Characteristics of living organisms *MRS GREN* Movement - change in place of an organism or part of it Respiration - chemical reactions that break down nutrients to release energy for metabolism Sensitivity - ability to detect and respond to stimuli in the external or internal environment Growth - permanent increase in size and dry mass by an increase in cell number, cell size, or both Reproduction - process that makes more of the same kind of organism Excretion - removal of waste products, toxic materials and substances in excess of requirement from the body *Egestion: expulsion of food waste that can not be digested Nutrition - intake of materials for energy, growth and development. (Plants: light, CO2, H2O, ions/ Animals: organic compounds, ions ,H2O) Features of organisms Kingdoms: -Animals -vertebrate - sh: scales, ns, eggs in water, eyes -amphibians: moist skin, four limbs, eggs in water, eyes & ears -reptiles: dry skin & scales, four legs(except snakes), shelled eggs on land, eyes & ears -birds: feathers, wings & 2 legs, eggs with hard shell, eyes & ears -mammals: fur, four limbs, live young, eyes & ears -arthropods -insects: 3 pair of legs, head + thorax + abdomen, pair of compound eyes, one pair of antennae -arachnids蛛形纲: 4 pairs of legs, cephalothorax + abdomen, several pairs of simple eyes -crustaceans甲壳纲: 5+ pairs of legs, cephalothorax + abdomen, 2 pairs of antennae, compound eyes -myriapods多⾜纲: 10+ pairs of legs, no obvious body division, 1 pair of antennae, simple eyes -Plants -ferns: water required for fertilisation, pollen/ owers/fruits/seeds absent - owering plants: pollen & owers/fruits present, seeds in fruit, no water required for fertilisation -Fungi -Protoctists -Bacteria Prokaryote: no nucleus - bacteria Eukaryote: protoctist, fungi, plant & animal -Viruses: very small, only characteristic of life is reproduction -unusual cell structure: DNA/RNA strand, capsid, spikes Cell structure & organization fl fl fi fi fl -Nucleus: control centre (cell activity & cell growth), contains DNA (in form of chromosome) -Cytoplasm: jelly like substance containing organelles and particles -Cell membrane: partially permeable membrane, controls what enter and leave the cell -Ribosome: site of protein synthesis -Cell wall: tough layer made of cellular, prevents cell from bursting -Chloroplast: contains chlorophyll - trap light for photosynthesis -Vacuole: uid- lled space surrounded by a membrane -Mitochondria: respiration takes place Diffusion, osmosis & active transport Di usion: net movement of particles from a region of higher concentration to a lower concentration down a concentration gradient Osmosis: net movement of particles from a region of higher water potential to a lower water potential down a potential gradient, across a partially permeable membrane Active transport: the use of energy to transport particle from a region of low conc to a high conc against the conc gradient *carrier protein change shape, active site Biological molecules -Carbohydrates -C H O -source of energy -simplest from: monosaccharides eg. Glucose -> disaccharide -> polysaccharide eg. Starch, glycogen, cellulose (all made from glucose) -Fats/lipids -C H O -source of energy (twice as much as carbs), insulation, cell membrane -1 unit glycerol + 3 chains of fatty acids -Proteins -C H O N -growth & repair, enzymes, hormones, cell membranes, also for energy -made by long chains of amino acids Food testing (-positive result) Starch: iodine test - blue/black colour Reducing sugar: Benedict’s test(equal volume, water bath) - blue to green/yellow/orange/red, depend on amount of reducing sugar Protein: Biuret test(equal volume o NaOH, few drops of CuSO4, do not shake) - blue to purple Fat: emulsion test(dissolve food in ethanol, pour the solution into a clean test tube of water) white emulsion Vitamin C: DCPIP test(add drops of testing solution into a test tube of 1% DCPIP, mix gently after every drop) - blue to colourless -DNA -Double stranded helix -strands connected by pairs of bases -four types of bases: A-T C-G Adenine, Guanine, Thymine, Cytosine Enzymes -proteins that act as biological catalysts. -increase rare or chemical reaction without being changed -essential to keep chemical reactions in our bodies fast enough for survival Active site + substrate —> enzyme-substrate complex —> products fi fl ff ff E ect of temperature and pH Temperature: optimum temperature(usually 40℃). *denaturation when temperature too high at low temperatures activity is low due to the low energies particles have pH: optimum pH (usually 7). *denaturation at high/low pH chemical bonds inside the enzyme become broken Photosynthesis 6CO2 + 6H2O → C6H12O6 + 6O2 Carbon dioxide + water ➝ glucose + oxygen Condition: chlorophyll, sunlight, carbon dioxide Test whether photosynthesis occur: 1. Boil a leaf in water 2. Boil the leaf in ethanal 3. Rinse with water 4. Add iodine *destarch: place plant in dark place Human diet Balanced diet de nition: a diet that contains all the essential nutrients in the correct proportions to maintain good health Nutrients are: carbs, fats, proteins, vitamins (C&D), mineral salts (Fe & Ca), bre and water Malnutrition Too much food - obesity Too little food - starvation Too much animal fat - heart attack and coronary heart disease Lack of bre - constipation Imbalance of nutrients (lack of protein) - kwashiorkor De ciencies VC - scurvy VD - rickets Calcium - rickets and slow blood clotting