and the diploid. with red cells. The allele I is recessive to both B Look Blood of not You any code can for see person one the can of these possible only molecules. genotypes have two for alleles each as we blood are all phenotype: parental genotype: blood A I group blood group O B I I A gametes × AB parental phenotype: parental genotype: A O I blood O I B I O I group blood × O I O I B I A Figure Look and at O. B O O I A I I phenotype O 1 blood group A 1 blood group B O I A I I B I ratio: O I I B O I A I I phenotype the genetic The the diagrams. children same parents all will have T wo parents blood have groups A blood or B. groups None of STUD Y AB them blood have four group blood blood as their A 1 blood group B 1 blood group AB 1 blood group O TIP ABO parents. groups A and B. They could have blood is an groups – A, B, AB and grou p exam ple children and O. Y ou SUMMARY can QUESTIONS aske d in There are varieties results in group will discon tinuo us 1 blood O I codo min ance with ratio: 1 17.7.2 syst em T wo O I A I T he have O I I B I O I I B I B I O gametes group B I A gametes I A tnemelppuS parental the red-owered, of of the a four o’clock number table. white-owered of Explain plant crosses the of of the each plants pink-owered photo between results number (see and on right). varieties the expect abou t sam e of also of varia tion. to bo th be to pics ques tion. The are shown cross. of each colour crosses red × pink white red × pink 2 Use of a The of 126 131 pink 39 and diagram as coat If white a 83 work the mother of codominance. known to where the inheritance homozygous 88 115 offspring A white 92 pink genetic the pink white × group 3 × red out father is blood colour in all the possible blood heterozygous group some homozygous bull, the is 43 red calves for groups blood O. cattle cow have is is an example crossed coats with with a allele causes Flowers R W causes white hairs. red hairs to be Heterozygous produced cattle have and the coats allele the that are KEY of of red genetic the o’clock plant. and white hairs giving POINTS a Codominance diagrams offspring in to the show the following a a roan bull and a roan cow b a roan bull and a red c a roan bull and a white cow occurs when roan. both Use four R 1 mixture of ‘roan’. R The a colour genotypes and the phenotypes alleles 2 The over as neither the other. inheritance groups A I expressed phenotype, dominant crosses: are involves B I of ABO three in is blood alleles: o and I cow 227 17.8 Sex Sex LEARNING Describe how sex is inherited in chromosomes 46 chromosomes Dene a and which these sex occur in you 23 are. In pairs. humans In there females all 46 humans chromosomes • determine determined are and determination OUTCOMES Y our • linkage can be matched together into pairs. This is done by taking sex-linked images of the chromosomes and matching them for size and shape. characteristic In • Describe an • colour example Use of genetic blindness sex the the results of and have sex X Figure the the you sex egg an X can of and a are have Y not two alike. X These are chromosomes known and chromosome. see how individuals. sex chromosomes Remember that in the the gametes number of cells contain fertilisation, of and Sex As XX the diploid in meiosis so each gamete can have only one egg is chromosome. of may with there child X half fuse with the an being the X a with Y Half sperm female either chance or the a of sperm Y contain chromosome. with Since and the a sperm chromosome. chromosome equal of contain sperm zygote an there X are with equal the inheriting Y XX or male. inheritance you can see is in the very electron small micrograph and much opposite, smaller than the the X. Y Therefore cell the testis in sperm sperm chromosome cell a an and the or chromosome, XY halved chromosomes. chromosome numbers XY is sex chromosome Y chromosome has far fewer genes than the other chromosomes ovar y and the has X chromosome 17.8.1 two All At Gametes: that Females linkage of in chromosomes crosses chromosomes diploid two chromosomes. an determine involving are Y to In predict there X males linkage diagrams males as as far fewer than development mutated) the of then X. One testes the in body gene the on the embryo. that Y If develops chromosome it is is not stimulates present (or if it female. Y Sex all X eggs have of an chromosome, X 50% sperm have a linkage an chromosome The 50% tnemelppuS X genes that are located on the X chromosome are described as have Y sex-linked even gender controlling or though they have sexual nothing to characteristics. do with Among determining the genes on the X X chromosome are genes involved with controlling vision and blood clotting. X 50% XX female Males if any only of have them one are copy of recessive, the then genes the that effect are on will be X chromosomes, seen. Because Y women 50% XY male linked have common Figure 17.8.1 The diagram shows X and Y . only Do not of the forget sex (egg and that sperm) each of contain to give the 228 than in this girls. is they why T wo are less affected sex-linked examples are by sex- conditions discussed are more here. blindness haploid of the genes on the X chromosome controls the ability to see known as cones, red other number green colours. The gene works in the receptors, of in 23. boys and the 22 and chromosomes chromosomes chromosomes, One gametes in X alleles the Colour inheritance two recessive the retina of the eye. There is an allele of this gene which does not tnemelppuS produce so any protein girl vision. the a or woman Males allele r necessary only they who have will is one be for colour vision. heterozygous, X Rr, chromosome colour The so allele has if is recessive, normal they have colour inherited blind. colour-blind normal-sighted × parents male female r R X R X X Y meiosis meiosis r R gametes X X Y Figure r gametes 17.8.2 What can cannot see familiar r R R X X you Figure 1 female carrier : 1 If you something then you may have R X X Y red-green ratio: see? Y X normal-sighted colour blindness. male 17.8.3 carrier normal-sighted parents × female male r R X R X X Y meiosis meiosis r R gametes X R X X Y R gametes Y X r X X X X R R X r r R X Y R R Y X X An F X chromosome on the left and a Y ratio: 1 chromosome normal-sighted female : 1 carrier female : 1 normal-sighted male : 1 colour-blind electron 17.8.3 shows what to expect if the mother is and the father is colour blind. Notice POINTS that none of Sex is determined children can expect to be colour blind, but the girls will inherit colour have this blindness allele, but on it the does X chromosome not affect their from their who are heterozygous are carriers of phenotype. colour XY and females 17.8.4 shows what to expect if the mother has normal colour vision. In this case, there sex Males XX. Any A sex-linked is one in characteristic which is a carrier is a 1 and is in 4 the gene located on a sex the chromosome, father Y . blindness. responsible Figure the and father. 2 females X the are for by the chromosomes, They in microscope. homozygous 1 dominant allele photographed 17.8.4 KEY Figure right, male an Figure the usually the X chance chromosome. that 1 in one 2 of the chance children that any will boy be will colour be blind. colour Note that there is a blind. 3 Males have only chromosome SUMMARY QUESTIONS are in tnemelppuS 1 Explain how 2 Explain the sex is determined in a sex linkage b terms: carrier males Females linked c likely than to in X re-issue be alleles expressed females. humans. 4 following more one so colour blindness green are carriers disorders, colour of such sex- as red- blindness. 229 tnemelppuS 1 on PRACTICE 1 Which QUESTIONS explains occurring in a the life advantage of 6 meiosis The of cycle? cell A meiosis allows sexual reproduction Indian 6. How and muntjac many in a deer has a diploid chromosomes sperm cell of this are number there species of in a skin deer? to occur skin B meiosis as four times C meiosis produces haploid D meiosis produces sperm A many A 6 6 B 12 6 and C 6 3 D 3 6 eggs discover that they albinism in are both which skin carriers of not made. What is the probability (Paper 2) child will A 0% B 25% C 50% D 100% (Paper have this that Which feature inuenced controlled by the only by a gene and environment? condition? 1) A blood group B concentration C heart D lung of glucose in the blood disease cancer (Paper 2) [1] Which describes [1] recessive causes the genetic code? allele: A A is their 8 A [1] pigment not 3 cell [1] condition rst sperm gametes 7 is cell cells 1) couple the as mitosis (Paper 2 produces a harmful the four different bases that are found in feature DNA B is never C is not expressed in the phenotype B expressed when in a genotype the in a D dominant produces mRNA a cell that is that making leave the nucleus proteins allele the homozygous same as phenotype when C the sequence D the triplet of bases in a gene when of bases in DNA and RNA that heterozygous code (Paper molecules with 1) for the different amino acids in [1] proteins 4 Which is meiosis involved with? (Paper A asexual reproduction B growth of C production 9 stems of and egg 2) (a) Dene (b) Explain [1] the repair (Paper 5 A man not sons normal colour blind. will be A 25% B 50% C 75% D 100% (Paper 230 [1] has 2) [2] the difference pairs of between the terms: tissues 1) have colour of inheritance. cells following D term roots colour vision. blindness What colour is the but His her wife father probability that does is their blind? [1] (i) genotype and (ii) gene allele (Paper 3) and phenotype [2] [2] 10 Brachydactyly is which with people ngers drawn and for a toes. this rare genetic the A rare condition condition pedigree have diagram in (a) short Use genetic was patterns condition: (i) without female with the condition (ii) the in following Key female diagrams proportions of cats the to predict with next the different generation coat in the crosses: homozygous dominant homozygous recessive, heterozygous × × [4] homozygous condition recessive. male without male with the (b) the [4] condition condition Explain why genotype (c) stripes, but Explain why with Use is a not with the possible tabby one male blotched kitten (d) it of cat with and stripes parallel example to state with parallel female cannot the blotched stripes. [3] tabby cats produce a stripes. of [2] inheritance in this 3 question to explain the terms gene and allele. 11 12 13 14 (Paper 15 12 (a) (i) State whether brachydactyly is (a) a dominant or a recessive 3) Explain allele. nd Give evidence from the family the you would genotype use of an a test cross organism that [1] could (ii) how caused to by [3] either be homozygous dominant or tree heterozygous. that supports your answer to part The Refer to the people shown in the four numbers. red-owered What are the chances of parents 3 and another child with this a genetic diagram to explain When these have (i) pink Explain (ii) [3] Show, the In is has are cross-bred the owers. why by this is so. [3] means result of of cross a genetic breeding diagram, the pink- 3) owered 11 jalapa, white-owered your answer. (Paper a condition? (b) Draw Mirabilis and 4 offspring having plant, variety [3] variety. (b) o’clock tree a by [3] (i). tabby cats controlled stripes (T) blotched is the by pattern a gene. dominant of The to stripes allele the in for allele the coat parallel (t) pattern. for a (c) Plants plants with 64 of (i) (ii) genetic why owered (Paper parallel of the were The When pink crossed seeds they [5] with were owered, variety and diagram to 78 explain results. Explain in owers owers. themselves. variety. a these among grown. were red Use red and plants the pink with collected plants this there plants cross. [5] were among no white- the offspring [3] 4) blotched 231 18 Variation 18.1 and Variation T ypes LEARNING Distinguish between variation humans and have many features in common as we are all members of the genetic same variation of OUTCOMES All • selection species. Now think about the similarities and differences between phenotypic ourselves and monkeys and apes. We have many features in common, variation but • State the differences there and signicant differences species. Biology, which we use to categorise animals between into continuous are different In the term variation means: discontinuous • differences between • differences It is species – we use these when constructing keys variation • Identify of and explain variation differences tnemelppuS Although • State that a species. we within all a belong species to the that we same are concerned species, there are with in many this unit. differences discontinuous between variation within examples is caused by us – even between identical twins. Some people are taller genes or heavier , others have different coloured hair , skin and eyes. There is alone considerable Variation that the we occurs cannot different examples As we of have Individuals alleles the of all one we show a lot of variation, we seen have these but of in two that continuous • discontinuous of of we the can same see, equipment that people species. but to also in detect, have. features such These are as all variation. 17, variation genotypes they between • that specialist haemoglobin Unit types individuals features use different genes the have also – exists different inherited. genotypes phenotypic of at the genetic combinations Genetic level. of variation is individuals. variation within a species: variation variation. are species. Continuous If you nd )slaudividni divide mean the of the fo .on( This ycneuqerf is into heights of of heights groups a 2 0 0 – 2 0 9 9 9 1 9 0 – 1 8 9 1 8 0 – 1 1 7 0 – 1 7 9 6 9 1 6 0 – 1 1 5 0 – 1 5 9 9 1 4 0 – 1 4 3 9 1 3 0 – 1 2 9 1 2 0 – 1 of 16 year olds / their all the from pupils the (170 cm to in your shortest 179 cm, to year the etc.) group tallest. you can If you you plot to histograms present continuous of is range take your to called of the and the mean group called a from your quality of your different the normal shortest the and you this in a the middle number of distribution. to Also be largest because tallest. height. food height. will variation overall ages height with continuous to inuence at is heights contribute spurts from that distribution quantity growth get likely correspond that you is But eat will There other and people there the go are factors amount through inuence the results class. cm data variation. features that you can measure also show this type of variation. are T ry drawn the It variation genes as Other Frequency type of exercise you and continuous such of histogram. This type many 18.1.1 the range class range people. Figure a height frequency height variation measured would 232 between phenotypic the are in see types differences There Although variation measuring the length of your index nger or your hand span. Y ou on collect data from the whole class and plot as frequency histograms. can Continuous lengths of clear stems extremes divisions with you many between the plants. will You get can the measure same intermediates in results the – between. a 35 range There 30 intermediates. variation eht Discontinuous and in egatnecerP no two or occurs fo are leaves also noitalupop between variation 25 20 15 10 5 Some people have attached ear lobes. Other people’s ear lobes are free 0 and In not this (e.g. If attached. type of collect is variation attached you This and data not an example there is usually attached about a of ear feature discontinuous variation. a of small lobes) number and showing no this A intermediates. type of Figure plot it as a bar chart (see question 11 on page 18.1.2 percentage variation, groups you B (A, of B, This bar people AB and O AB Blood phenotypes group chart with O) the in shows four the blood Maharashtra, 243). tnemelppuS India. Discontinuous environment example. O. There owers variation has Everyone are of no twins identical. will have womb an ABO they about have been are up often show alone blood blood Some the – it owering This and group group same different they exposed separated genes colours. because twins by ABO is the system is either plant is another A, B, species another AB or have example. environment from Identical apart The different versus However , and caused intermediates. develop come is effect. has distinctly Inheritance Identical no at to birth, striking embryo in many or genetically These slightly afterwards, These are differences differently environmental shortly similarities. are ways. developed different and and often in the inuences. to These plantlets Mexican hat grow plant. The The effect It shows You under the environmental shows reproduces leaves. them of of photograph plant. its which can the factors plant asexually detach different environmental inuence to these that can be and lots grow Any have on investigated sometimes make conditions. genes called of tiny them variation the do with shown all and will Whe n plants. the identical. TIP hat are around used you keep be the word s ‘distin guis h in need factors. thin gs. to POINTS to the ques tion, give the be tw een Here aske d be tw een be tw een’ a differ ence s because be KEY of with Mexican pots leaves genetically us. plantlets in the are brought STUD Y personality, on They you two could distin guis h two type s of varia tion. 1 Variation is the difference between individuals of the same species. 2 Genetic variation individuals; and is the phenotypic internal differences in variation the is the genotypes differences of in external SUMMARY appearance. 1 3 Continuous resulting in variation a range is of inuenced by phenotypes, genes e.g. and height the in Distinguish between continuous and environment Discontinuous phenotypes variation with no results in a small number tnemelppuS Discontinuous blood groups. and examples of of give three each. intermediates. 2 5 discontinuous humans. variation 4 QUESTIONS variation is cause by genes alone, e.g. human Describe how investigate you the environmental growth share of the would effect factor plants same that of an on the all genotype. 233 18.2 Mutations A mutation change • Dene • State the term the mutation in base a way in mutation which new is Describe alleles Gene the possible effects the and certain rate of are tnemelppuS Describe an • that condition gives of the of cell anaemia as of the of heterozygous sickle to cell to a rst trait malaria A similar the skin, eyes is They to versus white the Often and red, chromosome A this some gene that mutation change have studied but a red may no can effect be at is a cause change a harmful, but in some all. was in mutant the fruit form y. with The white normal eyes eye was of colour the gene had no changed. longer This coded was for due the albinos. It is The a cell gene gene anaemia is and are an the production protects mutate allele mutations controls which can recessive Gene Sickle A melanin, to a the form skin that homozygous cause of of and does recessive many human example. mutations are by the the before rate radiation gamma only damage occurs but and in light. albino. caused that eye that pigment melanin. are so pigment. eye ultra-violet ionising X-rays controlling DNA occurs and mutations are random, colour the diseases. process eye of produce Gene gene example Causes at in nuclear or by occur most alleles failure They is chemicals. the new a division. they some are which DNA which and rays way to in are the occur increased The naturally by Ultra-violet damaging. formed. copying at exposure radiation, greater the (mutant). dose of radiation, cigarette If smoke mutations example bombs were station at that can are be The for may cell is at cells are top a in the SCA rate like which can or than if long – may as it fatal This Benzpyrene is the in (A for cells. sickle the the 1986. these red red The a It is only themselves, mutations the have blood blood at the red tool abnormal cells cells sickle anaemia. blood blood These C -shaped cells abnormal causing of (SCA). is These distorted so power gametes disease anaemia cereals.) in For atomic variation. blood destroys cells, or cell sickle. the nuclear because of individual. after red difcult if spleen a the cells, inherited and the exploded forms sickle of grasses blood term. affect and Union normal with shape mutation. happened 1945 new an shows the in Soviet makes red they gamete-forming the of mutations. cells provide prove chance cancers, the in the Japan person plants vessels, greater in to in in and the from of body anaemia haemoglobin blood in lead occur important greater cause dropped that cutting oxygen. a Chernobyl blood bottom blood is inherited Sickle the occur they mutations 234 DNA. mutations ies in hair from genetic (normal) A change individuals Red of benecial fruit production mutation resistance 18.2.1 a chemicals not Figure or mutations sickle example State gene mutations discovered. • a of colour on in characteristic. are One radiation change the formed • a phenotypic sequence mutations that is OUTCOMES to carry block cells at a tnemelppuS LEARNING is a genetic disease A allele, Hb allele, Hb (or H S two from a gene mutation. The normal ), codes for normal haemoglobin and the SUMMARY QUESTIONS mutant S (or alleles have resulting A H are both ), codes for codominant forms of an so abnormal that haemoglobin form people in their of who red haemoglobin. are The 1 a Explain a heterozygous blood cells. b gene Explain what how mutation Heterozygotes of the SCA the disease alleles carry called puts abnormal oxygen who a sickle person form which one of causes SCA cell at a allele trait. great a Clearly, selective haemoglobin severe have is not problems. much the good at inherited of c two in West, Central and East List since by transporting SCA allele common. normal is This and common is because abnormal among people forms of problem with transport of disease is malaria as the parasite people who from are areas where heterozygous haemoglobin oxygen. that a What cells. Figure and do malaria have not both usually is b 18.2.2 that of alleles them The are are link have But causes shows of one shown as expressed between example a SCA natural in that four for in they this do have disease children chance of codominance the red body There is a strong a for is the of Explain of parents blood heterozygotes (see cells enter who and from page of 226), to is a selection sickle strong normal most are of areas pressure against cell anaemia, people So selection allele, where for badly the the on the anaemia. allele is commonly people who in live certain parts of Africa. Note since both people. malaria is STUD Y an TIP who are in allel e the for rst SCA place S H H , because they could arose by die H pressure against people homozygous for gives the but has H , because they could die from malaria is common, there from sickle malaria is heterozygous cell an anaemia allele individuals, and remains important they in are the selective H is a now strong kille r selective , since protected population they from in do diseas e × areas where POINTS normal S A H S Mutation is H gene caused base Ionising radiation S S H H A 3 Sickle A A H H 50% H Figure the rate. cell anaemia caused by is a an genetic allele of S phenotypes normal H 4 gene for Individuals haemoglobin. haemoglobin, no resistance to malaria with heterozygous SCA in condition the have S H S H increase some A A 25% and H the H DNA. S H disease H of in S A A a H mutation H in change sequence chemicals H a S A S change by H H H a S H A H gametes 25% a malar ia. malaria. 2 genotypes – not the A of agent H A H agai nst S H 1 A H it malaria. KEY normal becaus e adva ntag e A A advantage suffer cell both pro tec tion in effects selection. A But, sickle anaemia. There the of their SCA. heterozygous resistance the why increa sed • cause sickle mut ation, from caused resistance cannot suffering S homozygous genetic are have T he • human that Describe the in heterozygous increased. anaemia? groups red be of most found to rate Africa. c a by mutation. cell The the can some diseases 2 common meant form possession disadvantage, very This milder is mutation tnemelppuS SCA mixed normal and abnormal haemoglobin, to malaria resistance S H resistant abnormal haemoglobin, sickle cell to malaria. anaemia 18.2.2 235 tnemelppuS tnemelppuS • 18.3 Adaptive An to • Dene adaptive the term survive below adaptive on feature its Interpret images or seeds about a species its adaptive tnemelppuS Explain the of the of plants adaptive leaves, to stems pond The examples so to the Arctic fox feathery dispersed by they grows behavioural as and and together to that are features. carried has a by the The helps The thistle wind attened, three an organism to photographs has tufts disperse streamlined them body of rocks so it is not washed away. and In winter, white fur as a camouage. Adaptive features keep well as structural; for example, penguins huddle Adaptive features warm. roots desert an individual’s like those tness in which reproducing the photographs refers and to its having are chances of offspring. likely to increase surviving These in its offspring are tness likely The feature environment. adaptive nymph underside environment, Dene that mayy of its features environments • inherited in features are • an to the describe is reproduce other clings information and show widely. • feature OUTCOMES tufts the of thistle seeds are A mayy does wind. not to show larva get has a the same attened washed away in features. body so The it Arctic fox has to endure extreme cold. fast-owing streams. Pond plants Hydrophytes in water . Buoyed plants roots The for it Water lilies, Nymphaea alba. up if by to is water water absorb no plants energy and problem are to through respiration) leaves buoyancy oxygen to and air. since it have through both with they for an keep is ions, that or since there partially transport, xylem there are submerged benets. no little carbon water for soluble system diffuse plants dioxide. its water little have applies very gases for and through extensive the carbon need and or no or is tissue. no root no oating need for the hairs. cuticle, since water. same not which costs produce mineral diffuses is its hydrophytes conserve The no submerged anchorage or of grow hydrophytes photosynthesis, does has since water for that and stems need hydrophytes 236 in present, leaves there The Living save Roots, are close in of oxygen water. air quickly. to the dioxide, much Therefore spaces in air and is for their a than plant many stems spaces are needed slowly (needed These light which more and provide reservoir of tnemelppuS LEARNING features tnemelppuS Desert All adaptations plants have important Very high enough water is desert • • A to are water maintain prevent plants Cacti can that kill are water in a water their plant loss. cells, if it or It is they cannot will wilt. absorb wilting. able xerophytes reduce with turgor long-term are are uptake the transpiration Cacti regions. Their the of scarce. following balance they rates Xerophytes water to that to that loss exist in conditions survive in hot, and conserve dry water where (arid) in the ways: leaves leaf are over thick, reduced which waxy to water cuticle spines. can covers be the This reduces the surface area of Cacti store water in their swollen stems. lost. plant’s surfaces and reduces transpiration. • They have swollen • They have a • Many area from cacti so • They • Their shallow, rain have is open a their overnight round, less shiny stomata spreading and have there stomata at root to to tissue. quickly which which reect during night system shape through which closed water-storage absorb any condensation. compact surface surfaces are containing the heat day absorb reduces water to the and can be their surface lost. light. reduce carbon water loss. dioxide They which Spines they store for use in photosynthesis during the day. from occurs in the outer layers of cells in their provide Research a b an how the following animals are adapted to extreme POINTS camel to desert Arctic fox to An adaptive and helps feature an survive and Fitness is tnemelppuS a list of four arctic conditions. an the organism ways in which desert plants are able water loss and conserve probability surviving Explain each of the following statements about pond They need little xylem in Pond their stems and Their c They roots have stems and do an not have extensive plants root hairs. system of They air Freshwater spaces inside to their are higher stems water and plants potential are than surrounded the cell sap in store by a the solution cells of of carbon in how 4 their Desert have this is an advantage to the maintenance in the plants What Ions prevents in the these water mechanism dioxide diffuse spaces and very such as cuticles, to spines, cacti leaves swollen to store water and cells. cells from by are which at a very these root systems. Often bursting? their c water. air of extensive b since in water. thick stems turgor up a leaves. Explain need tissue extensive which reduced a not buoyed have oxygen roots. aquatic do transport slowly 4 and offspring. leaves. they b its reproducing plants. much a in of water. 3 3 to to having reduce inherited reproduce. environment, Make is organism conditions 2 2 protection QUESTIONS conditions: a and stems. 1 1 shade herbivores. KEY SUMMARY some Photosynthesis low ions concentration. are taken up by State plants. the the stomata day dioxide and at close absorb during carbon night. 237 tnemelppuS water stems 18.4 Natural Natural LEARNING selection tnemelppuS • Describe natural • Describe evolution pass selection well • adaptive Dene the as features process the over of on to their Variation the in a which An to term give example two alleles a organisms greater that generation be chance than summarised to are well those as breed that and are less follows. to of describe organisms. new genetic advantage having good is to all the Gene differences mutation material the is produced to by that the produced. individual camouage also is that avoid sexual only Some expresses being seen reproduction individuals. the from alleles in the the two Gene between of different gametes. different in are ‘shufed’ fertilisation, individuals mutation, individuals genes At meiosis every are and when to the combined fertilisation give gametes within give rise generation. man. Over-population of These return sockeye same in 15 000 eggs fairly salmon Colombia produce where millions other seeds and a (see eggs hatch starvation. may land from the places the of spite of Pacic in a of are poppy this animal Ocean order which example in to rivers breed. fertilised. plant huge and to The We releases in females see over-production plant species the over of remain 254). stable are because, eaten eggs. Similarly, in Yet, from hatched many for page remain the they populations most of offspring eggs, year. seeds, stable of species, Populations that the young poppy they in predators Many many where by seeds cannot case as of are salmon may grow sockeye many be as die of from eaten there by is salmon, the young disease birds; no soil and others or salmon. water . Production enough offspring population from Among the and gnu. a hyaena compete for food from large for and nutrients. and mates. for numbers into of eggs early and stages seeds of life ensures to that maintain the year . that resources. is the resources Animals This or it to organisms competition existence’ of make year Competition 238 may variation nucleus. variation an is But meiosis, same British dead next used completely may combinations fuse, a which populations populations predator. new the is within During young the process within between a The to Variation by Vultures by have adaptation them. as alleles adapted. mutations Sockeye process environment time way Darwin their change exist Charles the OUTCOMES adapted in is selection survive Plants compete referred ‘struggle to for by the early compete for food, biologists survival’ stages for water, as (see of space, the page life there light, space (territories) ‘struggle 255). is water for Competition have the ercest same between adaptive individuals features to of the obtain same their species resources KEY as from 1 the environment. Individuals of different species also POINTS compete, There is variation individuals often feed the at competition night different and foods the in is not other their as erce. during For the example, day, or one they species have individuals slightly 2 diets. 