# Explain why viruses are not classified within any of the recognised domains of life.

> IB DP Biology Standard Level (2023 syllabus) — A3.2 Classification and cladistics · Explain · 4 marks

## Mark scheme (4 marks)

1. Viruses are acellular / not composed of cells
2. The three domains (Bacteria, Archaea, Eukarya) are defined by cellular organisation, so viruses do not fit any domain
3. Viruses cannot carry out metabolism / do not carry out life processes independently
4. Viruses cannot replicate independently / require host cell machinery for reproduction

## Key terms

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

## 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)
- [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-why-viruses-are-not-classified-bd0db67f) · Published by Druglandscape Ltd.