# Explain how natural selection can lead to adaptive radiation within a lineage of organisms.

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

> Adaptive radiation is a process in which organisms from a single ancestral lineage rapidly diversify into many new forms, each adapted to a different ecological niche. The finches of the Galápagos Islands are a well-known example, where a single ancestral finch species gave rise to multiple species with markedly different beak morphologies.

## Mark scheme (4 marks)

1. Variation exists within the ancestral population due to mutation and/or sexual reproduction, providing heritable differences among individuals.
2. Individuals that are better adapted to a particular ecological niche have higher survival and reproductive success (differential reproductive success / survival of the fittest).
3. As different subpopulations become isolated (geographically or ecologically) and adapt to different niches, gene pools diverge through accumulation of different alleles / mutations over generations.
4. Over time, reproductive isolation develops between the diverging lineages, leading to the formation of multiple new species each occupying a distinct niche (speciation).

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard 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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