Iron - anaemia Fibre - constipation Water - dehydration Scurvy: causes pain in joints and muscles, bleeding from gums Rickets: bones become soft and deformed, common in young children in industrial areas Digestion Mechanical digestion: physically breaking the food into smaller pieces Chemical: breaking down food into simpler nutrients (simpler molecules) that can be absorbed and used by the cells Teeth Incisor⻔⽛ - to bite o pieces of food Canine⽝⻮ - to bite o pieces of food Premolar - tear and grind food Molar⾅⻮ - chewing and grinding food Dental decay: Bacteria present on surface of teeth, form a layer called plaque with food deposits. Bacteria in the plaque feed on sugars which produces acid, the acid dissolves the enamel causing a hole to form. If the hole reached the pulp the bacteria can reach the nerves which result in a toothache. fi ff ff fi fi fi Proper care: Avoid sugary food, regular cleaning, oss, visit the dentist regularly Enzymes involving in chemical digestion Amylase: starch to maltose in mouth & duodenum, optimum condition slightly alkaline. Maltose broken down into glucose by maltase Protease: protein to amino acid in stomach(pepsin) & duodenum (trypsin), optimum condition acid in stomach & alkaline in duodenum Lipase: fat to fatty acids + glycerol in duodenum, optimum condition alkaline *acid pH in stomach maintained by HCl acid, which also kills bacteria by denaturing their enzymes Alkaline condition maintained by pancreatic juice and bile Bile also has the function of emulsifying fats into droplets to increase the surface area for chemical digestion Digestive system = alimentary canal + digestive organs Functions: Mouth - mechanical digestion Oesophagus - carries food and liquids from the mouth to the stomach Stomach - digestion of protein + HCl acid Liver - produce bile Gall bladder - stores bile Pancreas - produces digestive uids and enzymes. Regulates blood sugar Smaller intestine - digests and absorbs soluble food Large intestine - absorbs water from undigested food and produces faeces Adaptations for exchange 1. Good blood supply 2. Large surface area 3. Thin membranes of villi Absorption Small intestine: -Absorption of digested nutrients -Absorption of water Large intestine/colon: Absorption of water Villi -increases the surface area of absorption Blood capillary: absorbs glucose and amino acids via di usion Lacteal: absorbs fatty acids and glycerol Epithelial lining: one cell thick to increase di usion rate, with microvilli to increase surface area even further Transport in plants ff ff fl fl Xylem: transports water and solutes from roots to leaves Phloem: transports nutrients from the leaves to the rest of the plant Water uptake: root hair cells increase the surface area for absorption *root structure: epidermis/cortex/endodermis/phloem & xylem Zone of cell di erentiation/elongation/division + root cap Transpiration: loss of water vapour from the plant leaves, by evaporation of water at the surfaces of the mesophyll cells + di usion of water vapour through the stomata Movement of water through a plant -water molecules attracted to each other (cohesion) -water molecules attracted to the walls of the stem (adhesion) -adhesion > cohesion -this causes water to “crawl” up narrow tubes. Narrower the tube higher the water can go —capillary action Translocation: movement of sucrose and amino acids, source to sink *source and sink not always xed Transport in animals Single circulation: sh Heart was only passed once in a full circulation of blood Double circulation:Blood travels through the heart twice -helps to maintain the blood pressure, making the circulation e cient Structure of the heart -arteries take blood away from the heart and veins take blood towards the heart -valves prevent blood owing back into the previous chamber (only allows one way blood ow) -muscles of left side thicker than right: blood must be pumped to the entire body via the left side (higher pressure required) Pulmonary - to the lungs Renal - kidneys Atriumventricular valves - between atrium and ventricle Aortic & pulmonary valves - ventricles to arteries Vena cava - “main” veins Aorta - “main” artery E ect of physical activities on heart rate / pulse rate -when exercising more nutrients required by the body and more waste products required to be get rid of -heart rate will increase since blood needs to circulate faster fi fl ff fl fi ff ffi ff Coronary heart disease -heart must contract in order to pump blood so the heart itself needs blood supply -the artery that supplies it with blood: the coronary artery -if the coronary artery gets blocked the heart will no longer have a blood supply therefore fail to pump blood around the body —“coronary hear disease” which can results in heart attack Coronary heart disease risk factors: 1. Diet with too much saturated fat - cholesterol胆固醇 build up in arteries and eventually block it 2. Smoking - nicotine damages the heart and blood vessels 3. Stress 4. Obesity 5. Lack of exercise 6. Inherited factors Blood vessels Structures of blood vessels -Artery: thick elastic wall, narrow lumen, valves absent -Veins: thin walls with little muscle or elastic bres, large lumen, valves present -Capillary: one cell thick, lumen is the size of an RBC Functions -Artery: carries blood at high pressure & maintenance of high pressure -Veins: low pressure -Capillary: allows for di usion and nutrient/waste exchange, blood pass through slowly slowing