# A population of finches lives on a mainland. Some finches migrate to a remote island far out at sea, where they cannot return to the mainland. Explain how, over many generations, the island finches could eventually become a new species.

> Pearson Edexcel A-Level Biology A (9BI0) — 3.4 Evolution and speciation · Explain · 5 marks

> Finches on the mainland eat hard seeds and have short, strong beaks. The remote island has a very different climate and food supply compared to the mainland.

## Mark scheme (5 marks)

1. The island finches are geographically isolated from the mainland finches, so they cannot interbreed with them.
2. Random mutations occur in the DNA / genetic material of individuals in both populations.
3. On the island, different environmental conditions mean different alleles / mutations are advantageous compared to those on the mainland.
4. Natural selection means individuals with beneficial alleles are more likely to survive, reproduce and pass those alleles on to offspring.
5. Over many generations the two populations become so genetically different that they can no longer interbreed to produce fertile offspring, and a new species has formed.

## 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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