# Explain why mammals have a double circulatory system rather than a single circulatory system.

> Edexcel GCSE Biology (1BI0) — 8.2 Transport in animals (blood and circulation) · Explain · 4 marks

## Mark scheme (4 marks)

1. In a double circulatory system, blood passes through the heart twice per circuit (once to the lungs and once to the body)
2. Blood returning from the lungs is re-pressurised by the heart before being sent to the body
3. This maintains a higher blood pressure / faster flow of blood to body tissues
4. This ensures that oxygen and nutrients are delivered to tissues more efficiently / meets the demands of a multicellular organism

## Key terms

- [double circulatory system](https://www.gradenine.co.uk/glossary/double-circulatory-system)
- [circulatory system](https://www.gradenine.co.uk/glossary/circulatory-system)

## 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-why-mammals-have-a-double-61d4f108) · Published by Druglandscape Ltd.