e cient di usion Sequence of blood vessels: Veins - heart - arteries - arterioles - capillaries - venules - veins - … *shunt vessels: connect an artery directly to a vein, can control blood ow via constriction/dilation (so do arterioles) Blood Composition -plasma: liquid that transports substances(amino acids, carbon dioxide etc. + blood cells and platelets) -RBC: contains haemoglobin which binds to oxygen, involved in the transport of oxygen around the boy -WBC: -lymphocytes: involved in production of antibodies *on diagram: large nucleus -phagocytes: involved in phagocytosis *lobes of nucleus -platelets: involved in formation of blood cots How do blood clots form? 1. Platelets immediately stick to the site of damage 2. Chemical signals are released from the platelets to attract nearby cells and clump them together 3. A series of reactions happen (the coagulation cascade), including the conversion of brinogen -> brin 4. This forms threads which trap red blood cells and create a clot Disease and immunity De nitions Pathogens: any organisms that cause diseases Transmissible diseases: diseases in which pathogens can move from one host to another (though direct/indirect contact) fi fl fi ff ff fi fi ffi Defence mechanisms of the body -mechanical barriers: skin & nose hair -chemical barriers: mucus & stomach acid -cells: phagocytosis & antibody production Antibody production Antigens on pathogens binds to speci c receptor, activating the lymphocyte to produce antibodies. Antibodies attach onto their respective pathogen antigens (Clump pathogens together to prepare for phagocytosis) Phagocytosis The process by which a cell engulfs a solid particle to from an internal vesicle known as phagosome Controlling the spread of disease -personal hygiene / washing hands -to prevent direct / indirect transmission of diseases -Sewage -can pollute drinking water -Waste disposal -waste that is not properly managed can attract rats, ies and other creatures which in turn can spread disease. Active immunity The immunity resulting from the production of antibodies in the presence of an antigen. Antigens can be exposed to the body via an infection or a vaccination Vaccination -Harmless pathogen given to the body with speci c antigens on its surface -immune response triggered as lymphocytes produce antibodies -memory cells are produced to give long-term immunity Passive immunity -short term immunity resulting from the introduction of antibodies from another person or animal(for example mother to infant) -memory cells do not get produced in passive immunity type 1 diabetes -pancreas cannot make insulin (which is needed to control blood sugar levels) -the immune system attacks the cells that make insulin -some diseases like diabetes, our immune system attacks our own cells: auto immune disease Gas exchange in humans Structure of lungs Ribs: bone structure, protects internal organs (eg. Lungs) Intercostal muscle: muscles between ribs, movement cause in&exhalation *internal&external Diaphragm: at the bottom of the thorax, help change the volume of thorax (in&exhalation) Trachea: windpipe, connects mouth and nose to lungs Larynx/voice box: when air passes across able to make sounds Bronchi(pl.bronchus): tubes branching o the trachea (one bronchi for each lung) Bronchioles: connected to alveoli Alveoli: tiny air sacs where gas exchange takes place Cartilage: support the airways and keep them open during breathing (otherwise collapse inwards when air pressure drops) fl fi ff fi Cilia and mucus -ciliated epithelial上⽪的 cells -cilia: tiny hairs, beat and push mucus up the passages towards the nose and throat (where it can be removed) -mucus made by mucus-producing cells called goblet cells -mucus traps particles, pathogens like bacteria or viruses, dust, prevents them getting into the lungs (and damaging the cells there) **function of cilia and mucus [3’] 1.mucus traps bacteria, dust, particles 2.the cilia beat 3. And push the mucus away from the lungs towards the throat Ventilation of the lungs Diaphragm: responsible for controlling ventilation in the lungs External and internal intercostal muscles work as antagonistic (di erent directions to each other) Inhalation/inspiration: External intercostal muscles contract rib cage moves up and out Diaphragm contract Volume increase, pressure decrease, air goes into the lungs Exhalation/expiration: External intercostal Muscles relax rib cage moves down and in Diaphragm relax Volume decrease, pressure increase, air forced out of the lungs Inhaled & exhaled air Atmospheric air contains 20-21% oxygen, breathing out air around 16% oxygen Atmospheric air 0.04% carbon dioxide, breathing out air 4% carbon dioxide Breath out more water vapour(from moist lining of the alveoli), temperature higher. *nitrogen 78%: very stable, cannot be used by body E ect of exercise on breathing -increase frequency and depth of breathing -investigate by counting breaths taken in one minute at rest and measuring average chest expansion over 5 breaths -result: number increase, extension increase Explanation: -Muscle working harder and aerobically respiring more so more oxygen required (and CO2 removed) -If cannot meet energy demand: anaerobic respiration, producing lactic acid -After exercise nishes, lactic acid needs to be removed as it lowers the pH of cells and can denature enzymes catalysing cell reactions -Remove by combining with oxygen (“repaying the oxygen debt”) -longer it