Explain how natural selection can lead to the evolution of larger body size in Arctic mammals over successive generations.
Answer
Larger body size is selected in cold environments because larger animals conserve heat better; allele frequencies for genes affecting body size increase over generations, leading to an overall larger average size.
Step-by-step solution
- Step 1: Recognise that in Arctic climates, thermal regulation is critical for survival.
- Step 2: Larger mammals have a smaller surface‑area‑to‑volume ratio, which reduces heat loss.
- Step 3: Individuals with alleles promoting larger body size thus have higher fitness and are more likely to reproduce.
- Step 4: Over successive generations, the frequency of these advantageous alleles rises.
- Step 5: Consequently, the population’s mean body size increases through natural selection.
Common mistake: Assuming that all mammals in cold environments become larger; neglects ecological and energetic trade‑offs.
Concept tested: Natural selection and adaptation
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