In four-chambered heart there is complete separation of oxygenated and deoxygenated blood, i.e. there is no mixing of blood. Therefore, the body parts receive oxygenated blood only loaded with oxygen. Animals having four-chambered heart are warm blooded and maintain high metabolic rate. This homeostasis can be maintained if the organs get rich oxygen supply. The four-chambered heart ensures complete separation of blood and good supply of oxygen, (as in birds and mammals).