# Explain how a new species can arise from an original population of organisms through the process of speciation.

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

> A population of birds lives on a large mainland. Over thousands of years, some birds become isolated on a remote island with a different environment. Eventually, the island birds and mainland birds can no longer interbreed successfully.

## Mark scheme (5 marks)

1. Genetic variation exists within the original population due to mutations and/or sexual reproduction
2. The two populations become geographically isolated, so they cannot interbreed
3. Different selection pressures act on each population, so different alleles are advantageous in each environment
4. Over many generations, the allele frequencies in each population change, so the two populations become increasingly different genetically
5. The populations become so genetically different that they can no longer interbreed to produce fertile offspring, and are therefore classified as separate species

## Key terms

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

## 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/explain-how-a-new-species-can-ef4f2ac3) · Published by Druglandscape Ltd.