Double circulation
Exam-ready definition
A circulatory system in which blood passes through the heart twice for each complete circuit of the body. Once in the pulmonary circuit (to the lungs) and once in the systemic circuit (to the rest of the body).
How this is marked
The advantage is the paying point at Extended: blood can be pumped at higher pressure to the body after gaining oxygen at the lungs, increasing the rate of oxygen delivery. 'Blood goes through the heart twice' alone is only the definition mark.
In an exam answer
Stating the advantage: 'In double circulation, blood returns to the heart after the lungs so it can be pumped at higher pressure to the body, increasing the rate of oxygen delivery.'
Full topic guide: Transport in animals
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