3 with features that adapt them to the conditions There is environment are those most likely to survive and that competition to are for reproduce not so well resources. or, if they adapted individuals the generation. They do have adapted may die reproduce, a greater are likely before have chance out have a offspring. pass on and disease. individuals than others and in tnemelppuS the environment already of does not organisms well are their their better new adapted unlikely to individuals conditions that are now pass on their alleles Explain over the a an are change, so to they their survive with at better do then not natural change environment. to breed. an features that advantage adapted, alleles. time. idea process their of terms natural variation, over- selection much, Any as that maintains not When the struggle survival, help over compete them others. Natural selection bring Thus selection is the rst proposed by to survive These Darwin of adaptation whereby populations environment over environment. a Antibiotics are prescribed in bacterial by in diseases. the Explain why to all people are told individuals survive, about mechanism Charles to well environment successfully, will for adaptation many are competition, breed take a change which 1859. become the antibiotics and to they are given rather a stopping when they evolution better . Evolution more Why do drug companies suited invest to alleles production, b is following context feel – to their QUESTIONS the than occurs on to that species pass offspring. SUMMARY for changes, adapted survive chance The 2 adapted better will selection populations are survival’ predation the selection: If for competition, Only in Natural species. in 1 next same reproduce. lose they few to to the ‘struggle to to Individuals a due breed their of may Reproduction The between but in nding new generations. antibiotics? tnemelppuS Antibiotic resistance Key bacteria Antibiotics Soon are after developed the a chemicals that introduction resistance to kill of bacteria antibiotics their or in inhibit the their 1940s, growth. some to bacteria not bacteria with mutation effects. giving antibiotic When bacteria are exposed to an antibiotic, such as penicillin, killed. However, there may be some individual bacteria that mutation giving them resistance to the antibiotic. The used to bacteria for the first able to produce an enzyme that breaks down the antibiotic. bacteria survive and now have more resources bacteria reproduce available non-resistant as all their competitors – the non-resistant bacteria – have died. bacteria survive to reproduce and pass on the gene to their offspring. This is an example of natural example aureus that of is this is the resistant to strain the of the bacterium antibiotic are by have been introducing responsible antibiotics, but for we the have not for new which are antibiotics resistant as to bacteria antibiotics. in the to environment consciously develop There be used (MRSA). chosen bacteria the is resistance a to constant existing now resistant antibiotic the selection bacteria to Staphylococcus methicillin change killed continues all Humans stop reproducing selection. antibiotic An and for or resistance bacteria The growing resistant grow These and individual time may resistant be treat have disease a resistance most antibiotic are resistant antibiotic search antibiotic has occurred for resistance ones. Figure 18.4.1 Selection for antibiotic resistance. 239 tnemelppuS they is 18.5 Selective Selective LEARNING Describe the role of in of Over animals and crops time and they kept have animals kept seed for at from least one ten year thousand to another have increased bred their livestock. Domesticated plants and animals have plants changed with grown that producing and varieties have selective years. breeding breeding OUTCOMES People • breeding considerably over that time due to this articial selection. economic These changes have happened in this way: importance 1 • Describe examples of Humans choose a desirable feature or features of an animal or plant articial to improve, e.g. fast growth, short stems (so less straw), docile (not selection tnemelppuS erce) • Outline how is carried State the Animals differences and or natural The 4 plants offspring This animals. are cereal in beef This is to The such as shortages of and to Zebu are conditions water. drought. features are bred to produce the to nd those that show an such the Plant as rice, yield increase breeders wheat dairy dogs to the features. have and cattle, and as as it improve yields of and it is These many their are kept for meat of crops the such who of breeders quantity natural and yield and ornamental humans which generations. importance Animal features, with and of increased growers is for economic maize. non-economic as to grain have quality plants are appearance. are the selection. individuals selective Humans survive to genes. been selectively successful from or continues features selection their have of in of other on particularly danger to improve feature Zealand breeding environment pass feature since bred being for their wool. introduced to They have Australia and Europe. selective breeding is that there may be too much breeds in Africa inbreeding recessive e.g. (a) of These sheep ram a are who thick between alleles of ewes have also from a hip of joint flock wool. with related passed breeds the thick mated closely being Many failure They this on dog to (b) – individuals. to the suffer develop to give some thick of offspring whom wool has may have and effects of leading (c) result but thicker a to Articial selection in sheep. harmful lameness. these wool selected in reduction inbreeding, to generation sheep. 18.5.1 the properly these This descendants from coat Figure 240 these desired want to prots. sheep variation. Merino to generation. articial which and the selective improve decide New (top) checked Breeders not been of milk called Merino adapted the agent, breed well their cattle. looking in want crops increased longhorn showing next farmers They maximise in the process Commercial cattle resistance selection breeding of resistance, generation. improvement Ankole disease between 3 articial yield, out next • high selective 2 breeding nature, sheep and breed have are the next in tnemelppuS Differences and natural Some (the between selection between evolutionary process) articial are selection shown selection Selection due to very in the breeding) human and natural selection table. Natural selection Selection inuences Produces (selective selection differences Articial articial due to environmental factors varieties different of from organisms native Produces greater biodiversity May to species generations Does not result Inbreeding A loss of is species common, vigour relatively new fast Proportion of individuals in in the leading to A heterozygous population new Outbreeding offspring process the lead is reduced hybrid slow is process, Proportion of individuals in remains common, leading vigour taking many years heterozygous the population high Hybrid There are two main Outbreeding This may be individuals, another with both results called in involves used for crop a to the high that yield tougher of carrying breeding combine example plant hybrid methods the crossing is a is to with a breeding: animals characteristics plant with disease, resistant individuals selective unrelated crop resistant and of good out to can disease. better of high or plants. produce of survival. often This Selective more offspring is vigour It involves breeding close relatives in an attempt to breeding for combines such as high yield a result characteristics. of inbreeding. population There is weakened also a greater However, These by a can lack there can include of gene susceptibility to a be loss harmful of diversity disease and as a with reduced that the fertility. KEY b sheep that are improved by Selective breeders from wild breeding in: cereal tnemelppuS 3 a milk List features, and the Selective crops, e.g. wheat, rice or with (articial humans with crossing selecting next the best generation. breeding the procedure yield four of a herd differences that of a farmer would take to natural selection and animals with improve cows. between new has varieties maize of Describe the involves organisms produced 2 varieties relatives. horses 2 c and crossing POINTS desirable features by result. QUESTIONS useful race features, as them a to resistance come or variety desirable commercial nding State many years breeders disease selection) 1 takes 10 the 1 SUMMARY vigour. retain effects vigour, hybrid commercial low-yielding desirable take plant a existing Inbreeding display KNOW? may develop that plants YOU years. with Outbreeding chance DID separate yield, maize and increased plants economic importance, e.g. crops, that cattle high-yielding produce more articial milk or that produce better meat and sheep selection. b What is meant by i outbreeding c What is meant by the and ii hybrid wool. inbreeding? 3 term more vigour? Differences and between natural summarised selection in the articial are table. 241 tnemelppuS to in PRACTICE 1 Merino wild QUESTIONS sheep sheep. have much Merino A mutation of B natural C phenotypic D selective a thicker sheep are wool the 6 than result Which row correctly continuous of: and identies the discontinuous causes of variation? gene discontinuous continuous selection variation variation variation environmental factors A (Paper breeding 1) [1] genes environmental Which is an variation in example only genes only and B 2 genes only of factors discontinuous environmental humans? C genes factors only only A blood B body group genes mass D genes and only environmental C foot D hand span (Paper (Paper 1) On very appear have 2) [1] [1] 7 3 factors length rare in a occasions wild brown a white population hair. This is the of mouse mice result that Sickle is may all of: cell most at risk of this anaemia common from is in malaria. similarity in a genetic areas disease where Which is an distribution that people are explanation of the two diseases? A adaptation B articial A both diseases are associated with tropical selection climates C competition D mutation (Paper 1) B malaria C people An island that was preyed butteries, invaded on by a butteries. only those species In the of bird population individuals that protection against D of toxic substance predation as survived. A articial B a This is an example to people with cell allele of: 8 selection Biologists use to term ability C immunity C the possession of D natural D the probability that selection ability the the 1) of burrowing beetle to a species almost colour reason Beetles as for are predators B for Beetles achieve to in leave the tness great very an of range black. the this well colour to a mean: feats many of endurance offspring attractive phenotype individuals in likely which to see (Paper 2) survive and Match each [1] from pale have they 9 the correct of the denition following on the C Beetles D Dark are beetles with the live. mutation outward variation genetic selection range phenotype change appearance of an organism be: so constitution of an organism that of forms found in a species them. colour subject terms right: to match in DNA their best adapted to their genotype environment 242 have sand- beetles camouaged cannot change in The sand is ightless surroundings. 2) cell environment organisms (Paper sickle [1] Individuals A more [1] B The are 2) competition same anaemia produced the brown anaemia malaria A (Paper cell malaria the to reproduce 5 sickle catch resistance (Paper a with sickle [1] likely 4 causes to absorb articial more survive and breed selection. heat. (Paper [1] 3) [5] 10 The distance and little students is between nger is the measured shown in the the outstretched handspan. their A handspans. (c) thumb group The A couple child of data is blood blood diagram to Before kidney group group explain how B. They O. Use this is have a a genetic possible. be handspan number / students of a carried / 160–69 7 4.7 170–79 12 8.0 180–89 25 16.7 (Paper 12 and 200–09 34 210–19 19 blood recipient why operation groups of may the it is must be important checked. to do this. [3] 3) Xerophytes They 45 transplant the % Explain 190–99 out, frequency donor have are plants many that adaptive grow in dry places. features. 30.0 (a) Dene (b) Describe 12.7 that the are term three adaptive features adaptations feature. of for [2] xerophytes growing in dry habitats. 220–29 8 5.3 150 100.0 (c) Total An area climate (a) (i) Calculate who the had between a percentage handspan 200 and of students plant measurement 209 mm. State the range in the frequency in the Gonorrhoea histogram of the (i) State table. the type of variation shown your a taken ensure answer to part (i). (b) were carried of become change. [6] disease. carried out Antibiotic on samples from people with of gonorrhoea that they are treated with an antibiotic. Describe how out in Pakistan bacteria become resistant [2] 3) Surveys species to environmental bacterial are antibiotics. Explain how transmitted 11 a of [1] to (Paper how time result in graph. Explain a [5] (a) (ii) is tests appropriate your this over as results to (c) Explain change to dry [1] bacteria shown very 4) sensitivity a change. may adapted 13 Draw becomes handspan measurements. (b) [3] [2] (Paper (ii) [3] antibiotic from one resistance bacterial is cell to and others. New Zealand to nd the percentage of in the different blood groups Explain ABO blood group why antibiotic results are shown in the sample in of people each blood in B Explain be the AB O Pakistan 31.0 36.2 7.7 25.1 New 35.5 8.8 2.6 53.1 (b) Draw (i) a bar What the (ii) chart type to of show the variation is data. shown data? Explain your a why used to Antibiotic problem which (a) to tests carry before course of antibiotics. [2] antibiotics treat viral should not diseases. [3] group (e) A Zealand important table. (d) percentage country is sensitivity system. prescribing The it of out the [2] the (c) population [5] table. (d) mm are who (Paper resistance worldwide. this problem is a serious Suggest may be medical ways in overcome. [3] 4) [5] by [1] answer to part (i). [2] 243 19 Organisms 19.1 this State that main source the Sun is of energy State the • that a food of organism Dene the chain energy to and shows from another terms consumers the Construct is at the ow of energy through living organisms of nutrients to organisms in biological systems. important difference between these two processes. is a principal energy to other when source ‘lost’. that food trophic absorbed organisms animals Eventually producers, decomposers simple all is feed the make up animals on energy Nutrients on of energy input photosynthetic chemical plants is the living and as by into biological and energy . when transferred other organisms. eventually to hand, Energy animals the are back and systems. of feed the taken into on as by animals. heat and is elements plants, biological available occurs other chemical up made transfer environment consist They recycled organisms passed systems. on This is chains as nutrient cycling, since they are constantly reused. level Communities Living organisms However, more useful Living own when to and Producers be group organisms food can placed looking make a them can those at be groups according divided that their into community up of to into based living the way those on similar things, that that it is they can features. often feed. make their cannot. own organic nutrients from simple raw producer materials, a source such of as energy photosynthesis. photosynthetic Some from of carbon the to or reactions make Some their are in water . from also energy involved involving and sugars bacteria obtain bacteria dioxide carbon from of plants dioxide producers recycling compounds Green and simple and they obtain (see light water are chemical nitrogen nitrogen use either reactions. their page as by energy 253). primar y Producers make energy available for all the other members of the consumer community in the carbohydrates, energy for form fats almost of and all energy-rich proteins. food carbon Sunlight chains. The is compounds, the major ultimate exceptions such as source are the of vent secondar y communities in the deep ocean that rely on chemical energy rather consumer than Figure 19.1.1 A food light energy. chain. Consumers plants make or their primary own eat and other Sunlight things 244 in is the this source of ecosystem. energy for all food, as they energy both. so are organic material eat Each of these from a feeding word by they have eat and and pages 6 groups meaning eating animals the to are is a ‘to other 7 eat (consume) T ertiary that for it. called gain their of can top (The put are are they word each carnivores from into a trophic level as you will see in these trophic organism food waste feed). living ecosystem are secondary carnivores. energy how either cannot Herbivores Carnivores level. Y ou They consumers details trophic feed’.) organisms, consumers. sometimes bacteria and are producers. herbivores. fungi (see All they carnivores, Decomposers Greek their or consumers consumers that obtain animals chains. comes in an tnemelppuS tnemelppuS Dene an Sun known • recycling Light to • looking systems transfer one are for The • we ow the There biological unit environment OUTCOMES and • their Energy In LEARNING and Food Food They next. chains chains show show the Look at ecosystem. ow the The the ingests the This can food one living food in show and always energy Figure the organism grass chain organisms and chain arrows from that of food transferred gazelle what feed from 19.1.2 direction to that the the begins in next. lion with on a in one an which to food tells gazelle. often a the African in chain the producer , East energy food ingests community. organism from This a us is that Notice green KEY plant. 1 include parts of a plant, such as seeds, fruits or even POINTS Sunlight energy leaves. the Food ow energy of chains not energy. chain only show Producers would look like the gain ow their of food, energy they from the is also for → producers → Sun, so an 2 this: primary A food chain transfer consumers → secondary we Food do not chains include start the with Sun in food chains, as it is not a ‘food’. food simple ows food to decomposers, but they are rarely included in these of in chains. the from another. one Food show interconnecting chains. the provide form of compounds energy carbon for consumers decomposers. webs 4 In shows energy to Producers and Food of systems. producers. 3 Energy source consumers webs But main biological show organism Sun the dead most communities, animals will eat more than one type of Energy is animals organism. A food web gives a more complete picture of the transferred to living when they ingest feeding food. in an ecosystem. 5 grey kestrel lizard praying A trophic level of organisms or a food is in the a position food chain web. tnemelppuS relationships mantis SUMMARY QUESTIONS spider 1 Look at the woodland moth a grasshopper grasses Christmas Give food web ecosystem one example the food web of the following: for from each i a producer ii a primary iii a secondary the here: of consumer bush consumer b Name the 19.1.2 A food web for a West African forest Draw four over-harvesting manner e.g. can result overshing. of in food a Also, species decrease the in by humans their introduction in numbers of foreign an the unsustainable and native organisms due to predation and (alien) species competition e.g food. Both of these result in disruption of webs, due to the removal of a species or a decrease food in chain organisms. with Indicate levels on the chain. can Dene the term explain trophic how energy level is chains transferred and food for and resources, a trophic food extinction, 2 displace in ecosystem. c The carnivores web. between trophic their levels. numbers. 245 tnemelppuS Figure the food 19.2 Pyramids and describe and pyramids of numbers pyramids of biomass chains plants pyramids food they webs do show not feeding show how relationships many living in a organisms are For and instance, many grasshoppers grasshoppers and feed on lizards many are grasses eaten by and grey other kestrels. of Food and and but and involved. numbers numbers interpret community, • Compare of OUTCOMES Food • Draw, numbers biomass Pyramids LEARNING of pyramids chains and food webs do not show this. of Look at Figure 19.2.1. There are far more plants than caterpillars biomass because fewer Look one This The at caterpillar than the 600 shrews numbers → of in eats can each this be box organisms in there leaves because are owl → in a plants. eats each mice many 10 pyramid pyramid at many There are far shrews. chain: 100 shown the from each food caterpillars information area living ten owls plants owl each shows trophic → of owl 1 numbers. roughly how many level. shrews hundreds of caterpillars The producers and are carnivores consumers than than primary primary the are rst the level, third. producers. consumers. consumers as There But they herbivores Notice that are also secondary have to eat tertiary 1 are there the are fewer second fewer level primary secondary consumers are consumers bigger than them! consumers thousands secondary 90 000 of primary 200 000 Figure 19.2.1 This shows the and consumers consumers leaves consumers producers producers 1 500 000 an owl for that several support days. number of Figure A 19.2.2 problem Pyramid with of numbers pyramids of for a grassland numbers is community that they do in 0.1 not hectare. take into tertiar y individuals account consumers the size of organisms at each trophic level. decreases secondar y consumers buzzard primar y consumers size of blackbirds individuals producers decreases Figure 19.2.3 Pyramids of numbers caterpillars and mahogany biomass show these tree trends. Figure 19.2.4 A pyramid of numbers for the organisms living in a mahogany tree. parasites For instance, a mahogany tree and a grass plant each count as one ladybirds organism. greenfly than one unusual rose 19.2.5 An inverted numbers. 246 one grass mahogany plant. As a tree result can some support many pyramids of more herbivores numbers can have shapes. bush In Figure But pyramid Figure 19.2.5 the tertiary consumers are parasites. Many of them feed of on a single ladybird so this pyramid is inverted and it looks top heavy . way instead biomass each to of biomass overcome numbers. pyramid trophic the problem Biomass shows the is of the actual size mass is of weight to measure living or mass of STUD Y biomass material. So living things Prod ucer s at plan ts) level. the To A draw a sample weighed. mass is dry it mass this much and The is does fats as constant for the rst each the needs trophic sample estimated is to be level is calculated. number of not food for in for the mass. change as it It plant is the recorded is is in in at by beca use and The inpu t their as to body Dry it mass mass tells carbohydrates, community. in an estimate instance, do not grass take often into such as The is time will be grows This us over a period into the the how proteins data is instant at a how fast fast in rate, an time. Biomass but organism because it grows. and cattle, its biomass at is grazed any POINTS For by Pyramids means it is better to calculate the of time, e.g. over a year or a of numbers show instant many individuals there are biomass at produced provid e metre. one account grasshoppers low. and energy water how in level abso rb oven 1 animals, tro ph ic green on the KEY pyramids of as alwa ys they sunl igh t average organisms drying possible plants. the square taken of present organisms per matter usually 65% does material grams rst collected. taken (suc h are ecosys tem . approximately biological mass by data from mass determined a expressed dry the community. animals: useful usually organisms multiplied the of pyramid, average reaches mass and The in dry until the then present The biomass of TIP a growing each trophic level but give no season. indication 2 of their size. Pyramids of biomass the of living indicate 2 5.8 g per m dog-whelks mass each trophic material level, but at give 2 71 g per periwinkles m no indication of the rate of tnemelppuS One of growth. algae 2 3987 g per on m and Figure 19.2.6 A Phytoplankton in water – pyramid consists both of biomass of tiny freshwater for a rocky seashore photosynthetic (lakes and ponds) growing seaweeds the rocks community. organisms and in the that sea. oat The SUMMARY plankton and the grow sea is quickly warm at times with of plenty the of year light. when They there live for are only a few days 1 as they are grazed by animal plankton. So their biomass at any Draw two is small. But over say a year, their biomass is huge. This records only a few days’ growth and so is of with different biomass shapes. pyramid pyramids one numbers time QUESTIONS nutrients Explain their shapes. inverted: 2 Draw for a an pyramid of ecosystem biomass and explain 2 21 g per m its zooplankton shape. you Make include the measurement 4 g phytoplankton your sure unit for that of biomass on pyramid. 2 per m 3 Figure 19.2.7 Biomass pyramid for the English What criticisms made about numbers Biomass can vary with the seasons. In have been Channel. temperate latitudes, pyramids and of pyramids of deciduous biomass? trees than shed it is their in leaves winter as in winter. they will Their have biomass leaves, is greater owers, fruits in summer and seeds. 247 tnemelppuS tnemelppuS Pyramids 19.3 Shortening the food chain tnemelppuS The LEARNING The • Explain energy losses of energy transfer levels in efciency of energy transfer between trophic levels can be seen between by trophic efciency OUTCOMES food using energy pyramids. These show the energy transferred from chains one trophic level to the next. The energy pyramid in Figure 19.3.1 2 • Explain the shows increased that 87 000 kJ per m per year is passed to the tadpoles from 2 efciency green in supplying plants compared plants to as to human feeding food the plant plankton. the small sh, and The so tadpoles pass on to a tran sfer char ts consumers in 14 000 primar y 87 000 producers consumers Ano ther water char t o ppos ite. the as to T his energy respira tion able tertiar y energy ow decom posers . be 67 weeds show n show s to 1600 of energy is year TIP ecosys tem . way per crop tadpoles an m animals Pyram ids show per on. pike STUD Y 14 000 kJ Figure 19.3.1 An energy pyramid for a lake. Figures are in kJ per m per year. and Y ou shou ld interp re t that 2 losses 2 The tadpoles obtain 87 000 kJ per m per year from the water plants 2 but ow only pass on 14 000 kJ per m per year of this to the small sh. 2 show energy ow. The remaining chain. they The will energy it tadpoles have that biomass – is they a will passed their swallows Energy 73 000 kJ do per m have out pass muscles per used some on in to and year a lot of waste the other has small – been energy urine sh organs lost is that in the the swimming and the from faeces. energy sh and The in eats food only their every time tadpole. always ‘lost’ in this way as it passes from one trophic level to 2 STUD Y the TIP next. Of the 87 000 kJ per m per year of energy in the producers 2 only As you will Phys ics, proce sses efc ient. ‘lost’ is no as energy are page per m carnivore, the pike. trophic is not heat. energy the by next the of it only an size becomes some energy of the of energy the in energy pyramid organisms is the is never or how esh of passed inverted. many the from of Its top one shape them there since it simply looks at the energy that is passed on. is Birds re tain a and this heat cons tant tempe rature (see Energy Energy plants it is losses ow through absorb leaves. Much reected them, Plants or is use only of green As 2 this from much respiration. 248 to year Since Resp iratio n except ion. 168) . level affected per 100% are maint ain body from trans fer neve r Muc h mam mals to know 67 kJ 5% energy the light of an ecosystems to the of is not surface which energy energy is the of they in leaves, cannot trap inefcient. energy trapped the they transfer relatively light in process, that At strikes best, their photosynthesis passes straight because through absorb. photosynthesis respiration is in their about own 40% so about 60% of the energy is lost tnemelppuS efcient as released heat to the plant and then to the atmosphere. in Much of the plant’s biomass is lost respiration to tertiar y decomposers in the form of dead leaves, twigs, consumers dead remains, released fruits, etc. About 10% of the energy trapped by faeces, in the plant Much is of available what they to eat secondary consumers. is edible not very or etc. respiration secondar y easy production digest. So primary consumers make dead available released only about 10% of what they have eaten remains, faeces, etc. to in secondary sresopmoced consumers to respiration consumers. primar y However , the animal esh in primary for example heat consumers dead consumers, of grasshoppers remains, and faeces, etc. released gazelles, is easier to digest and carnivores may in obtain slightly more than 10% of the respiration energy. producers At each trophic level, energy is lost as heat to dead the environment and consumers lose energy remains, in their faeces and urine to decomposers etc. energy which means trophic level. that there Food is chains less on for the land input next rarely have sun more than When four farmers trophic grow crops, human consumption, grain available is farmers They grow may to or buy levels. all us buy as the as such food as rice, energy primary plant cereals such of for in Figure consumers. to feed barley 19.3.2 Energy their Livestock level, animals. or maize or grass, alfalfa and used i.e. in grow fodder crops, such as consist clover , for grazing. Animals, such as pigs, cattle use up much of the energy in their that there is not as much energy food. vegetarian diet can support far more available to cut down the number of links in people. the food individuals This is at the because end we are of the food cutting chain down the of energy that occurs between in of many food countries of plant developed diet which poultry, human can provide tend origin to includes sh, lamb, population enough a and is b Give to change each and less to one food sh. of a meat pork. If farmers our diet are may of that includes animal more plant origin. trophic POINTS Energy losses occur between QUESTIONS is the ultimate form of energy input in a food levels two ways in which energy is ‘lost’ from food why food chains usually have fewer than ve as and a result in of waste chain? produced. chains. 2 Explain mainly or be materials 2 or have proportion everyone, respiration, What that meat people increasing. for trophic a diets some many higher beef food 1 1 undigested have with countries KEY SUMMARY uneaten, level. 90% foods ‘wastage’ is each chain have fed. that at If to more energy us. The we ecosystem. This from A the respiration Western varied means an and In chickens, in they People may losses the More energy is available in trophic foods for human consumption levels. if 3 a Explain supply b Explain why it green why inefcient in is efcient, plants a diet terms as rich of in terms human in energy transfer, to products loss. feed secondary food. meat energy of we is relatively as consumers 3 A more that than as consumers. vegetarian far primary rather diet people includes can than meat support one products. 