Question

Why is double circulation only in humans and not in other animals?

Answer 1

During a single cycle blood goes twice in the heart which is known as double circulation. It is necessary in human being to separate oxygenated and de-oxygenated blood because this makes their circulatory system is more efficient and helps in maintaining constant body temperature.

Double circulation describes the fact that our oxygenated and deoxygenated blood is kept separate in our hearts. In fish (two-chambered heart) and amphibians (three-chambered heart), the oxygenated and deoxygenated blood is allowed to mix in the ventricles, in mammals and birds (four-chambered heart), the oxygenated and deoxygenated blood is kept separate. Fish and amphibians are cold-blooded, meaning that they conform to the temperature of their environment. Mammals and birds are warm blooded. They maintain a constant internal temperature, despite the environment. Maintaining a constant internal temperature allows mammals and birds to carry-out body processes more efficiently, but it requires more energy. Without double circulation, the body tissues would not receive enough oxygen to maintain a constant temperature, and would die.