# Explain how antibiotic-resistant bacteria can develop in a population of bacteria through natural selection.

> Edexcel GCSE Biology (1BI0) — 4.1 Evolution by natural selection · Explain · 4 marks

> A patient is prescribed a course of antibiotics to treat a bacterial infection. After the course is completed, some bacteria remain in the body and are resistant to the antibiotic.

## Mark scheme (4 marks)

1. A random mutation occurs in the DNA of some bacteria, giving them resistance to the antibiotic
2. The antibiotic acts as a selection pressure, killing non-resistant bacteria
3. The resistant bacteria survive and reproduce, passing on the resistance gene to offspring
4. Over time, the frequency of the antibiotic-resistance trait increases in the population

## Key terms

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

## Related

- [Revision notes for Edexcel GCSE Biology (1BI0)](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-antibiotic-resistant-bacteria-can-develop-604f9714) · Published by Druglandscape Ltd.