The heart receives blood in the atria and ejects blood from the ventricles - so you need two chambers for that function. read more
During the course of evolution the evolving species began to adopt for terrestrial conditions. Amongst the different types of heart in vertebrates four chambered heart is the most evolved. read more
At first, the tube-like heart is much like a fish heart. When it divides into two chambers, it is similar to a frog heart; with three chambers, a snake or turtle heart. Finally, with four chambers, the fully formed heart looks like what it is: the heart of a human being, the most highly evolved mammal. read more