Full biology unit 4 powerpoint


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Full biology unit 4 powerpoint

  1. 1. Biology 4 •Populations •ATP •Photosynthesis •Respiration •Energy and Ecosystems •Nutrient cycles •Ecological succession •Inheritance and selection
  2. 2. Back • • • • • • • • • • Populations Ecology- study of inter-relationships between organisms and environment Ecosystem- interacting biotic and abiotic factors in a specific area Populations- group of inter-breeding organisms of 1 species Community- all populations living and interacting in a specific area Habitat- place where community of organism lives Niche- how an organism fits into the environment (no two species occupy same niche) Abiotic- temperature, light, PH, water and humidity Biotic- living organisms (competition and predation) Intraspecific competition- same species for; food, water, breeding site Interspecific- Different species; food, light, water
  3. 3. Back Investigating populations • Quadrats- factors, size, number and position should be considered • Random Sampling- avoid bias -1. long tape measures at right angles -2. Co-ordinates from random number generator -3. place quadrat on intersection • Systematic sampling- distribution of species- straight line or belt (two lines) • Measuring abundance-Frequency: e.g. 15/30= 50%- useful for species such as grass -Percentage Cover: estimate area within quadrat that particular plant species covers, useful for abundance of hard to count species
  4. 4. Back Mark-Release-Recapture: Estimated population size = Total no. of individuals in 1st sample x Total no. of individuals in 2nd sample No. of marked individuals recaptured
  5. 5. Back Human populations • Immigration and emigration (leaving) • Pop. Growth= (births+immigration) - (death+emmigration) • %pop. Growth rate= pop. Change during period pop. At start of period x100
  6. 6. Back Birth and Death rates • Birth: -Economic conditions -cultural/ religious -social pressures & conditions -Birth control -political factors • Birth rate= no. of births per year x1000 total pop. In same year • Death: -age profile -life expectancy at birth - food supply -safe drinking water and sanitation -medical care -natural disasters -war Death Rate= no. of deaths per year x1000 Tot. pop. In same year Change in population= demographic translation
  7. 7. Back ATP & Energy • ATP is an energy source for: • • metabolism, maintenance, movement, active transport, repair and division, production of substances, maintenance of body temperature • ATP+ H20  ADP + Pi + E Hydrolysis reaction Synthesis of ATP: reversible reaction (Pi to ADP – condensation reaction) ATP immediate energy source -released in small bursts of energy from mitochondria -manageable -fast reaction
  8. 8. Back • Photosynthesis 6CO2 + 6H20  C6H O + 6O2 12 • Light energy  Electrical  Chemical energy • Chloroplasts: Grana (Thylakoids) – light dependant stage- pigment chlorophyll Stroma- fluid-filled matrix – light independent stage- starch grains • Factors effecting photosynthesis rate: light intensity CO2 Temperature
  9. 9. Light- dependant reaction • Involves capture of light for: -to add Pi to ADP for ATP -to split H+ ions (protons) and OH- ions by light known as photolysis • Making of ATP: -Chlorophyll molecules absorb light energy, boosts energy of electrons raising energy level (excited state)- then leave chlorophyll -electrons taken up by electron carrier -Having lost electrons the chlorophyll has been oxidised- electron carrier gains electrons (reduced) -In thylakoids they pass through oxidation-reduction reactions -energy along is lost for ATP production • Photolysis of water: -2H O  4H+ + 4e- + O protons electrons • H+ ions (protons) taken up by electron carrier NADP. NADP becomes reduced 2 2 • Reduced NADP aand electrons from chlorophyll enters light independent reaction • Oxygen waste product/ used for respiration Back
  10. 10. Light- independent reaction • • • ATP and reduced NADP from light dependant reaction used to reduce CO2 Calvin cycle in stroma Stages: 1. CO2 diffuses into leaf through stomata 2. In stroma CO2 combines with 5-carbon compund (RUBp) using an enzyme 3.Combination of CO2 & RuBP produces 2x molecules of glycerate 3 phosphate (GP) 4. ATP & reduced NADP from light-dependant reaction used to reduce activated glycerate 3-phosphate to triose phosphate (TP) 5. NADP re-formed and goes back to light dependant reaction to be reduced by accepting Hydrogen 6. Some triose phosphate molecules are converted to useful organic substances, such as glucose 7. Most triose phosphate used to regenerate ribulose biphosphate using ATP from light dependant Site of light independent reaction: fluid of stroma- contains all enzymes for Calvin cycle stroma fluids surrounds grana, so products of light dependant reaction in grana can easily diffuse Contains both DNA and ribosome's, so quickly and easily manufacture proteins for Calvin cycle