249 19.4 Nutrient Nutrient LEARNING Describe the carbon far we Describe the role ow (fungi in recycling Describe the different the water with food ecosystems and from energy. the There Sun, and is a energy through the This different topic trophic and the levels next are and is about then lost some of to the the elements comprise living organisms and how they are cycled in nature. stages Most of into carbon that • concerned energy and atmosphere. bacteria) been of of ows decomposers have cycle constant • cycling OUTCOMES So • cycles living matter (95%) is made up of six elements: carbon, cycle hydrogen, have a oxygen, constant carbohydrates, a nite source nitrogen, supply fats of and phosphorus these other of these to continue, elements organic nutrients. Life and if sulfur . they are materials. has Living to Unlike existed on things make energy, Earth must proteins, for there is millions faeces consumers and of urine years. become For it locked up in dead these elements bodies and life must will be recycled become or they will extinct. feeding death and Bacteria decay feed producers decomposers on breaking that and the down they water a aerobic Many warm are feed on matter of dead of fats these temperature catalysed by and animals carbohydrates, absorb. and respiration nutrients fungi waste and are as decaying (urine and proteins respired. the enzymes. matter. into To do processes They They faeces). also of They small this by molecules they digestion need also feed oxygen require and for respiration. in environment Decomposers Figure 19.4.1 The role of decomposers in They also release break carbon down as amino carbon acids dioxide releasing when they ammonia respire. into their ecosystems. surroundings. the most absorbed These in by this plants nutrients plants. carbon In important We say are that way they elements and recycle for converted then passed nutrients carbon organisms. into on are to and nitrogen Simple complex animals – two compounds of are compounds. when they eat the cycled dioxide air The carbon cycle respiration photosynthesis and decay Carbon is used important carbon in to make biological carbohydrates, molecules. The proteins, carbon fats, comes DNA from and other carbon compounds dioxide animals and in use the it in compounds air. Plants absorb photosynthesis by eating to carbon make dioxide food. from Animals the get atmosphere the carbon plants. feeding Carbon • carbon in Plants and carbon plants • formed of years dead ago animals fuels: peat, dioxide Decomposers of dioxide the 250 carbon (as some use well dead decaying Fossil (plus fuels water like dioxide in of the their following food as water plants and for ways: respiration, releasing and energy). material for animals for food. They respiration, releasing oil, and also use natural contain carbon energy). is peat, one of coal, the and gases gas released gas combustion The air carbon. oil, Carbon 19.4.2 use the from vegetation • Figure into millions some coal, gets compounds burning fossil dioxide cycle. when these fuels are burnt. into the air during STUD Y TIP Durin g These processes release carbon dioxide into the air and this carb on the uptake by photosynthesis so the concentration of pho to synt hesis balances carbon is suga rs. in the atmosphere remains constant. Sometimes, dead plants do not decompose. Their dead bodies become fossilised coal, oil and gas – fossil The effects of combustion concentration Topics 21.2 of and carbon of fossil dioxide fuels in the and deforestation atmosphere are on the discussed sam e in cycl e, The water water cycle cycle water Follow moves demonstrates the on how important water is to life arrows between on the living diagram organisms to see and how their the world’s from the the nitrog en no t muc h than as use carb on more nitrog en ). 2 gets More powers is T he – environment. It Energy (N into xatio n beca is reactiv e on – the but dioxid e gas Earth. in a of compo und. idea occu rs 21.5. simpl e conv erted compl ex comm The is fuels. a as means compo und to carb on form T his and simpl e animals xed dioxide colder water as the air condenses rises. out. Sun water cycle. The droplets heavier or condensation to form from clouds tiny of and snow. get fall This is bigger as rain, and hail precipitation. water made water droplets animals water some breathe out vapour water evaporates from evaporation from the of the soil and 19.4.3 The SUMMARY water (especially vapour through returns streams to the and sea via a Describe what and two living c is meant living by the term cycle, in the context the organisms. substances six POINTS of that are absorbed and recycled by Carbon of elements that make up 95% of living is cycled ecosystems organisms. Name water cycle. 1 State feeding, matter. by State the roles of the following in nutrient 3 Look decomposers at the diagram b of green the plants water cycle c State three b Explain ways in which water c State the it rains source of when the clouds energy respiration, decomposition, and combustion. Decomposers, like and important fungi, are bacteria in above. gets into the recycling of nutrients. atmosphere. 3 why processes animals the a the cycles: 2 a through photosynthesis, fossilisation 2 water QUESTIONS nutrients b lose rivers underground KEY 1 trees) transpiration sea water Figure plants water Evaporation, condensation precipitation are and rise. that powers the water cycle. processes in the important water cycle. 251 19.5 The nitrogen cycle tnemelppuS Nitrogen LEARNING OUTCOMES Nitrogen • Describe the roles is molecules. microorganisms an element required for many biologically important of in Amino acids, proteins, DNA and chlorophyll contain the nitrogen. Approximately inert very 80% of the air is nitrogen gas (N ) but it is 2 nitrogen • cycle Describe the stages nitrogen cycle in and most the to The as and xed nitrogen and below changes that in cannot nitrogen proteins, diagram the organisms microorganisms them acids few the in as shows happen can use the ions the to make it in form such use this of as Plants, It has compounds cycle as it. form. nitrate nitrogen nitrogen of it is and animals to be such available as amino ammonium which and ions. summarises all recycled. air lightning animal protein fertilisers plant animal proteins wastes death and decay nitrogen-fixing denitrifying bacteria in nitrogen-fixing bacteria decay soil bacteria nitrate act ions the on dead plants and remains and up of by in bacteria in taken soil root nodules roots animals animal wastes nitrifying bacteria nitrate Figure 19.5.1 The nitrogen in the soil cycle. Most STUD Y ions of nitrate TIP the ions nitrogen (NO ). that They plants use this obtain to they make absorb amino in acids the in form their of leaves. 3 The Be carefu l ‘plan ts when you abso rb Also do the they eat plants Any the no t add and so process of used obtain amino acids to form their are proteins, nitrogen broken deamination. in the down Animals such by that as form enzymes. of animals live on plant to land, Animals protein. ammonia such as by the ‘plan ts cow in the cycle above, convert ammonia to urea and excrete it in urine. that nitrog en Decomposers (bacteria and fungi) break down dead remains and + T hey don’ t, fertili sers nitrat e animal wastes releasing ammonium ions (NH ) into the soil. Bacteria 4 also break down urea in urine to ammonium ions. This process that is sometimes called ammonication. Deamination results in the ions . production urine 252 are ions ’. write add acids excess their soil ’. provid e writi ng nitrog en’ mean nitrat e ‘farm ers to abou t abso rb amino (see of the Topic excretory 13.1). product urea, which passes out in animal ions. These reaction If you bacteria instead are where T wo bacteria of tracing we Nitrogen-xing nitrogen gas themselves. available The These a can suitable all the cycle in source light the of or air they are into die energy feeding of help found in the compounds and are a by soil. this we are back plants. nitrogen. These nitrogen decomposed, nitrate oxidation realise recycle of into decomposer. will ions to ions from as you nitrate microorganisms the ammonium diagram absorption bacteria alfalfa bacteria bacteria plants their change this can convert that they xed use nitrogen is plants. beans, trees. soil bacteria from Nitrogen-xing peas, of When to gain with groups the absorbing the started other in tnemelppuS Nitrifying and are to that clover and they amino for found need. gas the In the the legume trees, ammonia (in of roots return bacteria Nitrogen roots tropical on into acids. the in many swellings nitrogen make environment sugars also inside change use are the that requires the like ame nodules. legume plants and a as root legume nodules) xation such called plants also lot of provide provide energy. The Denitrifying bacteria live in water-logged soil. They change nitrate top root to nitrogen gas. It is thought that they balance the uptake of by nitrogen-xing nodules. the cells reveal bacteria causes temperatures. washed into nitrogen Nitrogen the soil ions can washed be are lost by and oxides rain from out of oxygen are to formed where they react in together the form at reactions. nitrate of the the soil soil before by plants rainwater . can This is the some nitrogen-xing bottom a root photo nodule thousands that you broken can open live of nitrogen-xing inside. high These are ions. KEY Nitrate the bacteria. to Lightning shows In nitrogen see gas photo ions absorb called them as POINTS they 1 leaching Nitrogen as a gas is in (N ) the but atmosphere is not 2 Farmers add fertilisers containing nitrogen, e.g. ammonium nitrate. available These are manufactured from ammonia made in the Haber add replace Some extra the sources nitrate farmers do of nitrate absorbed not use by ions the inorganic for crop plants plants. and fertilisers, The removed but most organisms process as and to it is not reactive. fertilisers at instead harvest. use 2 Some (N natural ) bacteria x converting nitrogen it to 2 fertilisers nitrogen such cycle as at manure. the This point provides where the dead material decomposers that enters ammonia. the live act. inside legumes. Some root 3 Bacteria and QUESTIONS are to List the four substances element present in living organisms that Describe the the protein ammonia. to convert nitrate ions. nitrogen. 4 2 bacteria. bacteria ammonia contain of called decompose urea Nitrifying 1 these nodules They nitrogen-xing SUMMARY of roles following of microorganisms (bacteria and fungi) Denitrifying nitrate in (N processes: bacteria ions to convert nitrogen gas ). 2 a decomposition b nitrication c nitrogen d denitrication xation 5 Plants and acids 3 Explain how nitrogen in the protein of dead animals absorb convert which 4 is Explain made how available to available farmers crop to can plants. plants increase in the the form of quantity nitrate of they to use ions amino to make and proteins. plants nitrate them Animals obtain the ions. nitrate amino acids eating and animal they need digesting by plant or protein. 253 19.6 Populations, and ecosystems Population LEARNING Dene the term population State the factors affecting same of growth of a Identify of growth growth • the State different in a phases interbreed. that of food disease are factors that affect and population the of the the same species individuals in a living in population Sometimes such or on like This it as a on is is difcult easiest to tell an island, mountain, wildebeest where the in like the like the geographical organisms Komodo Protea game kilimanjaro, parks live dragons of East or in on a islands they are Africa. species into terms are very separate widely distributed populations. and However, it is there difcult are to usually divide barriers reproduction, such as rivers and mountains, that divide them into growth community so there populations. is Some interbreeding individuals between migrate across these barriers, populations. ecosystem The • All Describe and different phases population explain of growth table shows some animal and plant examples. the the population habitat creole coral place curve reefs wrasse around Tobago in the reef Caribbean wildebeest grassland dry Komodo Nepenthes Komodo rajah carnivorous A community organisms Wildebeest in East a Africa. – An factors, their log (the such shrubland includes decomposing component as in Indonesia Mount Kinabalu in Mount Kilimanjaro Malaysia forest all the ecosystem and Island forest mountain plant kilimanjaro ecosystem. Africa grassland dragon and Protea East is populations a unit environment, or a lake. community) light, water, An interacting ecosystem and pH of different containing the and is abiotic the in Kenya species in community together, made for up of component an of example the in biotic (physical temperature). immigration Population + Figure 19.6.1 population. population size number of shows The the factors number deaths of that births decreases it. determine adds to the Individuals the size of population may enter or a and leave the a size population Animals are xed plants leave emigration Figure 19.6.1 Factors migrate so use one affect from you seed so there would the rate of mixing think dispersal population is of populations. to that between migration colonise plants population to new join populations. is not areas another . growth are and The food Flowering possible. in this main supply, plants However , way individuals factors that predation inuencing population size. and disease. growth. An exponential predators 254 neighbouring Figure 19.6.2 organism and and that stationary no disease. shows enters the a phases different new if stages habitat there is may plenty of population show of the food, no lag, tnemelppuS tnemelppuS Dene area, visible, separate • time. the to of individuals the them rate of same supply, Some main the population. Indonesia, highly and a restricted in population curve predation group at population limits • a habitat the may rate is population the • growth OUTCOMES A • communities Competition water and East • nutrients. and mates. factor for Plants Animals compete Competition species of compete for for food herbivores, for is food, a such light, space, space common as wildebeest rebmun limiting soil resources. fo (territory) for airetcab tnemelppuS • in Africa. Predation. Predators often take young, sick individuals or less time lag well-adapted individuals. Predators may limit the growth of exponential phase population of prey animals, but it is more often the case that (log) of prey animals limit the population size of the death phase phase phase the Figure numbers stationar y a 19.6.2 Growth of a bacterial predator . population. Disease is an important control factor when KEY populations individuals increase. more Pathogens easily when are transmitted organisms live close together. 1 A population of The growth of a population: POINTS between of growth a of a population bacterial population changes. A small is a good number of way to bacteria show are how placed the into size habitat with a warm nutrient solution which is aerated so the bacteria aerobically . Bacteria grow The and divide under these of bacteria divide every 20 minutes if conditions conditions. are ideal. the growth work to out reach a give two how very cells, many large two cells cells there divide will be to give after 4 four , hours and and so on. you One Y ou will quickly 3 There and are sigmoid you look phases • The the in at the lag the phase, numbers make graph growth new in of when are so a Figure 19.6.2 population doubling small. cytoplasm, of Bacteria DNA and you of will see four main The exponential rapidly. The limiting growth a while, • The rate factors, • The at which of death food, The such no they are phase, the shortage curve lack which or shown phase food phase, food so as as the numbers take up has little and effect species resources algae, of grow them fairly show become of food slows when being when the and down waste graph is this and four This are stable Most over by by disease. in the growth exponential death (log), known species species When do not inuenced phases. factors, such by as food QUESTIONS of But wastes that the do of as no in can – b Give be than rapid the because are c State and same of 2 up. examples sigmoid wild. are an lack products. growth When used up, populations Explain growth be rapidly, in of natural the ways 3 like how most may each can of a example act which increase food b predation c disease each and following the limit the giving case: supply reference describe of to population, in a With in decrease. following being may waste reproduce their three ecosystems. limit at death toxic the population populations after building of the resources this Dene populations are dying growth a increasing are phase dying may Causes build-up population available, exponentially. die. by phases and are SUMMARY stops. cells are of is there growth. products cells and build-up and declines. a population During produced. or the population bacterial more oxygen this food, as nutrients, curve Some of availability. water doubling water. limit population in or when by to because of size enzymes. increases factors such growth, stationary produced, of are factors shortage log) population there population (or of population lag, limiting bacteria. 1 • nal inuenced growth These If is cell number . bacterial same time. can stationary in and availability curve: Phases same Some predation divides the living at population the species in same may a respire group the a 2 ask a of bacteria species, The is individuals tnemelppuS Disease. to Figure explain 19.6.2, each of the phases: remain a lag b c stationary exponential (log) time. d death 255 tnemelppuS • 19.7 Human Human LEARNING Describe and explain in the population present, and its of social the world. in the human were and of TIP your self world cur ve was a a estimated years Lack of that Look cont ro l snoillib of not food live and the to make crops remain shelter meant population by an and human impact together that was with mortality about in from the communities activities. on keeping food so scattered their the case wild, of the and 0.2 the rates billion However, much They by relied although shing of people environment livestock. clearing less these on were still industry. 3.0 1950 0 2 0 0 0 2 2 1 1 7 9 0 1 1 5 0 0 0 9 0 0 0 0 that AD 19.7.1 Notice the long lag phase and short exponential phase of no sign of a stationary phase. species . human for population the Improved following has agriculture nutrition those increased exponentially over the past 300 reasons: means means they caused by that are most better people are defended better against fed. diseases, malnutrition. TIP • Public health drainage a good the place section to on be page on awar e contro l ts Y ou popu lation s. of of to care antibiotics; how in Medical diseases, improved. and There sewage waterborne are clean treatment. diseases such as water This supplies, has decreased cholera. has improved. people such as are also Since the 1940s vaccinated diphtheria and doctors against many have used infectious polio. the The sujec t has waste birth 206. of of epidemics • effects of these improvements have been: hum an • decrease • decrease • increase In is in in in Europe for 256 and wars 4.0 especially broade r people increase 5.0 be Better birth slow cont ro l • shou ld billion a 0.4 years revis e 7 1.0 The contro l be only long. world’s small, collecting and Figure is an 6.0 with T his at po pu latio ns from STUD Y to was 0 hum an anim al growing 2.0 how have may in 0 0 5 the and decide these Y ou how differ s there and year of is 7.0 long fo chan ged. planet 8.0 shor t phas e. and effect s aske d has predat ion – the the compe tition food, diseas e the – did unaffected growing elpoep fo r why and factor s species were of diseases ago lived beginning po pu latio n phas e the people years People hunting expone ntia l at there thousands population. and important lag 2011, malnutrition, high forests, grow th In For thousand were Ask on growth the hum an people human people. STUD Y of and Six population number impact graphs diagrams rate. in effects Interpret the human environmental • growth the alarming increase population OUTCOMES At • populations men 68 the death life and and years. infant and rates from expectancy North 80 child – starvation people America years for mortality the women. are and now average In rates, malnutrition, living life India, much longer. expectancy average life is 76 years expectancy In spite of housing, these water population and life improvements and live in health poverty expectancies services. with that there are huge Many high half are of infant those inequalities the and world’s child in food, human mortality rates, aforementioned. KEY Controlling There are oods, life. still wars, But the estimated human controls on tsunamis, overall that it population earthquakes trend could population is a rapid double in increase. and other increase the next POINTS growth in 30 Famines, epidemics, disasters the lead world’s to 1 loss of population. Improved public It is care years. have Europe places and North populations America continue the to population grow. The is virtually Earth has stable. limited In space and the population will have to stabilise and resources even some time in the future. The most obvious way to do this is birth rate. But many groups of people have strongly held to in an the and Fewer children are dying from decrease to and lack of food, and reduce people the increase population. disease at better medical other 2 limited and contributed exponential human In agriculture, health religious are now living much or longer. moral views on birth control and family size. This means they may often 3 have large families. China has had a ‘one-child’ policy since 1979 and The increase population is claimed this has restricted population growth in that country . No in has has such a base of the population pyramids below show the percentage food below the age of 5 years. The oldest people appear at The rate proportion Increasing of of needs increase in populations child-bearing human women population size in is most the brings inuenced by of food, and problems housing, for transport the how to dispose demands of our and greater environment, energy rubbish needs. (see – to the demands such There as is the on also supply Unit the QUESTIONS of problem Study the population 21). pyramids Ethiopia space rubbish. population. 1 of and our SUMMARY resources as housing, the dispose top. supplies, of energy children such policy . on The human social other implications, country the it on the left. 2014 a State which country has 100+ Male Female 95–99 the greater proportion 90–94 85–89 of i young people, ii old 80–84 75–79 people. 70–74 65–69 60–64 b Suggest reasons for the 55–59 50–54 differences 45–49 between the 40–44 populations 35–39 of the two 30–34 25–29 countries. 20–24 15–19 c 10–14 Suggest what you think 5–9 0–4 9 7.2 5.4 3.6 1.8 0 will 0 1.8 3.6 5.4 7.2 happen (millions) Age group Population United States – to i the numbers (millions) of women of child- 2014 100+ Male each 9 country Population in bearing age in 10 years’ Female 95–99 90–94 time, and in years’ ii the birth rate 85–89 80–84 75–79 10 time. 70–74 65–69 d Outline the likely effects 60–64 55–59 that 50–54 your answers to part 45–49 c 40–44 will have on the two 35–39 30–34 countries in the future. 25–29 20–24 15–19 2 Explain why infant and 10–14 5–9 child 0–4 15 12 Population 9 6 3 0 Age (millions) 0 3 6 group 9 12 Population 15 19.7.2 Population pyramids for Ethiopia and the USA and rates why have people (millions) are Figure mortality decreased living much longer. (2014). 257 PRACTICE 1 The for QUESTIONS diagram an shows ecosystem. tertiary a pyramid Which level of numbers indicates 6 the Some species nodules consumers? do of these of bacteria legumes. bacteria A compounds B protection C sugars, D water live Which provide of inside of to the the the root following legumes? nitrogen A from infection by fungi B C D (Paper (Paper 1) Fungi and carbon they and as ions sucrose from the soil 2) [1] [1] 7 2 such bacteria and are nitrogen important in in ecosystems recycling What is the population best size explanation shown in for the the change in graph? because are: A decomposers B herbivores C parasites D producers population size 0 (Paper 3 In the 1) [1] carbon carbon cycle, dioxide to which the A combustion and B decomposition C feeding D photosynthesis and two processes add atmosphere? respiration and fossilisation A birth B emigration C an outbreak rate and D no limiting death of rate and 1) is a factors 2) [1] The diagram shows a pyramid → simple food grasshopper arrows → bird in a food in chain decrease numbers B the ow of C the increase in complexity D the increase in size between of 2000 weeds the 20 000 organisms Which energy 400 represent: the of 10 fish tadpoles A the the of organisms the is pyramid organisms A a correct shown Biomass 1) From the and about the diagram? less between secondary producers and primary consumers primary than consumers. [1] B 5 statement in decreases consumers organisms between (Paper biomass. chain: water The of [1] small grass same disease pike Here the respiration 8 4 are fossilisation (Paper (Paper time 0 which A maize B soya food → beef beans → chain is cattle most → energy lost? The very humans C The is humans biomass of each of the individual producer is large. biomass more than 20% primary of the consumers biomass of the producers. C grass → dairy cattle D phytoplankton → humans D → (Paper small 2) sh → → mollusc tuna → There are humans (Paper many producers. [1] 9 (a) 2) Use [1] this Flower black that 258 very larvae information beetles cherry eat eat trees. ower to the draw pollen a and Kookaburras beetles. food chain: nectar are of birds [2] (b) State the chain role you of have each organism in the food drawn. (a) [3] The plant energy absorbs that photosynthesis (c) Dene (d) State the term population. factors that inuence the growth of a State population. Outline the reasons for the human the population two plants large State over the years. The Only dry three as about shows square the metre total of biomass grassland formed during in one plant gures mass were and obtained not the by fresh measuring mass of the State uses the to living (ii) 2 organisms in are produced sugars. which adapted to [2] the trap leaves as much [3] of the energy dry mass / g m photosynthesis plants trapped by carnivores 0.1 the biomass percentage between Show decrease green (c) Name (d) Suggest in plants your the plant available how antelopes [2] much each energy year. reaches Express your as kJ m . Show your working. process the advantage rather than of trophic mass as antelope faeces loses more compared of with its the [2] This food chain has three trophic levels it. Explain why there are no more. [4] during 4) levels. 12 The following substances measuring fresh the intake [1] [2] formed between why X. cheetah. working. biomass decreases mass the not and [3] dry is –2 (Paper Explain which that –1 in why year in herbivores. year (e) herbivores. the ways energy Calculate energy Explain to [3] 0.9 the passed 480 herbivores Calculate is antelopes. two the answer green (c) that simple possible. like the the (b) the ways are 10% in herbivores material. (a) sugars. year . (i) The in 3) table one it [4] the 10 the past (b) (Paper compounds from plants light 250 simple of uses increase of in make 1% and [3] (ii) (e) about plant rate in of to the [3] (i) three only strikes when urea, are that ammonia biologically contain (NH ), the important element amino acids, nitrogen: nitrite 3 investigating different biomass production in ions, ecosystems. Choose match 4) may 11 The diagram shows the passage of a food light chain energy in that a grassland strikes the each year is 400 000 kJ m of of each the the one substances statements once, more from (i) the to than (v). list to Y ou once or all. ecosystem. leaves of the main nitrogen-containing the excretory 2 grass each use at (i) The one energy not along ions [3] (a) (Paper nitrate product of animals . (ii) absorbed by (iii) a (iv) synthesised (v) the plants 33% process radiant from X 70% energy process product of deamination X into proteins sun 400 000 kJ (b) 10% end Nitrogen product gas (N ) in of nitrication the atmosphere [5] is 2 inert. very 12% in 10% in Unlike few carbon organisms Describe how dioxide are nitrogen able gas body of body antelope (N ) oxygen, use it. present in of the faeces faeces to 2 20% 55% and atmosphere is made available to be cheetah used (Paper by organisms. [4] 4) 259 20 Biotechnology and genetic engineering 20.1 Microorganisms and biotechnology The LEARNING use of microorganisms Biotechnology • State how bacteria are biotechnology biotechnology and is the use of microorganisms, such as bacteria and useful fungi, in and OUTCOMES to make useful products or to carry out services for us, such as genetic making wastes harmless. engineering The • Describe the role of yeast of anaerobic breadmaking • Describe the respiration in production • role yeast of in the ethanol use of both bacteria and fungi are in various processes is widespread. in Bacteria taken • for Unlike the biofuels or • reproduce for numbers animals nished quickly double) plants, product very with that microbes quickly, a is generation often can i.e. as convert in time little hours as raw (the 30 time minutes. materials rather than into months weeks. The use of bacteria independent • or very to Bacteria can antibiotics) harvested. of means that food production can be climate. produce that pass Enzymes complex out into made by proteins the (like enzymes surrounding microorganisms and medium are used and in can the be food industry. Examples food • of enzymes industry amylase that are produced by bacteria for use in the are: for breaking down starch in the production of glucose syrup of the products of pectinase • sucrase • protease for for extracting breaking for making juice down meat from fruit sucrose more in (see page making 263) confectionery tender traditional biotechnology. With the aid microbes of In plants and addition with, since In copies The of use people have concerns about the of and health of chickens 260 the and and contrast, long bacteria the the bacterial the same cells are alter new multiply gene can can be rapidly, (see varieties of concerns contain to be work cut spliced making page manufacture ethical also easy Plasmids organism inserted in breeding Plasmids quickly. another quickly time. DNA, very fungi raise In can open into many 267). complex over their the kept in and growth as would be the case in the use of other these living conditions. not of from media a scientists plasmids. replicate plasmid does take loop called gene bacteria manipulation welfare a nutrient chemicals Many can and products. can single DNA they enzymes them. the of engineering, modify animals to circles genetic so and small by of organisms, for example keeping chickens in battery farms. tnemelppuS Some • Biofuels Many and microbes respire When with or yeast breadmaking can respire without respires successfully without oxygen. Yeasts can oxygen. without oxygen (anaerobically) it is called fermentation. Glucose → alcohol + carbon dioxide + energy released Biofuels Some Biofuels are fuels made from biological material. Sugar-rich products This biofuels biobus cooking from sugar cane and maize can be fermented anaerobically own uses to produce and have fermenters sugar cane to juice maize starch starch with ethanol. developed is another is and when as fuel ethanol dioxide Car Oil a in called good a the engines seed raw burned need is to a be for raw oil supplies for material is obtained other from waste made waste from material. used of food products from industry. their example, often carbohydrates. This petrol that not there As a that because produce is no result modied crop of material. does atmosphere. rape The lot no Brazil, fuel used Glucose by is from treating the enzymes. substitute means a have substitute. ethanol. contains carbohydrase content countries biofuel produce which Ethanol Some a and made on with the yeast oil are runs to overall this be provides it fuel able oil has toxic high increase is to that a gases. in carbon use is pure energy Using carbon neutral ethanol. converted into fuel biodiesel Bread-making Yeast Baking is another Bread is made yeast. This the Bubbles of rise. gas sugar, carbon When make the the evaporate, from mixture ferment it example dough, is kept at using dioxide bread is mixture a warm are behind in a our, inside hot texture. the of help dioxide trapped in to produce water, temperature. carbon baked ‘light’ yeast a producing bread leaving of gas the oven The traditional taste of sugar the and starts produced bread their light carbon dough to dioxide rise and the of the alcohol to bread. POINTS Bacteria are useful reproduce 2 a Write b In ways in which bacteria are useful in a word equation for anaerobic respiration in why is yeast mixed to our and with sugar before it to Make of a table ethanol as the ethanol summarising a fuel for make Yeast carries out anaerobic in the production water? made by yeast in the cars. advantages and ethanol for biofuels. bread-making? 