Question

What is double circulation of blood why do birds and mammals have double circulation?

Answer 1

when heart flows twice in a sec in vertabretes

Answer 2

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It is called a double circulatory system because blood passes through the heart twice per circuit. The right pump sends deoxygenated blood to the lungs where it becomes oxygenated and returns back to the heart. The left pump sends the newly oxygenated blood around the body.