Biology iGCSE Notes

Section 1

a)MovementRespirationSensitivityHomeostasisGrowthReproductionExcretionNutrition

The Kingdoms Plants Animals Fungi Bacteria Protoctists (The waste men) Plants - store carbohydrates as starch/sucroseAnimals - store carbohydrates as glycogenFungi - store carbohydrates as glycogen

Virus - Not a kingdom

Pathogen - A micro-organism that causes diseasesCan be fungi, bacteria, virus or protoctists

Section 2

a) organelles - cells - tissues - organs - systems - (organism)

c) Biological moleculesCarbs = C,H,OProteins = C,H,O,NLipids = C,H,OCarbs (starch or glycogen) - made from simple sugars (glucose & fructose)Proteins - made from amino acidsLipis - made from 1 glycerol molecule + 3 fatty acid molecules

TestsGlucose - 4cm3 of sample + 1cm3 of Benedict's Solution in a test tubeHeat in a water bath at 50C for 2-3 minsTurns light blue to brick red Starch - 5cm3 of sample in a test tubeAdd drops of Iodine solutionTurns golden brown to blue/blackLow temperature = Inactive enzyme. Substrate and enzyme collide less oftenOptimum temperature = Lots of kinetic energy, colliding more and enzyme is most activeOver optimum temperature = Active site shape changes. No longer complementary to substrate. Enzyme denaturespH - As it changes (high or low) the shape of the active site also changes ∴ less collisions successfulExperiment Place separate boiling tubes with fixed volumes of starch and amylase into different temperature water baths Wait 5 mins for solutions to reach temperature Mix the starch and amylase and immediately do step 4 Every 1 min transfer a small sample using a pipette into a spotting tile well and add iodine solution. Will immediately turn blue/black Record colour. When the iodine turns golden brown no starch is present because all the starch has been digested by enzymes. Compare results to see at which temperature the iodine turned golden brown first. Rate = volume of starch/time taken to go golden brown

d) Osmosis, diffusion, active transportRate affected by SA:V ratio, temperature and concentration gradientPlants cells are usually turgid because the cell wall is much stronger than the cell membrane. It keeps leaves firm and plant upright if it has no woodPlant cells can plasmolyse & Animal cells can shrivelThink : Hyper = lose energy = lose waterRemember - Iso/Hypo/Hyper tonic to the cell

e) NutritionFlowering Plantsmagnesium ions - for chlorophyllnitrate ions - for amino acids (to make protein)Hydrogencarbonate indicator:Yellow = High CO2Orange = Normal CO2Purple = Low CO2

h) TransportFlowering PlantsXylem - Water and mineralsPhloem - Sucrose and amino acidsMore light so stomata open, so more water is lostHumansHepatic artery/vein = LiverHepatic portal vein = Digestive system to liverRenal artery/vein = KidneyPulmonary circuit - Heart to lungsSystemic circuit - Heart to bodyDouble circulatory system: More efficientAllows higher levels of activity as oxygen + glucose can be pumped to muscle cells quickerRespiration needs to take place quickly to maintain body temperature of 37CSingle cell organisms have a high SA:V ratio so can supply the demandMulticellular organisms have a low SA:V ratio. & skin does not allow much diffusion

i) ExcretionFlowering PlantsExcrete O2 and CO2 through stomataHumansThe Kidney carries out excretion AND osmoregulationUltrafiltration in glomerulus. Glomerular filtarte is what gets past into the Bowman's CapsuleSelective reabsorption (uses active transport) in proximal convoluted tubule of glucose,amino acids and some waterUrine contains water,urea and saltsNegative feedback. ↓Little water - ↑ADH - Collecting duct permeability↑ - ↑ water reabsorbed in bloodUrinary system = Kidneys → Ureters → Bladder → Urethra

j) Co-ordination and responseFlowering PlantsPhoto,Geo,Hydro tropism. +ve = towards, -ve = away the direction of stimulus.HumansStimulis → receptor → coordination → effector → responseAccommodation - Focusing of the lens by the changing of its shape. (depending on object's distance)First think of what the suspensor ligaments do (contract or relax), then remember the ciliary muscles do the oppositeADH - Pituitary gland, permeability of collecting ductInsulin/Glucagon - Pancreas. Change blood glucose levelAdrenaline - Adrenal glands. Fight or flightOestrogen/Progesterone - Ovaries. Regulates menstrual cycle/Secondary sexual characteristicsTestosterone - Testes. Secondary sexual characteristics

Section 3

a) ReproductionFlowering Plants Asexual reproduction by runners (natural) and cuttings (artificial) Germination needs O2, H2O and the correct temperature

