# A species of finch lives on an isolated island. The finches feed on seeds found on the ground. Over many generations, a drought reduces the availability of small, soft seeds, leaving mainly large, hard seeds. Explain how the finch population may change as a result of natural selection over many generations.

> Pearson Edexcel A-Level Biology A (9BI0) — Topic 7 Genetics, Populations, Evolution and Ecosystems · Explain · 5 marks

> A species of finch lives on an isolated island. The finches feed on seeds found on the ground. Over many generations, a drought reduces the availability of small, soft seeds, leaving mainly large, hard seeds.

## Mark scheme (5 marks)

1. There is variation in beak size within the finch population
2. Finches with larger or stronger beaks are better able to crack open large, hard seeds and so are more likely to survive
3. Finches with smaller beaks are less able to obtain food and are more likely to die / be selected against
4. Surviving finches with larger beaks are more likely to reproduce and pass on the alleles for larger beaks to offspring
5. Over many generations the proportion of finches with larger beaks increases in the population

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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/a-species-of-finch-lives-on-b8ef19b0) · Published by Druglandscape Ltd.