EVERYDAY SCIENCE

Detailed explanation-1: -In amphibians, reptiles, birds, and mammals, blood flow is directed in two circuits: one through the lungs and back to the heart, which is called pulmonary circulation, and the other throughout the rest of the body and its organs including the brain (systemic circulation).

Detailed explanation-2: -The adult human heart consists of two separated pumps: the right side, which pumps deoxygenated blood into the pulmonary circulation, and the left side, which pumps oxygenated blood into the systemic circulation.

Detailed explanation-3: -Amphibians and reptiles demonstrate incomplete double circulation. They have a three-chambered heart with two atria and one ventricle.

Detailed explanation-4: -Most non-avian reptiles have a three-chambered heart, but have little mixing of the blood; they have double circulation. Mammals and birds have a four-chambered heart with no mixing of the blood and double circulation.

Detailed explanation-5: -All animals need blood to be transported to the lungs (or gills in fish) in order to be oxygenated. After the blood is oxygenated, it travels back to the heart in amphibians, reptiles, mammals and birds in order to be transported to the rest of the body. This is called double circulation.