# Explain how sympatric speciation can occur within a single population occupying the same geographic area.

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

## Mark scheme (4 marks)

1. Sympatric speciation occurs without geographic isolation / within a single interbreeding population sharing the same habitat.
2. Reproductive isolation can arise through mechanisms such as polyploidy, resource / habitat specialisation, or disruptive selection acting on different sub-groups within the population.
3. Accumulation of genetic differences / divergence between the sub-groups occurs as gene flow between them is reduced or eliminated.
4. Over time, divergence becomes sufficient that the sub-groups can no longer interbreed / produce fertile offspring, completing speciation.

## Key terms

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

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-sympatric-speciation-can-occur-887e40aa) · Published by Druglandscape Ltd.