 This means the blood flows from the capillaries to the heart and back to the capillaries instead of to the lungs.This process is useful to ectothermic (cold-blooded) animals in the regulation of their body temperature.Birds, mammals, and crocodilians show complete separation of the heart into two pumps, for a total of four heart chambers; it is thought that the four-chambered heart of birds and crocodilians evolved independently from that of mammals.