Question

Why is it necessary to separate oxygenated and deoxygenated blood in mammals and bids?

Answer 1

Mammals and birds have evolved to sustain a terrestrial life form and homeothermic ability that needs more energy as compared to other life forms. So, it is important to separate the blood coming in from the pulmonary circulation from that going through the systemic circulation. The oxygenated blood is not only rich in oxygen but also moves under high hydrostatic pressure so that it can reach the tissues quickly and metabolism can be performed at required rate. Also, this type of arrangement is required to maintain the body temperature through the differential contraction of the blood vessels.