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Mark schemes
Q1.
(a)
all 4 correct = 2 marks
2 or 3 correct = 1 mark
0 or 1 correct = 0 marks
2
(b) Geospiza fortis
ignore underlining or attempted italics or
upper and lower case letters
1
(c) offspring have similar beak depths to parents
ignore same beak depths
ignore positive correlation / described
1
(d) parents of a given beak depth produce offspring with several beak
depths
allow spread of results for a given
parental beak depth about line of best fit
allow range of phenotypes for a given
parental beak depth
1
(e) colonisers of Isabela have a range of beak depths
allow colonisers of Daphne have a
range of beak depths
1
due to different combinations of alleles of several genes
or
due to different alleles of one gene
or
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due to mutation
1
large range of (sizes / species of) seeds / food (on Isabela)
or
large(r) seeds (on Isabela)
allow small range of (sizes / species of)
seeds / food on Daphne
or
allow small(er) seeds on Daphne
1
more competition for seeds / food (on Isabela)
allow less competition for seeds / food
on Daphne
ignore competition unqualified
1
birds with larger beaks get enough food to (survive and) reproduce
(on Isabela)
allow birds with smaller / medium beak
sizes get enough food to (survive and)
reproduce on Daphne
1
(survivors) pass on (beneficial) alleles to offspring
allow pass on genes / mutation ignore
pass on chromosomes / characteristics
1
(f) Isabela is a large island with more species of plants
or
Isabela is a large island with more variety in seed / food sizes
or
Isabela is a large island with more plants / seeds / food
1
less competition for seeds / food
or
enough seeds / food for both bird species
1
[13]
Q2.
(a) 3.7
1
(b) 2
1
(c) (different combinations of alleles cause) many / 22 values
allow continuous variation
or
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in-between values
or
large range of values
or
there are not only two values
allow there are not only 3 values if 3 is
given in part (b)
1
(d) different protein made
allow change in shape (of enzyme) or
change in 3-D structure
ignore denature
1
active site changed
1
so substrate does not fit / bind
allow description of substrate
allow cannot form E-S complex
ignore lock and key description
1
(e) produces (some) offspring with high-fat milk
or
not all offspring have low-fat milk
ignore reference to alleles
1
(f) takes less time (to obtain results)
or
more offspring at the same time
allow other sensible suggestion − e.g.
allows screening or allow cow 7 to
continue to produce eggs or avoid injury
to cow 7 during mating or giving birth
1
(g) male gametes correct: d (and d)
1
female gametes correct: D and d
1
allow 1 mark if gametes are correct but
gender not identified
correct derivation of offspring genotypes from given gametes
allow 2 × 2 or 2 × 1 derivation
1
Dd identified as low-fat and dd identified as high-fat in offspring
if DD offspring are produced, must also
identify as low-fat
1
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(h) find female with low(est) fat in milk and high(est) milk yield
allow choose from 7, 9, 12, 13 which
has the highest yield
1
find male whose female offspring have high(est) milk yield and
low(est) fat in milk
allow choose from 16 or 18 whose
female offspring has the highest yield
1
or
find female with lowest fat in milk
or cow 13 (1)*
*or
allow female with high(est) milk yield
find male whose female offspring have high(est) milk yield (1)*
*or
allow male whose female offspring have
lowest fat in milk / male 16
cross the best (for both features) female with the best male
1
select best offspring (for both features) from each generation and
repeat for several generations
1
[16]
Q3.
(a)
Classification
Name
group
Class Mammalia
Order Primates
Family Lemuroidea
Species catta
all 4 correct = 2 marks
2 or 3 correct = 1 mark
0 or 1 correct = 0 marks
2
(b) Lemur catta
ignore capitalisation / non-capitalisation
of initial letters
ignore italics / non-italics
ignore underlining / non-underlining
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(c) carried by (favourable) currents on masses of vegetation
allow description of currents from Figure
2
ignore swimming
1
(d) isolation of different populations
1
habitat variation between lemur populations
allow examples − biotic (e.g. food /
predators) or abiotic (e.g. temperature)
1
genetic variation or mutation (in each population)
1
better adapted survive (reproduce) and pass on (favourable) allele(s)
to offspring
allow natural selection or survival of the
fittest and pass on (favourable) allele(s)
to offspring
allow gene(s) / mutation as an
alternative to allele(s)
1
(eventually) cannot produce fertile offspring with other populations
allow cannot reproduce ‘successfully’
with other populations
ignore cannot reproduce unqualified
1
[9]
Q4.