takes after exercise for the breathing rate and back return to normal, more lactic acid produced during exercise and greater oxygen debt that needs to be repaid Carbon dioxide and brain -Acidic gas, a ect the working of enzymes in the cells -blood ow through the brain, increase in carbon dioxide concentration stimulates receptor cells -these send impulses to the muscle of the lungs, causing them to contract faster and more strongly -frequency and depth of breathing to increase until CO2 conc. has lowered su ciently. Respiration ffi fi ff fi ff fl ff A chemical process that involves the breakdown of nutrient molecules (speci cally glucose) in order to release the energy stored within the bonds of these molecules. -occurs in all living cells, most of chemical reaction in aerobic res. takes place in mitochondria -controlled by enzymes Gas exchange surface(adaptations for good gas exchange): 1. Large surface area 2. Thin surface 3. Good blood supply 4. Good ventilation Use of energy -contract muscle -synthesis proteins -cell division -grow -enable active transport -allow nerve impulse to be generated -maintain a constant body temperature Aerobic respiration -Chemical reactions in cells that use oxygen to break down nutrient molecules to release energy -complete breakdown of glucose -Takes part in mitochondria Glucose + oxygen → carbon dioxide + water C6H12O6 + O2 → CO2 + H2O Anaerobic respiration -incomplete breakdown of glucose (relatively small amount) Respiration is an enzyme controlled reaction: unlikely to work faster beyond around 40 degree Celsius Anaerobic res. in animals Glucose → lactic acid + energy C6H12O6 → C3H6O3 Lactic acid lowers the pH of the cells, which could denature the enzymes in cells -cells excrete lactic acid into blood -blood pass through liver -lactic acid taken up into liver cells, and oxidised, producing carbon dioxide and water (lactic acid reacts with oxygen: aerobic res. with lactic acid) Anaerobic res. in yeast -used in bread making and brewing酿酒 Glucose → alcohol C2H5OH + carbon dioxide Excretion The removal of waste products(of metabolic reactions), toxic materials and substances in excess of requirements Organs involved in excretion -Lungs: carbon dioxide, a waste product of aerobic respiration -Kidneys: excess water, salts and urea, which are formed in liver from excess amino acid by producing urine Role of liver -Assimilation of amino acids (important for making proteins) -deamination: break down nitrogen containing parts of excess amino acids, which turns into urea which is excreted by the kidneys The urinary system -urea excreted as urine (mineral salts & urea dissolved in water) *urine conc. depend on temperature, exercise and water intake Kidney structure kidney: lter the blood ureter: tube connecting the kidney to the bladder Bladder: stores urine (excess water, salts and urea) Urethra: tube that connects the bladder to the exterior where urine is released Nephron 1. Ultra ltration -smaller molecules being carried in the blood forced out of the capillaries into the Bowman’s capsule -glucose, water, urea, salts 2. Selective reabsorption -glucose at proximal convoluted tubule, by active transport (*nephron adaptation: many mitochondria) -water & salts at Loop of Henle by osmosis and di usion -water also reabsorbed at collecting duct Treatment to kidney failure: 1. Dialysis*usual treatment Dialysis uid contains glucose and salt with concentration similar to a normal level in blood, no urea 2. Transplant Transplant vs dialysis Transplant are better long term solution, disadvantages are: 1. Immune response 2. Not enough donor Dialysis disadvantages: 1. Less freedom (dialysis takes 3-4hrs each time) 2. Diets restrictive 3. Dialysis machines expensive *Kidney transplant is a long term solution, dialysis only work for a limited time Coordination and response Nervous system Central nervous system (CNS): brain+ spinal cord Peripheral nervous system (PNS): all of the nerves in the body -allows us to make sense of surroundings & respond Nerve impulse: chemical signal that pass along nerve cells(neurones) Nerve: a bundle of neurones Types of neurones Sensory sense organs ————— CNS Relay(inside CNS) connect Motor CNS ————— e ectors Sense organ: group of receptor cells that respond to speci c stimuli fi ff Re ex does not involve the brain Actions are automatic fast and protective ff fl fi fi fl fl Re ex arc Synapse Presynaptic neurone release chemical messenger (neurotransmitter) Di uses across the synaptic gap and bind with receptor molecules This stimulates the second neurone to generate an electrical impulse Neurotransmitter then destroyed *synapse ensures one-way transmission of nerve impulse The eye Iris - controls pupil size Cornea - refracts light Pupil - controls amount of light entering Lens - focus light onto retina Retina - contains light receptors (rods & cones), converts signal Fovea - high concentration of cones Optic nerve - carries impulse to the brain Pupil re ex Bright light: Circular muscles contrast radial muscles relax - pupil constricts Dim light: Circular relax radial contrast - pupil dilates Accommodation of lens Distant object - ciliary muscle relax, lens thinner Near object - ciliary muscle contract, lens fatter Rods & cones Rods for light cones for colour Three types of cone cells (red blue green) Hormones & homeostasis Hormones: a chemical substance produced by a gland and carried by the blood which alters the