Humans Placenta allows. O2, Glucose, Minerals to diffuse, and amino acids by active transport M→F CO2,Urea to diffuse, Water by osmosis F→M Bloods don't mix as blood type could be different so mother's body sees it as a pathogen and kills it Mother's blood pressure to high for the weak foetus Placenta takes over from empty follicle and produces progesterone to maintain uterus lining Amniotic fluid in amniotic sac protect foetus from bombs and jolts and keeps the temperature constant

b) Inheritance Adenine - Thymine & Guanine - Cytosine XX = Female, XY = Male Mitosis - 2 identical diploid cells (occurs during growth,repair,closing,asexual reproduction) Meiosis - 4 different haploid gametes (occurs during gamete formation) Ionising radiation (gamma,X-rays, UV rays) & chemical mutagens (chemicals in tobacco) increase the incidence of mutations Selection pressure,survival of the fittest,variation within the natural population, genes, inherited, beneficial mutation,rare/random,adaptation,evolution,reproduce/mate

Section 4

a) The organism in the environmentPopulation - All the organisms of the same species living in an ecosystem at a particular timeCommunity - All the populations of different organisms interaction with their habitatHabitat - A place where specific organisms liveEcosystem - A community of organisms interacting with each other and their habitat/environmentQuadrats. Populations size - Count no. of species in square. Repeat and avg. Multiply avg. by area of field. Quadrats. Distribution of organisms - Place quadrants in different locations. Compare the density/no. of species

b) Feeding Relationships Only 10% of energy transferred because: Some parts of the organism are not eaten (roots) Some of the food is indigestible (Bones,cellulose) Some of the food absorbed forms excretory products (urea) Most of the food is used for respiration, movement, active transport. Little is left for growth or protein

c) Cycles H2O - evapouration, transpiration, condensation, precipitation C - respiration, photosynthesis, decomposition, combustion

d) Human influences on the environment SO2 = Sulphuric acid. Acid rain (SO2 & NOx) = Acidification of water and sea ∴ kills aquatic life and trees, erodes limestone buildings CO = Binds to haemoglobin. Asphyxiation Greenhouse gases = Water vapour, CO2, nitrous oxides (NOx), Methane (CH4), CFCs (refrigerator coolants) Global warming= Polar ice caps melt, Sea level rise, Changes in rainfall (drought/floods), Extinction of polar species Deforestation = leaching, soil erosion, disturbance of water cycle (less transpiration, more drought/flooding), disturbances of the balance of O2 and CO2 in atmosphere (less trees & trees burnt) Leached nitrates from fertilisers = algal blooms develop, sun blocked, plants die, ↓O2, fish die, (NO3 supply stops so algal blooms die), lots of decomposition by fungi/bacteria, Biological Oxygen Demand (BOD) ↑, everything dies. EUTROPHICATION Sewage - Contains lots of bacteria/micro-organisms + nutrients, bacteria decompose sewage, bacteria respire, BOD ↑, fish die (∴ nutrients ↑,algal blooms, eutrophication) Detergents,fertilisers and sewage can cause eutrophication

Section 5

a) Food production Pesticides : +ve = Very effective. Kill all the pests. -ve = Expensive, pests can become resistant, cause env. damage as some remain in soil and food chain, kills other organisms too Biological control : +ve = Cheap. Self regulating as predator won't kill itself + reproduces. -ve = does not kill ALL the pests. Predator may enter the wild and affect biodiversity CO2 production by yeast experiment - Add sucrose solution + oil layer (blocks air) andplace in different temp water baths. Collect Co2 over water in measuring cylinder to measure rate. Use limewater to test Lactobacillus bulgaricus Fermenter: aseptic conditions = Sterile. Filter air and sterilise the fermenter Intraspecific predation - Fish of the same species eat each other. Separate different age, gender & feed often Interspecific predation - different species eat the fish

b) Selective breeding Selective breeding - Individuals with desired characteristics are bred together to produce offspring that express both desired characteristics. Plants - Higher yields, more nutritional to humans, resistant to diseases and pests, hardier to survive in harsher climates and conditions for longer year productionAnimals - More meat/eggs/milk, more fur/higher quality fur, more offspring, resistant to diseases

c) Generic modification Restriction enzymes - Cutting + Ligase enzymes - Sticking Recombinant DNA - DNA from 2 different organisms that has been recombined Transgenic Organism - The organism that receives the new gene from a different species GM Plants are : Increased resistance to pests,pathogens,heat,drought, high salt. Extended shelf lives,contain more vitamins, higher yields, easier to eat/process -ve = Could be more vulnerable to change in conditions or diseases as they are GM

d) Cloning Micropropagation/tissue culture - Explants, Sterile, tissue culture, grown in vitro, clones, hormones + nutrients (optimum growing conditions), agar medium, controlled conditions (temp., light, humidity) +ve = Large numbers produced rapidly, planted all year round, species that are hard to grow can be reproduced, GM only small no. of plants but then introduced into thousands quickly, plants can be stored easily -ve = Plants could be vulnerable to change in conditions or a new disease Dolly the Sheep - Diploid nucleus from body/stem/udder cell electrically zapped with enucleated egg cell, divided by mitosis to form an embryo, implanted into surrogate mother transgenic animals - Can produce antigens of a specific bacteria/virus for vaccines given to people, grow human antigens on their organs for transplant as body is less likely to reject them, sheep produce milk with specific proteins for humans needed to treat diseases like cystic fibrosis