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

> Cambridge International IGCSE Biology (0610) — 9.1 Circulatory systems · Explain · 4 marks

## Mark scheme (4 marks)

1. In a double circulatory system, blood passes through the heart twice per circuit / returns to the heart after visiting the lungs before being pumped to the body
2. This maintains high blood pressure when blood is delivered to the body / blood pressure is restored / boosted after passing through the lungs
3. Mammals are larger / more active and have a greater demand / need for oxygen
4. Mammals are warm-blooded / maintain a constant body temperature and need more energy / oxygen for respiration to produce heat

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](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-cffae6c4) · Published by Druglandscape Ltd.