activity of one or more speci c target organs Endocrine glands & hormones they produce Adrenal gland - adrenaline Pancreas - insulin Testes - testosterone Ovaries - oestrogen Nervous control vs hormonal control Nervous control: electrical impulses transferred by nerves, with high speed and short term e ect Hormonal: transfer in form of chemicals by blood, slow speed but long term e ect ff ff fi fl fi fl ff ff Adrenaline -secreted in “ ght or ight” situations -e ect: increase breathing, push rate and secretion of glucose from the liver, cause pupil dilation (Essentially increase supply of oxygen and glucose) Homeostasis Control of internal conditions within set limits for maintenance of a constant internal environment. Body temperature Vasodilation & constriction - vasodilation increase volume of blood passing through the vessels near skin, allowing more heat to be radiated out which lowers down body tem. Vice versa. *Skin structure Basic insulation: 1.Fat layer 2.Hair follicles trap air which is also an insulator Shivering: increase metabolism in the muscles to increase hear circulation Sweating: when water evaporates from sweat it removes heat from the skin Blood glucose concentration -pancreas secretes glucagon and insulin -these hormones act on the liver which alters glucose levels in the blood -excessive glucose stored as glycogen High glucose level: insulin acts on the liver to make glucose in to glycogen for storing Low glucose level: glucagon to make glycogen into glucose for use Negative feedback Mechanism by which homeostasis is achieved Eg. Abnormally high blood glucose detected by sensor glucose abnormally low blood glucose insulin increase detected by sensor reduction in blood insulin secretion ceased Tropic responses De nitions Tropism - a plant growth response in which the direction of response is determined by the direction of stimuli Phototropism - plant growth response to light Gravitropism - plant growth response to gravity Shoots: positive phototropism, negative gravitropism Roots: negative phototropism, positive gravitropism Auxins A growth hormone produced by plants, controls the direction of growth of roots/stems Mostly made in tips so can di use to other parts of the plant *stimulates cell elongation Plant hormones & weedkillers Most weedkillers contain synthetic hormones known as 24D (selective, only a ect weeds but not crop plants) So weeds grow very fast and then dying - more space & nutrients & water for crop plants to grow Drugs ff ff fi ff fi Any substance taken into the body the modi es or a ect chemical reactions in the body Two main categories: medicinal and misused Medicinal drugs -Antibiotics Drugs that treat bacterial infections by: 1. Attacking bacterial cells walls 2. Preventing bacterial protein formation 3. Inhibiting bacterial reproduction *Do not work on viruses Some bacteria may have resistance to antibiotics Misused drugs Alcohol & heroin -both depressant drugs: lowers neurotransmission levels -increase reaction times & slows down impulses (a ect impulses) -addiction and withdrawal is a common long-term complication -negative social implications including crime, nancial problems, dangerous driving, violence, etc. Other problems: -sharing needles can lead to infections e.g. HIV -alcohol can cause liver damage (where alcohol is broken down) Tobacco -chronic obstructive pulmonary disease (COPD) -lung cancer -coronary heart disease Toxic components of cigarette smoke: -CO: takes place of oxygen in RBCs -nicotine: addictive drug -Tar: contains cancer-causing substances Testosterone in sports Main e ects on body: 1. Promotion of muscle building 2. Development of make characteristics Anabolic steroids: synthetic variations of testosterone Appealed to athletes for muscle growth and faster recovery time after a work-out Reproduction in plants Asexual reproduction: process resulting in the production of genetically identical o spring from one parent Advantages include: 1. Quicker 2. Only one parent required 3. Good characteristics of parent passed on 4. No dispersal so o spring will grow in the same favourable environment as parent Disadvantages include: 1. Little variation and thus unlikely to adapt to changing environment 2. If parent not existent to certain disease, then o spring will not either 3. Lack of dispersal can lead to competition for nutrients, water, light etc. Sexual reproduction: a process involving age fusion of two gametes to form a zygote, producing o springs genetically di erent to each other and to parent cells Fertilisation: fusion of two gametes ff ff ff fi ff ff fi ff ff Advantages: 1. Variation bene cial for adapting changing environment, increase the survivability of species 2. More variation, more chance for resistance to arise 3. Seed dispersal allows less competition Disadvantages: 1. Two parents required 2. Process slower Structure of owers Insect pollinated Stamen: 雄蕊 - anther + lament Anther: contains pollen Carpel: ⼼⽪（可理解为雌蕊）- stigma + style + ovary Stigma: sticky surface that catches pollen Ovary: contains ovules(female sex cell) which develop into seeds once fertilised Sepal: protects ower while in bud Wind pollinated Insect pollinated vs wind pollinated Features Insect pollinated Wind pollinated Petals Present Absent Stamen Inside the ower Outside the ower Stigmas Smaller surface area inside the ower Large and feathery, often hanging outside Pollen Smaller in amount, can Larger in amount, be