The diagram shows a population of deer on a mountain where winters have become colder. Deer vary in the thickness of their winter coat. Thick coats reduce h...
Question 1 Report
The diagram shows a population of deer on a mountain where winters have become colder. Deer vary in the thickness of their winter coat. Thick coats reduce heat loss but require more food to grow. In the coldest years, deer with very thin coats are more likely to die. In mild years, deer with very thick coats may have less food available for breeding. Scientists record coat thickness and survival.
Table 1 gives survival after one unusually cold winter.
| Coat thickness | Deer at start | Deer surviving |
|---|---|---|
| Thin | 40 | 9 |
| Medium | 45 | 30 |
| Thick | 42 | 34 |
(a) Describe the relationship between coat thickness and survival in this winter. [2]
(b) Calculate the survival percentage for thin-coated deer. [2]
(c) Explain why a sequence of cold winters could change the allele frequencies in this deer population. [2]
Answer Details
(a) Survival increased as coat thickness increased. Only 9 thin-coated deer survived, compared with 34 thick-coated deer. [2]
(b)
\[\frac{9}{40}\times100=22.5\%\]
The survival percentage for thin-coated deer was 22.5%. [2]
(c) During repeated cold winters, thick-coated deer are more likely to survive and breed. They pass alleles for thicker coats to their offspring, so these alleles increase in frequency in the population. This is natural selection. [2]
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