3 3 and is of happens rapidly molecules. respiration added What genetic they yeast. 2 bread-making, as biotechnology. complex c in and QUESTIONS engineering four loaves texture. biotechnology List caused these make 1 1 which give to KEY SUMMARY and alcohol. bubbles causes food. yeast dough the heat salt, The and a disadvantages Yeast carries respiration out anaerobic during bread- making. 261 20.2 Enzymes and biotechnology Enzymes LEARNING • have Investigate pectinase the in use the of Biological production Investigate enzymes washing tnemelppuS • Explain the important in industry. washing powders washing powders may contain one or more of the juice following • very of Biological fruit become OUTCOMES in the use biological powders the types of enzymes: of • proteases • lipases – – break break down down protein fats in stains, grease e.g. stains, blood, e.g. grass butter, and egg lipstick and mayonnaise use of lactase production of lactose-free in • amylases – • cellulases break down starch, e.g. food stains containing starch milk fabrics The the to – enzymes high water listed down the powders. the and are of removed been alkaline a the bres attached have and During products cellulose dirt above temperatures washing stains; break remove to reactions the the modied so conditions washing when on outside of cotton them cycle, the dissolve washing that they required for enzymes or are withstand some break suspended machine empties. down in For BIOLOGICAL example, Washing proteins cellulose Contains Works More Avoid Do protease best at effective using not use low and boiling are broken down into into amino acids and starch and glucose. (40°C) detergent water PRACTICAL silk Comparing Figure broken down lipase temperatures thanordinary with are Powder 20.2.1 Biological washing the action of biological and non-biological powder. washing powder 1 what Decide soya 2 sauce, Decide linen 3 Add you what or sort sort wool. the put of Also, same it of stain mustard, fabric the are you decide amount into you going to have, e.g. egg, etc. of are what stain beakers to going size to of the to use, fabric fabric e.g. to and cotton, use. let it dry before ‘wash’. 3 4 Granules of biological washing Weight out water at 5 Add piece 6 Decide a 30 °C Inside as of the these cleansing granules granules are are partially enzymes each a the powder dissolve each in 500 cm which act 7 Decide you fabric are with going the to same stir the stain to each ‘washing’ beaker . over a period. how to compare the cleanliness of each fabric after agents. 8 Repeat Safety: into You your Wear contact could tests to gloves with of beaker. same often and opened. washing. 262 in of how of powder. 10-minute Some 5 g produce see and your if do skin a you not to scale get let avoid of the the a cleanliness. same results. washing possible powders allergic come reaction. Extracting Pectinases molecules for fruit are that extracting juice enzymes act like fruit a apples that break ‘glue’ juices and in for down plant pectins, cell walls. softening which are Pectinases are used vegetables. PRACTICAL juices Extracting juice from apples with pectinase Figure 1 Cut an apple in B A 20.2.2 Extracting apple juice using half. pectinase. 2 Chop each half into small pieces and put them into separate the juice in from a apple water each of in bath the in beaker beaker at of and 10 cm of B. 40 °C beakers A for 20 apple minutes. 31 30 20 eciuj Filter beakers the apple emuloV 5 both over the fo Place solution over decudorp 4 water / 3 of 10 cm pectinase elppa Pour mc 3 3 40 3 beakers. 10 2 pieces. 0 water • Explain the results shown in the pectinase graph. A • How does the pectinase release this juice from the apple cells? Figure 20.2.3 Why was 10 cm of water added to beaker tnemelppuS SUMMARY use Some people problems get lactase do not digesting diarrhoea, milk be of broken into enough lactose, and Lactose down making produce and wind products. in the stomach is a sugar cramps, complex simple lactose-free lactase sugars sugar, by the and found if to from extract the juice A? from The results practical 3 • B Sample milk. to enzyme or that Describe what following may milk sucrose 1 have They consume similar QUESTIONS milk therefore in they apples. each enzymes a amylase c lipase b of the do. protease can d pectinase lactase. 2 Explain the advantages of lactase using glucose + sugar) (2 simple can using investigate test strips the test use Benedict’s strips reducing the that that test sugars detect are as and effect used all of the lactase in breaking concentration to detect glucose three sugars in give a positive powders. sugars) 3 You biological galactose washing (complex in the of in down glucose. urine. equation lactose These You Explain: by a are water beaker cannot above why are b result. the was added to A, results in the graph above, c 4 a how pectinase juice from How is releases apple tissue. lactose-free tnemelppuS lactose enzymes milk produced? KEY POINTS b Why for 1 Biological wash washing powders temperatures and in contain alkaline enzymes that work at is there Pectinase conditions. c Outline an in is used the cell to extract walls in fruit fruits juice such by as breaking down tnemelppuS Lactase breaks down lactose to is the to best the to produce apple. lactose-free 3 milk? experiment which temperature pectin demand low discover 2 a lactose-free produce lactose-free milk. milk. 263 20.3 Fermenters tnemelppuS You LEARNING may without • Describe the Penicillium of • the role in it of the antibiotic how fermenters used penicillin refers useful production oxygen to any may Industrial production inoculated • Adding for Penicillium Fungi are growing cultured on like whether they are suitable as that carry uses out with However, as or a in meaning an respiration industrial microorganisms useful without process to for context produce us. The agar this to organisms of in a of such culture This inside then the nutrients, penicillin large-scale antibiotics a of of industrial as a penicillin. suitable proceeds fermenter. such as fermentation to grow These sugar or The fungus, fermenter in under this the conditions starch, as is a is case Penicillium conditions should source include: of Ammonia or • Vitamin complex • Maintaining a constant temperature • Maintaining a constant pH Batch B urea is added is as added a source for of of nitrogen to make proteins respiration about of about 30 °C 6.5 culture sources takes about 30 hours for penicillin production to start. of is biomass secreted into the surrounding liquid 100 of by the 10 fungus. yield of penicillin Penicillium 90 9 –3 –3 / g / dm 80 g dm 8 penicillin 70 7 60 6 50 5 TIP 40 4 biomass Ferm enters suita ble of carbon respiration Penicillin grow th the nd antibiotics. STUD Y a oxygen. • It out to use with maintained dish. fermentation 140). production chrysogenum. fungus or respire important production Petri word page are One The the (see process product involved penicillin Explain in recognise OUTCOMES 30 me ta bo fo r lism micro orga nism s, 3 Penicillium provid e cond ition s and of 20 2 10 1 such 0 as If bacter ia the high , fung i. tempe ratu re enzy mes micro bes the 0 and 60 80 in / 100 120 140 160 hours too the Figure 20.3.1 This graph production and 140 and shows of 160 the growth penicillin of during a the fungus Penicillium fermentation that and lasts the between hours. die. Look 264 40 time is dena ture orga nism s 20 at the graph production. This a which substance is above. You because is not should penicillin necessary see is for a that there is secondary the growth of a delay in metabolite, the fungus. production starts after the exponential growth phase in motor response in is the one or fermenter then as to puried batch cleaned more is ltered, into culture. and limiting a the penicillin crystalline After sterilised the ready 6 factors. salt. day for After is This extracted type period, the next about the of 6 days, using a is mixture solvent production fermenter the is and steam for foam breaker sterilisation reduces known emptied, foaming of the culture batch. culture broth Industrial Industrial fermentation fermenters are large tanks (see right) that can hold as much probes for monitoring pH, 3 as 500 000 dm of fermenting mixture. Conditions inside these huge oxygen and tanks are carefully controlled. We will use the production of the temperature antibiotic penicillin to show how these fermenters work. large stirrer to • The fermentation with a medium sugars and vessel containing ammonium is made the salts. of stainless required To this steel nutrients. some of the and These fungus is lled mix contents include Penicillium water-cooled jacket removes is added. excess heat • The fungus grows well in the conditions inside the fermenter. sterile air – Sugars provide energy for respiration and ammonium salts are used provides by the fungus to make proteins and nucleic acids (DNA and RNA). oxygen for diffuser – sends After a few days the fungus starts to produce penicillin, respiration bubbles of air which through the accumulates in the fermenter. mixture har vesting • A stirrer keeps the microorganisms suspended so they always have drain access even • An to temperature air supply fungus. to • A nutrients (No make at alcohol. 6.5 to See oxygen page a Stirring the supplied jacket the adding Explain is give monitor by SUMMARY 1 provides water-cooled Probes oxygen. throughout oxygen fermentation • and for to maintain an Figure the the aerobic yeasts respiration respire of without 20.3.2 Large industrial fermenter. the oxygen 261.) removes the heat produced temperature temperature if helps fermenter. as constant alkalis also and make of by 24°C. sure the pH is constant necessary. QUESTIONS the function of each of the following in an industrial Industrial fermenters. fermenter: a a stirrer b an d temperature air supply c a water-cooled jacket KEY and pH 1 2 Explain 3 State in a the the role of Penicillium conditions POINTS probes in necessary the for production the of production Microorganisms reproduce quickly conditions penicillin. of found penicillin the fermenters fermenter. products 4 Explain how and fermentation why these factors change during ideal inside large, such temperature b 2 oxygen concentration c The What is meant ideal conditions batch for include adding correct nutrients and by: maintaining a useful penicillin. pH the 5 as a process: fermentation a industrial producing culture b secondary metabolite? and a constant pH temperature. 265 tnemelppuS Penicillin 20.4 Genetic Genetic LEARNING engineering Dene the term is genetic engineering • State can of that be human and tnemelppuS • in Outline engineering the production medicines, insect providing vitamins in how herbicide resistant plants, species never the of DNA changing the DNA achieved one of humans is of by species transfer codes the the genetic material of a gene This selection, another. between totally from individual production species. with and inserting the transfer articial bacteria or for another breed genes to changing that engineering to be would removing, of from is a because specic the DNA an only in species, A one can rare for gene protein. of that engineering unrelated to a process Genetic bacteria of genes. cases allows example plants. plants Examples genetic is by section from additional crop engineering a Genetic genetic used resistant, involves OUTCOMES organism • engineering used to of genetic engineering make Human medicines insulin Many • Discuss the advantages and disadvantages of human blood clotting modied are Herbicide A a makes with the the affected weeds insulin, human produced by appropriate reduce the can be sprayed competition of variety growth bacteria hormones that human genes. have been These the herbicide of to from medicines. so rape a has soil herbicide this itself. and as oilseed it the rape crop used plants into resistant oilseed also the and crop transferred rape but by are Insect soya is elds weeds, in modied gene to produced resistance oilseed applied Herbicide-resistant mass genetically which to are crops proteins herbicides including agents, genetically genetically modifying proteins, and the would GM continues developed This glufosinate. herbicide But been bacterium. to not oilseed grow When only rape while in gene kill is not only the destroyed. resistance in crop plants with from Maize and attacked weeds maize and cotton by are are insects root cotton worm boll both which important reduce larvae weevils are and cash their crops, yields. The stem-boring pests of cotton but both major can pests caterpillars. be of Caterpillars plants. th At the beginning produced for this The a toxin toxin that pesticides, people giving to it available disease glasshouse 266 resistance conditions. in GM rice under on it. only genes make its to people who reduce the grow eat high has the in crop A. on it. a to In their feeding own on was the maize environmental rice scale be rates have a soil resultant Rice™. will mortality caterpillars. and The large They bacterium 1990s and toxin crop that the cotton than gene plants. which impact the found kills insect spraying plants are killed. plants of maize Golden soil produce less insects varieties from a transferred plants vitamin name, certain and This vitamins century kills isolated modied transferring 20 which because Genetically the modied feed Additional Assessing was genetically larvae of If, it able as a or will to been developed bacterium, rice is when, pale this improve make result of that yellow rice the vitamin poor by enables diets A. in colour becomes of This immune the will systems. production Genetic engineering cheaply on a large makes scale. it The of tnemelppuS Industrial insulin possible human to make gene insulin that codes quickly for the and production enzymes used to cut bacterium of insulin cut A the is identied. human circular insulin-making piece bacterium. Restriction of The DNA same enzymes gene called a from the plasmid restriction enzymes is act as rest chemical of the removed are then scissors to open DNA. from used a to cut the open is the plasmid. The two ends of the DNA of the plasmid insulin-making gene new put human plasmid into a put new insulin into gene plasmid are bacterium an exact called match ‘sticky Another with called insulin-making gene now a bacteria. as The two DNA ends and the plasmid. These are ends.’ enzyme known the ligase to the is used sticky recombinant bacteria now has to ends attach and plasmid the gene the sticky plasmid. and code is The ends back insulin. The cell the plasmid inserted for of is into the bacteria each multiply very rapidly inside an industrial fermenter and produce insulin. modied The • and disadvantages of bacterium make has Advantages division insulin the can now because insulin it gene genetically crops benets: Solving global hunger – genetic modication could feed more insulin people as climate the crops conditions marginal that and are produced soils. Food are able production to tolerate could be increased in Figure areas. 20.4.1 Human by • Environmentally friendly can be insects, less use – GM crops, like soya, maize purified extreme and insulin genetically is made engineered rice, bacteria. would resistant of pesticides. mean less environmental Consumer an avour and require for that benets improved produce Also, need threat weeds – genes improve fertilisers so there would nitrogen and be uptake lessen the cause. crops better fewer diseases that chemical they GM and and have already keeping been qualities. produced They are with easier to additives. SUMMARY The concerns: 1 • Environmental become safety successful – weeds. there are Pollen concerns from GM that crops new that GM are plants will Food may safety – be transferred new gene to other plants combinations may by insects resistant have or effects the Explain what genetic unknown. They may result in harmful substances that being Describe three in crops are which Biodiversity reduce the – increasing number of use plant of herbicides varieties and and wild plant breeding ways been engineered to them. will 3 What 4 List is the meant by stages a plasmid? involved bacteria human insulin. Discuss the in that make POINTS Genetic engineering involves taking a gene from one and putting it into another and human plasmid. insulin The gene bacteria can grow the of GM concerns species. people The benets species crops 2 have relatives. 5 1 different so producing KEY by produced. improve • meant wind. genetically far is engineering to 2 weedkillers • QUESTIONS be to transferred produce lots into of a bacterial human have about their safety. insulin. 267 tnemelppuS • to PRACTICE 1 In QUESTIONS order to to transfer another it is a feature necessary to A a chromosome C B a gene D from one species 6 a a Which is the best temperature transfer: genotype nucleus in a reason 1) Yeast high temperatures enzymes B at high temperatures the is used biofuels. in the production of too denature of much at low This is yeast cells yeast bacteria reproduce fast because: are cells a good produce source oils that of are at low of nutrients temperatures there is no diffusion energy added into bacteria to (Paper petrol temperatures some D B increases rate bacteria? [1] too A contains at C 2 controlling that A fermentation (Paper for fermenter 2) [1] (gasoline) 7 C yeast cells respire D yeast cells to produce carbon The following modication respire without oxygen processes occur in the genetic dioxide of bacteria to produce a human to protein: produce (Paper 3 A to alcohol 1) student is planning compare powders 1 a gene is at the a laboratory 2 a plasmid 3 bacteria divide 4 bacteria are effectiveness removing controlled stains. of three a human cell factors during the Which inuences washing is cut open by restriction enzymes the by binary ssion washing grown in a fermenter to combination activity of human protein the 5 enzymes from investigation produce of isolated [1] recombinant plasmids are taken up by process? bacteria A size of container, frequency of stirring, 6 type of washing type of fabric, bacteria make recombinant B length of washing of type of stain, appearance D washing pH 4 of size of of fabric, plasmids Which temperature, 1) Which substance volume of water, [1] A carbon B ethanol Which causes dioxide bread C dough lactic D to sequence used not bacteria 5, 7, 6, 3, 4 B 2, 1, 7, 6, 4, 5, 3 C 1, 2, 3, 7, 6, 5, 4 D 1, 2, 7, 5, 6, 3, 4 (Paper acid a in many reason do their bacteria not An for industrial 268 events? is of growing herbicide-resistant that: A less herbicide B there have needs to be sprayed on the crop processes. is less competition between weeds this? complex soya plants requirements have many enzymes so can there is less risk of disease attacking the sets of reactions to plants carry the soya plants grow faster make reproduce slowly under optimum conditions are fewer safety the genes of bacteria the genes of crop 2) of products bacteria (Paper order [1] advantage (Paper there correct environment complex useful D to oxygen D C combine 2) soya out the 1, C B genes plasmids [1] are from is 2, and A human rise? 1) is and recombinant A soya Bacteria plasmid mixture 8 5 the nal fabric washing (Paper (Paper of fabric form C copies time, 7 size multiple powder concerns with compared plants and modifying with modifying livestock [1] 2) [1] 9 A student on the were pulp investigated extraction cut up was and of crushed divided Sample A Sample B was the apple into mixed effect juice. to two with of pectinase Several make a pulp. samples, A pectinase 12 apples growth growth and treatment The and Human made B. used as a for 188 to reduced amino (HGH) young promotes people growth. It is as a a protein acids. (i) State how many bases in DNA code control. for (a) hormone given powder. (a) was of is this protein. [1] your [2] Suggest: (ii) (i) what should be added to sample B Explain Genetically it is being used as a control, three variables that the student hormone and bacteria a similar make human hormone found should in keep engineered [1] growth (ii) answer. as constant. cattle. HGH is used to treat children who [3] do not grow properly. There may be a genetic 3 (b) The student obtained 35 cm of juice reason from for this or they may have received 3 sample A noticed and that appealing 15 cm juice than from from the sample sample juice from A B. looked sample radiation She a more brain Explain juice why from there sample was much Suggest the why juice the from A. student sample A thought was Suggest in which the effective of fruit the investigation to nd Many pectinase is at increasing such modied as HGH.[5] advantages to of produce using genetic HGH. [3] may children, suffer who from do not blindness have a caused a lack of vitamin A. Lack of this vitamin in the juice. diet also harms their immune system. [3] Explain the consequences of an ineffective 3) organisms can be genetically that they can be used in but bacteria are [4] is the main foodstuff in many parts of biotechnological the processes, system. engineered Rice so the especially diet immune 10 genetically out (a) (Paper are protein, 4) People, their yield human student by how had [2] ways improve bacteria a engineering that varied could have more 13 three how produce (Paper State or [3] appealing. (c) leukaemia tumour. Outline to more (c) (ii) for B. (b) (i) treatment one of the world. Researchers have used genetic most engineering to produce a strain of rice that has common. seeds (a) Dene (b) State the the term genetic advantages industrial engineering. of using rich in the State bacteria the human (b) Suggest examples of body selective genetic converts why (d) at 265. Penicillium rice and had not State three other crop the produce an Name diagram of the fermenter on State is grown in fermenters the Discuss (Paper antibiotic by [2] reasons for genetically [3] the arguments produced conditions the each condition, maintained inside from the and against food. [3] 4) by that are maintained fermenter. and Describe for [1] maintained (Paper genetically produced to antibiotic. ve inside (d) be page Penicillium. For to simply plants. genetically-modied (c) A. 3) Look (b) vitamin breeding. modifying (a) into [3] (c) 11 which [2] engineering. (Paper carotene in processes. three beta [2] engineered (c) chemical how [5] describe explain the the it is it is must fermenter. antibiotic fermenter. how why be [5 + 5] obtained [2] 4) 269 21 H uman on in f l u e n c e s e co s y s t e m s 21.1 Food Increased LEARNING Describe ways in modern technology resulted in increased 60 Arable food elds. years farms negative ecosystems of monocultures and resulted in advances in agriculture over the improved food supplies in many parts of the world. large are and agricultural tractors combine and machines ploughs harvesters for for to work preparing harvesting very land crops. large for Chemical impacts of the encourage crop. the Pesticides growth intensive kill pests of crop like plants, insects increasing that feed on the yield crops. crop Herbicides plants has large- of scale use seeds fertilisers on and Examples sowing the technology has production Describe production which past • food OUTCOMES Modern • supply kill weeds that compete with crop plants for water, light livestock and nutrients. Selective breeding has increased yield and made production crops • Discuss the has and implications of food transferred human an Intensive global yields over of In large many by intensive especially and this gas Mongolian surroundings farmer’s of his farm. such waste sh, A as High engineering There has to crop plants soya are and even their pests Thailand. and some and plant often high crop in plants large restricting their and of indoors the faeces, the sea large numbers. environment. methane and in which often where it is a known can cause have mean using growing of and that of of parasites and crop allowing specic effects on on the such to as large cages The surrounding pathogens these large in controlled. and to farmers crops, kept antibiotics resistance same are carefully serious pesticides the tilapia, to treat can the chemicals. areas, year concentrate wheat, after on barley, rice. that inside lots on conditions problems effects pesticides agents, achieve livestock and reared Urine bass can sh quantities and sea advantage negative eggs selective is the to growing 21.4). farms come keeping effects 21.5). growing of involves supply are generate trout, means this food waterways and sh This large Herbicides in resistance, indoors. negative Topic densities with This maize, farming food monoculture growing 270 Genetic technology This and animals Topic lakes, modern their them cattle, (see from easily. and year. sh diseases. herbicide densities have salmon, their food waters. high (see pollutes have spread Intensive as livestock. systems Animals, slurry, using and keeping methods Fish, the such supplementing eutrophication from at Intensive as is plants areas greenhouse pollutes and species. farming crop movement waste features, unrelated numbers, cows drought providing for population The to economic from increasing resistant social, environmental sufcient more may pest of kill plant help species. resulting in pathogens monoculture the and insect crop, such Continuous the (see evolution T opic on 18.4). environment. species as use of the that parasitic of these resistance are harmless wasps that chemicals among act lay as weeds, The the large soil scale so that organisms matter, not such the as manure, food to in from starvation and their or of to food is Many ooding, most places Social, Food that most often have pests production of where is the The the structure biodiversity addition good the also but caused enough to and soil of of of soil organic structure ability of increased. every requires year politics, the but is world’s There many is enough people to do may die because of have plantations and lived political land. for to to to food wars Machinery like farmers grow sell to for for food damage that is pressures in labour increasingly force so rural mechanised, there unemployment is or war. Often this has meant forcibly, from years. has resulted in T opic 21.2. As has not the farming driven demand the of oil palm South-East cover Asia. huge Here a areas lorry of from a in for movement a in Indonesia carries away the fruits has these trees to be processed into palm oil. large of people KEY to allows elds. at of become large implications sometimes ranching described harvester very to plantation environmental in but those land clearance combine crops food Plantations Land this feed fail, to transporting displaced, ancestors have crops economic areas been of but food currency. supply problems and so, cause to economics, enough foreign failure are large have land gain a by produce diseases by there famine people their has countries caused Often there increased, everyone, environmental groups places feed often starvation. where supports growth. maintain food cash-crops famine of to has poorer Drought, risk crop reduce malnutrition. or non-food is helps enough and populations grow longer can supply world poverty. no good population food Shortage it fertilisers out. produce the time supports carried world’s farmers chemical POINTS cities. Intensive fossil who agriculture fuels. own does not It also farms reach requires requires and local large much inputs of investment plantations, often energy by taking from large prots burning 1 that use of breeding corporations so The and chemicals money increase people. 2 negative crop How have the following increased food Famine improved use of production? agricultural machinery b articial Describe fertilisers d use of the negative monoculture tnemelppuS Describe on impacts of the reasons result transport, of intensive livestock the people. from lack of and drought, an ever human population. production Intensive agriculture has crops social, 3 on pesticides 4 and and selection increasing 2 livestock many problems, ooding c and impacts can political food a an QUESTIONS 3 1 in production. have environment SUMMARY resulted food production selective agricultural has in Intensive machinery, tnemelppuS tnemelppuS As of over that always World use for food shortages in the world. environmental economic and implications. 271 21.2 Habitat The LEARNING pressure Describe habitat the reasons natural for is destruction State that humans have losses deliberately by altering food • impact List food on the chains on Reasons negative effects has the on effects on on been for a natural and variety are has resulted continues of to reasons, ecosystems, such many in be but as reasons why destroyed. we have pollution. the Land many There Earth that is unaffected by human is no activity. for habitat destruction that natural habitats of plants, animals and microorganisms are habitats for a number of different reasons: of • deforestation has There and destroyed Explain population habitats The • world habitats. a webs deforestation natural cleared effects ecosystem negative increasing of environment indirect • an OUTCOMES signicant • of destruction The clearance of land for crop production (see Topic 21.1) and for the the production of biofuels (see Topic 20.1). environment • Space of • as More build for Digging such • to land mines iron people The human needed (see • Marine which wells Open of cast coal mining destroys large for Topic and At high coral If we or • • • otters or and latter of half being have preyed less their the upon prey to numbers 20th by hunt killer but because of in now whales Killing Killing to and and this coal the and is mineral ores, produced. associated etc. huge of of aluminium shops, pollutants cause algal industrial destruction In the been quantities waste and of for waste. Space recycling is it of the blooms sea in include the sea, fertilisers, oil from oil chemicals. by pollution Caribbean destroyed cleared them of large they of on areas by it and of the is are are chains natural we coral reefs estimated many food pollution, of predators were large from has species in an – have humans dangerous herbivores these Overshing that which over considered and at very of high risk. webs environment removed have 23% completely organisms either huge for food numbers. estimated had (see 60 signicant results in have also – killed Topic there The many were many population million in of these 21.9). 1492 of to different American 750 in bison 1890. effects. that that are further unbalanced at risk of food damage webs by and other unbalanced factors. the they are Top predators control the populations of primary consumers. Their may removal means so is that populations of herbivorous animals increases overshing. there The 272 clearance are increased century, and indirectly: ecosystems protected housing storage inuences haven’t Removing Sea extraction which produces Major thought of decreased crab. production 21.8). destroyed species a long-term the from industries, population have because eating more roads, ships, risk reefs directly otter for bauxite require biodiversity. Human sea livestock areas land. high A intensive quarries and pollution. are for rearing. and ore infrastructure: • units cattle effect increased can be competition overgrazing for and the plant habitat food that destruction. they eat. and The Pacic sea otter, Enhydra lutris, is a secondary consumer that KEY feeds on invertebrates, century the change to animals such were as sea hunted urchins for their and fur crabs. and In there the was a striking 1 the whole of the food web as urchins exploded POINTS 19th in Habitats by and ate many of the giant seaweeds that provided a habitat have and clearance many the other species. catastrophic web, such as loss many The of loss many small of one other species, animal invertebrates, the species sh, sea otter, from octopus the and of destroyed land for food farming, for been numbers led extraction of to resources, such and ores, as fossil fuels food metal housing and scallops. industry. 2 Pollution has destroyed many Deforestation marine Humans food have and been provide clearing land for forests for settlements over and 10 000 provide years to grow transport are now very few forests in temperate regions that have cleared at some time in the past. Tropical forests in Humans and South America have been cut down over the of these forests are rainforests rich in past 100 food has resulted in a number of the extinction of impacts removing chains and species webs. Deforestation leads to biodiversity. environmental of species, loss of problems: soil, • negative by years. extinction Deforestation coral South-East 4 Many have habitats from Asia as not on been such links. 