UNIT 1 BIOLOGY: STUDY GUIDE Experiments Term Hypothesis Control Variable Experimental variable Responding variable Definition suggested explanation for observed facts, experimental hypothesis used to make predictions that can be experimentally tested Verifies or regulates an experiment by conducting parallel experiment where nothing is changed or affected Single factor that changes in a series of identical experiments to eliminate possibility of random factors affecting results variables that may affect outcome of series of experiments (e.g., temperature, season, time of day, noise level, light, etc) variable which has a ‘response’ that is being tested/observed Scientific method ▪ Careful observation and consult prior knowledge ▪ Making a hypothesis ▪ Design an experiment including appropriate controls ▪ Collect analysis data ▪ Consider results in light of prior knowledge ▪ This may either support the hypothesis or not support it ▪ Draw conclusions ▪ ‘Peer’ review ▪ Controls are important in experiments as they show what happens in the experiment when nothing is changed or affected and prove that the observations and results from an experiment were caused by a variable and weren’t the natural progression of events Strengths and weaknesses in experimental design Strengths Weaknesses - if all variables were kept constant, can be - factors that no one can control may affect the assumed that experiment was as accurate as series of experiments and therefore affect the possible result - subjective experiments may have varying results as people may disagree on results of experiment - may have to repeat experiment numerous times to ensure accuracy = time consuming Cell Structure ▪ The Cell Theory: - all organisms made up of cells - new cells created by old cells dividing - the cell is smallest living organizational unit Characteristics of livings things and their requirements ▪ Common characteristics of living organisms: Move Respire Show response to stimuli Grow Reproduce Excrete wastes Need nutrients Organise their body: cell organism ▪ All living organisms: - are made of cells - are chemically complex and highly organized - exchange energy and matter with environment - over succeeding generations, show changes that are adaptive ▪ Common requirements for life: - source of energy - nutrients and water - removal of waste substances - exchange and distribution - response to stimuli Adaptation ▪ Adaptation: - fundamental principle of biology - inherited structures, functions and behaviours of organisms make them well suited to environment and lifestyle - process by which a species becomes well-suited to its life style and environment ▪ Natural selection: - result of species becoming structurally, physiologically and behaviourally adapted to particular environment - therefore more likely to survive than organisms who aren’t = natural selection Organic and inorganic compounds ▪ Organic compounds: - characteristic complex compounds that are energy-rich - produced by organisms - contain hydrogen and carbon ▪ Inorganic compounds: - simple in chemical structure that are energy-poor - found in both living and non-living things Roles of inorganic compounds in organisms Inorganic compound Role Water - important to biological processes because many occur in watery environment Oxygen - needed to release energy from food molecules (respiration) Carbon dioxide - used in photosynthesis - end product of cellular respiration Nitrogen - key component in proteins Minerals - mineral ions found in cytosol of cells, structural components and molecules of enzymes and vitamins Roles of major organic molecules in organisms Organic compound Elements Role Carbohydrates C, H, O - energy source - energy storage Lipids C, H, O Protein C, H, O, N Nucleic acids C, H, O, N, P Vitamins - structural support - energy storage - structural component - structural component - enzymes, hormones, carrier molecules - genetic material - carry instructions to make proteins - required for normal functioning The Cell Theory and evidence that supports it ▪ Theory of ‘spontaneous generation’ stated that worms, beetles and frogs could arise spontaneously ▪ Louis Pasteur disproved theory by showing microorganisms arose only from other microorganisms ▪ Pasteur laid foundation for development of ‘cell theory’ and provided scientific basis for ‘germ theory of infection’ ▪ Cells are basic functional