# Explain why the human circulatory system is described as a 'double circulatory system' and outline the advantage this gives to mammals compared to a single circulatory system.

> Eduqas A-Level Biology — 2.1 Classification and biodiversity · Explain · 5 marks

## Mark scheme (5 marks)

1. Blood passes through the heart twice in one complete circuit of the body
2. One circuit goes from the heart to the lungs and back (pulmonary circulation)
3. The second circuit carries oxygenated blood from the heart to the rest of the body (systemic circulation)
4. Oxygenated and deoxygenated blood are kept separate / the heart has four chambers to separate the two types of blood
5. This allows a higher blood pressure to be maintained, so oxygen is supplied to cells more efficiently / mammals have a greater need for oxygen for respiration

## Key terms

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

## Related

- [Revision notes for Eduqas A-Level Biology](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-human-circulatory-system-624f4d72) · Published by Druglandscape Ltd.