# A population of Galápagos finches lives on an island where the main food source is large, hard seeds. Explain how natural selection could lead to finches with larger, stronger beaks becoming the dominant variety in the population over many generations.

> Pearson Edexcel A-Level Biology A (9BI0) — 2.6 Adaptation and natural selection · Explain · 5 marks

> On the island, a random mutation caused some finches to develop slightly larger, stronger beaks. Other finches in the population had smaller, weaker beaks.

## Mark scheme (5 marks)

1. There is variation in beak size/strength within the population
2. Variation is caused by (random) mutation / inherited genetic differences
3. Finches with larger, stronger beaks can crack/eat the large hard seeds more successfully, giving them a selective advantage / better chance of survival
4. Finches with larger beaks are more likely to survive and reproduce / pass on their alleles/genes to offspring
5. Over many generations the alleles/genes for larger, stronger beaks increase in frequency in the population, so larger beaks become more common

## Key terms

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

## 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-population-of-gal-pagos-finches-lives-59efc750) · Published by Druglandscape Ltd.