unit of living organisms Common properties of cells ▪ All (or most) cells have: - plasma membrane - cytoplasm - DNA - flagella/cilia Prokaryotes and eukaryotes Prokaryotes ▪ Cells with ‘primitive nucleus’ which lack membrane-bound organelles ▪ Unicellular or simple multi-cellular organisms ▪ Classified in kingdom Monera ▪ Take in and release materials efficiently and rapidly ▪ Replicate quickly ▪ Contain single, circular DNA chromosome in region called nucleoid ▪ Contained by cell wall of proteins and complex carbohydrates ▪ Many have flagella or cilia for movement ▪ No obvious structural organization Eukaryotes ▪ Cells with membrane-bound nucleus ▪ Cytoplasm includes specialized membrane-bound organelles ▪ Complex multi-cellular organisms ▪ Classified in kingdoms Protista, Animalia, Plantae and Fungi Plant cell Animal cell Organelles in cells Organelle Cell Membrane Cytoplasm DNA Cell wall (in plant cells only) Ribosome Nucleus Mitochondrion Chloroplast (in plant cells only) Endoplasmic reticulum Golgi apparatus Lysosome Vacuole ▪ ▪ Function - phospholipid layer that encloses the contents of cell - controls the movement of substances into and out of cell - fluid content of cell - consists of cytosol and organelles - long molecule that carries genetic information in cell - found in chromosomes - rigid cellulose wall outside plasma membrane of plant cells - protects cell from bursting when turgid - contributes to structural support of plant - tiny spherical organelle that is site of protein synthesis - large spherical organelle that contains genetic information of cell - controls cell activities - site of aerobic stages of cellular respiration - green organelles containing chlorophyll - site of photosynthesis - network of membranes involved in protein transport within cells - stacks of flattened membranous sacs modify and package substances for secretion from cell produce digestive enzymes break down complex compounds into simpler molecules compartments that keep substances separate from cell contents Amino acids are found in ribosomes and membranes Carbohydrates and lipids are found in Golgi apparatus, rough ER and membranes Characteristics of cells from different kingdoms Features Animalia Prokaryotic (P) or eukaryotic (E)? E Unicellular (U) or multicellular (M)? M Location of DNA Nucleus Membrane-bound organelles? (Y/N) Y Cell wall?(Y/N) N Chloroplasts? (Y/N) N Vacuoles? (Y/N) Y Microscopic techniques Type of microscopy Light microscopy Autoradiography Fluorescence microscopy Confocal microscopy Electron microscopy Plantae E M Nucleus Y Y Y Y Monera P U Nucleoid N N N N Protista E M Nucleus Y Y Y Y Fungi E M Nucleus Y Y N Y Values Can observe live specimens Limitations Cannot see organelles High resolution, very clear Can view thick slices of specimens 3D viewing of living structures High resolution Software is very expensive Software is very expensive Energy transformations in cells Enzymes ▪ Enzymes: - biological catalysts that increase rate at which chemical reactions occur - are globular proteins - are not used up in chemical reactions (i.e. can be re-used) - work fastest in optimum conditions (optimum pH, optimum temperature) - chemical reactions regulated by hundreds of enzymes working in ‘chains’- so product from one reaction become substrate for next - can catalyze synthesis reactions or decomposition reaction - located at particular sites within cells - are specific and catalyze one given reaction only ▪ Essential to the function of living organisms because: - vital because speed up chemical processes that would otherwise be too slow for organisms to survive - increase efficiency of controlling chemical reactions ▪ Other factors that affect rate of enzyme catalysed reactions: - amount of substrate/enzyme present or accumulation of a product affects reaction rate - changes in pH or temperature - competitive inhibitors = other molecules present that also fit active site Energy in cells ▪ Cells need energy to: - obtain nutrients - synthesise materials - eliminate wastes - produce a varity of biological molecules - divide ▪ Adenosine triphosphate (ATP): - “energy currency” of cells - immediately usable chemical energy stored in cells - high energy terminal phosphate bond easily broken to release ‘packet’ of energy - once ATP gives up energy, becomes adenosine diphosphate (ADP) - ADP can be ‘recharged’ and used again as