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Unit 3 End of topic test mark scheme Section A 1. B 2. A 3. A 4. B 5. B 6. D 7. A 8. C 9. A 10. D Section B 1 (a)(i) Enzyme X: RuBisCO = 1 Substance Y: G3P/glyceraldehyde-3-phosphate =1 (ii) Glucose: for respiration/ATP (production)/cellulose formation/starch formation/ other biosynthetic pathways/ processes = 1 RuBP: for continuation of the cycle/to allow cycle to occur/ repeat OR to make G3P/intermediate substances =1 (b)(i) ATP: increases = 1 NADPH: increases = 1 (ii) Procedure: randomisation of plots/treatments Explanation: reduces/eliminates bias OR Procedure: replication/number of replicates Explanation: to take account of variability/reduce the effect of atypical results OR Procedure: selection of treatments/inclusion of both GM and non GM crops Explanation: to make/ensure a (fair) comparison Any 2 for 2 marks 2 (a) Parasite/it/Schistosoma gets energy/gets nutrients/benefits/ gains AND host/human is harmed (by loss of resources) = 1 (b) Secondary host: (fresh water) snails = 1 Benefit: allows development into free swimming parasite = 1 OR allows them/immature parasites to complete life cycle (c) Prevent urine/faeces/eggs from entering (fresh) water OR stop people entering the affected water OR control the population of fresh water snails OR medication given to kill the eggs/mature parasite/parasite in humans = 1 3 (a)(i) naturalised = 1 (a)(ii) no/free of (natural) predators/parasites/ disease/competitors = 1 (a)(iii) they may become pests/damage the habitat OR they out-compete native species to extinction OR they may become invasive OR they may predate/eat native species to extinction/be endangered = any for 1 mark (b) introduce (natural) predators/parasites/pathogens to control/reduce numbers/eliminate pests = 1 4(a)(i) 25 =1 (a)(ii) 9 =1 (a)(iii) (130 – 132 x 104) 1.3 – 1.32 million = 1 (b) 1 allows gene flow between fragments OR allows groups/populations to interbreed OR increases chance of finding mates OR increases number of possible mates OR allow movement to other fragments to mate. 2 allows movement to other fragments for food 3 allows recolonisation/ re-inhabiting of a new area following local extinction = Any 2, one mark each 5(a) BAC (all 3 = 2, 1 = 1) (b) Same age / stage of plant used OR planting density /initial number / mass of seeds planted the same / temperature/ sunlight / CO2 concentration OR same fertilizer / pesticide treatment OR same irrigation / soil factors / pH / volume of water / fertility of soil etc = 1 Valid reason = 1 Must state the effect on growth/yield/photosynthesis (c) i 0·6 = 1 (c)(ii) Coteau Has a higher harvest index OR higher economic yield OR higher mass of desired product (both variety and reason) = 1 (d) 1. There is a loss of energy between trophic/food chain/feeding levels OR 2. Livestock produce less energy per area/volume OR 3. Plants produce more energy per area/volume Alternatives to energy = food/biomass =1 Section c 1a) in context of altruism use of donor and recipient altruistic behaviour harms and benefits / increased survival or descriptions of examples reciprocal altruism involves reversal of roles at a later stage / favour returned or a description of reversed roles reciprocal altruism often occurs in social animals/social insects OR mention of the prisoner’s dilemma altruism is (more) common between kin / related individuals / kin selection is altruism between kin donor can benefit indirectly (through shared genes) increased chance of shared / their genes surviving / being passed on (in recipient’s offspring) Max 5 (from 7) primates have a long period of parental care / spend a long time with their parent(s)/ look after young for a long time this gives opportunity to learn complex social skills (social) primates use ritualistic display / appeasement (behaviour) to reduce conflict/aggression / ease tension any one example of appeasement / alliance forming / ritualistic behaviour e.g. grooming / facial expression / body posture / sexual presentation second example of appeasement / alliance forming / ritualistic behaviour individuals form alliances which increase social status OR Social hierarchy exists complexity of social structure is related to ecological niche / resource distribution / taxonomic group Max 5 (from 7) Total 10 1b) light absorbed (for photosynthesis) some light is transmitted / reflected chlorophyll (a) absorbs mainly in the blue and red regions /colours /wavelengths of the spectrum chlorophyll b / carotenoids / accessory pigments extend the wavelengths of light absorbed / broaden/widen the absorption spectrum / absorb light wavelengths/colours not absorbed by chlorophyll chlorophyll b / carotenoids / carotene and xanthophyll / accessory pigments pass energy/electrons onto chlorophyll (a) (NOT light energy) Absorbed/captured) energy excites electrons in pigments / pigment molecules / chlorophyll (Not : Chloroplasts) Max 4 (high energy) electrons pass through electron transport chains /electron transport system / cytochrome chain / cytochrome system (to release energy) ATP generated by ATP synthase energy is used for photolysis energy is used to split water to produce / release hydrogen and oxygen hydrogen transferred to/reduces/joins to (coenzyme) NADP OR NADPH /NADPH2 is produced oxygen evolved/released OR oxygen produced as a waste product/ by-product ATP is transferred to / used in / needed for / needed in the carbon fixation stage/Calvin cycle (Not : light independent stage / dark stage / stroma) NADPH2 transferred to / used in / needed for / needed in carbon fixation stage / Calvin cycle Max 6 Total 10