3 There habitats, reefs. of species ooding carbon and dioxide increase in the atmosphere. • the • an • the of soil increase in increase in removed degraded Local of tropical formation the of ooding carbon rainforests soil is gullies after weather dioxide all are easily and the the very of are change and away plant cut atmosphere. thin washed loss trees patterns in when causing nutrients. the soil The vegetation erosion, land is rapidly SUMMARY down. with more frequent and severe 1 storms. much Flooding quicker happens and is not more frequently absorbed by as plants water and QUESTIONS runs off transpired the into Outline some Forests act as ‘stores’ of water, their leaves slow the that increasing effects an human the population atmosphere. of land has had on the down environment. the rate water of evaporation reaches the from the soil and decrease the rate at which 2 soil. It is estimated 1880 Carbon dioxide is added to the atmosphere because vegetation There is increased decomposition that also releases that 1980 between about 40% is of burned. and all tropical rainforest was more destroyed. carbon dioxide which is not absorbed by plants. a Rainforests have no effect on maintaining the correct balance Give three large-scale carbon dioxide and oxygen in our atmosphere. They produce much such a carbon huge produced oxygen that of all of plants rainforests of other rainforests many be reserve by concentration the plenty dioxide species. identied, of reasons There the to are in the photosynthesis atmosphere makes little atmosphere. ‘lungs’ stop loss of many and use in Earth the the studied they oxygen on are means as of the cutting many species that the difference There earth. down is no There forests. habitats in and and rainforests to there this Outline some of the is effects that has the deforestation quantity the on environment. overall 3 evidence are for deforestation. about b as reasons of however Explain the negative effects of deforestation. Destruction the extinction that have yet of to classied. 273 tnemelppuS tnemelppuS Soils is loss 21.3 Pollution Anything LEARNING that • State of the sources pollution of and land tnemelppuS Discuss the effects of the chemical effects and has material power the biodegradable plastics in environment in both as and as harm is as a a result of fertilisers, animal noise and from pollutant. human activity oil and human Pollutants carbon wastes; industrial and are monoxide; heat released domestic is sources. the of substances aquatic from terrestrial such such stations; cause the release environment, to nonPollution and into potential substances, biological water from • released OUTCOMES human activities ecosystems that are harmful to the environment. We expect natural ecosystems and absorb breakdown these substances. Topics we to 21.3 will look examples of to In 21.5 at some pollution We of land, sea and throw away mountains places a this visual rubbish pollutant is as undesirable pollutant of rubbish every day. In many air. taken well to as a effects rubbish danger of dumps, to the becoming environment. pollutant on the sources environment carbon dioxide burning cattle; fossil paddy fuels elds for coal human sewage and and contains oil industrial – chemical includes a variety waste ammonia, carbohydrates, effect (see page 278) enhances greenhouse effect (see page 278) extraction livestock urea, greenhouse growing methane rice; enhances fats and protein, pathogens reduces oxygen destruction (see page of concentration freshwater in rivers; communities 276) waste of toxic can be fatal to wildlife and humans; can factories substances mercury such and fertilisers as lead, accumulate N and P) arable agriculture arable agriculture eutrophication spray for killing weeds the pesticides for killing pests and and livestock waste (non-pest) (biodegradable non-biodegradable buried domestic and industrial waste rubbish) nuclear (beta 274 gamma atomic radiation) power bomb; accidents stations; nuclear at nuclear tests in rubbish toxic fall-out and kills fresh water harmless (rivers, plants; lakes) persist in in food chains; kills harmless agriculture diseases solid drift in environment accumulates arable and organisms cyanide (mostly herbicides in species ground tips; liquids; death with humans; (landll) health release high hazard; of in left on leakage of methane exposure; mutations or cancers non-human in species pollution STUD Y Rubbish is chemicals not that only a leach visual from pollutant, rubbish but dumps it contains into the many ground. Examples are T he heavy metals that enter water courses and the drinking water table applied such as chemicals, correctly DDT can and such affect dieldrin as areas have herbicides locally been and and also detected in pesticides, far the away. body if not you Insecticides fat sum need Paper 3. mammals and birds, many thousands of miles the mar to If where away used of they would in aircraft disease, forests, can such have destroy drift onto as been used mosquitoes. to control the habitats areas of of natural Herbicides, crop animals pests especially and vegetation when and kill you Paper by materials are because a we called they problem into this sprayed from POINTS – throw these away are are called broken when a it long time comes to and in the biodegradable. non-biodegradable. last down do Plastics not disposing are decay of Some used easily. plastics. environment are for But Most not 1 to and landll sites or rubbish dumps where they take up a is the Biodegradable conventional plastics are designed non-biodegradable to break plastics once down they release of by example, structures some which is plastics now digested by have starch bacteria in incorporated the lot can recycle many thermoplastics that we by into Pollutants affect them into new shapes. Burning plastics in they the volume of waste, but many plastics them the Nuclear fall-out testing and threats to produce aquatic and toxic gases are threatened jellysh. discarded United try to Fish and if they plastic Arab reduce other swallow nets Emirates and aquatic plastic other banned animals bags forms of can life too. plastic Some plastics are In plastic others but are some non- can them entangled waste. non-biodegradable from Sea mistaking get from nuclear as be for of leakages biodegradable turtles comes use reactors. biodegradable; pose rivers, incinerators 4 plastics like sea. and burn. Non-biodegradable air, and their nuclear reduces the land ecosystems and weapons remoulding on quickly 3 melting activities. dumped. soil. use substances human of the We done by waste more are harm environment produced becomes plastic the the packaging this Pollution lakes For an rest plants. aquatic than is the unit. ecosystems space. to and 2 goes it plastics decomposers these 4 , recycled. in 2014, the products to pollution. SUMMARY 1 List of 2 three the QUESTIONS pollutants of each following: a the atmosphere b aquatic c the a State ecosystems land the main sources of radiation. b Describe effects 3 Explain to Most plastic bottles have a recycling symbol with a category number. These bottles the the of the problems environment be category recycled 1 as to they make are made products of polyethylene such as terephthalate packaging materials (PET and or PETE) which fall-out. caused by non- are biodegradable in undesirable nuclear plastics. can carpets. 275 tnemelppuS tnemelppuS Some fo r are when KEY Waste what from of vectors ises know introd uctio n places previo us of taki ng Antarctic on supply. page Agricultural TIP harmful tnemelppuS Land 21.4 Water tnemelppuS Pollution LEARNING Describe water pollution and toxic Describe rivers the and sewage seas pollution lakes and due the and and industrial into the pollutants are often discharged straight into sea. chemicals Rivers • and by rivers sewage rivers OUTCOMES Domestic • of pollution empty toxic wastes into the sea, resulting in the following: of to over-use • of Fertilisers and sewage encourage the growth of algae that release toxins. fertilisers • Describe of the female negative • Pesticides • Radioactive hormones in water the effects Toxic and pesticides metals, Sewage environment algae The As is and of water found the in in higher is molluscs (shellsh). concentrations and and river , not lead, are around found in tissues know the and farmer wrong The how result pollution enriched • sewage of is much too e.g. of in can be land to to of that use washed This of sh in a organic and river it matter. organisms add. the rivers oxygen is as more treated suspended sewage is concentration so that raw lakes. We But have particular Problems is seen farmers can soil occur added at need and if the rain. can cause means sequence soil may no crops. which the If fertiliser heavy is improves their fertilisers through The growth 284). for the eutrophication, leaching. the the and yield if as sewage rivers or period nutrients. on bacteria. page the fertiliser is killing dumped freshwater recovers into fertiliser these is gradually by (see fertiliser a oxygen, feed many countries rivers the before plant called of that water increase of much either with the can type resulting Fertiliser this best uses time, from into of the away. community many encourages sewage decomposed In deposited drain using the It lots that migrate are the up bacteria means or increases. pollutant. use downstream, out fertilisers a raw die how crop world copper untreated of oxygen so the water raw growth of travels single which If Fertilisers to into ow of rivers into a water that the water is events: and streams – lake. rivers. • Once in the Nutrients water • • in and Animals their water, the so that this stimulates fertilisers limit eat the the are growth algae population usually do of the not in low growth of algae. concentration in the algae. multiply fast enough to control growth. Algae plants cover at the the • These plants • Algae also shaded 276 some stations. mercury, biggest the settle sewage the as bacteria survive dumped of such the shortage wastes parts are power invertebrates. cannot into of organisms. encourages many chemicals nuclear marine small drains tissues on of In the of of herbicides the in courses • Describe concentrated contraception coastal • are impact by surface bottom of eventually die the as there algae layers the die is on of water, and rot on competition the reducing the light reaching lake. surface. the for river bed. resources and many are Decomposers, • Bacteria respire dissolved • The chain of multiply result the The they ions act added of are as in feed multiply a the oxygen cannot events quickly, death problems These of that Bacteria in bacteria, aerobically, concentration same as on dead rapidly plants and use and up algae. a lot of oxygen. invertebrates The such tnemelppuS • of decreases respire can use happen up short limiting form this kills sh and if sewage oxygen in gets into respiration, waterways. which can sh. eutrophication in and properly. supply factor of are in to the fertilisers, caused most growth plant by natural of nitrate plants. growth and aquatic phosphate. ecosystems, When they so are increases. Fertilisers Farmers make up. are sure encouraged that Phosphate they are tends to to reduce applied remain the at in a fertilisers time soils they when and apply crops much of will the and take water to water comes detergents has from domestic helped to sources. reduce this Removing in the sea – nitrate in the type sea of pollution. causes growth which produce toxins and kill other marine algae, of contraceptive Water pollutants women Topics 16.12 therefore in take and nds its contraceptive contraceptive 16.13). way pills The into is a pills human containing is oestrogen excreted sewage. The oestrogen in urine If excess are not broken down in fertilisers active known pass through unchanged to all sewage nutrients amphibians respond to this leached nutrients for enter rivers treatment and oestrogen in lakes. the they causing by supplying algae. EE2. plants Female contraceptive so Male are water by causing the sh feminisation and are lakes eutrophication ingredient as and hormones they pesticides metals. rivers provide (see and 3 Oestrogens fertilisers, toxic hormones hormone synthetic include life. into Many this events 2 effects turn many and The and POINTS sewage, of grow from Similar of to phosphate phosphate 1 happen algae them KEY in caused green. of aquatic gaining organisms. certain female characteristics ‘feminisation’, testes, having protein found as it is some in also yolk a condition called, female egg – involves reproductive which is known producing structures carried as in their intersex. eggs and This inside making blood. In their a addition, SUMMARY their sperm Drinking rivers water water works. the cells An do is may often be increase decrease in not develop taken taken in from downstream oestrogens sperm rivers, counts in of and the drinking recorded in in the case efuent water men in of from has long been some 1 a sewage parts linked over the past 20 of Dene the pesticide, to terms insecticide and herbicide the b world QUESTIONS properly. Explain why they are years. used. This in is the the only same from part of the environment effects. agriculture story and These and as many there other chemicals industry, are other synthetic are in including the sources plastics food of chemicals oestrogens that and processing in c have the can waste those There no that deal with implicated. works so easy EE2 the is rest solutions removed could be to of the drinking effective water ways this from problem the waste upgraded. treatment to the a Explain the negative soya. The as many water use of chemicals from some charcoal are do this. works will Upgrading be sewage sewage lters works of female contaceptive water hormones in courses. is b one pesticides environment. effects are how damage plants 2 especially Explain What steps taken to could be and rectify the expensive. problem? 277 21.5 The greenhouse Greenhouse LEARNING Describe the contribution atmosphere greenhouse gases and methane tnemelppuS change Explain how in greenhouse climate air pollution gases heat like the that so-called vapour • of a blanket gases in surrounding the atmosphere the act Earth like a keeping it greenhouse to otherwise would be radiated into space. These are to the climate Some carbon keep dioxide is of warm. the gases OUTCOMES The • effect and greenhouse methane. Some (chlorouorocarbons), by causes other problems. These greenhouse gases are which man-made greenhouse are air carbon dioxide, pollutants, gases as well such as the water as CFCs cause of change surface. Some atmosphere Some heat gases energy as heat, energy allow enters which is escapes solar food energy chains radiated into to and away pass is from space, but gases keep through eventually the much to lost Earth’s is the to Earth’s the surface. reected back greenhouse towards the Earth. Greenhouse our atmosphere at the gases temperatures It is important process be that and about build-up Power to it the to exist. that the average However, greenhouse stations, life understand without –17 °C. of allow over greenhouse temperature the last 100 effect on years, the is a natural Earth there has would been a gases. factories, domestic heating and transport use fossil fuels solar and release huge amounts of carbon dioxide into the atmosphere. As radiation we Figure 21.5.1 The greenhouse have seen, removed. are In burned, and other South even There also the has release the oil huge reneries and quantities atmosphere when of power carbon they burn fossil into Of all the severa l areas a due of forest to the is and into the decomposed farming being and atmosphere. by microbes in they Roots the soil, dioxide. signicant increase expansion released found material oil are dioxide for in in by of sites gas, are methane rice cattle ooded landll natural in (another cultivation and rice and also elds by and rubbish other and bacteria tips, sources of in natural as well as methane. greenhouse and has gases CFCs risen by the cannot greenhouse gases 10% largest be in the increase ignored than last as carbon 30 has they years. been in carbon are However, much more dioxide. know . table that Look on you back page your self change air Human pollu tants need to 274 of causing to these . activities greenhouse has the the the is are gases by so the 0.7 °C an increase atmosphere greenhouse over the past is in the getting effect. century. concentration warmer. The This surface There are of fears of is the Earth that this 0 °C then increasing. temperature polar causing enhanced warmed warming If 278 large cleared TIP are remin d of carbon carbon conditions which Climate the in are fuels. effective to resulted trees stations dioxide methane T here has the parts Methane Rotting extraction dioxide, STUD Y more gas) anaerobic tree been rearing. wetlands. the releases remaining producing cattle America which greenhouse Factories, deforestation effect. ice of would the start Arctic to and melt. Antarctic This would was to cause a rise above rise in sea level ooding would of include many some low-lying of the areas, capital for cities example of the in Bangladesh. These KEY world. 1 There could rainfall leading become as very parts mean also of a be to dry. the change more Some USA massive a in wind extreme of and these Asia, reduction in patterns weather. are so and Some important that the crops the parts distribution are expected agricultural warming grain of of the areas, climate Central Asia of America. The pattern of the world’s food The naturally greenhouse to such could blanket around prevent some escaping distribution could with economic and political carbon to reduce emissions. using energy cattle to the This more effects may be efciently, of by recycling change involve encouraging and reducing public Air pollution changing the effect transport, diet to them releasing a method combined domestic is to heat use and fossil fuels power and more plant in efciently which the as happens heat is used in and tnemelppuS The diagram in for of in effect more detail possible Earth how the greenhouse effect cools heat down back into in sea and from the level, low-lying the some in be changes climate crop and a production areas. QUESTIONS radiates Sun Copy and complete: and carbon radiate part energy into of the dioxide absorbed energy space atmosphere space Solar passes the Space water and absorb air radiates absorbed infra-red Earth carbon radiation Earth’s dioxide and through and radiate surface. heat the The energy Earth back into CO O H could ooding areas, world’s warms the consequences space water warms contributing works. 1 some radiation is change SUMMARY the has greenhouse change. climate rise in shows carbon methane this climate The a heating. greenhouse space. by the reduction The and energy methane. of One a of 3 stop as Earth consequences. climate done heat into increased Measures act the be dioxide affected occurring gases and 2 North POINTS tnemelppuS and some 2 2 H 2 CO of the energy back O to Earth CO 2 2 CO This is mainly radiation. 2 CO 2 CO Some 2 H the heat energy is O H O of 2 2 by the greenhouse atmosphere H Earth gases. O How the to CO 2 21.5.2 effect radiation List passes through the atmosphere and warms the the The red Earth radiates heat energy back into space. This is mainly infra- as Some and in each a human source of this causes vapour Human the the heat air heat activity dioxide and greater impact energy is absorbed by the greenhouse is give the that acts gas. a Describe the likely gases. to warm energy is other up. would causing a carbon pass large greenhouse than Without carbon straight increase gases dioxide such (see in as dioxide back the out and into space. atmosphere methane, question 12 of which on page b carbon has a 291). the increases in these gases in the atmosphere that Describe which for the enhanced greenhouse the global ways people governments the emission and and can of in their reduce greenhouse attempt to are reduce responsible of warming. water gases It case activity of consequences This contribute greenhouse radiation. 3 • that surface. one • gases enhanced the effect Earth’s the up. works. to Solar warm 2 greenhouse 2 • causes 2 CO Figure This the effects of global effect. warming. 279 21.6 Acid tnemelppuS Sulfur LEARNING rain dioxide (SO ) is released when fossil fuels are burned. 2 OUTCOMES T ogether with nitrogen oxides (NO ) from exhaust fumes, they cause x • Describe effects the of causes acid acid and dioxide. rain in • State the measures that taken to reduce acid Rain in the nitric when acidic sulfur atmosphere acids as be as low acid in clouds dioxide and react acid which lower the pH. and as and dissolves nitrogen with oxygen carbon oxides they dissolve produce In some places the pH of sulfuric the rain 3.0. polluted by the air wind nitric be water considerable and droplets become polluted acid distances) dixoxide water produces (may sulfur the rain blown sulfuric naturally can may oxidation is However , water and be rain. nitrogen (nitric and sulfuric acid) oxides wet deposition (acid rain) dr y deposition power and stations, vehicles into the industries release gases trees atmosphere rivers and affecting decreasing the lakes water and polluted pH and affecting soils These gases winds dissolved both can before of in carried being the these be 21.6.1 over deposited rain. types The The of term causes and large as dry ‘acid effects of distances particles rain’ acid by to deposition. are acid rain falls on trees it kills leaves their ability to resist disease. Many European forests have been killed trees by sulfur is affected dioxide. Most by high sensitive lichens, Increasing 280 of sulfur dioxide in aluminum from soils algae their Some grow can and water species only fungi and are where tolerate high living together. nutrients very the from sensitive air is free of concentrations. the to sulfur the gas Others tolerate useful intermediate indicators the of concentrations. pollution. By Lichens looking at the rain. of growing average b concentration of c atmosphere → in an concentration which a leaches in acid concentrations are and some species Vegetation rain polluted life and are central acid all atmosphere. can reduces absorb dioxide the and composed They and When polluted lakes water rain. or refers affected life rivers Figure vegetation area, of you sulfur can deduce dioxide. the acid because the falls on and there out of these on is of soils affected The • by • ue station and and chimneys catalytic aluminium water converters Acid little rain effect, When already it acidic causes soluble low waste or pH plant and coal live and the can in pH increase Trees these aluminium have been in exhaust These fumes solutions are of but are and sulfur washing its from with before being the damage America China’s are cleaning rapid stations means b Name d Explain country time the the with a content, powdered can escape, nitrogen introduced has when damage and use of oxides gradually Europe done coal problems Sulfur Acid normal gases rainfall which sources the of effects aquatic in catalytic by in with and acid its carbon they convert acid also reduces monoxide oxides of pollutants and by hydrocarbons; nitrogen (NOx) to North rain, many converter oxidising nitrogen. palladium when The which vehicles catalysts are are are recovered platinum and or recycled scrapped. power rain. is slightly dissolve in the acidic. water in clouds to form these of acid gases. rain on coniferous trees, soils animals. what dioxide from rain also Acid can be done to reduce the effects of acid rain. from car dissolves causes rain the burning exhausts useful the are nutrients release damages of the leaves of fossil main out of aluminium and kills fuels causes the soil ions trees. and of rain. making that Fish nitrogen acid are and it infertile toxic to sh. invertebrates A die if lakes become ue gas power Measures taken to reduce acid rain include removing fuels and acidic gases from waste sulfur dioxide plant station that from which burns waste coal. gases The at a product sulfur of from desulfurisation acidic. extracts 4 rain. POINTS and 3 the Explain oxides 2 of a acid rain. State KEY some At expansion the why the c e up rain. by QUESTIONS Explain and 1 that a acid acid industrial SUMMARY 1 from killed power wet they it sulfur into stop Europe as: cars. expensive, Central them. A the in ions badly animals reducing reduce 5.5. lowers no such gases gases to pH, few the tted that Norway Crushing the be a compounds acidic below rivers sh rain removes can is acid. is become and very acid used. the the concentration and have sulfur treating neutralising there soil rain. to and with Scotland be the the soluble streams combat could by become some to dissolves acid invertebrates Canada, fuels neutralises calcium, lakes, tolerate chalk infertile. soils The or granite, the and them in of exists this as neutralise enters rain limestone such desulfurisation limestone, • in acid that gas to water. cannot sulfur solvent rocks, leaving of technology low alkaline Species Lakes on potassium that bodies toxic. soils compounds considerably. are are hard as water ecosystems on nothing such Aluminium Acidied falls soils soils nutrients, wash rain tnemelppuS When this process is gypsum (calcium sulfate) gases. which is used in the construction industry. 281 21.7 Sustainable A LEARNING resource Dene any substance, organism or source of energy that we OUTCOMES take • is resources the term from the environment. sustainable A sustainable resource is a resource which is renewed by the resource activity • Explain the need to organisms the environment State that stocks can forests be that there is always enough for us to without it running out. Examples of take these resources sustainable • so conserve from non-renewable of and sh timber for or renewable building and resources, sh that harvested can from be maintained, the sea and are lakes. managed Non-renewable resources include energy sources such as fossil sustainably tnemelppuS fuels • Explain how forests and cannot sh stocks are minerals, e.g. copper, zinc and lead ores. gone, they are These resources and be replaced: once they are gone forever. managed sustainably The • Dene the term development that it at and requires planning local, and The explain management, is world’s supplied conserve cooperation national international need to conserve fossil fuels sustainable by and by future There • the for sources various fossil fuels energy energy fuels – coal, non-renewable generations are Use fossil these renewable levels demand of until we more released so can oil increasing and a time that natural so by we burning combustion, have e.g. all fuels them most We they supply fossil and gas. that that they conserve efciently on ever resources such energy ways is be this to used developed for to need can our combined of energy the needs. future: make heat full and use of power plants. • Reduce houses wastage in cold conditioning that • use Reducing public • Heat and Power plants like and or in Berlin, Germany, distribute steam to heat houses surrounding in generate the and form hot in water from the fast to is a As soon an example to quotas 282 has alternatives more for energy petrol/gasoline, encouraging (see fuels nuclear willow as production of contributed the tree cover charcoal to the from for removal the of country. so trees of at be by timber valuable products. forests all insulation to of conventional efcient, such as air those Topic car e.g. by providing better pools. 21.8). as sources power, of and energy burning are wind, rubbish solar, and wood trees. area. tend almost and fossil and growing harvested cooking using are the cooling. materials hydroelectric many the improving this Timber Haiti, and that demand Sustainable In e.g. electricity of industry for the Alternatives one countries systems transport Recycling energy, resource Some are felled, same softwood, issuing they trees restocking the as can they so rate it not that many in a replanted. the resource becoming trees. logging more in grown are without to take used be coniferous permits do production Some industries The can than continue They are regrow. is to These governments can make way. replanting depleted. companies. trees to sustainable be trees manage given tnemelppuS Combined ice of tnemelppuS Sustainable Populations now For example, Some so of are steps • need the sh to • Quotas too • can • them of of the a other cod sea Many that To of they collapsed creatures sustainably. sea to are This the ‘no in in these are the such continue declared ensures stock take’ to off that each zone shing sustainable. 1990s. as to populations not crustaceans do this and various limits a year. help for suitable The shing Cayman conserve during number a of young Islands sh in known the as to sh captivity in be a red so that boats cannot take be restocked them where sea minimum size so that small sh breed. raise Japan including certain to can and authorities season. survive of are by each have and stocks sh stocks. taken: issued nets in sh overshing Atlantic and season. sh Examples the as by grouper. escape Some sh has are many Fishing of recruited Nassau known depleted hunted be areas Caribbean the of be breeding are are stocks can Certain sh severely species molluscs shing in if is possible facilities shellsh, bream it and known prawns ounder, and are to as breed hatcheries. several released Sustainable forestry: ready felled as to and into the released into Sustainable Sustainable increasing Many Sturgeon Caspian Sea aims population signed up development Janeiro, impact the year. development countries de each by to provide facilities in caviar are Brazil. assessments to Agenda that arose Agenda that to provide without 21 assess 21, from a risk of needs the global the promotes the the harming action 1992 the of trees have use Earth of plan 20 years to The grow. for Summit in environmental developments to the This is one way in which cooperation exists at national and local factory ships like this one have taken the many sh from the oceans that stocks are levels. sustainable to and some species are being extinction. POINTS SUMMARY A another an driven 1 are trade. environment. not KEY trees timber Iran. so international, mature the reared Large environment. for development human sustainable Rio sea be young young stages the species sustainable resource is one which can be removed from the 1 environment without it running QUESTIONS Dene the term sustainable out. resource There is a need to conserve non-renewable resources, such as 2 fossil fuels, for future Explain tnemelppuS stocks 3 Forests and sh stocks can quotas and restocking. be sustained using education, legal but 3 4 Sustainable increasing development human provides for the needs of an Cooperation between organisations is List may forests fossil ve fuels be and sh fuels ways can be sustainable, are in not. which fossil conserved. population. 4 5 why generations. international, essential for national sustainable and local development. Discuss in the role conserving of education forests and sh stocks. 