# Explain how genetic variation within a population contributes to its ability to remain stable when environmental conditions change.

> IB DP Biology Standard Level (2023 syllabus) — D4.2 Stability and change · Explain · 4 marks

## Mark scheme (4 marks)

1. Genetic variation means individuals within a population differ in their alleles / genotypes / phenotypes.
2. When the environment changes, natural selection acts on existing variation so that individuals with favourable alleles / phenotypes survive and reproduce at a higher rate.
3. Favourable alleles increase in frequency in the population over successive generations, allowing the population to persist / avoid extinction.
4. A population with low genetic variation is less likely to contain individuals able to survive environmental change, increasing extinction risk / reducing stability.

## Key terms

- [genetic variation](https://www.gradenine.co.uk/glossary/genetic-variation)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-genetic-variation-within-a-22a48972) · Published by Druglandscape Ltd.