Explain how genetic variation within a population contributes to its ability to remain stable when environmental conditions change.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
Genetic variation means individuals in a population differ in their alleles, genotypes and phenotypes.
When the environment changes, natural selection acts on this existing variation so that individuals with favourable alleles or phenotypes survive and reproduce more successfully.
Over successive generations, the favourable alleles increase in frequency, allowing the population to persist and avoid extinction.
A population with low genetic variation is less likely to contain individuals able to cope with the change, so its stability is reduced and extinction risk rises.
When the environment changes, natural selection acts on this existing variation so that individuals with favourable alleles or phenotypes survive and reproduce more successfully.
Over successive generations, the favourable alleles increase in frequency, allowing the population to persist and avoid extinction.
A population with low genetic variation is less likely to contain individuals able to cope with the change, so its stability is reduced and extinction risk rises.
Examiner tips
- Use the term ‘genetic variation’ first. Explain the role of natural selection. Show how allele frequencies change. Mention the risk of low variation.
Common mistakes
- Confusing genetic variation with environmental variation. Failing to link allele frequency changes to population stability. Using vague terms like ‘differences’ without specifying alleles/genotypes/phenotypes.
Mark scheme (4 marks)
- Genetic variation means individuals within a population differ in their alleles / genotypes / phenotypes.
- When the environment changes, natural selection acts on existing variation so that individuals with favourable alleles / phenotypes survive and reproduce at a higher rate.
- Favourable alleles increase in frequency in the population over successive generations, allowing the population to persist / avoid extinction.
- A population with low genetic variation is less likely to contain individuals able to survive environmental change, increasing extinction risk / reducing stability.
Key terms in this question
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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