283 tnemelppuS 2 21.8 Sewage treatment and recycling Sewage LEARNING Raw • Outline how sewage is make the water sewage that faeces safe environment to or return for made and up urine, of but a number industrial of unpleasant waste and materials, run-off from not roads and it paths. contains is treated just to treatment OUTCOMES to Not only is it unpleasant, but it is also a major health hazard. the human use sewage aeration settlement tank • State and that metal paper, can glass, be plastic reused tank outlet or recycled river air pump pump screening for and grit disposal generator anaerobic sludge tank processed Figure There • 21.8.1 are solids • Activated sludge three Primary twigs, Components main means are of allowed Secondary a stages treatment by of sewage in the involves lters to or settle treatment treatment removing out in involves of large Then large out plant. treatment screens. sludge sewage: solids, the grit like and paper and organic tanks. microbes, mainly bacteria, treatment. decomposing material suspended in water. This may happen in two ways. • The activated sewage respire with in proteins Trickle lters the large rotating • T ertiary the any may population which provide dumped Trickle put is a passes into break The sea down methane or for is waste spread on the the down microbes. these beds through settling. tanks. out may to go matter burned operating of large it the which carbohydrates, broken with over secondary or is through protists to the The liquid from gravel, the matter. settle the and ions. trickles period into material back covered sprayed pumped down Urea nitrate liquid is fungi break organic microorganisms energy at the the air as a form anaerobic an increase methane in the soil from in the stage water make it to all kill return leaving safe. to For the plant example it microorganisms. the environment will be may Water or for treated be in treated a works may also be conditioner. variety with leaving the human use. of chlorine process is in anaerobic sewage Sludge and This to to a sludge. to fuel as liquid microbes stage machinery. land The Here lters. The 284 of bacteria conditions. to organic be to gravel involves process remaining sludge As down treatment secondary and dioxide. treatment arms. break of which bacteria, converted beds primary microbes carbon then are from to in of conditions fats and process community aerobic and ammonia • sludge a ways or now to ozone safe to Recycling Another of more of, it and sites This to than a them. saves be to same such the savings mass of in which in of metals, paper aluminium tips animals and the you raw extracted of useful less carefully can For plants managed habitats. all be materials ore, disposed materials recycled its production and animals, energy materials. from the their plastics compare to and recyclable and is handled harm conserving from if cause rubbish quantities, material energy population properly and because large is can plants problem materials in make the increasing waste waste deprives Glass, raw made 95% Dumping to an this pollution also solution of Unless cause ourselves. recycle waste consequence waste. may landll The our is is to recycled. do not used to example, have recycle there aluminium to is the bauxite. This recycling bin says it all? What do you recycle? Paper is a However, paper These Waste paper pulp pulped, toilet resource the is are be are and up and it is made recycled. The waste the converted paper and as and required. removed other bundled supply collected is dried and SUMMARY limited trees dyes paper paper can from sheets in pulp into from This paper is then wood. means is rolled newsprint, that less collected, into paper sheets. towels, products. shredded. This saves it being otherwise thrown into landll sites, like the KEY QUESTIONS 1 1 Outline what happens one to raw sewage as it passes through above right. POINTS Sewage treatment screening sewage treatment to remove a Make a list of materials that can be material, recycled. decomposition b Describe on the the effects that recycling of these materials have and following: i the raw ii the energy iii landll materials used needed sites settling suspended in making and in making rubbish to Make a list of the different these goods Decomposition populations that dumps types of digest packaging that of by protein, In and fats, cellulose in wastes. shops. 3 b requires bacteria are human used microbes material. carbohydrates a by remove goods 2 3 non- plant. biodegradable 2 involves a what ways does this packaging cause problems Recycling materials, such for as paper, saves money, raw society? materials, c Explain how the recycling of paper helps the energy and reduces environment. pollution by waste. 285 21.9 Endangered A LEARNING species becomes Explain why become and organisms endangered or extinct tnemelppuS Explain the risks to a they time. far • the size of decreases its so in the are we reducing variation in the of becoming numbers We have already hunting (T asmanian wolf) died and difcult becomes been to extinct, Reserve there in know but periglenes, seen predation past the last was Costa since the when as Golden restricted Rica and the to the has the wild. Extinction that past. are This is captivity occurs occurring as a result all the now are of all the decrease most and of are to is to the causes habitat Others kill such described a level as of that it is at endangered species destruction, becoming climate are: animals that are a threat to livestock that humans have moved from one part or alien species. the ancient the ago. habitats, here trees that Jurassic They but in are occurring in cooled most ice is as of sheets. the As warming heated North the land result Climate and Europe, species a atmosphere. world will with equator. tropical Plants outcompete lower Brazil Florida. over threatened grow have little period are can is of even changes at was more, to was different America world that of change and warmed, a the feature times. much the ice of During of Asia melted and exposed. regions better other able are and plants to species. extending and survive Examples in their animals ranges changing of this are away from environments evident on 1989. safe in 100 Plants in adapted altitudes there will and be destruction have the largely is not habitats been drained and lion as cold in of cause provide migrating to provide for down. tamarin they towards left covered cut only leisure conditions retreating was the for to nowhere been golden grounds development their peaks. If this go. 21.2. The robbed Atlantic many forests species, habitats. habitat Many for to has ecological birds. land Topic disappearing mountain them This of are loss. Wetlands services wetlands farming, for us across housing, are and the very also world industrial facilities. their botanic Pollution reefs Sea oil are is occurring endangered otters, like pollution. they 286 the species survival the world associated feeding as alive in another colonised important gardens, in overshing. species the of Deforestation years the extinctions These introduced age covered including natural left only a of million to by to ice Habitat since and change continues are extinct. with world the from changed considered sport mountains. Cycads in alive Unit. the or • Now not individuals kept 1936. sometimes Monteverde of been species food, organisms Incilius no are in was Toad, a crops competition the of for composition species extinct this life, • Climate is in extinct pollution Threats It have describe risk of thylacine as number they When human Zoo are species population • Hobart there Some species change, last the than endangered The world. described However, higher activities if if OUTCOMES anywhere • extinct species ingest many Oil toxic on a global ecosystems marine sticks to a animals, their chemicals scale. as fur that are and cause As we result at stops organ of have seen, coastal risk of coral pollution. extinction providing damage thanks insulation (see T opic to and 21.2). Many sea Exxon otters Valdez Introduced Sometimes sport • or half in small 1872 by crop. They parts of have done Alaska been this small to become foxes Indian to of the release in of oil from the tanker 1989. moved around deliberately by the globe introducing by humans. animals for pests: the have predation The Bay have control Australia • the following species we to Almost in died medium-sized extinct introduced mongoose control rats proved due so by was that native eating to in rabbits Jamaica much they with and colonists. introduced that marsupials competition European were successful to of were the from sugar introduced India cane to other A the Caribbean. However, as with many such project tamarin the to • mongoose fed on other prey as well as the one it was intended to Plant species can become introduced species damage many hunted to has for remove involved natural the golden captive habitat breeding in in lion Brazil many has zoos. food, and populations the for sport, ago of 15 000 years moved southwards People have because goats, extinction for animals harvested many extinct especially of which overgrazing have done by untold islands. caused dangerous animals or plants these people they of trade and pests. from some migrated a the wild have for Asia many of policy been to hunted With increasing unsustainable. into the have always food. became from They deliberate Humans populations destroyed as species. the large About Americas. mammal As they species. Coral collected been hunted beautiful trapped materials and became deliberate policy T asmania, some and shot animals, interesting for their available. as is people the In case hunted such plants fur in some with the as ‘big for the show. days places, or for before that sport Animals animals elephants thylacine, cats’ and by reef tnemelppuS There is very and With little in no it genetic individuals are evolving because endangered few species partly at alive, left. to believed variation species left longer response was This in to small particular many of reduces changes in the the are threatened change and overexploitation. have shot invade as a farmland. wolf, to POINTS sheep. populations, risk the climate man-made are T asmanian kill communities pollution, KEY extinction rare reintroduce its control. Hunting In to introductions, of so becoming alleles of chances the of environment makes 1 in left that are 18.4). become there alive in captivity. population Topic Organisms when extinct. genes the (see this are the no extinct individuals wild or Endangered those that are at in species risk of extinction. SUMMARY 2 QUESTIONS An at 1 Dene the following terms: a extinction, b endangered endangered risk because species. small 2 Explain a d how these hunting habitat b threaten the overshing destruction e survival c of Use examples to explain the of species may climate population very When a population population survival of decreases decreases. a species What when in are this little is genetic species: variation that adapt changing to effects that is needed to conditions. Causes on food webs of extinction size, the variation and change, habitat ecosystems. within implications happens? are the destruction, 4 is extinct change possible have its with climate introduction species becoming hunting 3 3 of for the the pollution by hunting, and introduced competition predation species with or them. 287 21.10 Conservation Endangered LEARNING by • Describe species how can area endangered be putting tnemelppuS Explain why important conserved species a alone. changes • should to to in No can for National be • and the legs information of birds about has how • live and how migrate far over they travel. thousands Some of in parks • like this should Lanka. bred of rare plants be and in for the enjoyment of conserved animals, future it had zoos and reintroduced being on in planet closely and East them. East a the so it monitor counting Africa Other duty which land Africa areas set to this aside which of Island animals to the Pacic are such the as sea Marine and wild. use is the ocks of aeroplanes techniques conserve is have to ecosystems done: for wildlife patrolled Masai from by Mara damage Reserve breeding Many islands ready was become them but which wardens, in Kenya and in New them in by shing Zealand. species of captivity Partula and snails during the 20th century. Some are which in bred to in nearly released and back into their reintroduced to habitats. Oman extinct. plants the be zoos in botanical gardens and re- wild. destruction, e.g. deforestation issuing and licences protecting for logging wetlands to in prevent drained. establishing Preventing may of dry take ecosystems forest up in to where land Guanacaste 300 years to has become National Park degraded, in Costa achieve! trade in Trade endangered in species. Endangered CITES, Species, the Convention imposed a of worldwide generations. on the ivory has into in Encouraging Seed for in 1989. like sustainable forests natural are cold seeds wild. Their from or produce may to of an increase in elephant conserve in the case for products by planting Trees or allowing seeds. around useful ecosystems. replaced from species be valuable be that banks many genes led management stores Seed This Kenya. should replacement species. store to trade countries from banks they crop such seeds world as of endangered hope become to extinct improvement medicinal collect in in the drugs. or and the future Seeds been the collected from plants in the wild and are put into long-term wild, storage. Seeds of many species are stored by dehydration so they successfully. contain 288 of in of Goat them Re-establishment are in tagging have and protect e.g. prevent valuable sometimes and the as • bred to habitat time Ieucoryx, parks we ways tracts endangered to removed Oryx on and • oryx, radio people captivity populations Arabian by forests ban The habitat count so some large oryx International also are Reducing Rica Areas • habitats – extinct Growing e.g. Sri everywhere Researchers and isolation endangered Arabian them Park, affect bird • wilderness simply leaving T anzania. establishing the achieved and miles. • National in returning where of never elephants. Here Parks Rescuing The Plains is habitat long now Horton This organism’s labelling, elephants game became species of pollution, then they an organism’s animals. occupied the Marine of lives Serengeti onto the involve forest habitats. e.g. ring conserved. activities manage herds species may a be population. herds used and • and nd be scientists can around Human Monitoring birds given barrier be conserved Putting species OUTCOMES only 5% water and can thus survive being kept at –20 °C. Removing that they remain are water viable removed germinate. made if in seed from This their for banks takes to every up’ the affect and ve and metabolism seeds tested years. bank wildlife their However, Some thawed knowledge actions down years. forever. place ‘top slows many storage, people’s conservation seeds viable possible Increasing which from remain for seeds from to see help if to sample they will continue to be species. understanding will not each Collections each so do of ensure the the way in success of programmes. tnemelppuS These Reasons We • should for conserve Ecosystems providing provide • • • for example not are more to support do in useful help we take with fuels habitats services and giving substances maintain the and such us species as treating areas such as balance for Fuels fully by few from plants a wide variety understand, keeping foods, the smaller – apart wild in and from large animals of often pests quantities, and fossil provide Drugs • Genes in Papua eggs Guinea are turtles. medicines. of life on the planet, e.g. organisms to diseases some sh quantities. such that as we that continue Brazil could in But on there that are There utilise this in ways planet, check. species, nuts. interact life as we many may food take be that we many sources. The fuels fuels, will such as not last forever. biomass fuels We (see still Topic need timber Svalbard cut into – drugs for treating cancer have been – as a result of selective breeding diversity in our three main staples – rice, to conserve any locally is wheat adapted in wild relatives that have genes we can be kept in botanic very and varieties could gardens Norway little POINTS Endangered maize. that use in and their species can be genetic It exist by the monitoring the is of their populations, and habitats, using future. captive plants northern plants. protecting any in permafrost. to sizes important bank Arctic 21.7). discovered there seed the conserved These New leatherback They 1 also of waste, recreation. KEY • the because: is • wardens conserving cycles. Habitats directly us and with Ecosystems There ecosystems, provide food us nutrient conservation seeds in breeding programmes seed and putting seeds into long banks. term Prevent directly species by becoming human extinct, especially those storage 2 activities. Educating about the practices SUMMARY Explain QUESTIONS the meaning of essential each of the endangered species b species captive There State two country. importance of Explain species Describe the for part a national c botanic are that the are endangered steps being in taken your to region conserve or and survival is of species. many them. reducing protecting reasons such extinction, vulnerable environments played by each of the following in parks gardens b zoos d cycling seed tnemelppuS why it is necessary to banks conserve and such and resources habitats and ecosystem conservation: drugs, Explain the conservation, functions, 4 ages conservation maintaining 3 all breeding as 2 of monitoring for c banks. following: 3 a seed people endangered 1 in threatened tnemelppuS • nutrient providing such fuel as and as food, genes. ecosystems. 289 PRACTICE 1 QUESTIONS Competition for between resources causes of is one reduced competition chemical B herbicides C pesticides D selective the yields. between A crop of plants and biggest Which crop weeds 6 potential and stocks major reduces plants Fish method weeds? fertilisers The pest of decreasing B setting C breeding up reducing weevil shown plants. below What is a notorious at should be of the boll used When the sh herbicide C insecticide mesh exclusion the time quotas stocks size of zones nets and ‘no-take’ that shing boats can for can the be maximum numbers caught. 2) [1] a population genetic D molluscicide 1) becomes variation This population means there are A alleles B chromosomes C DNA D genes base within that endangered the population within the fewer: sequences [1] ecosystem is all the: (Paper A organisms in an area B organisms in an area factors that inuence and the 8 physical them 2) [1] Eutrophication may fertilisers bodies enter concentration C the that decreases. B An make to 7 3 to many a weevil? fungicide (Paper used in not sea issuing (Paper A be is [1] cotton control decline Which zones 1) boll serious could A D 2 that in areas. sustainable? stay (Paper are shing physical factors that inuence an in happen the of when water. water may sewage The or oxygen decrease organism because: in D an area plants and animals interactions (Paper 4 What between an area and is acid them decomposers B less C more carbon D there are the negative on effect of the over-use respiring aerobically oxygen dissolves dioxide in is water from released by the (Paper farmland? bacteria more animals in the water 2) [1] rain Human which wastes use complex C global D more enter sewage microorganisms compounds in treatment to urine works breakdown and faeces. warming (a) Outline what happens in the primary, photosynthesis secondary 1) and tertiary stages of sewage [1] treatment. 5 Which pair enhanced of gases contributes greenhouse A carbon dioxide B oxygen and to the (b) effect? and carbon State three treated sulfur dioxide and (c) dioxide water water vapour and 290 2) why safety of sewage humans should and recycle be the [3] in sewage carbon as treatment part of the carbon vapour oxygen (Paper (Paper reasons the Microorganisms cycle. D for [6] environment. methane works C air of eutrophication (Paper are [1] 9 B A the 1) fertilisers A in [1] 3) Explain how they do this. [2] 10 (a) Dene the term pollution. [2] 12 The table three When populations reach a certain size they to be State the concentrations increased between of 1890 and It also shows how effective they are endangered. as (b) how have are 1990. declared shows gases what is meant by the greenhouse gases compared with carbon term dioxide. endangered (c) The tusked insect that Zealand. species. weta used It did is to not [2] a large live concentration carnivorous throughout survive the the New certain introduction years / relative in atmosphere effect in as greenhouse parts gas of alien species breeding and and a was rescued reintroduction by per captive gas million compared programme. 1890 1990 2030 with CO 2 Suggest: carbon (i) why the tusked weta did not survive 400– dioxide the introduction of alien species 1 354 500 (CO New 290 to Zealand ) 2 [2] methane (ii) how a captive such an breeding programme 0.9 (CH insect would be carried 2.2– for out. 30 1.7 2.5 ) 4 [2] nitrous (Paper 3) 0.33– oxide 0.28 160 0.3 0.35 11 The Asian elephant, Elephas maximus, is a (N O) 2 large herbivorous International as an Union endangered researchers the in the for in the centre It of is classied Conservation animal. published population Park animal. the In January rst T aman of Peninsular the Nature (a) 2009, estimate Negara by of atmosphere Show counted piles of dung to your population. Their estimate was The main Suggest why the researchers could the of elephants, dung but had to Suggest why it is the population why Explain have reliable sizes of been (i) List if estimated can there four limit the that T aman Explain large Asian the concentrations and (ii) of methane the twentieth century. [4] the gases global shown in the table warming. [5] why it effects is of important these to gases know as the shown are no a a rate limiting that population in at are in why it of is Asian the population likely to of Park important animals, elephant, too 4) 2% Asian such as [4] herbivorous the [3] factors. growth National table. elephant Negara. increase (Paper increase factors elephants (ii) in how Suggest (Paper year are [3] populations per oxide endangered the has nitrous fertilisers. estimates species. It of and dioxide, cause relative (c) [2] for (d) of 1990. [3] important to sources carbon may conservationists and the the count instead. (c) (b) 1890 in in not increased piles between increase dioxide 631. (i) count carbon working. vehicles Explain (a) of estimate motor the percentage The (b) researchers the concentration National Malaysia. Calculate in a much. but to conserve such not as allow National Park to [5] 4) 291 Alternative to practical paper Experimental 1 Use a 2 4 techniques, sequence Make 3 and Interpret Plan and possible or of skills and are Pancreatin / time °C to for go the clear student A / is digest minutes turn from milk powder. 14.0 10.0 25 11.5 8.0 30 10.0 6.5 35 7.0 4.0 40 6.0 2.5 1 are such a together as the mixture in one of the methods selection of data. and suggest techniques, an alternative to practical paper below. enzymes, Pancreatin white given the powder 2 Mix 3 Record The the to clear. table a Plot the the will T wo following milk powder including make a trypsin, sample students, A and of B, that will skimmed are given milk dried the on instructions: in water and stir until there is left. dissolved experiment SKILLS evaluate and materials). proteins. Dissolve no EXPERIMENTAL observations B They 20 following 1 solution student (including measurements. experimental (including assessment appropriate). and investigations, tested test QUESTION temperature out improvements for materials where observations evaluate carry abilities and instructions, and practical and apparatus, record apparatus These skills time the at taken left ve results milk and for obtained pancreatin the shows different a milk their to solution go results together. clear. when they carried out their temperatures. for student B in the form of a suitable graph. • Following a sequence [4] of instructions • Interpret experimental data: Example 1 STUDY 12 • Select suitable scales TIP and Examination axes Draw graphs from given data requiring the rae lc T his the graph: make possible and the to graph be easy as to • Plots is • Scale • Plots • Axis clear clear but but not not too too large. emit Line are thick. graph 292 that f ul l in this that we th e ch ange ex periment is is with ruled T his th e independent variab l e 6 is used as co lumn 4 the of the x-axis T he ‘time to goes 2 into co lumn tabl e the go clear ’ righ t the and gr aph . variabl e the of straight axis with labels are headings. units. the Note same as that the 20 25 30 temperature 35 / °C 40 of the and lef t-h and the of dependent 0 labelled th e temperature. is th e wh ic h h and tabl e labelled. joined lines. table the paper . gains No te variable y-axis the include on 8 rof read. eht as to noitulos large drawing chosen printed marks. ot for Scale graph examination og • grid a 10 / Tips questions graphs se tunim • from graph . and th e Example 2 STUDY TIP 14 T he plots there In in are this seven bio logy graph errors. graphs are perfect What points are are but they?* joined * Answer 1 Cur ves for bo th students were 12 with ruled freehand be 10 used but straigh t lines. if Lines requested normally r ae l c bio logy. lines, they of in best the are Uncertainty no t t plo tted, can question, no t is with used was 2 in common T he even asked plo t shown 3 T he 4 T here only one for . markers in red though red line for student too large. are is too A thick. 8 in bio logy where ot emit variation and to all contro l there it can o ther is be gene tic difcult variables. T his 6 uncertainty points 4 with chemistry less are is shown ruled and joining In with and lines then of 5 physics, mathematics uncertainty drawn by lines. there best t. no units y-axis and has numbers T he no x-axis chosen is graphs are is no t 6 Lines 7 T he as large lines are on has and best on x-axis scale well of the the as t it the scale it. no t been graph could have been be. used. extrapo lated. 2 Example 2 markers for good has used the practice two when different cur ves. two plo t T his cur ves is are 0 t e m p e rat u r e b From this your graph, enzyme /ºC required describe between and 20°C explain and on the the same effect of grid. temperature 35°C. on EXPERIMENTAL • Example Interpret 1 greater milk and to 4 faster go 6 A good ‘T he have changes T he the answer practice good ideas co llisions The At of means very STUDY Example is do a Second, answer 2 to be T he trend changed the well carry to as out do the less includes as more time at a a is the 10 are to moving collide for At faster wi th the is • Recall should say how independent time least is for gures calculation In of a the the the the enzyme. from In of this milk the question rate physiological TIPS dependent variable. needed two the simple experiments 35 °C and data the minutes reaction temperature. calculation. to case go graph such change Join points ruled on straight a graph with lines. to as this, without so. moving likely gives at the 20 is 10 faster 2 at marks minutes reaction temperatures higher temperatures and (of maximum marks). the 3 of rate and falls enzymes at will 2.5 the minutes higher denature so at 40. temperature. the rate falls. makes know the and the asks effect when 40 refer Units for the trying to should effect be tween ‘20’ to because describe units always be tween and be given 20°C ‘40’, so the are and the effect. no t in First, given. an 35°C example T his answer . but has the no t question. that confusing graph. mistakes 20 mistake. question the means two what describes discussion this graph mo lecules common answered ‘T his so likely 20°C that needed TIP no t very to that high reaction we higher is evaluate observations 2 reaction This also asked of being Example a we change directly two of as it T he at means energy more temperature the being the time time TOP illustrate is This less TIP greater clear ‘. at more are the reaction 35 °C. minutes description variable The at molecules STUDY temperature clear. molecules milk the minutes by and experimental and The SKILLS [3] the time of No reaction with rate rate enzymes of falls at the higher temperature’ seems reaction. denaturing is true but it is no t relevant to marks. 293 EXPERIMENTAL SKILLS c Suggest reasons for differences between the results of the two students. • Interpret and experimental and observations Example data Student to • Evaluate [3] evaluate methods B an the have milk used more milk powder or less water in. used Student in may dissolve B may have may have had used a greater volume of the enzyme investigation solution. They STUDY T his T he as rst would two milk concentration suggestion care these d EXPERIMENTAL Interpret and to It or Suggest write and can be the change and no t B clear 3 the were PH has the that vo lume, rate of carried or the from marks. identify enzyme reactions pH of o ther have variables, no t enzyme out at a been such contro lled. reactions different so pH the is good. ph. smaller answer times so whe ther the larger rate of concentrations are explain at what would happen if student A carried out 80°C. [2] evaluate 1 observations enzyme will be denatured. data Example The milk 2 would denatured. work 1 makes de tailed a only eggs. their eggs The banded form The non-banded of Cepaea form of C. clear at that the all b ecause active the sites of enzyme the will be enzymes do not pair eggs snail, of hortensis Figure 2.1 so gains Cepaea These banded placed hatched hortensis explanation and 2 so then only goes scores on to 1 mark. give a Example correct, more marks. 2 population. A an suggestion explanation banded single gives correct QUESTION The go means TIP Example 2 not This anymore. STUDY 294 out and student must experiment The and pH the 2 correctly smaller . Example experimental pH. SKILLS the • and that results reaction. greater gain sentences T emperature In different TIP answer T ake a the in a hortensis, forms snails glass number can was tank of exists breed with to food. was two with allowed snails as forms each breed T wo other and together months counted. within a lay and after the a i Count the the tank number shown non-banded in of banded Figure columns in 2.1 the snails and table and non-banded complete the snails banded ii of Make and • Perform the total number of snails and complete the table above. [1] number TIPS Make your one iii for numbers. snails 18 Tip: clear, snails especially STUDY handwriting non-banded of Figure mathematical calculations TOP total in simple number snails 1 of observations snails banded number record 2.1 Calculate Example • non-banded of Figure SKILLS [2] total in EXPERIMENTAL and below. banded number in 6 24 2.1 TIP cross twice out or Calculate Fraction Answer the of snail in pencil as fraction banded of banded snails count so that you do no t count snails in the sample. [2] = 1 of banded snails = number total Answer you one. = Example Fraction each miss of banded number of snails snails 2 / = 3 Example Fraction Answer 2 of = banded snails numb er = total 18 / of banded numb er of snails snails 24 STUDY TIP Example and in the the only Care b 1 1mark is about STUDY is and that the fraction what of do paper handwritten the have may given fraction units require is numbers these the how no t no t are results banding in but units. was calculated o ther calculations Example 2 gains simplied. clear . the pattern table in above indicate snails. [3] is EXPERIMENTAL • example data. a of Marks 3:1 a question would ratio, be banded that given : tests interpre tation of for: Interpret and experimental and SKILLS evaluate observations data non -banded. dominant. 3. Non -banded original is recessive. parents were he terozygous, or the non -banded snails homozygous. 5. Correct a showing TIP ano ther 2. Banded T o practical explain 1. Recognising were to for Fractions inheritance experimental 4 . T he marks because needed the 2 answer . alternative Suggest T his gains correct use of maximum the of term 3 ‘allele’; e.g. the banded allele is dominant. marks. 