ATP - when energy is converted, some is lost as heat to surroundings ▪ Cells get energy to make ATP by breaking apart glucose molecules ▪ Chemical energy released in series of small steps involving many enzymes Cellular respiration Aerobic respiration ▪ When oxygen available, respiration occurs along aerobic pathway ▪ The formula for the complete aerobic breakdown of glucose is: C6H12O6 + 6O2 6CO2 + 6H2O + 36-38 ATP (glucose + oxygen carbon dioxide + water + energy) ▪ Two parts of aerobic respiration: - glycolysis (cytosol) - Krebs cycle (mitochondrion) Anaerobic respiration ▪ When oxygen isn’t available, respiration occurs along anaerobic pathway (or fermentation) ▪ The formula for the complete anaerobic breakdown of glucose is: (in plant cells) glucose alcohol + carbon dioxide + energy (in animal cells) glucose lactic acid + energy ▪ Glycolysis occurs in cytosol and pyruvate produced undergoes fermentation Glycolysis ▪ Initial stage in breakdown of glucose ▪ Glucose molecule is split into two pyruvate molecules ▪ Occurs in cytosol and is anaerobic ▪ For each glucose molecule, 2 ATP molecules are produced Process Aerobic respiration Fermentation Glycolysis Function Process that uses oxygen to produce energy Process that doesn’t use oxygen to produce energy Breaks down glucose molecule into two pyruvate molecules Photosynthesis 12H2O light + light energy 6O2 + ATP (18) + 24H + 6CO2 ATP production 36-38 2 2 Released into environment C6H12O6 + 6H2O Taken in from environment 6CO2 + 12H2O C6H12O6 + 6O2 carbon dioxide + water glucose + oxygen ▪ Chloroplasts = contain chlorophyll which trap light when excited electrons return to ground state ▪ Mitochondria = site of aerobic respiration where Krebs cycle occurs in cristae and oxygen is used to produce 36 ATP molecules Cell membranes and environments ▪ In unicellular organisms: - the external environment is the watery environment in which it lives that is in contact with outside - the internal environment is the cell’s cytosol ▪ In multicellular organisms: - the external environment is the medium they live in - the internal environment is the extracellular fluid that surrounds their cells ▪ ▪ Extracellular fluid = watery environment of living cells that is in contact with the plasma membrane Intracellular fluid = fluid contained within the plasma membrane (cytosol) ▪ Plants don’t have a clear distinction between the external environment and the extracellular fluid of the internal environment and do not regulate the composition of their internal environment to the same extent as animals ▪ Animals regulate the conditions of their internal environment so that their cells can function more efficiently including, concentrations of particular salts, temperature, acidity/alkalinity or concentrations of nutrients, water and wasts. ▪ Plasma membrane = key structure which forms: - barrier between cell and its environment - “gatekeeper” for nutrients, water and ions (entering) and waste molecules (leaving) - exclusion of dangerous chemical and inclusion of vital cell contents - composed of phospholipid bilayer, carbohydrate chains, protein channels and cholesterol - phospholipids = polar molecule with hydrophilic head and hydrophobic tails ▪ Rate which materials exchanged between organism and environment depends on TSA and volume of living tissue TSA is supplying ▪ SA:Vol = indication of what ‘share’ of surface available to supply exchange needs of each part of organism - larger SA:Vol = faster exchange - smaller SA:Vol = slower exchange - increase in size = decrease in SA:Vol - decrease in size = increase in SA:Vol ▪ Diffusion: - Movement of molecules from where they in high concentration to where they in low concentration - Once evenly distributed net movement of molecules stops - Molecules in liquids and gases in constant random motion - When different concentrations in contact, molecules move so equal concentration throughout ▪ Factors which affect the rate of diffusion: - Surface area- greater SA = greater rate of diffusion - Difference in concentration- greater difference = greater rate of diffusion - Size of molecules- smaller molecules pass through faster than larger molecules - Presence of pores- pores = speed up rate of diffusion - Width of membrane- thinner membrane = faster rate of diffusion ▪ Facilitated diffusion: - Special form of diffusion where protein carrier molecules involved - Faster