In four chanmbered heart, left half is completely separated from right half by septa. It serves following two purposes
(a) ensures complete segregation of oxygenated and deoxygenated blood (i.e., no mixing).
(b) allows a highly efficient supply of oxygenated blood to all parts of the body.
This is useful in they warm blooded animals (like mammals and birds) which have high energy need , because they constantly require energy to maintain their body temperature.
