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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