than regular diffusion because of carrier molecules - Each carrier bind only with specific molecule - Binding changes shape of carrier which then deposits molecule into cytoplasm - No energy used = passive process ▪ Osmosis: - Movement of water molecules across a selectively permeable membrane from: o lower concentrated solution to higher concentrated solution o where water molecules at higher concentration to where at lower concentration o hyperosmotic solution to hyposmotic solution ▪ Active transport: - Molecules move from where in lower concentration to higher concentration = against concentration gradient - Protein carrier molecule is used - Energy always required = active process ▪ Endocytosis and exocytosis: - Substance comes in contact with membrane, surrounded by membrane and ‘engulfed’ into cell - Pinocytosis = when liquids enter cell this way - Phagocytosis = when solids enter cell this way ▪ Cell interaction includes: - chemical communication using hormones - cell-cell interactions involves chemical interactions between membranes of adjacent cells - intercellular connections involves cells connecting together Cell replication ▪ Cell replication in eukaryotes allows growth, maintenance and repair of a multicellular organism to occur properly ▪ Interphase: - before cell divides, chromosomes appear as network of fibres - DNA of chromosomes replicates so chromosomes consists of two chromatids - cell prepares to divide ▪ Prophase: - chromosomes condense and become tightly coiled and attach to spindle - nuclear membrane begins to break down - centrosomes move away from each other and spindle fibres form between them ▪ Metaphase: - nuclear membrane completely breaks down - chromosomes line up along centre of cell - centrosomes now at poles of cell and spindle fibres extend across cell from pole to pole ▪ Anaphase: - centromeres of each chromosome separate and chromatids pull apart - spindle contracts and chromosomes move towards poles of cell ▪ Telophase: - two groups of chromosomes now at poles of cells - chromosomes become tightly less coiled - new nuclear membranes form around chromosomes to create separate nuclei - division of one nucleus into two genetically identical nuclei is completed Cytokinesis: - in plant cells = occurs by cells laying down a new plasma membrane and cell wall between the two daughter nuclei to separate the new cells. Components of the new cell wall, called the cell plate, are initially deposited into the centre of the cell and grow outwards until the two daughter cells are completely separated - in animal cells = occurs by plasma membrane moving inwards and pinching the two daughter cells apart ▪ Cell replication in early embryo ▪ The role of cell replication in the early embryo - regulatory signals in the egg cytoplasm control the cell cycle from within - cells begin to produce and release substances (growth factors) that affect the development of nearby cells ▪ The role of cell replication later in development - individual cells become different from one another and become specialized for specific functions - process of specialization (differentiation) is under the control of genes Controls of the cell cycle ▪ Apoptosis - too many cells growing cause cell to ‘commit suicide’ - e.g., breakdown of cells forming ‘webbing’ in developing of human hands ▪ Stem cells - can turn into any other cells that are needed in the body - e.g., embryonic stem cells = gut cells, skin cells, blood cells, nerve cells, gut lining, skin ▪ Tumors - release growth factors that direct the development of its own blood supply ▪ Prokaryotes replicate as a simple form of reproduction and replicate by binary fission, where a new cell wall and membrane material are laid down between a cell which separates the chromosomes and divides the cell in two. Nutritional needs of autotrophs ▪ Common requirements for organism are: - energy - oxygen - water and nutrients - removal of wastes - reproduction ▪ Autotroph = organism that can make its own organic molecules from inorganic molecules ▪ Heterotroph = organism that must obtain organic compounds by eating other organisms or their products ▪ Nutrients = raw materials required by an organism ▪ Nutrition = the means by which organisms obtain nutrients Balancing photosynthesis and cellular respiration ▪ Photosynthesis = plant process involving the use of light energy to combine carbon