In Mammals and birds it is important to separate the oxygenated and deoxygenated blood because they are homoeothermic and warm-blooded animals. Due to this character, they can maintain their temperature constant throughout and the changes in their environment do not affect their body temperature regulation. This process also results in a good supply of oxygen in the case of birds and mammals so that optimum oxidation of glucose can take place. So to supply the required amount of oxygen it is important to have separate oxygenated and
deoxygenated blood.