Question

Why do human beings and birds have 4 chambered heart and Amphibians with 3 chambered heart ? List any two featuresby which the circulatory system of fish different from humans.

Answer 1

In mammals  there is a double circulation. The right side of the heart receives blood returning back from the body; this blood is low in oxygen . This “deoxygenated” blood enters the right atrium and then the right ventricle to be pumped to the lungs were the blood will be oxygenated. The oxygenated blood  from the lungs enters the left ventricle via the left atrium and is then pumped out into the larger body circulation.In fish, the heart only has one atrium and one ventricle. The oxygen-depleted blood that returns from the body enters the atrium, and then the ventricle, and is then pumped out to the gills where the blood is oxygenated, and then it continues through the rest of the body.
Mammals  have the most efficient heart with four chambers that completely separate the oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.