Question

Incomplete double circulation is observed in

• A. Reptiles
• B. Birds
• C. Amphibians
• D. Both a and c

Answer 1

The correct option is D Both a and c

Incomplete double circulation is a type of circulatory system in which the blood comes into the heart by two different routes but goes out in a single route.
In such cases the heart is three chambered. It has two auricles and one ventricle. Due to this the oxygenated and deoxygenated blood gets mixed. The right auricle receives deoxygenated blood from the body and the left auricle gets oxygenated blood from the lungs. But the oxygenated and deoxygenated blood are mixed up in the ventricle. The reptiles and amphibians have three chambered hearts. So incomplete double circulation is observed in both reptiles and amphibians. But crocodiles are an exception to this as they have four chambered hearts.

Birds and mammals have four chambered hearts in which there are two auricles and two ventricles. The right auricle and right ventricle are involved in receiving the deoxygenated blood and pumping it to the lungs respectively whereas the left auricle and left ventricle are responsible for receiving the oxygenated blood and pumping it to the body parts respectively. There is no mixing of oxygenated and deoxygenated blood in this type of circulation. This type of circulation is called complete double circulation.