# Explain how sexual selection can drive speciation even in the absence of geographic isolation.

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

## Mark scheme (4 marks)

1. Sexual selection involves individuals of one sex choosing mates based on specific heritable traits / characteristics.
2. Different subpopulations / groups within the same area may develop different mate preferences, leading to assortative mating within each group.
3. Differential mating reduces gene flow between the groups, so allele frequencies diverge over generations.
4. Over time, the groups become so genetically distinct that they can no longer interbreed successfully / are reproductively isolated, fulfilling the criterion for separate species.

## Key terms

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

## 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)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-sexual-selection-can-drive-1f07ba86) · Published by Druglandscape Ltd.