sticky/spiky smooth and light Pollination: transfer of pollen from anther to stigma Self-pollination vs cross-pollination Self-pollination increases chance of fertilisation but less variation and adaptability to environment Vice versa After the ovule is fertilised it will become the seed. Germination is the process in which a seed becomes a plant. Factors a ecting germination: water, oxygen and temperature Reproduction in human fl ff fi fi fl fl fl fl fl Testis: sperm production Penis: can become rm for insertion into vagina Scrotum: holds testes outside the body to keep it cooler than body temp Sperm duct: connects testis to urethra Urethra: passes semen/urine out through penis Prostate gland: adds nutrients& uid to sperm to make it into semen Female reproductive system Ovaries: produces egg cells Oviduct: 1.Site of fertilisation 2.prolusion of egg cell to the uterus via cilia in the wall Uterus: location of fatal development Cervix: ring of muscle separating vagina from uterus Vagina: entry point for the penis Gametes Jelly coat of egg cells: protection + initiation of acrosome reaction Flagellum: mobility Mitochondria: provide energy Acrosome: contains enzymes helping the sperm to penetrate through the wall of egg cells Adaptive features of sperm: agellum, mitochondria and enzymes in acrosome Egg cells: energy stores and jelly coat that changes at fertilisation Pregnancy Umbilical cord: transfer nutrients and water from mother to fetus, waste products from fetus to mother Amniotic sac: contains amniotic uid Amniotic uid: cushioning the foetus from bumps to mother’s abdomen Placenta: prevents mixing between mother’s blood & fatal blood *substances di use *placenta can not stop toxins or pathogens Stages of birth: 1. Amniotic sac breaks and amniotic uid released 2. Muscles of the uterus wall contract 3. Cervix dilates 4. Baby passes out through the vagina 5. Umbilical cord tied and cut 6. Afterbirth is delivered Secondary sexual characteristics In girls: *Controlled by oestrogen 1. Breasts develop 2. Body hair grows 3. Menstrual cycle begins 4. Hip gets wider fl fl fl ff fl In boys: *controlled by testosterone 1. Growth of penis and testes 2. Growth of facial and body hair 3. Muscles develop 4. Voice breaks 5. Testes start to produce sperm The menstrual cycle *ovulation occurs about half way through the cycle (day 14) menstruation lasts around 5-7 days Hormones Oestrogen - cause uterine wall to start thickening, inhibits FSH&LH production after ovulation Progesterone - uterine wall maintains and thickening, inhibits…, if fertilisation doesn’t occur levels drop FSH - stimulates egg maturation in the follicles of the ovary & follicles to secrete oestrogen LH - at peak stimulates ovulation, result in formation of a corpus luteum Pituitary gland produces FSH→stimulates development of a follicle in the ovary→egg develops in the ovary, follicle produces oestrogen→growth and repair of the lining and inhibits production of FSH→stimulates release of LH→ovulation→follicle becomes corpus luteum, starts producing progesterone→maintains the uterus lining If the ovum is not fertilised corpus luteum breaks down and progesterone levels drop → menstruation If pregnancy does occur corpus luteum continues to produce progesterone STIs & HIV/AIDS STI: sexually transmitted infections HIV: human immunode ciency virus, which usually leads to acquired immunode ciency disease HIV can be spread via sharing needles, blood transfusions, mother to fetus through placenta, and mother to baby via breast-feeding Spread of STIs may be controlled naturally(abstinence), chemically(pills eg. IUV), via barrier(condom) or surgically(vasectomy/female sterilisation) Inheritance De nitions Chromosome: thread-like structure of DNA, carries genetic information in the form of genes Gene: length of DNA that codes for a speci c protein Alleles: an alternative form of a gene Bases: Adenine - Thymine, Cytosine - Guanine ATCG Sequences of bases determine the sequence of amino acid used to make a speci c protein Haploid vs diploid A normal human cell nucleus has 23 pairs of chromosomes Diploid - contains two sets of chromosomes Haply - single set eg. Sperm/egg cells Mitosis Nuclear division giving rise to genetically identical cells -used for growth, repair, replacement and asexual reproduction *chromosome doubled before cell splits to maintain chromosome number Stem cells: unspecialised cells that divide by mitosis to produce daughter cells that can become specialised for speci c functions fi fi ff fi ff fi fi fi Meiosis Nuclear division giving rise to genetically di erent cells -used for production of gametes Diploid into haploid cells (chromosome halved) *combination of two games will use genes from two di erent individuals and introduce variation as a result Monohybrid inheritance De nitions Inheritance: transmission of genetic information from generation to generation Genotype: genetic make-up of organism Phenotype: characteristic visible in an organism (controlled by genotype) Homozygous: having a pair of identical ballers controlling the same characteristics. Pure-breeding Heterozygous: having a pari of di erent alleles for a characteristic Dominant allele: a gene that always shows in the phenotype whether the organism is heterozygous or homozygous Recessive allele: only shows in phenotype when organism is homozygous Co-dominance A situation where both alleles in heterozygous organisms contribute to the phenotype Eg. Blood type: phenotypes A,B,AB and O blood groups, alleles Iᴬ,Iᴮ and Iº Iº dominated by the other two Sex-linked characteristic A feature in which the gene responsible is located on a sex chromosome which makes this characteristic more common on one sex than the other Eg. Red-green colour blindness Variation and selection Variation: di erences between individuals within the same species Continuous vs discontinuous variation Continuous - results in range if phenotypes between two extremes (i.e. height/weight)*use histogram Discontinuous variation - results in limited number of phenotypes with no intermediates (i.e. tongue rolling), mainly due to genetics alone rather than environment in uence.