Question

What is double circulation? What is the benefit of double circulation?

Answer 1

In humans, blood passes through the heart twice during a cardiac cycle. Once, the deoxygenated blood passes through the heart and then the oxygenated blood passes through the heart. This is called double circulation. In this case, deoxygenated blood is completely separated from oxygenated blood. Hence, this is a highly efficient method of blood circulation. Animals which show double circulation are more active, more energetic and are warm blooded animals. Double circulation is present in mammals and birds.