# Explain how variation within a population enables natural selection to occur.

> IB DP Biology Standard Level (2023 syllabus) — A4.1 Evolution and speciation · Explain · 4 marks

## Mark scheme (4 marks)

1. Individuals within a population show heritable variation / differences in phenotype or genotype
2. Some variants / alleles confer a selective advantage, making those individuals better adapted to survive in their environment
3. Better-adapted individuals are more likely to survive, reproduce, and pass on their advantageous alleles to offspring / differential reproductive success
4. Over successive generations the frequency of advantageous alleles increases in the population / the population becomes better adapted over time

## Key terms

- [natural selection](https://www.gradenine.co.uk/glossary/natural-selection)

## 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)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-variation-within-a-population-09c27abb) · Published by Druglandscape Ltd.