  11. 11. Back Respiration • Aerobic respiration- needs O2, produces CO2, water and ATP • Anaerobic respiration (fermentation)- takes place without O2, produces lactate in animals and or ethanol/CO2 in plants but only a little ATP in both cases • Aerobic can be divided in to four stages: 1.Glycolysis- splitting 6-carbon glucose to two 3-carbon pyruvate 2.link reaction- conversion of 3-carbon pyruvate molecule into CO2 and a 2-carbon molcule= acetylcoenzyme A 3.Krebs cycle-acetylcoenzyme A into cycle of oxidationreduction reactions that yield ATP and a large no. of electrons 4.electron transport chain-use of electrons produced by krebs to synthesise ATP (water is by-product)
  12. 12. Back • • Glycolysis Initial stage of aerobic and anaerobic respiration. Occurs in cytoplasm of all living cells Four stages: 1.activation of glucose by phosphorylation- glucose more reactive by adding 2 phosphate molecules so it can split. Phosphate comes from hydrolysis of ATP to ADP- provides energy to activate glucose 2.splitting phosphorylated glucose- split into 3-carbon molecules known as triose phosphate. 3.Oxidation of triose phosphate- Hydrogen removed from each 2 triose phosphate & transferred to hydrogen-carrier molecule known as NAD to form reduced NAD 4.production of ATP- ezyme controlled reactions convert each triose phosphate to another 3-carbon molecule- pyruvate. In process two molecules of ATP regenerated from ADP. Energy yield from Glycolysis: -two ATP molecules (two were used for phosphorylation) -two molecules of reduced NAD (has potential to produce more ATP -two molecules of pyruvate
  13. 13. Back Link Reaction • Pyruvate produced during glycolysis can only release energy using oxygen in krebs cycle. -1st oxidised in link reaction -Krebs & Link take place in eukaryotic cells inside mitochondria • Link reaction: Pyruvate actively transported to matrix of mitochondria. -Pyruvate oxidised by removing hydrogen- hydrogen is accepted by NAD to form reduced NAD (later used to produce ATP) -2-carbon molecule, called acetyl group, combines with a molecule called coenzyme A (COA) to produce acetylcoenzyme A - a CO2 molecule is formed from each pyruvate Pyruvate + NAD + COA  acetyleCOA +reduced NAD + CO2
  14. 14. Back 1. Krebs Cycle 2-Carbon acetylcoenzyme A combines with 4-carbon molecule to produce 6-carbon molecule 2. 6- Carbon loses CO2 and hydrogens to give a 4-carbon molecule & single ATP 3. The 4-carbon molecule can now combine with new molecule acetylcoenzyme A to begin cycle again Link & Krebs produce: -reduced coenzymes NAD & FAD potential to produce ATP -one molecule of ATP -3 molecules of CO2 Because 2 pyruvate molecules are produced for each original glucose, yield is double of quantities above Significance of Krebs: -break down macromolecules into smaller ones -production of ATP provides metabolic energy -regenerates 4-carbon molecules which would otherwise -accumulate -source of intermediate compounds used by cells in manufacture of fatty acids, amino acids and chlorophyll
  15. 15. Back Coenzymes • Coenzymes are molecules that some enzymes acquire for energy • Carry Hydrogen atoms from one molecule to another Examples: NAD- important throughout respiration FAD- important in Krebs cycle NADP- important in photosynthesis • In respiration NAD is most important carrier. Works with dehydrogenase enzymes that catalyse removal of hydrogen ions from substrates and transfer them to other molecules
  16. 16. Back • • • • • • Electron transport Chain Cristae (inner folds) in mitochondria is the sight of electron transport chain Hydrogen carried by coenzymes NAD and FAD to electron transport chain from Krebs are 1st attached to cristae Releases protons from H-atoms- protons actively transported across inner membrane Electrons meanwhile pass along chain in oxidation-reduction reactions- elec. Lose energy down chain- some used to combine ADP and Pi. Remaining energy released as heat Protons accumulate in space between 2 mitochondrial membranes before diffusing back into matrix through protein channels End of chain electrons & protons and O2 combine to form H2O. O2 is the final acceptor of electrons in chain Importance of O2: H-atoms (protons) and electrons would otherwise back- up- respiration would come to a halt Cyanide (non-competitive inhibitor)
  17. 17. Back • • • • Anaerobic Respiration In eukaryotic cells: plants convert ethanol to CO2 animals pyruvate to lactase Pyruvate + reduced NAD ethanol + CO2 + NAD (plants) When O2 is low: lactate production occurs mostly in muscle reduced NAD must be removed for glycolysis- each pyruvate takes up 2 H-atoms from reduced NAD pyruvate + reduced NAD  lactate + NAD (animals) Lactate can cause cramp and muscle fatigue- must be oxidised back to pyruvate Energy Yields from anaerobic and aerobic respiration: Substrate level phosphorylation in glycolysis and Krebs produces ATP Oxidative phosphorylation- electron transport chain- ATP In aerobic respiration Krebs or electron chain can’t take place. Less ATP for anearobic- only from glycolysis