(a) less sweating so less water loss
1
(as) no / little water available in desert
1
(b) (fat store) can be metabolised / respired to water
1
(little urine…) conserve water
1
(hard mouth) not damaged by spines on plants / on food
or
not damaged by hard / dry food
1
(c) dromedary / C.dromedarius
and bactrian / C. bactrianus
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no mark for the names, but must be identified
because
same genus
ignore ‘both are Camelus’
1
(d) any two from:
• the fossil record
• oldest fossils in N. America
or
• newer fossils in S. America / in Asia / in Africa
allow numbers for ages (45 Mya and 3 Mya / 6
Mya)
• chemical / DNA analysis of living species
allow radioactive dating of fossils
2
(e) isolation of separate camel populations by sea
or
by mountains
1
habitat variation / described between populations
allow examples – biotic (e.g. food / predators) or
abiotic
1
genetic variation / mutation in each population
1
45 million years is sufficient time to accumulate enough mutations
1
natural selection
or
better adapted survive to reproduce
1
pass on favourable allele(s)
allow gene(s)
1
[14]
Q5.
(a) white blood cells have the same DNA / genes / chromosomes
or
have the gene for GH
allow have all the genes
allow all body cells (except RBCs) have all of the
genes
1
(b) enzyme has specifically-shaped active site
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the 2 antibiotic resistance genes have different (sequence of) bases
1
only Tetracycline-resistance gene fits (active site of) enzyme
or
only Tetracycline-resistance gene is complementary to (active site of)
enzyme
1
(c)
Ampicillin Tetracycline
✔ ✔
1 mark for each correct row
if no other mark, allow 1 mark for one correct
column
1
1
1
(d) clone produced by asexual reproduction
allow by ‘mitosis’
1
all DNA / all genes are copied
allow GH gene copied
allow plasmid copied
1
every cell receives a copy
or
receives every gene
or
receives GH gene
or
receives plasmid
or
genetically-identical cells
1
[10]
Q6.
(a) any two from:
• so that they do not have specific genetic defects
• to produce docile cats or so they are not aggressive
allow descriptions of aggression such as biting and
scratching
• for aesthetic reasons
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allow descriptions of suitable aesthetic reasons
2
(b) (cats) are more likely to pass on (recessive) disorders
or
more likely to be susceptible to diseases
1
(c) Level 2 (3–4 marks):
A detailed and coherent explanation is given, which logically links the
process of selective breeding with explanations of how this produces cats
that do not cause allergic reactions.
Level 1 (1–2 marks):
Simple statements are made relating to process of selective breeding, but
no attempt to
link to explanations.
0 marks:
No relevant content.
Indicative content
process:
• parents with the desired characteristic are selected
• the parents are bred together to produce offspring
• offspring with the desired characteristics are selected and bred
• this is repeated over many generations.
explanations:
• parents who produce the least Fel D1 are initially selected
• in their offspring there will be individuals with differing amounts of Fel
D1 produced
• care is taken to ensure cats are healthy and avoid possible problems
associated
with selective breeding
• over time the population of (selectively bred) cats will produce less
Fel D1
4
[7]
Q7.
(a) three billion
1
(b) mutation(s)
1
breed / reproduce
in this order only
allow pass on their genes
1
[3]
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Q8.
(a) any two from:
• larger / longer / thicker
allow examples eg fewer toes or bones fused
• fewer (bones in total)
allow smaller surface area touching the ground
• fewer bones touching the ground
2
(b) (i) large(r) surface / area in contact with the ground
or
low / less pressure on ground
1
(so) less likely to sink into mud / ground
or
(so) could run fast(er)
allow easy / easier to escape predators
1
(ii) variation (in size / number / arrangement of bones)
allow mutation(s) (in size / number / arrangement of
bones)
1
(and) those with large(r) / few(er) bones more suited to running or
run faster (on harder / drier ground)
1
these survive and breed
allow ref to offspring for breed
1
(so) genes / DNA (for larger / fewer bones) passed on
allow alleles passed on
1
[8]
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