# Explain how natural selection leads to a population of organisms becoming better adapted to their environment over many generations.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 2.6 Adaptation and natural selection · Explain · 5 marks

> In a population of beetles, individuals vary in the colour of their bodies. Some beetles are dark brown and others are pale green. The beetles live on green leaves and are hunted by birds.

## Mark scheme (5 marks)

1. There is variation in the population (e.g. some beetles are dark brown and some are pale green)
2. Pale green beetles are better camouflaged on leaves and are less likely to be eaten by birds (selection pressure / predation)
3. Better-adapted (pale green) beetles are more likely to survive and reproduce
4. The advantageous alleles / genes for pale green colour are passed on to offspring
5. Over many generations, the proportion of pale green beetles in the population increases

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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-natural-selection-leads-to-beb80296) · Published by Druglandscape Ltd.