  18. 18. Back Energy and ecosystems • Consumers (Primary, secondary and tertiary) • Decomposers- fungi and bacteria • Detritivores- certain animals such as earthworms • Each stage in the food chain is a Trophic level
  19. 19. Back Energy transfer between trophic levels • Energy losses in food chains: 90% of suns energy reflected back in space by clouds and dust not all wavelengths can be absorbed light may not fall on chlorophyll low CO2 may limit photosynthesis • Gross production= total quantity of energy that plants in community convert to organic matter • Net production= gross production – respiratory losses
  20. 20. Low percentage energy transferred at each stage: -some of organism is not eaten -some parts are eaten but can’t be digested & therefore lost in faeces -some energy is lost in excretory materials, such as urine -Heat respiration/ body to environment Must food chains have 4/5 trophic levels, insufficient energy for more Total mass of organisms (biomass) is less at higher trophic levels Total amount of energy stored is less at each level Calculating efficiency of energy transfers: Energy transfer= energy available after transfer x100 energy available before transfer Back
  21. 21. Back Ecological pyramids • Pyramids of numberno account is taken for size no. of individuals is so great that its impossible to represent them accurately • Pyramids of biomasswater in organism may make it unreliable no seasonal difference apparent in both pyramids • Pyramids of energyenergy through food chain difficult and complex to obtain the results
  22. 22. Back Agricultural ecosystems • Gross productivity- rate plants assimilate chemical energy • Net productivity= gross productivity- respiratory losses • Net productivity is affected by: -efficiency of crop carrying out photosynthesis -are of ground covered by leaves/crops • Comparisons of natural & agricultural ecosystems: • Energy input – only source is sun- additional energy- food and or fossil fuels • Productivity- Natural eco. Prod. Is low, fertilisers and pesticides added
  23. 23. • Pesticides effectiveness: specific biodegrade cost-effective not accumulate • Biological control: not as quick control organism may itself become pest • Intensive rearing and energy conversion: Movement restricted (less energy used by muscle contraction) Environment kept warm Feeding controlled Predators excluded Selective breeding Hormones to increase growth rates Back
  24. 24. Back Nutrient Cycles • Basic sequence for nutrient cycles: -nutrient taken up by plants (producers) as simple, inorganic molecules -producer incorporates nutrient into complex organic molecules -when producer eaten, nutrients pass into consumers -passes along food chain -when producers/consumers die, complex molecules broken down by saprobiotic microorganisms that release nutrient in simple form
  25. 25. Carbon Cycle Back CO2 in atmosphere & dissolved in oceans Photosynthesis Combustion Fossil Fuels Respiration Carbon containing compounds in producers (plants) Feeding Carbon-containing compounds in consumers (animals) Death Decay Living component Carbon-containing compounds in Decomposers (saprobiotic microorganisms) Non- Living component Basic sequence Additional pathways Decay Prevented
  26. 26. Greenhouse effect & Global warming • Greenhouse effect- solar radiation reflected back into space, some reflected back- gas traps heat near earths surface • Global Warming: -melting of ice caps -rise in sea level -faliure of crops -disease may spread Back
  27. 27. Nitrogen Cycle • Four main stages: Ammonification, nitrification, nitrogen fixation and denitrification each involving saprobiotic organisms A>N>N>D Nitrogen fixation by free- living bacteria Nitrification Nitrite Ions Nitrification Ab so rp t io n Ammonium ions Nitrate ions Denitrification Nitrogen in atmosphere ion ia ixat nf c t er oge c ba N it r lis t i t ua mu By AmmoniumAmmonium- containing containing molecules Feeding and molecules e.g. proteins e.g. proteins, in producers digestion in consumers Death Ammonification Back Ammonium- containing molecules e.g. proteins in decomposers saprobiotic microorganisms Death & excretion
  28. 28. Ammonification: Production of ammonia from organic ammonium containing compounds Sprobiotic microorganisms (fungi/bacteria) release ammonia which forms ammonium ions in soil. Returns to non living component. Nitrification: Conversion of ammonium ions to nitrate ions, using oxidation reactions (release energy)- carried out by free-living soil microorganisms called: nitrifying bacteria. 2 stages: 1.Oxidation of ammonium ions to nitrite ions (NO 2-) 2.Oxidation of nitrite ions to nitrate ions (NO3-) Needs O2 so ploughing (aerated) and good drainage (no water) Nitrogen fixation: Nitrogen gas is converted to nitrogen-containing compounds, carried out by: free-living nitrogen-fixing bacteria: reduce gaseous nitrogen to ammonia, used to manufacture amino acids mutualistic nitrogen fixing bacteria: Nodules of roots/plants- obtain carbohydrates plant and plant acquires amino acids from bacteria Denitrification: Soil becomes waterlogged, so short of O2= few nitrogen fixing bacteria and increase denitrifying bacteria (convert soil nitrates to gaseous nitrogen) Back