dioxide and water to make glucose ▪ Cells release chemical energy to make ATP by breaking apart glucose molecules ▪ In plants, cellular respiration occurs continuously, while photosynthesis occurs only during daylight ▪ When photosynthesis and cellular respiration are occurring, usually a net production of oxygen and utilization of carbon dioxide ▪ Light compensation point = level of light at which the rates of photosynthesis and cellular respiration are equal and there is no net exchange of oxygen Structural adaptations of plants for photosynthesis ▪ Typical plants have green leaves (for photosynthesis and gas exchange), stems (to raise leaves to air and towards light) and roots (to anchor plant and draw nutrients and water from soil) ▪ Leaves = primary photosynthetic structures of plants, provide vast SA for trapping light ▪ Structures of leaves related to balancing three requirements for photosynthesis – trapping sunlight, obtaining carbon dioxide and transpiring water ▪ Environment in which plant grows affects plants’ leaf shape and size ▪ Cells containing chloroplasts (mesophyll cells) localized under dorsal surface to receive most sunlight ▪ Stomata found on ventral surface to reduce loss of water ▪ Mineral salts and water are obtained through the soil by the roots of plants ▪ Mineral ions actively transported through specific channels in root cell plasma membranes ▪ Root hair cells = greatly increases SA of roots to increase rate of exchange of materials ▪ Plants store carbohydrates mainly in the form of starch, then sucrose, glucose and others ▪ Proteins and lipids also stored in smaller amounts Nutrition in heterotrophs ▪ Heterotroph = consume other organisms or their products to obtain organic materials as they cannot make their own ▪ Nutritional requirements of animals include: - carbohydrates for energy - lipids for energy and structural components - amino acids for protein synthesis - vitamins for particular cell processes - minerals for structural components, enzyme and vitamin molecules and cytosol of cells ▪ Essential amino acids = 9 amino acids that cannot be synthesized by animals and must be obtained through diet ▪ Vitamins = diverse group of organic compounds that are needed in small amounts for particular cell processes ▪ Minerals = needed in small amounts for structural components of animals as well as molecules in enzymes and vitamins Digestion ▪ Digestion = the rapid breaking down of organic food into molecules small enough to pass through membranes and into cells ▪ Chemical digestion = breaking apart complex molecules into simple molecules carried out by action of digestive enzymes ▪ Physical breakdown = physically breaking down complex molecules to allow better absorption and increase SA for enzyme action ▪ Extracellular digestion = enzymes released directly onto molecule ▪ Intracellular digestion = cells engulf small pieces of food, then enzymes released ▪ Characteristics of highly efficient digestive systems include: - effective mechanisms for capture and preliminary handling of food - appropriate physical breakdown of food - one-way guy with separation of tasks along its length - efficient transport and storage of ingested food - efficient sequential release of digestive enzymes - adequate SA for maximal absorption of nutrients and water - efficient egestion of unwanted materials ▪ Herbivore = animal that grazes directly on a producer such as a plant ▪ Carnivore = animal that catches live prey for food (predator) ▪ Omnivore = animal that eats both plant and animal foods The Digestive System ▪ Mouth and mouth cavity: - ingests food - contains teeth which mechanically break food into small pieces - has saliva which lubricates food and begins chemical breakdown of starch (amylase) ▪ Oesophagus: - passage in which bolus travels from the mouth to the stomach ▪ Stomach: - acts as a food storage organ - food becomes chyme via mechanical churning and chemical breakdown - glands in stomach wall secrete gastric juice - gastric juice contains HCl, pepsinogen and gastric lipase - pepsinogen begins digestion of proteins into peptides - gastric lipase begins digestion of lipids into fatty acids and glycerols ▪ Pancreas: - produces enzymes and neutralizes acid ▪ Liver: - produces bile, which emulsifies fats - plays important role in metabolism of glucose, amino acids and alcohol ▪ Gall bladder: - stores bile between meals ▪ Small intestine: - duodenum receives bile and pancreatic and intestinal juices with enzymes to digest food - absorption of digested food into blood occurs in duodenum and ileum - nutrients and water are absorbed - amino acids, monosaccharides, vitamins and minerals absorbed via active transport ▪ Ileum: - long tube, therefore more time for soluble end-products of digestion to be absorbed - villi/microvilli provide large SA to increase rate of absorption - microvilli contain blood and lymph vessels, which transport absorbed food around body and return proteins and fluid lost in capillary beds to vena cava respectively ▪ Large intestine: - minerals salts actively absorbed from colon and water follows passively - remainder of colon and rectum store faeces = undigested food, dead cells, mucus and dead bacteria ▪ Anus: - expels or egests faeces Herbivores utilize cellulose ▪ Cellulose: - probably most common organic compound found on Earth - strong complex chain of glucose molecules - too large a molecule to be absorbed without digestion - cellulase = enzyme used in chemical digestion of cellulose - only fungi, protozoans and bacteria can produce cellulase - breakdown occurs anaerobically ▪ Symbiotic partnership = where microorganisms that produce cellulase live in intestine of host and, in return for converting cellulose into simpler molecules, receive shelter and free food (mutualism) ▪ Herbivorous mammals are either hindgut or foregut fermenters, where bacteria break down cellulose in the caecum (enlarged intestinal pouch at junction of small and large intestine) either before the stomach (foregut) or in the first part of the colon (hindgut) Food and energy storage in mammals ▪ Mammals can store excess carbohydrates and fats but not amino acids ▪ Glycogen = large molecule of glucose sub-units, storage carbohydrate in animals ▪ Animals use fats as their main form of energy reserves because: - 25% more ATP is produced per carbon atom - fat is 50% lighter per carbon atom - fat doesn’t attract water molecules like carbohydrates - one gram of fat provides 39kJ of energy ▪ In humans, daily energy requirements depend on: - basal metabolic rate (BMR- amount of energy required to maintain basic functions) - body size - activity level - enviromental temperature Gaseous Exchange ▪ Oxygen and carbon dioxide dissolve and diffuse directly through plasma membranes along their concentration gradient ▪ Organisms must exchange oxygen and carbon dioxide with environments to maintain important energytransforming processes – cellular respiration and photosynthesis: - oxygen is needed for cellular respiration - carbon dioxide must be removed as an accumulation of it because of cellular respiration can slow down the rate of cellular respiration - Advantages of gas exchange with air - water isn’t a good source of oxygen as amount of oxygen dissolved in water is very low - less oxygen dissolved in warm/salty water - water is viscous and requires more energy to move it - more oxygen available in air - less energy required than breathing water Advantages of gas exchange with water - can use countercurrent flows to exchange optimum amount of gas - water doesn’t evaporate from gas exchange surface ▪ Features of an efficient gas exchange surface: - moist membrane (to dissolve gases so they can diffuse) - large SA compared to V of organism (to increase rate of exchange) - thin and permeable (to allow gases to pass through easily) - adequate supply of gas (to maintain sufficient rate of exchange) - efficient removal of gas (to prevent slowing down transfer of gases) - greater concentration one on side of membrane (to maintain concentration gradient) ▪ Structure and complexity of gas exchange organs related to level of activity, body temperature and size and availability of oxygen Ventilation of gills - moves gills through water/moves water past gills - energy-efficient to moe water slower over large SA because of weight and consistency of water - countercurrent flow allows more efficient exchange between fluids Ventilation of lungs - requires less energy than breathing water - actively ventilating lungs occurs by either a “pressure pump” or a “suction pump” - water continuously evaporates from gas exchange surface ▪ Mammalian respiratory system consists of: - pharynx - trachea - bronchi - bronchioles - alveoli ▪ Mammalian respiratory system provides gas exchange