*use bar chart Mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations Mutation A spontaneous change in gene or chromosome, can be caused by error during DNA replication Mutations generate new alleles *ionising radiation and some chemicals increase rate of mutation Gene mutation is a random change in the base sequence Sickle-cell anaemia -Mutation in gene that codes for haemoglobin -Sickle-shaped RBCs are less e cient at oxygen transport *heterozygous genotype will hame some abnormal RBCs (no life threatening) Adaptive features Inherited feature that helps an organism to survive and reproduce in its environment Examples - hydrophytes & xerophytes Hydrophytes Wide, at leaves - increase surface area to oat on water and gain as much light as possible Reduced plant structure - less need of strong plant support Very thin or no waxy cuticle - less need for water preservation Small roots - water attains directly through stem and leaf tissue Stomata mostly open on upper leaf surface - maximise gas exchange fl fl ff ffi ff fl fi Xerophytes Thick cuticle - minimise evaporation Small leaves - less surface area for evaporation Smaller amount of stomata - less surface area for di usion Sunken stomata - maintains humidity around stomata Rolled leaves - maintains humidity around stomata Extensive roots - maximise water uptake Selection Natural selection -variation within population -many o spring produced -competition for resources amongst individuals within population -struggle for survival -greater chance of reproduction by individuals that are better adapted to the environment than others -these individuals pass on their alleles to the next generation Adaptation: by which population become more suited to their environment over many generations Selective breeding (arti cial selection) -individuals with desirable feature selected by humans -crossing these individuals to produce next generation -genetics will be carried over to the o spring thus also having desirable characteristics Organisms and their environment De nitions Ecosystem: a community of interdependent organisms and their environment Food chain: representation of feeding relationship & energy ow amongst organisms Food web: network of interconnected food chains Trophic level: an organisms position in a food chains, food web, or food pyramid Consumer: an organism that obtains its food by feeding on other organisms Producer: makes its own food via energy from sunlight (photosynthesis) Carnivore: an animal that eats other animals Herbivore: an animal that eats plants Decomposer: an organism that obtains food by breaking down dead organisms Energy ow Principle source of energy input into biological systems (sunlight) Food chains Trophic levels Grass→grasshopper→mouse→owl (Producer→primary consumer→secondary→tertiary) Ine cient energy transfer 90% of energy is lost at each trophic level: 1. Respration 2. Movement 3. Maintenance of body temperature in mammals/birds 4. Some material in organism not eaten or digested by consumer Higher the trophic level, lower the energy intake. So rare to have more than 5 trophic levels as organisms above that level will not able to survive due to lack of energy *more energy e cient for us to eat plants directly than to eat animals Food webs fl ff ff fi ffi ff fl fi ffi Food chains interconnected together Food pyramids Populations De nitions Population: a group of organisms of one species, living in the same area, at the same time Community: all of the populations of di erent species in an ecosystem Ecosystem: a unit containing the community of organisms and their environment, interacting together Factors a ecting population growth Food supply Predation Disease Nutrient cycles Carbon cycle Sigmoid population graph -Lag phase: population growth begins slowly from a few individuals -Log phase: exponential growth occur, conditions ideal and maximum growth rate reached -Stationary phase: carrying capacity for the population reached so number becomes stable. (The population size that can be supported by a particular environment) -Death phase: sudden change in the environment causing population to crash, and the whole process start again (eg. Drought causing food shortage) Nitrogen cycle Nitrogen xation: lightning/bacteria Roles of microorganisms: Decomposition, nitrogen xation, nitri cation&denitri cation Human influences on ecosystem ffi ff fi fi fi ff fi fi Modern technology has increased food supply 1. Agricultural machinery to use larger areas of land and improve e ciency 2. Chemical fertilisers to improve yields 3. Insecticides to improve quality and yield 4. Herbicides to reduce competition with weeds 5. Selective breeding to improve production by corp plants and live stock Impacts to an