  29. 29. • • Levels of mineral ions in agriculture falls To replenish this fertilisers are used: Natural (organic) fertilisers- dead, decaying animals/plants Artificial inorganic fertilisers- mined from rocks & deposits- contains three compounds: nitrogen, phosphorus and potassium • Effects of nitrogen fertilisers: Reduced species diversity e.g. nettles and grasses out compete other species Leaching- may lead to pollution of watercourses Eutrophication- caused by leaching of fertiliser Leaching – Nitrates with rain draining into streams/rivers then drain into freshwater lakes- harmful effect to humans if source of drinking water- cause eutrophication Eutorphication – In lakes/rivers a limiting factor for plants/algae is nitrate- as nitrate increases the algae & plants grow Upper layers of water become densely populated with algae (algal bloom) Absorbs light and prevents light at bottom. Plants at bottom die. Saprobiotic algae feed on dead plants but they need oxygen. O2 concentration is reduced in lake so fish has no O2 and die- further decompose (dead organism) more nitrate water is putrid Back
  30. 30. Back Ecological succession • First stage is colonisation of inhospitable environment by organisms called pioneer species. • The abiotic environment is continuously changing • Climax community- final stage of ecological succesion • During succession: -non-living environment becomes less hostile- e.g. soil -great number/variety of habitats produce: -increased biodiversity -more complex food webs -increased biomass • Primary colonisers secondary colonisers Tertiary colonisers  shrubland  Climatic climax
  31. 31. Back Conservation of habitats • Main reasons for conservation: Ethical- other species have inhabited earth longer Economic- may be useful in long term Cultural/ aesthetic- habitats/organisms enrich and inspire lives (writer, artists and composers) • Succession- changes over time
  32. 32. • • • • • • • • • • • • • Inheritance and Selection Genotype- genetic composition of organism Phenotype- visible characteristics of an organism resulting from genotype & environment Gene-section of DNA that determines characteristics of DNA Allele-different forms of a gene Homologous chromosomes-pair of chromosomes that have same loci therefore determine same features Homozygous-alleles are identical for particular gene Heterozygous-alleles of gene different Dominant-allele that is always expressed in phenotype of organism Recessive-allele only present in diploid phenotype if another identical allele is present Diploid- when nucleus contains 2 sets of chromosomes Haploid-only contain 2 set of chromosomes e.g. Sex cell/ gametes Co-dominant-both alleles code for one gene in heterozygous individual Multiple alleles-gene that has more than two possible alleles Back
  33. 33. Monohybrid Inheritence • Law of Segregation: In diploid organisms, characteristics are determined by alleles that occur in pairs. Only one of each pair of alleles can be present in a single gamete” • Sex Inheritance and Sex linkage: As males have one X and one Y chromosome they produce 2 different types of gamete -X chromosome is longer so there is no equivalent homologous portion with Y. Haemophilia is inherited from the mother to male - Pedigree charts are a good representation of inheritance Back
  34. 34. Co-dominance and multiple alleles • Co-dominance example: Red and white snapdragon = pink snapdragon • Multiple Alleles example: Blood groups - Io is recessive in B.G • Hardy Weinberg: Frequencies of alleles- proportion of dominant and recessive Five conditions: -No mutation -Population isolated -No selection -large population -Random mating p + q = 1.0 p2 + 2pq + q2 = 1.0 Heterozygote= 2pq Back
  35. 35. Selection • All organisms produce more organisms than food, light and space can support • Therefore Intraspecific competition • Organisms with the better fitting alleles survive and then reproduce Types of Selection: • Directional selection: individuals that vary in one direction to the mean of population some individuals that fall to left/right of mean will possess a phenotype more suited to new conditions -extreme of the populations • Stabilising selection: favour average individuals- preserves characteristics of a species -If environmental conditions stay stable individuals with closest phenotype to mean are favoured Back
  36. 36. Speciation • Speciation: evolution of new species from existing species • Geographical Isolation: When a physical barrier prevents 2 populations from breeding with one another -In the split Land A has organisms with more suitable phenotypes and Land B has organisms with more suitable phenotypes -In time difference becomes so great in gene pools that they become 2 separate species -Once united they cannot breed Back