Question

why mammals have four chambered heart

Answer 1

The blood is pumped from a three-chambered heart with two atria and a single ventricle. ... (d) Mammals and birds have the most efficient heart with four chambersthat completely separate the oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.

Answer 2

Birds and mammals are warm-blooded animals and maintain a constant body temperature by cooling themselves when they are in a hotter environment and by warming their bodies when they are in a cooler environment. Hence, these animals require more oxygen for more cellular respiration so that they can produce more energy to maintain their body temperature. Thus, it is necessary for them to have a four-chambered heart so as to separate oxygenated and de-oxygenated blood, so that their circulatory system is more efficient and can maintain their constant temperature.