ecosystem -Large-scale monocultures of crop plants Reduced diversity of ecosystem Increased pests Problems associated with insecticides -Intensive live stock production Diseases easily spread Welfare issues between livestock Habitat destruction Biodiversity: the number of di erent species that live in an area Reasons for habitat destruction 1. Increased area of housing, food crops and livestock production 2. Extraction of natural resources 3. Marine pollution Humans can have a negative impact on habitats through altering food webs and food chains Undesirable e ects of deforestation 1. Reducing biodiversity 2. Reduction in food resources and breeding grounds of animals may lead to extinction 3. Removal of trees causing loss of soil 4. Flooding 5. Increase of carbon dioxide in the atmosphere Pollution E ects of untreated sewage and excess fertiliser on aquatic ecosystem 1. Eutrophication 2. Pathogens in untreated sewage may kill aquatic animals 3. Water borne diseases can spread rapidly - infection on people that drink polluted water *Eutrophication of water 1. Increased availability of nitrated and other ions 2. Increased growth of producers 3. Increased decomposition after death of producers 4. Increased aerobic respiration by decomposers 5. Reduction in dissolved oxygen 6. Death of organism requiring dissolved oxygen in water E ects of non-biodegradable plastics Aquatic ecosystems 1. Trapping of animals Terrestrial ecosystem 1. Toxic cases when plastic is burned 2. Plastics deteriorate in to smaller pieces, these pieces can be consumed by animals Pollution of the air Sources: methane and carbon dioxide 1. Enhanced greenhouse e ect Greenhouse gases in the atmosphere prevent infrared radiation pass through - important in regulating surface temperature of the earth 2. Climate change fi ff ff ff ff ff Conservation Sustainable resource: resources that does not run out (produced as rapidly as it is removed from the environment) Resources that can be conserved and managed sustainably: forests and sh stocks Forest can be conserve using: education, protected areas, quotas and replanting Fish stocks: edu, closed seasons, protected areas, controlled net types and mesh size, quotas and monitoring Organisms become endangered or extinct due to: 1. Climate change 2. Habitat destruction 3. Hunting 4. Pollution 5. Introduced species Conservation of endangered species: 1. Monitoring and protecting species and habitats 2. Eduction 3. Captive breeding programmes 4. Seed banks Conservation programs important as 1. Maintains/increases biodiversity 2. Reduce extinction 3. Protect vulnerable ecosystem 4. Maintain ecosystem functions (nutrient cycling & resource provision - food, drugs, fuel and genes) Arti cial insemination (AI) & in vitro fertilisation (IVF): 相当于体外受精 Risks to a species if its population size decreases: reduces genetic variation, a ect the ability of the species to cope with environmental change, leads to greater risk of extinction. Biotechnology & genetic engineering Yeast Anaerobic respiration: glucose→ethanol + carbon dioxide + energy Ethanol production for biofuels -yeast respire anaerobically in the absence of oxygen -sugar added and kept in warm conditions -as yeasts repair the sugar ethanol I produced Bread-making -yeast activated via mixing with sugar and water, mixture added to our to make dough -dough rises due to carbon dioxide which gets trapped -temp important (respiration controlled via enzymes) -when bread is cooked high temp kill the yeast and ethanol evaporated Fruit juice production -pectinase is an enzyme that breaks down peptin -used to break down pectin in fruit cell walls in order to squeeze out higher volumes of juice Biological washing powders -enzymes used to break down organic substances -mainly protease and lipase -enzymes need to have a high optimum temp -enzymes obtained from thermophilic bacteria Lactose-free milk - xed immobile enzymes on static surface to improve e ciency of reaction -enzyme conc. conserved as enzyme not dissolved ff fl ffi fi fi Penicillin production -antibiotic made by a fungus called penicillium -sugars, ammonium salt + penicillium added to fermenter -temp maintained at approx. 24 deg -stirrer keeps the bacteria suspended -air provided oxygen for respiration Genetic engineering Changing the genetic material of an organism by removing, changing or inserting individual genes Examples -the insertion of human genes into bacteria to produce human proteins -the insertion of genes into crop plants to confer resistance to herbicides -the insertion of genes into crop plants to confer resistance to insect pests -the insertion of genes into crop plants to improve nutritional qualities Insulin -human cells with healthy insulin genes selected -chromosomes from those cells removed -insulin gene from the chromosome removed via restriction endonuclease enzyme -suitable bacterial cell selected, some bacteria DNA present in form of plasmids -plasmids removed from bacterial cell -plasmids cut open via the same restriction endonuclease enzyme -human insulin gene inserted into plasmids using ligase enzymes -plasmids returned to the bacterial cell -bacterial cell reproduce Advantages and disadvantages of genetically modifying crops - soya, maize and rice Advantages: more nutritious, taster, disease- and drought resistant Disadvantges: disrupt natural process, increase cost of cultivation, endangers farmers and trade along with the environment
