Question

Assertion : Double circulation is incomplete in amphibians and reptiles
Reason : Unlike in birds and mammals, in amphibian and reptiles, the left atrium receives oxygenated blood and right atrium receives deoxygenated blood.
A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Answer 1

Correct Answer - C
Amphibians and the reptiles (except crocodiles) have a 3-chamered heart with two atria and a single ventricle, whereas crocodiles, birdds and mammals possess a 4-chambered heart with two atria and two ventricles.
In amphibians and reptiles, the left atrium receives oxygenated blood from the gills/lungs/skin and the right atrium gets the deoxygenated blood from other body parts. However, they get mixid up in the single ventricle which pumpsout mixed blood (incomplete double circulation). In birds and mammals, oxygenated and deoxygenated blood received by the left and right atria respectively passes on to the ventricles of the same sides. The ventricles pump it out without any mixing up, i.e., two separate circulatory pathways are present in these organisms, hence, these animals have double circulation.