295 EXPERIMENTAL c SKILLS Figure Cape • Make and record 2.2 shows Rock Make a clear drawing from a of Make labelled a Thrush, observations Monticola • a a labelled drawing specimen head photograph of Ensure of ×2 the thrush. your has magnication compared the the that drawing a rupestris. with photograph. [3] Figure DRAWING 2.2 TIP Example 1 nostril beak Draw a grid with a ruler over the eye relevant and part draw onto help and the you of the the same grid lightly answer space. get proportions the magnication This will STUDY T he correct. TIP drawing is of the head only ˙ a T he Magnication x2 asked to beak the magnication of are smoo th giving a clear is in eye perfect correct and pro portion nostril are T he in label lines precisely place. Tip: to are avoid the clear part and go labelled. arrows. calculate T here the lines outline. ˙ the be magnication. ˙ and could T he ˙ at You markings photograph your is minimum shading. ˙ T he drawing is accurately labelled. ˙ 3 marks drawing: drawing Magnication size = actual size Example If the photograph already magnication, do include your that in not has forget nal 2 eye a to answer. wing TOP TIPS STUDY Use smooth much lines shading without for TIP too drawings. T he drawing the body includes some of ˙ T he lines are no t smoo th; they do ˙ no t x2 and the head part is no t magnication. give a clear lines outline. T he label the part labelled. do T he line for no t go precisely to ˙ T he beak is out of pro portion ˙ and the eye and nostril are the eye goes to the ˙ in the T here wrong is too places. much shading. feathers is above labelled but the the eye and the question wing asks for ˙ a 296 drawing of the head. No marks QUESTION 3 EXPERIMENTAL • Describe an investigation to compare the rate of water loss Plan and carry SKILLS out between investigations plants in Figure 3.1. as the reliable light In and your and plants answer valid as in the dark, describe how using you the will apparatus make the in results possible. [5] TOP cut leafy from TIPS Keep shoot plant controlled constant Good capillar y air tube taking 3.1 Shows uptake Example a potometer by leafy that is used to readings to your distance minutes. will get measure the rate of resul ts travelled Divide the the rate in by by measuring the bubble distance mm per by 2 in and 2 variable) you ✓Gives how minute. 2 sure your apparatus has no that the kept the temperature same. Use and the check Do for the in anomalies same in the the and light take dark. three an Draw times, ✓T he average. a compare If you the bar chart ✓A you water can lost diameter Example work per in have the of the be out the rate as mm bar one A minute. set and the this of apparatus another distance with the experiment b ecause is important with the the plant plant in the • variables, are leaks. T his temperature, contro lled. carry is out of repeat the and explains student wind Humidity has speed could readings,check average suggested de tail careful used and also the have is because for anomalies stated. there are only two values variable. about when maximum T he rates writing is given. Candidates superscript numbers should by hand. of 5 marks is given. TIP rst ✓How bubble moves. When to ✓Time the bubble did not sentence measure our apparatus was the to time keep with everything a stop the whole an average. experiment the measured Variables kept bubble with the repeats dependent is the question. variable by measuring the explained. sto pwatch. same the experiment 3 need times’ to is be named. acceptable as referring to broken. the readings. same. ‘T ake an average’ is too vague, which gures are averaged? watch. 3 Do of simply the move • Measure prevent independent repeat It to chart the ✓‘Do all time of • at to calculation movement did standard capillary light. we the 2 dark Measure as mentioned. STUDY You (dependent averages. the 3 tube need plant ✓Further know bubble measured. contro l of need and of to the the of been experiment is of speed piece plant. the movement explained. apparatus. piece Do collected. leaks wind same the is minutes rate ✓T hree are the data TIP ✓Measuring the and the water ✓Shows Make improve of 1 collect the always repeated shoots. STUDY You investigation. bubble reliability Figure an investigations involve rule in variables three times and marks awarded out of 5. take 297 Glossary This glossary some used of in words the this are provides denitions important book. key The terms of biological relatively terms underlined as dened from glucose, in which you are required in for the examinations. Y ou be expected to than energy presence of Antitoxin as a lymphocytes oxygen. poisonous chemical that waste by explain – result a collection from a of diseases weakening of the Arteriole type artery capillaries. and of immune by any forms system following relaxation HIV . ow of of of a two or more Absorption movement molecules intestine of through into the of muscle blood Artery digested the blood wall or Alveolus where of lymph. the a tiny air exchange air and sac of blood in gases the Acid of the the rain acidic. rain and react with form acid the lens adjustment so as to of focus into or the snow gases in which such oxides water acid carbon, hydrogen, of the as acids bonds to amino acids a molecule link consists form made oxygen together protein a and by up nitrogen. chemical molecules. of and Some Articial Amnion nitrogen atmosphere the antigen, either pathogen or on in a in body to produces response the surface also the the contain site enzyme fetus in that the surrounds uterus. means of part of the to of uid an a is contained and which the within liquid the protects mechanical of which fetus from of high the through the cell in or movement out of membrane a down of their lower without enzyme of region of their higher steroid substance production from that a a crop gradient, that increases released from of protein to a build that to survive in its cells to the feature that tness, i.e. an increases small in the helping amount of energy absence of red reproduce in its a drug so when a regularly a disorder blood of cells the blood without the a for carry person that has they taken cannot glands produced that emergencies by a which joint. muscles brings other When relaxes, which move one e.g. the pollen the a pair about the biceps of deposits the internal of walls slows down the of rate of a chamber blood of from the veins heart and that pumps to a ventricle (plural atria). a plant growth controls cell hormone elongation. the and triceps B arm. increasing of the in cells a ower where produced. the a drug that is stop the growth of consisting a bacterial taken bacteria. to kill of type cell surrounded cell wall, single of microorganism has by but cells. Each cytoplasm a cell has no membrane and nucleus. glucose a protein released by Balanced diet a diet that provides blood. respiration happens are of stress, the process pathogens. 298 narrowing by movement prepares and lymphocytes that a of contracts, lower part grains Antibody concentration Aerobic cells. sufcient which or example the ow. Auxin Antibiotic for of environment. hormone adrenal body cells used, it. Adrenaline the are means survive Anther by of the haemoglobin which cannot in Bacterium do into oxygen. at Addiction they caused which receives muscles and where part arteries Atrium the organism’s to molecules oxygen. an inherited it parent. from environment. an the movement a blood Antagonistic by gametes. process release it feature reproduction of genetically of the food body arteries that Adaptive are (clones) cholesterol in organism formation individuals the the in using helps called up respiration. feature Also reproduction the Atherosclerosis respiration happens Anaemia Adaptation yield. breeding characteristics, the to glucose energy useful hormone- concentration concentration their selection for breaks a relatively against a muscle. cell concentration the animals Assimilation that a as starch. Anaerobic region placing oviduct breeding. becoming ions (AI) or infertility selection of or jointed exoskeleton. uterus and digested transport the treating plants Asexual ts. molecules that have amnion the the like Active which heart. that damage. the Anabolic substrate that of New surface into phylum Articial because vaccine. molecule the insemination into identical an the sulfur . membrane developing Amylase Active through from protective semen e.g. antibodies See is rain. immunity own and controls vasodilation. vessel away animals a selective its wall of sulfur Amniotic Active the capillaries. and blood travels Arthropods occurs. Amino Amino retina. Polluting dioxide in lungs between legs Accommodation onto between alternative gene. blood shape vessel Contraction these. Allele light blood terms A the (toxins) bacteria. immunodeciency vasoconstriction the products by the to infection food released neutralises may, body’s other of such produced that however , the Acquired syndrome know amount substances, the AIDS syllabus, large food to release a to protect against sufcient and all correct energy the food for a person’s nutrients proportions. in needs the Glossary Bile an liver and It is alkaline stored released through the uid in into bile made the the gall small duct to in the Carbohydrase bladder. intestine help with the an enzyme digests carbohydrates sugars, e.g. amylase to that Chloroplast simple digests starch to and absorption of plant Carries cells. ssion a in type of which asexual one substance that a class of provides food by energy, a two. Bacteria cell divides starch and glucose. Composed reproduce by carbon, hydrogen an intestinal Binomial naming system a organisms two names: method in a which genus for compounds each name cycle is and trivial name, e.g. Homo the caused e.g. in the a lipid-based liver and chemical found in the oxygen. ow through decomposers High levels of cholesterol and of carbon plants, their animals, environment. the blood risk of are linked to atherosclerosis an in increased and heart disease. and Carbon a disease ssion. Carbon given in of blood. binary found bacterium. made into is photosynthesis. sugars. Cholesterol reproduction that out fats. Carbohydrate Binary structure chlorophyll Cholera digestion small containing sapiens dioxide the gas produced Chromosome a thread-like structure for as a waste product during respiration made up of genes. They are found humans. and Biodegradable broken down something by biological that can be processes. absorbed during by plants photosynthesis and to used make inside simple the when a plastics Biomass in a are the of living material Carnivore an animals meat-eater. – a animal that eats other that the Carrier the use of organisms has a (1) an recessive individual allele for useful and useful products, medicines, services, such or as such to as carry making disease out wastes harmless. next is and infected by infectious control prevention of a by contraception or a muscular sac and passes it out (2) the of a it to person only process found pathogen the does that and oviducts they for not disease, microbes the on it to have but Ciliary an is that (plural: beat out the muscle controls cells to e.g. cilia). move In dust of the lungs and up during a the muscle shape in of the the eye lens focussing. able system the organ others. system a organs, throat. Circulatory transmit tubular the who abortion. substance that speeds and made the up heart of that blood vessels transports blood. stores up urine transmit disease, Catalyst Bladder visible genetic birth to either can generation; symptoms Birth are who a to make tiny some airways, and foods a line airways area. Biotechnology to and dividing. biodegradable. mass particular is sugars. Cilium Some nucleus cell through a chemical reaction and is not Mammals have a double circulation the changed by the reaction. with blood passing through the heart urethra. twice Cell Blind spot part of the retina structural are no organisms. the unit part of the central All organisms coordinates of the of cells. membrane Viruses are Classify not. groups which a small branch of sort living to organisms features into they the boundary of in common. the which ends in alveoli into controls and out the of materials that it. Clone an identical organism to its that is genetically parent. a Cell bronchus to according body. pass Bronchiole body. most cell activities the of are have that of nervous Cell system circuit receptors. composed Brain functional one where living there and in sap the liquid that lls the Clotting a series of chemical (air vacuole of a plant cell. reactions that cause blood cells to sacs). stick Cell Bronchus one of the two tubes wall the outer layer of a the trachea and pass made of cellulose, which (plural: this stops loss of blood and results in the into the lungs wound supports formation the a plant the off At that cell branch together. cell and gives it of a scab. shape. bronchi). Codominance Cellulose a complex alleles that makes up the the existence of two carbohydrate cell walls of for a particular characteristic plant C where neither is dominant over the cells. Capillary the smallest blood other Central vessel with walls only one cell are exchanged system brain walls between heterozygous blood Chemical and of uid. digestion the large, small, a disease uncontrolled more parts resulting division of the of body. in individuals. insoluble from cells in soluble molecules or rectum found in absorbs the many light of the the alimentary small where the intestine absorption and of molecules. water Chlorophyll part between into the one the breakdown the Cancer expressed through canal tissue are cord. Colon capillary both and thick. spinal Substances nervous and green plant for occurs. pigment cells that photosynthesis. 299 Glossary Community and a all the animals, microorganisms particular that are plants found Cuticle in habitat. the epidermis that waxy in covering plant reduces the stems loss of of and movements the leaves water out of the cause air to ow in and lungs. by Diarrhoea a condition where the transpiration. Competition contest organisms for water mates. and faeces between resources such as food, Cystic brosis affecting the an lungs inherited and the disease released symptom of decaying plant remains caused by a faulty, loose diseases, and such watery. as A cholera. digestive Dicotyledon system, Compost are a type of owering recessive plant used with an embryo that has allele. as a source of nutrients in two gardens. Cytoplasm Concentration gradient in substance between e.g. either between concentration side air in of a the two cell of not including the the of the arrangement (Also nucleus. of alveolus known Diffusion membrane, and molecules D a blood the process, as higher with place in the liver, the or sensory cell in the where retina of nitrogen-containing part of eye that intensity responds and detects to light of high colour. acids is removed Ammonia is to then form a condition faeces are a lower of the where difcult to Decay pass body. the organisms converted breakdown and waste its energy an by organism on that gains Decomposers other mainly organisms. into urea. Digestion their feature variation that of with many shows a range between two intermediates, energy of by and Deciency extremes when e.g. a human an and fungi breaking waste disease Contraception any method of birth important vitamin results gradient prevents the that breaks into the down any fertilisation. device prevents arteries from a the in or a nutrient, mineral, is such missing humans in the removal order Denitrication fertilisation. ions into to that to of exploit conversion nitrogen Denitrifying supply which live to heart muscle. such as convert in down nucleus gas in two of the transparent eye which rays onto the layer at body heart helps to refract retina. by bacteria anaerobic water-logged nitrate ions Development complexity disease by muscle with new an as an of heart intermediates, no which embryo of plant – a seed leaf. In of of the cotyledons are food stores groups. the molecule material. in DNA that The forms the sequence codes for the of sequence bacteria amino acids in soil, into an proteins. allele that is expressed and nitrogen it is present (e.g. T or G). gas. increase any grows organs substance taken into the in that and modies or affects chemical and in the body. organ the rst part of the a medical the blood condition glucose not diabetes to is controlled. the failure One of E the secrete the use of all the living organisms insulin. (the permeable transfer is intestine. Ecosystem Dialysis the feature human bacteria. for embryo. Cross-pollination e.g. nitrate many pancreas plants a a cause owering limited for land. Duodenum Diabetes in the variation phenotypes of supply blood. part chromosomes conditions, embryo tissues, concentration Cotyledon of heart blockage that a interactions partially membrane to community) separate physical in a between place, them and and the their environment. of substances. pollen ower grains to different the from the stigma plant of the anther of a of ower same Egestion a on species. a Diaphragm and the 300 it cells). with small arteries system absorbs trees the systems. caused coronary organ and nucleus of reactions disease processes. the gains Coronary a number body light the food sets Discontinuous Drug front using chemical as and disease. Deforestation by or arteries aorta blood the large, small, condition if Cornea molecules and Dominant oxygenated of into blood. Diploid of branch of dead material. bases Coronary a result gain genetic that down a breakdown molecules system that DNA Contraceptive substance as by blood that with place variation height. control a dead material (e.g. phenotypes to concentration food containing a of place microorganisms, bacteria organisms in a decomposers. feeding Continuous movement from movement. Digestive Consumer leaves. ammonia. mechanical out its the water-soluble compacted net concentration insoluble Constipation in amino random the veins eudicotyledon.) ions, concentration a net-like which lungs. takes Cone a a places, Deamination in contents and the cell difference jelly-like cotyledons brous thorax a sheet tissue from of that the muscular separates abdomen. Its that has absorbed, anus. the not as passing been out digested faeces, of food or through the Glossary Embryo animal the or fertilised early plant which are the broken surface stage it of an develops from a egg. Emphysema in as a medical walls of down. area for This gas condition the alveoli reduces exchange Fermenter a which fungi or under sterile, and female egg, to that the sex form grows container bacteria are controlled Fertilisation and the large a into a of e.g. zygote the a a length Gene and base egg) to that the person cannot mutation new oxygen into their large fat the globules breakdown into on for a alleles a of of change DNA in that the gives rise genes. individual. chemicals that provide the engineering genetic material changing of an organism blood. plant Emulsication found codes get Fertilisers enough DNA, that characteristic. sequence Genetic means of chromosome, particular male sperm (fertilised new Gene conditions. fusion cells, in grown many of tiny land and nutrients to and increase produce a are the put on growth higher the of a by crop removing, individual changing or inserting genes. yield. Genotype the genetic makeup of globules. Fertility Energy energy transfer from one the transfer trophic of to (feeding) drug increase becoming a the drug that chances of is a used an woman organism possesses to the Enhanced greenhouse increase greenhouse in a concentration gases in the of a to global speed up reactions in rate the with of catalysts that chemical the plant growth inherited all the major of a group organs the characteristics, leo the indigestible cellulose provides food bulk plant and to through material, lignin and the same enrichment nutrients of algae process features assist the gut the by the passage of peristalsis. to tiger , a Excretion that and of can in surviving and environment of an of reproducing in which it the is in the removal toxic products a plant osmosis longer over time. from materials, of wall is Food the metabolism excess when the a are in produced so push cell that that the has cell outwards described as chain this relationships in lost by of and requirements. beginning species no organism with is organism in show the ow no the as a an complex energy a by the chain. of the liver Goblet cells mucus-secreting cells. plant to the a growth stimulus response of by gravity. warm effect food because the Earth carbon is dioxide Each other greenhouse gases in the next Food energy network interconnected in muscles. atmosphere reduce heat into escape of energy space. Greenhouse nutrients. of and chains the chains and gases web carbohydrate store feeding Earth. Food so accid. producer . on the and glucose cell longer the of community a fed glucose concentration liver water contents against shows a to the blood. found and in tigris stimulates glycogen the Glycogen found. and by in organisms the of substances on similar organism plants. which change probability convert kept exists with lion, Panthera Panthera that Greenhouse Extinct species the hormone pancreas increase a waste of e.g. Gravitropism populations organisms it GG). genus. Glucagon that in Flaccid Evolution when development body. Eutrophication stimulate alleles atmosphere Fitness waters or the warming. biological the during recognisable. mainly Enzymes stage mammal are Fibre leading Tt of next. Fetus effect (e.g. terms pregnant. Genus level in showing the radiate heat maintain than it the would be towards the temperature Earth higher otherwise. F energy ow through an ecosystem. Growth Fats lipid molecules that consist and glycerol and three fatty acids. energy rich proportion of as they carbon contain and a hydrogen number Gall bladder stores the with acids glycerol molecules to form that bile bile respiration converted dioxide; which in an or sac into it in is the the liver released small useful increase increase in in size cell cell size or both. H intestine. combine fats. Haemoglobin Gametes glucose ethanol and industrial microorganisms a an which down sex of cells with the haploid chromosomes. red blood oxygen to is process are Gas carbon used in to exchange system system comprising and lungs into the that alveoli organ trachea, involves where Haploid bronchi cells the that form red pigment combines in with oxyhaemoglobin. moving oxygen air product. carbon dioxide are exchanged a a single chromosomes (e.g. nucleus set of unparied sperm and egg). and portal vein the vein with through the nucleus containing Hepatic make by anaerobic which into (2) (1) a before duct number Fermentation permanent mass high atoms. Fatty dry Fats G are a of which absorbed food travels blood. from the small intestine to the liver. 301 Glossary Herbicide a chemical that kills weeds. Ingestion the process of taking in Leaf food. Herbivore an animal that feeds the light plants. Inheritance of Heroin a highly addictive, derived from from poppies. opium genetic a genotype alleles of a gene to (Human chemical photosynthesis. transmission the from one Lens next. disorders by dominant are light part rays of the onto eye the that focuses retina. disorders or Limiting recessive is in the factor the shortest factor supply that and that are passed from one restricts processes, such as the rate different. generation HIV during where alleles two absorbs into extracted caused the the information Inherited Heterozygous that convert depressant generation drug organ to only energy on plant energy to the next. of photosynthesis or the rate of immunodeciency growth. Insulin virus) the virus that causes a pancreas HIV attacks and destroys the body’s ability to against by the that to stimulates store the glucose as liver and glycogen Lipase so to a reduction in the Liver of glucose in the maintenance of environment. controlling factors, such in and the the Homologous concentration chromosomes chromosomes a that for same the muscles amino the ribs; external intercostal during inspiration; intercostal muscles contract same expiration. vitro acids ammonia the form characteristics fertilisation outside and the eggs (IVF) body by fertilisation mixing Lymph uid in a laboratory embryo is placed a a genotype a gene are chemical an the activity in the blood of one organs. the the drains to living in do not the action have to or coloured the an action that think part like pupil. It the alters eye the size a e.g. formed lymph system vessels lymph cells are when tissue vessels. that system of transport thin- lymph nodes where white blood found. Magnesium pupil and so controls the for light entering the that is the element needed amount the synthesis of chlorophyll. It is eye. absorbed by the roots in the form of ions. adapted Malnutrition hyphae) a uid K that of chemicals, M liver. plant (plural: structure toxic of are water. (mycelium) in out about. of more Hormones Kidney Hypha of into magnesium Hydrophyte carries dish. and of by and gland the target destroyed glycogen messenger endocrine transported specic of uterus. around alters converts glucose identical. Iris is stores where we that urea, into and of by into Lymphatic resulting Involuntary produced down ammonia, in the Hormone into detoxication walled Homozygous alleles abdomen alcohol. positions. The both the breaks pair sperm the in bile, carry occurs genes organ of in matching the produces blood. during of muscles contract internal glucose fats as muscles temperature digests This between involves that glycerol. a Intercostal internal and blood. that constant enzyme acids concentration disease. Homeostasis the fatty defend causing itself produced lymphocytes muscles reducing hormone AIDS. is thin part mould of the organ that lters waste by eating an the condition unbalanced caused diet. thread- the chemicals out the and of the blood and controls Undernutrition occurs when a diet is body water salt levels in the body . decient in one or more food types. fungus. Overnutrition coronary can heart lead to obesity and disease. L I Maltase Lactase Ileum the part of the small the enzyme that down down between the duodenum the and lactose (milk maltose the major function of absorption which is Lacteal a of digested food. inside a lymph villus, capillary system tissues, cells which that act against together to give a pathogens. Lactic in acid muscles the chemical when anaerobically. protection without food glucose by chemical change to molecules. produced is Some a type of division of the respired bacteria to reduce the chromosome also number provided the smaller against produce disease into contains nucleus Immunity food fats. Meiosis defence digestion of and the chemicals breaks found pieces absorbed Immune that glucose. sugar). breakdown the to the Mechanical colon, enzyme breaks intestine the lactic acid during by half. Diploid nuclei give anaerobic immune rise to haploid nuclei. Also called a respiration. system, including lymphocytes and reduction antibodies. Large intestine the nal parts of Memory the Implantation the embedding of alimentary canal that the lining of the and store the rst invasion of produced a faeces. uterus. pathogen 302 lymphocytes an water into cells absorb during embryo division. or to a vaccine; these cells Glossary provide a fast immune response to about infection. movement Muscle our Menstrual cycle the sequence tissue gut and of also bones moves keeps our at joints. food heart Nutrition along beating. are that occurs in a ions, woman, Mutation a change in a gene or in the thickens lining in of order the to uterus receive a after ovulation. The containing by cycle hormones a network of thin for gland and the growth and from that make up the body the tissue or repair , assimilating them. of a O the Obesity when a person is extremely ovaries. overweight Menstruation materials and threads is fungus. pituitary raw which mineral chromosome. (hyphae) controlled nutrients and fertilised Mycelium egg of a absorbing where in substances of energy events, taking organic breakdown of the in which (see this is page 75 for two ways determined). N soft lining of the uterus, discharging Oesophagus Natural blood and cells through the selection factors such connecting competition Metabolism all the that take place microscopic sp ecies. fungi Mineral salts those and such individu a ls a as have pass on as iron and for by in plants feedback such Mitochondrion aerobic as respiration near constant to a type that of cells in which where central nervous part the of the to which number nerve pass peristalsis. hormone ovaries that of secondary the in females menstrual nerve from eye to Nerve the exact duplication and helps to cycle. from the retina in brain. system to the a certain Organ a together number to carry of tissues out of a nerve a working function in the cell. the Organ conversion of organs to nitrate ions by system a number of different ammonium genetically that work together to carry bacteria. out bacteria bacteria functions for the body. found maintained Osmoregulation the the sexual body. in by secreted stimulates cells the is a body. body. Nitrifying chromosome in occurs. rise the the ions identical of the muscular mechanism conditions bundle of acids. structure division gives called Oestrogen Optic a down wave maintaining make Nitrication nucleus n ext control Neurone Mitosis the diet. amino cell the for a chan ce to by homeostasis (neurones) compounds, grea ter gen es passes by characteristics used Nerve required Food development that balanced tube the to generation. nutrients calcium a the their with result, adapted viruses. inorganic muscular mouth aff ect As contraction to Negative needed the oesophagus (microbe) organisms, bacteria, Also a a survive are of organism. Microorganism such preda t ion stomach. inside survival only living and chemical the reactions the as vagina. the soil that convert the control of the ammonium of water ions into into nitrate nitrite ions and nitrite content of the body. ions chromosomes. Monocotyledon a type of ions. Nitrogen-xing plant with an embryo with Osmosis the molecules through bacteria permeable and parallel veins in its both in the soil and in Monohybrid inheritance inheritance one of legume plants that with higher membrane, from concentration molecules two nitrogen into a region to a concentration compounds water region of lower nitrogen- or containing of convert the atmospheric more water the of gene of partially leaves. roots of a bacteria one found cotyledon diffusion owering such as of water molecules amino alleles. (or from a region of higher water acids. Motor (effector) neurone a potential neurone Nitrogen that transmits or spinal impulses cord to away from effector muscles and organism or an plant growth, taken in the form part of an by an Chemical nitrate a change that in a traps the air slimy, of position dust sticky or and pathways. It fertilisers acts to help the passage the will not break e.g. as female are sex organ where ova produced. supply from the the release of an ovum ovary. materials Nucleus part down many in the Ovule plastics. of of a the plant gamete. the of the cell develops genetic information structure that After inside contains the the fertilisation ovary female an ovule which a in into a seed. the food of chromosomes. The nucleus Ovum the female sex cell (gamete) gut. controls Muscle eggs Ovulation environment, form along water place. contains lubricant often ions. microbes also lower by (egg) substance some of nitrate organism that Mucus of or Non-biodegradable causing up Ovary roots glands. action region for the ions. Movement needed organs, plant e.g. element a potential). healthy brain an to tissue contracting that and is capable relaxing to of Nuclei the may activities be of haploid the or cell. diploid. produced the in the ovary. Also called egg. bring 303 Glossary Oxygen that is lactic debt the needed acid by extra the produced oxygen body to during Pituitary respire anaerobic gland of the brain to control that the a gland at secretes activity of the base hormones other Protease down an enzyme proteins to e.g. kidneys, testes and Placenta through Palisade mesophyll tissue in that contain many chloroplasts the main site of the in the digestive insulin in the the and glucagon and on not allow that to large molecules a mixture of food remains, body. bacteria the surface which of can teeth; build (2) and an the animal; to does antibodies himself not or in the the lining liquid transports carbon Plasmid of an part a an used as a of the blood foods, sexual cell and piece of vector the membrane plant receiving make and by the the enzyme in genetic of cell that that when the heart separation from when the water cell of leaves causes of pulse the of small pieces substances cell of that cells cause in the elements oxygen, nitrogen at which secondary appear in boys in as transfer of the anther of a ower to pollen the system Pollution nerves the release by and ventricle forces along the this various the of the blood out arteries. The can parts be of felt the as body, wrist. Pupil the hole enters the eye. Pyramid show the left it by through The the size which of the light pupil is iris. that blood clot. Pollination breaks plants. nervous tissues the a an of biomass biomass at a each ecosystem. The way to trophic area of level each from bar is proportional to the stigma. mass Peripheral of the wall