between erythrocytes and inhaled air in the lungs ▪ Haemoglobin = respiratory pigment carried in erythrocytes that has an affinity for oxygen ▪ Carbon dioxide transported in mammalian blood by: - dissolving in plasma - combining with Hb molecules - converting to hydrogen carbonate ions in erythrocytes ▪ The rate of photosynthesis usually greater than rate of respiration in green plants during the day which means that the total gas exchange would differ between day and night because of an increase/decrease in oxygen/carbon dioxide production ▪ Stomata = tiny pores in epidermis of leaves bordered by guard cells ▪ Exchange of oxygen and carbon dioxide in leaves, stems and roots occurs by diffusion through stomata ▪ Stomata closed = exchange of gases between plant and environment virtually stops Transport systems – animals ▪ Transport systems = needed to transport substances from the external environment of a multicellular organism to the all the individual cells inside the organism ▪ Effective transport systems have: - large surface areas - reliable and responsible means of moving fluid around the body - fluid that maximizes amount of material that can be transported - control mechanisms that regulate the transport according to need ▪ Open circulatory systems = systems for fluid circulation in which there is no specialized transporting fluid, such as blood, and interstitial fluids flow more or less freely between the cells of tissues ▪ Closed circulatory systems = systems in which specialized fluid carrying nutrients, such as blood, is circulated through the body in a closed system of vessels ▪ The mammalian blood circulatory system contains: - the heart - veins and arteries - pulmonary vessels - systemic vessels - capillaries - blood Blood vessel Artery Vein Capillaries Structure and function - thick muscular walls to withstand pressure from heart - thin muscular walls with valves to blood travels in one-way direction towards heart - one-cell thick walls to allow for efficient exchange between blood and cells ▪ The heart: - has four chambers, two on either side - pumps blood to lungs and around body so cells can exchange materials with blood - has a muscular left ventricle as blood has to be pumped a further distance - has valves between atria and ventricles so blood flow is in one direction - has a rich blood supply and thick muscle to provide strength and energy for continuous beating ▪ Blood pressure: - caused by the contraction of ventricles - changes throughout the circulatory system as pulmonary arteries have less pressure than aorta ▪ Systolic pressure = when the ventricle contracts and blood is forced through arteries ▪ Diastolic pressure = when the ventricle relaxes ▪ Capillaries = tiny blood vessels with wall only one cell thick where exchange between blood and tissues occurs ▪ Blood is composed of plasma (water, dissolved chemicals, plasma proteins) and cells (erythrocytes, leucocytes, platelets, phagocytes) ▪ The lymphatic system returns interstitial fluid, containing proteins, that leak out of the capillaries back into the circulatory system in the vena cava - fine, blind-ending lymphatic capillaries in the tissues join to form increasingly larger vessels structures are similar to capillaries and veins of the vascular system Transport systems – plants ▪ Xylem: - made from empty remains of dead cells - walls are coated with lignin for extra support - conduct water and dissolved salts around plant - supportive and conductive tissue ▪ Phloem: - made from living cells with sieve plates, sieve tubes and companion cells - conduct dissolved nutrients around plant - sieve plate has holes in it which allow sugar through and sieve tubes carry sugars - companion cells regulate function of sieve tubes and help carry sugar around ▪ Cambium (meristems): - forms extra xylem and phloem cells - provides additional strength and thickness for stems of plants - increases transport capacity of vessels in plants ▪ Transpiration = evaporation of water from leaves and is responsible for movement in xylem - energy comes from sun so plant spends no energy in moving materials from xylem ▪ Translocation = transport of soluble products of photosynthesis - occurs by cytoplasmic streaming which requires expenditure of energy Excreting wastes ▪ Waste products produced from the breakdown of: - carbohydrates and lipids = carbon dioxide and water - proteins = nitrogenous wastes (ammonia, urea, uric acid) ▪ Four organs involved in excretion of unwanted or toxic wastes in mammals are: - kidneys remove urea, unwanted salts and excess water - lungs remove carbon dioxide - skin removes salts ▪ ▪ ▪ liver removes waste products from break down of amino acids Nitrogenous waste products appropriate for: - an aquatic animal – ammonia = soluble, easily diffused and diluted - a desert animal – uric acid = insoluble, relatively non-toxic Three steps involved in production of urine in a mammalian kidney: 1. Filtration = blood is filtered in glomerulus and small substances pass through capillaries into the Bowman’s capsule 2. Reabsorption = Any important substances that were filtered are reabsorbed in the tubule and loop of Henle 3. Secretion = active removal of particular substances by cells of tubule wall Plants manage their unwanted wastes by: - excrete wastes into surrounding water - stored in fluid of vacuoles - separated into organelles Waste material management in plants - slower metabolism so lower production rate - most of waste is gaseous and CO2 and O2 reused in photosynthesis and respiration - capable of recycling nitrogenous waste - less turnover of protein in plants because structural components are carbohydrates Waste material management in animals - fast metabolism - wastes are not just gaseous and must get rid of carbon dioxide - nitrogenous wastes cannot be recycled - most structural components are proteins Reproduction ▪ Sexual reproduction = reproduction involving the fusion of two gametes which are the haploid products of meiosis- can be external or internal ▪ Asexual reproduction = one parent giving rise to a new individual from its body cells (offspring are genetically identical to their parent) Advantages of asexual reproduction - no need to find another individual of opposite sex - can produce sexually as well ▪ Advantages of sexual reproduction - helps species survive because of adaptations - allows harmful recessive mutations to be eliminated by genetic recombination Meiosis = a cell division that produces four daughter cells, each with half the number of chromosomes of the parents cell. The products of meiosis are gametes - has two cell divisions - daughter cells have half the number of chromosomes that were in parent cell - I, P, M, A, M2, A2, T ▪ Features of meiosis that generate diversity: - genetic information may be exchanged between members of pairs = chromosomes with new combinations of genetic information (recombination) - gametes receive only a single set of randomly chosen chromosomes from the parent cell Reproduction in unicellular organisms ▪ Can reproduce sexually and asexually ▪ In asexual reproduction, macronuclei pinch into two roughly equal pieces and fission occurs ▪ In sexual reproduction, mating partners become attached, micronuclei undergoes meiosis and new micronucleus produces DNA Features of reproduction and development in animals ▪ Gonads (primary sex organs) = ovaries (produce ova) and testes (produce spermatozoa) ▪ Secondary organs = glands that provide nutrition and lubrication, ducts and chambers for storage and development of gametes, organs for mating and for protection of developing embryo Fertilisation of animal eggs and sperm ▪ Recognition and penetration of the egg cell by the sperm so that sperm nucleus enters cell cytoplasm ▪ Activation of egg cell recognizes the cytoplasm and initiates development ▪ Fusion of egg and sperm nuclei Male reproduction system ▪ Produce and secrete male sex hormones (testes) ▪ Discharge sperm within female reproductive tract ▪ Produce, maintain and transport sperm and protective fluid (semen) ▪ Paired accessory glands which produce secretions that make up about 95% of the volume of semen and a paired system of ducts leading up to the urethra ▪ LH stimulates secretion of testosterone ▪ Testes affected by FSH to stimulate sperm production ▪ Epididymis stores sperm for up to 6 weeks ▪ Vas deferns transports sperm towards urethra Female reproductive system ▪ Produces female egg cells necessary for reproduction (ova/oocytes) ▪ Conception (fertilization of egg by sperm) normally occurs in fallopian tubes ▪ Uterus offers safe and favourable environment for baby to develop ▪ System designed to menstruate (monthly shedding of uterine lining) ▪ Produces oestrogen and progesterone which maintain reproductive cycle