osmosis. release the swell horizontal walls age contracts, controlled to cell of for girls. heart in down up needed hormones. circular herself. organism an repair contain characteristics arteries Plasmolysis disease. Pectinase made are artery. dissolved dioxide small Platelets Pathogen which hydrogen, Puberty DNA pass person person does and They Pulse but providing another the antibodies e.g. sulfur. such or compounds acids, carbon, fatty a from diet, waste. small through, immunity the and engineering. antibodies in kwashiorkor. dioxide glucose through. Passive limited and and membrane allows pass form energy that of urea, membrane carbon which and which molecules (1) Plasma permeable are marasmus in abdomen enzymes concentration protein growth blood. Partially removes chemical deposit regulate food a and amino up makes receives mother photosynthesis. organ produces it connects its malnutrition Proteins saliva that which and Plaque Pancreas that to and and are organ embryo leaves oxygen a the mammalian malnutrition ovaries. of P breaks acids. organs, Protein-energy respiration. that amino humans of living material at each trophic of level. that arise from the brain and spinal cord materials or energy that will harm the Pyramid and go to all the organs of the show Peristalsis a contraction that wave of Population muscular a group of food down of the same species living in the oesophagus to the habitat stomach. at the same a chemical that kills a white pests. Population type of blood ingests and destroys way to of growth a at of level each in an ecosystem. horizontal growth proportional population. In to the bar number of in at each trophic level. absence cell of that trophic area individuals numbers Phagocyte a organisms time. is Pesticide of same The the numbers numbers individuals each squeezes of environment. body . limiting factors growth is usually pathogens. Q exponential. Phagocytosis the ingestion of food Quota Predators particles into a animals that hunt and of other Phenotype the physical or of an organism genotype and its for their due to a limited animals that are resource number that can or be quantity taken from food. the hunted environment, e.g. timber and sh. and both killed its animals other Prey features a kill cell. for food by predators. environment. R Producer Phloem the plant tissue an organism that makes that Receptor its transports sugars and amino own organic nutrients, sensitive using Photosynthesis process by energy from sunlight manufacture materials or organs that are stimulus. Recessive an allele that is expressed carbohydrates Progesterone raw a through only from to which photosynthesis. plants cells usually acids. using energy a hormone when there is no dominant allele secreted from of by the ovaries and by the the gene present (e.g. t or g). placenta light. that Phototropism a growth response maintains plant to the direction of of Rectum the during the second half of the intestine the last where part faeces of the are large stored light. menstrual 304 lining of uterus a the cycle and during pregnancy. before passing out through the anus. Glossary Recycle a form to convert that Reex can action response to a be an material useful back to automatic, stimulus into humans. Self-pollination pollen grains the from ower to the ower or different transfer the stigma anther of the Stem of of the leaves, a contains same organ owers xylem that and supports fruits tissue to of a the plant. transport It water rapid which is ower on and the mineral salts and phloem tissue to often same transport plant. sugars and amino acids. protective. Sense Reex arc the arrangement is neurones that controls a reex sensitive (connector) neurone to stimuli, e.g. in the transmits central nervous impulses from motor in dialysis remove the use of a make the body’s cells divide by the kidneys light, cells sound, that specic chemicals. the the ability to the processes same (stimuli) the neurone that reactions, a kind of complex taking impulses brain down series place in all nutrient living Response a neurone from Stoma that receptors to or spinal in the gases cord. chromosomes the pair organism from the to a (plural: to diffuse is sex. that In determine humans, XX reaction enzyme of XY is female the linkage a sex the location chromosome, an of of the sensitive reproduction to hole allows and out. by The guard size of cells. muscular that sac at mixes the food end of with The begins chemical in the digestion of stomach. the X Suspensory ligaments hold in the lens the eye bres in that place the alter its shape when the ciliary process fusion of haploid contract and relax. nuclei cut form a diploid eye zygote and of genetically the dissimilar Sustainable development development that cell is able to so that they conserve that natural resources are cells. Sexually small structure transmitted infection in the future. a where disease that is transmitted through Sustainable resource a resource, made. body sensory that a juice. available are small genes usually offspring. Ribosome a that places. part light ) leaves enzyme production eye a stimulus. to the in oesophagus gastric male. involving the in by an engineering specic of controlled Stomach a is muscles a change food. particular genetic stomata epidermis hole and Rod a detected to Sexual Restriction proteins is of chromosome. contains stimuli) that cells, molecules on Retina (plural: of Sex energy at for organ. protein DNA specialised organism. and break in become make person’s used can environment sense responses. chromosomes Respiration release that daughter functions. Stimulus detect environment the that cells produce fail. Sex of to chemicals the Reproduction more unspecialised mitosis machine waste transmits when Stem neurones. Sensory to that stimulus system and Renal organ sensory changes to touch, and Sensitivity that receptor particular a temperature neurone a a action. or Relay organ of cell in the responds to retina light e.g. of of uids during sexual e.g. activity, as HIV . timber rapidly or as it environment low Sickle cell anaemia an sh, is so which is removed that it produced from does the not run out. inherited intensity. disease Root the organ into the ground and mineral that and anchors absorbs plants water alters and that hairs a of large cells surface water and in a system area mineral alimentary for endoplasmic of red which blood cells membranes ribosomes digestion the are reticulum inside canal and the region that are in the to heat lose neurones absorbs digested food. a by found which secrete evaporation. a substance that dissolves a gap between in is which released the second a two chemical to stimulate an neurone. in a liquid that T dissolves and T est cross a genetic cross used to made. with are Sclerotic the of which tough, Secretion the substances by white keeps release it in of outer layer shape. useful a group similar Sperm of the which interbreeding fertile and sex cell or T estis sex offspring. male an insoluble the genotype (plural: organs gamete. carbohydrate testes, from glucose breeding see articial store in plant molecules. cells An of the an organism. and an human the sperm male cells and produced. the that hormone, stimulates produced the of secondary sexual males the energy in and important development component of made development cells. are T estosterone the testes) where testosterone by Starch out organisms characteristics capable producing of characteristics selection. glands skin solvent. cells attached S Selective the across transmitter nd eye coiled of impulse Species the glands dermis Synapse of completes substances. proteins Sweat sweat anaemia. salts. Solvent where the severe intestine root Solute Rough in haemoglobin, of salts. specialised provide absorption shape results Small Root affecting the of sperm cells. diet. 305 Glossary Tissue a together Tissue cells group to uid when blood of similar perform the uid plasma cells pass the that and out cells same the act bathes some of that function. the white Urinary lters Urine the capillaries. It an a poisonous substance. organ produces excretory kidneys contains excess T oxin system blood, and uid stored excess system and urine. produced in water, surface that stores the in bladder. urea, Virus be toxins as waste nucleic bring disease, about e.g. high the Uterus the womb; a symptoms of a fever . the and amino movement acids in than acid a disease which chamber with the develops. fetus a soft lining in a one pathogen host to can phloem. disease be passed or dead a Vitamin preparation pathogenic stimulate and the water surfaces consist of surrounded coat. They can reproduce cells. small a micronutrient, amounts in the needed diet. is provided evaporation in the If diet not a V Vaccine another. Transpiration cannot which containing disease give the microorganisms production of can result. mild action an action that we to decide from for microscope. they DNA) living Voluntary in that light bacteria, intestine food. of the a the (e.g. protein inside deciency Transmissible small microorganism under enough sucrose the digested muscular in T ranslocation of of Bacteria products only which a seen Smaller and salts. by release area absorption to make. antibodies immunity . of W cells from in water the leaves followed vapour through of by mesophyll diffusion stomata of Vaccination provide a vaccine to Water immunity. water into Vacuole the giving uid-lled sac Water Trophic level the position of sap present in a food chain, food of numbers, biomass For example, herbivores consumers and form a to tube the trophic diffuses potential leading outside. from It water potential. during birth sexual a plant to a stimulus, by e.g. of of higher lower blood of the body’s Lymphocytes differences in cells they form intercourse the defence features release system. antibodies and between that may to combat pathogens. show ingest and kill pathogens. part continuous of area area canal. antitoxins response an an the level. growth to the receives Phagocytes a from water part the individuals Tropism for diffusion. cells. White penis is Variation second plant are and primary most or erect energy. by web, uterus pyramids tendency move an Vagina organism in the to containing atmosphere. cell potential molecules light variation or discontinuous or Wilting loss leaves droop of turgor causes plant variation. gravity. Vasoconstriction Thrombosis a blood clot that a vein or an Withdrawal in arterioles to reduce that through a swollen stem of a potato storage and asexual plant the cell pressure onto its exerted cell wall. by arterioles are rm because through this can they support relaxation that of increases addictive side they effects give up drug. ow are Xerophyte full a plant blood vessel through a plant adapted to dry which of conditions. travels towards the heart. organs Xylem as when capillaries. Ventricle such feels muscles blood T urgid blood water; symptoms person X a Vein cells a reproduction. in Turgor lacking. for Vasodilation food is capillaries. an T uber water blood artery. ow if of occurs muscles in contraction to the lower, more the plant tissue that transports muscular stems. water chamber of the heart. In and right the lungs ventricle salts from roots to mammals, leaves, the mineral pumps blood owers and fruits. to U Umbilical the cord placenta to the the cord connecting fetus. It blood to and the umbilical arteries and rest left of ventricle the pumps body. Y contains Vertebrate two the a an animal with a backbone. Urea a waste product formed amino acids in the liver. ltered out of the blood and in small and passed out in the a tube through which from the kidney to by membrane the made that by cells, Yield crop the or as enzymes or the bladder 306 tube to that the passes outside quantity from a of product fermentation (plural: villi) tiny, nger-like Z bladder. urine at dioxide. neurotransmitters. from the wall of the Zygote a that ethanol structures substances projection Urethra fungus produce urine Villus passes carbon to urine. such Ureter cell sugar from a the contain kidneys single-celled It surrounded is a ferments from Vesicles excess Yeast vein. from intervals. small intestine. Villi increase the a fertilised egg. process. Index aorta A abiotic environment absorption 78, accommodation acid rain desert pond plants asexual the temperature respiration effect on of the rate by using respiring energy uptake seeds of disadvantages reproduction brain 219 in of plants seeds 78, atherosclerosis cleaning control plant hormones (BMI) 106–7 75 261 201 132 breathing 170 synthetic to 82 depth oxygen adapted 107 function index breast-feeding 144 are 107 and breadmaking 108 112–13 154 breathing assimilation of germinating auxin the 184, 185 of 139 investigating and asexual 138 3, vessels vessels mass bolus 240–1 reproduction advantages 164–5 respiration investigating selection body 208 110–11 110, functions structure (AI) 22, cells 106 blood shunt 107 insemination articial 236 93 adrenaline aerobic articial 237 blood their 11 113 cells vessels how 11 100 arterioles 236 adaptations adhesion arteries 34–5 features blood 12–13 spinnerets 192 transport adaptive buds 110, blood white 96 arachnids 280–1 acrosome active apical 163 red 96 stylets 84–5 platelets 103 aphids 254 and the of of exercise air 134–5 133 breathing breathing 135 135 171 expiration 139 (breathing inspiration 138 out) (breathing in) 133 132 B afterbirth vital 201 babies agriculture bronchi breast-feeding agricultural chemicals (Acquired 6, can C cycle 253 calcium HIV/AIDS be in bacterial growth prevented? capillaries basal metabolic rate (BMR) pairing carbohydrates batch culture Benedict’s solution beta-blockers alcohol effects social problems carbon dioxide effect 128, amino acids 223 chemical uid amniotic sac tests for the steroids anaemia 77 angina breadmaking environment cells membrane cell organelles differences birth 200–1 birth control diffusion methods methods implications size methods of cells cellulases 119, 218–19 specimens cells 21 22–3 262 146 201 cellulose blood mitosis 41 239 112–13, of and 207 specialised solution bladder 39, 18 309 240–1 surgical 39, cells signicance biuret resistance 30–1 30–1 206–7 175 antibodies and 207 9 social antitoxins methods plant natural antibiotics plant 18–19 28–9 cell osmosis (warm-blooded) breeding between cells 206 18–19 chemical selective 30 206 model animals 6, 20–1 8–9 animal homeothermic 34–5 18 254 141 barrier antigens transport cell 4 cells 281 262–3 140 6 animal converters 261 108 animals 36 46 260 and 234–5 birds 35 34, 18 active biotic anatomy 32, 262 cells enzymes 140, 180 108 proteins animal acid release 247 biofuels anaemia dioxide washing 179 respiration rate 262 262 biotechnology lactic arrest catalytic 84, the biological 8 anabolic cell of non-biological powder sickle monoxide cardiac catalysts biomass anaerobic powders action 159 82, carbon carbon catalase and 79, on 61 41 carrier washing comparing amylase C 198 biological amphibians dioxide 40–1 vitamin 198 amphetamines carbon photosynthesis 38–9 58 testing amniotic and 130 121 molecules 131 39, air 261 biological alveoli of measuring biofuels alleles 144 267 226–7 recessive 63, inspired 261 of and 57, in 184 179 biodiversity dominant 56, dioxide expired ssion 222–3 codominance 200 250–1 84 179 biodiesel anus cycle carbon binary alleles carbon 159 178 bile long-term 114–15 72, 40 178 of 38, 264–5 145 biology capillaries 42–3 234 addiction 100 70 lymph base alcohol 200 255 211 albinism 128 250 210 phases how 135 bronchioles 201 Immunodeciency nitrogen Syndrome) and 275 bacteria AIDS capacity 200 270–1 110, 23, 38, 58 119 120 centipedes blood circulation blood clotting 120 central nervous system (CNS) 154 113 86 cervix oxygenated 10 100–1 blood 100, 194 110–11 307 Index chlorophyll 12, chloroplasts cholera on the symptomless meiosis 87 86 108 disease 180–1 circulatory single 22 system circulation circulation binomial 101 system 4–5 286 diploid 93 disease 169 colon activity blindness competition 228–9 244–5, liquid a 238–9, DNA 6, 71, 109 role digestion number 118, 214, 3, of eye diseases against disease diseases 118–21 276 144 liver 144 145 and exercise 134–5 10 286 160–1 of focusing 124–5 lactose-free 40 control 122–3 making 105 extracts 255 in products the extinctions 78 46 144 exoskeletons 220 47 129 breathing 78–9 protein 263 41 exercise 29 of juice 263 excretory 28–9 50–1 work lactase excretion 29 solvent transmissible 255 us? 262 47 48–9 eutrophication 70–1 for diffusion digestion defences 254 of milk 78 control communities bad effect autoimmune 86 colour as fruit assimilation mechanical 226–7 use 206 14–15 pH powders complex made enzymes epiglottis be that digestion 226 alleles control) 28 versus water 278–9, and are temperature 13 fat 47 washing enzymes how 123 keys and chemical codominance cohesion can factors 194 multiple sex why gas change 1) 74 216 enzymes ethanol diffusion 4 DNA 70 age, site extracting (birth 100 see 176 diaphragm 100 100 acid 128 100 circulation 78, biological blood (Type 7, 244 output enzyme-substrate diaphragm diet active 252 48 dicotyledons classication climate 273 dichotomous cells double 244, deforestation diabetes pulmonary 133 blood decomposers depressants transfer and enzymes 145 deoxyribonucleic 214 intake 218 deoxygenated 73, 83 22, cells denaturation 220–1 ciliated cold daughter 86 therapy obstructive (COPD) clitoris 64 86 71, chromosomes cilia body carriers transmission cholesterol chyme 54, deamination rehydration chronic energy D 23, 86 effects oral 56 12, rods the pupil reex 162 162 and cones 162–3 118 214 F concentration gradients 28, 30, 130 base pairing 42–3 faeces conservation 288–9 genetic code 86 216–17 farming reasons for conservation 289 sequence of bases fats constipation 75 structure 270–1 216 39, 71, testing consumers 244 double helix 206–7 drugs 145, for acids implications 309 41 39 174 feedback social fats 42 fatty contraception 72 42 addiction 174, 166 176 fermenters coordinators 155 excitatory and misuse drugs inhibitory drugs 159 batch cornea 160 coronary arteries angioplasty 108 of recreational 109 duodenum in drugs 83, sport culture 264–5 179 industrial fermentation industrial production 265 174 of penicillin 84 264 coronary artery bypass operation ferns 12 108 E coronary heart disease (CHD) fertilisation ecosystems risk factors for CHD 108–9, 154, 78, nerves 157 86, implantation 145 cells 23, seed 185, 192, 194 197, formation fertilisers 195 fertility 190 203 191 66, 270, 276 treatments 208–9 266 electrocardiograms advantages and disadvantages crops monocultures 185 208 implications bre, dietary brin and 73, 309 75 270 84 brinogen 113 10 endocrine system 164 sh 8 10 comparing cephalothorax the compound endocrine and shing 283 10 nervous eyes systems 165 accidity 33 10 endorphins gills drugs social 181 emulsication antennae 104 267 emphysema crustaceans (ECGs) of embryos genetically-modied 176 owers 12–13, 186 10 energy cytoplasm 36, 70 insect-pollinated owers 186 6 communities 308 188, 196 154 ejaculation crops 186, fertilisation 13 egg cranial human 109 egestion cotyledons 254 181 effectors treatment 185, 108 244–5 energy losses energy pyramids 248–9 248 wind-pollinated ue gas owers desulfurisation focusing 162 187 281 Index accommodation follicles gravitropism 163 203 follicle stimulating hormone (FSH) food chains food preparation food production social, 245, food fruit food webs fruits cells passive 278 218, economic in 65 vitro 197, habitat destruction 272, human on food 119 2, 78 214, and webs and alleles need to 7, conserve 102, coronary heart disease linkage (CHD) fuels (ECGs) cell 11, heart action 11 103 7, heart and heart sounds exercise 11 105 insulin 184 166–7 104 industrial 184 septum muscles intestines 102, bladder 84–5, heat 84 hepatic 184–5 portal vein and female gametes 192–3 herbicides 266, exchange heroin 29 159, out carbon dioxide social 130 problems 77, 200 (intra-uterine exchange at gas exchange surfaces plants the alveolus 131 heterozygous HIV 130–1 structure of the gas exchange how genes juices 42, gene what genetic 109, and is a gene? 222–3 215 engineering 266, vitamins in plants advantages and disadvantages genetically-modied herbicide resistance insect genetics in crops crop medicines resistance code variation genotypes in of crop insulin plants 267 period glucagon glycerol of blood 38, 166–7 growth human 256–7 population 257 destruction 167 272–3 287 lactic 85 acid 241 larynx 236 253, a 56, 64–5 65 57, lightning lipase immunity leaf 63, 95 photosynthesis 84 response 276 64 stomata light 124 141 86 128 inside 83 140, intestine leaves hydrophytes active 6–7 76 263 leaching vigour immune 36 4, 200 lacteals large 95 acid ileum 148 149 L labour I glucose 2, kwashiorkor 60, 58 39 glycogen water 202–5 hydrochloric hygiene 63 the 167 38, control 198 production in 164 population hunting hybrid glasshouse kingdoms 166 147 147, 151 energy lactase habitat 191 transplants kinetic 223 7 humidity 232 4 gestation organs controlling 216–17 tubules reabsorption 166 hormones 148 kidneys 277 growth 223 germination 164–5, 148 the kidney 166–7 166 organisms hormones human 266 glucose feedback supply sex 214 genetic glucose conditions hosts 266 production genetic genus controlling 267 plants 150–1 glomerulus 211 inside blood contraceptive of 146 dialysis 135 controlling target 184, kidneys prevented? transmitted? homozygous 266 industrial be ltration HIV hormones 266 human is negative 270 crop IUS virus) 211 HIV/AIDS homeostasis 234 alleles additional tracing can how 216 mutations genes immunodeciency 211 83 and 206 223 K contact system 128–9 gastric (human organisms 210 67 device) system) 177 (intra-uterine gas 155 176–7 IUD breathing actions 40 270 iron gas 86 10–11 85 iodine male 267 169 involuntary 3, insulin 103 invertebrates gametes of 128 102 ventricles G production 102 intercostal valves 234–5 266 104 cuticle 282 228–9 anaemia 108–9 insects electrocardiograms fossil 233 224–5 103 spiracles 7, mycelium (atrium) sickle 281 environment inheritance 102–3 sex atria 250 hyphae gall versus 220 monohybrid 261 222–3 77 inheritance 261 226–7 272–3 22, number 100, 222 chains genes fuels 208–9 273 inuences haemoglobin haploid sulfur (IVF) 124 codominance heart low 201 241 inheritance 271 fuel 122, 286 ingestion deforestation 272–3 neutral system 203 fertilisation barriers 271 fuels carbon immune H and 263 biofuels the immunity implantation 219 infections 270–1 supply 245, 70, inbreeding 191 fungi gases 3, of 122–3 278–9 124 environmental juice greenhouse guard 272–3 implications world effect growth 204 malfunction 170 greenhouse 120–1 121 liver 84, 84, and light intensity 62 253 262 145 cirrhosis 179 309 Index lungs 103, lung 128–9 cancer luteinising lymphatic lymph nodes lymph vessels lymphocytes HIV and lysozyme natural hormone system ovules N 181 (LH) 204 competition 114–15 115 119 lymphocytes selection 241 variation cells medicine meiosis between meiosis 219 70 rate (BMR) 70 73 138, between meiosis of mitosis and 157 bacteria production pepsin resources 282 limbs nervous cycle 244, cycle 2, variation phloem 2, needs nutrients 74–5 72–3 limiting oxygen stem cells of monocultures monohybrid of ratio) parental test cross mucus causes gene sickle swallowing 82 respiration 140–1 2–3, mutations cell 234 anaemia 156 10 234 234–5 plant 204 rate 6–7, systems orgasm 24 rate 58 54–5 62 and light intensity and temperature organs 25 65, animal cells 33 osmosis in potato cells 32 plants in outbreeding (ovum) effects gas 194 of 199, 203 201 and monocotyledons nutrients of on owering growth plants 12 exchange inheritance mineral 194 4 202 12 hydrophytes 241 192, gland 198, 67 13 ferns 77 194, 6, 60–1 170–1 (phyla) pituitary features 33 32 osteomalacia ovulation respiration dicotyledons 31 in ovaries 56–7 plants 92 58–9 photosynthesis requirements placenta 30–1, osmosis ova 62 products of phylum 24 and 195 turgidity mutations the 59 phototropism plasmolysis 234 202, 261 tissues osmosis 163 of myriapods 194, osmometers 162, on 61 62 61, 24 organ 2 anaerobic dioxide photosynthesis photosynthesis 109 82 58 organs 4 and 75, rape organisms 224 24 mutations seed oils 82 muscles oil plant movement 310 (3:1 82 chewing myelin oestrogen 224 generation 225 morphology eye F1 74, oesophagus 224 cross mouth obesity 13 inheritance 96 54 photosynthesis factors 58, 60, O 270 the 38, 218–19 219 monocotyledons crossing mitosis transport 23, carbon photosynthesis signicance 119 232 photosynthesis investigating energy 112, 90–1 and of 119 31, 223 importance 251 154 30 112, 12, of 252–3 70–1 of 28, phenotypic effect 250–1 cycle (PNS) 270 photosynthesis 250 system 82 phenotypes aphids 42 4–5 50–1 phloem 42 264–5 83 phagocytosis 253 201 28 118 phagocytes 253 122, 263 pentadactyl pH 253 25 192 pesticides 252 cycling sources movement peripheral xing-bacteria balancing 218 156, 157 158 bacteria nutrition 221 mitosis 156, nitrifying water 218 immunity penis 23, 84 passive permeability nitrogen 193 neurones 253 carbon 65 20, duct passive penicillin 158 158 cells 166 7 pectinases 157 neurones lightning nutrient 84, peristalsis acids photosynthesis 111 mesophyll pathogens 156, neurones nucleotides 10 nutrients process actions 66 nucleic in P parasites voluntary neurones cycle 141 oxyhaemoglobin pancreatic and 165 156 non-renewable 149 differences 154, nitrogen 260–1 190 mitochondria mitosis and denitrifying 38, metabolic minerals 238 180 nitrogen microorganisms millipedes nitrates 203–5 25 3, 89, endocrine (connector) nicotine 202 cycle 23, microvilli 238 pancreas systems neurotransmitters 77, mesophyll metabolism populations neurones sensory 203 meristems micropyles the presynaptic 121 menstruation menstrual offspring 154 postsynaptic and relay cells menopause plant mitosis 221 234 memory basal motor 220–1 differences melanin neurones produced 59 155 266 debt oxygen palisade system involuntary 109, 58 oxygen 239 within nervous 76 218, of and 22 comparing 66 9 238–9 natural nerve M marasmus resources 185 oxygen 239 articial reproduction 210 238, between nervous mammals for over-population 115, 160 magnesium 189, differences 115 112, selection 223, salts nitrogen in plants 67 236 224–5 65 cycle 252–3 66 12–13 Index pyramids of biomass 67 pyramids of energy 18–19 pyramids of numbers photosynthesis plants plant cells plant products plant tissues selective systems plasma rectum reexes 90–1 roots plastics 6, artery renal vein pollen tubes pollination insect pollen tubes female 190 male 190 13, 186, pollination self-pollination 186, and 189 wind pollination pollution land 274, pollutants pollution size products care 200 photosynthesis prokaryotes protein 39, enzymes testing puberty 58, 72, (PEM) 76 stem seeds eye 202 in boys girls reticulum (ER) 20 tubers stimulants artery investigating 103 the effect 105 160 161, sphincter 162 83 sulfur of exercise for germination 3, valves 100 determination sex hormones sex inheritance linkage sex organs 124–5, 276, 284 228 and characteristics 195 closing 202 65 238 47 58 for reducing dioxide to sugars 40 280–1 resources conserve 282 fossil fuels development 282 283 sustainable shing 283 sustainable timber production effect 156, transmitter of drugs of on the substance 159 synapse synaptic transmission bulbs 156 synaptic gap 158 158 158–9 158 postsynaptic presynaptic 282 158 synaptic synaptic sexual intercourse 91 65 structure 228 stem 157 transmission 228 202–5 184 secondary and 180 chemical 3 treatment 76–7 83 synapses 160–1 55 58 need 160 structure sex root sustainable organs 40, 207 154, sustainable 191 270 192 sex sexual 240–1, 56 starch 184 the testing 77 breeding 184 12 sugars 192 286–7 193 needs stem sucrose 109 species 219 substrates 71, of 193 76 cells struggle 82 191 sewage 105 glands survival 185, 154 for opening 262 279 287 58 sterilisation 7 fats 76, sensitivity 202 202 56, salivary semi-lunar 41 sense in 41, and semen 216–17 protein reex 38, inside 92 253 180–1 29 154 stem stems 91 180 184 stimuli conditions 200 7 pulmonary nerves stomata selective puberty pupil 216 275 40, scurvy malnutrition puberty pyloric 22, and endoplasmic scrotum 192 262 47 for rate hairs nodules saprotrophs 204 synthesis protocists root root saturated gland protein the root saliva 58–9 194, energy proteins (mRNA) 13 safety 6 51, spinal starvation S progesterone duct testing RNA the 23, cord stomach 58 to species species de-starching 207 20 smoke smoking 232 sporangia 157 by solutions spinal spores 138–41 169 96–7 4, cells starch 6, and sperm 184–5 244 47 protease 154, tobacco caused nutrient rubbish 208–9 3, 77 rough 206–7 treatments by-products prostate 3, of endangered sperm 195 282–3 67, method inside 198–9 200–1 producers 2–3, species temperature 84 84–5 introduced 9 roots 255 fertility 238–9, messenger contraception pupil RNA 254–5 192–3 160 rickets 95 ante-natal pulse 256–7 194–5 8 ribosomes growth solvents threats reproduction rhythm 276–7 system 198–9 sexual retina 254 population pregnancy 185, 239 intercourse respiration 275 population potometers selection responses water predation 184, system sexual resources 274 plastics populations reproductive reptiles 188–9 275 waste birth 187, 286–7 pollution human 3, sources reproductive pregnancy 188 cross-pollination body 109 diseases reproduction natural 188 of intestine biology 184 234–5 168 smoking 219 185 anaemia absorption 157 146 146 asexual (STIs) 96–7 control 3, 184–5 infections 12–13 cell small arcs renal 275 growing skin 285 reproduction 260 sinks 157 155 reex 92–3 237 154, 3, transmitted 210–11 246 86 recycling 110 plasmids pollen by reproduction sexually sickle receptors 240–1 94–5 uptake sexual 247 248 R 25 96–7 transpiration xerophytes in shoots organs breeding transport respiration 58–9 and translocation water and membrane membrane 158 158 311 Index trypsin T tar teeth 80 healthy tooth teeth decay temperature control effect of on and body 169 and 48, temperature 193, tissues uid and organs translocation 96–7 146, water 194 system transpiration transpiration 95 translocation transpiration pull 93 transpiration stream systems 90 100–1 124 and 63, non- materials 275 72 146 121, 96–7 23 3, 185, types of contraceptive veins 170 170–1 versus within environment populations hormones potential water uptake weight loss wilting 32, and seas in 30, 92–3, 171 74 94 233 X 238 xerophytes 12, 237 22, 90–1 169 yellow veins 103, 20 villi 89 8–9 203 115 115 Z zidovudine 107 column body 10 zygotes (AZT) 185, 276–7 92 plants Y vesicles 35, rivers 251 water xylem 207 subclavian vertebral 233 230 64 cava 232–3 variation 100 leaves vertebrates 170 variation of cycle weedkillers 189 variation vasectomy venules 244 of vasodilation 93 water 125 194 discontinuous vena 90 90–1 phototropism 56, pollution variation 95 and gravitropism 29, effects inheritance 94 levels 155 biodegradable continuous and affecting ow disposal biodegradable 145 194 vagina transpiration 312 waste 71 146 vacuoles 25 96 measuring tropisms 144, variation transpiration actions 194 W 198 fats V 282 114 transpiration 76 77 277 128 translocation trophic cord vaccination animals voluntary 32 108 production plants urea uterus 24 mass pressure 266 41, U urinary 202 tissues transport D urethra timber factors vitamin ureter 62 thrombosis trachea 32 unsaturated 61 128 tissue turgidity umbilical 48–9 temperature testosterone plant C vulva 193 thorax vitamin 139 temperature 175 73, 181 turgor 95, photosynthesis testes 80–1 7, vitamins 184 tumours 81 63, enzymes optimum 61, gums viruses 84 tubers 180 211 186, 193, 197 95 Essential Biology ® for Cambridge Gareth Lawrie Ryan Biology syllabus, misconceptions. concepts, ● ● Fully it will to clear for the – skills next directly learning language EAL exams IGCSE key and students’ stage focused – clear and subject study and language latest of extend support the Cambridge common coverage language coverage tips the clarifying comprehensive comprehensive – matches points of key errors IGCSE and scientic knowledge. course performance eases the transition to study Empowering Complete ever y Reviewed learner Cambridge Comprehensive by Embedded exam subject critical Progression 978 Cambridge support advanced Progress 16-18 for emphasising With prepare Develop Also edition Fosbery Essential ● 2nd Williams Richard Biology IGCSE to the to succeed syllabus and progress match preparation specialists thinking next skills educational stage available: 0 19 837 467 1 IS B N 9 9 7 8 -0 -1 9 -8 3 9 9 2 0 -9 7 8 0 1 9 8 3 9 9 2 0 9
