Question

Incomplete double circulation is seen in.

• A. Fish
• B. Amphibians
• C. Birds
• D. Mammals

Answer 1

The correct option is B

Amphibians

The correct option is B.

Explanation of the correct option:

Option B:

1. Incomplete double circulation is found in amphibians.
2. They have a three-chambered heart.
3. The heart comprises one ventricle and two atria.
4. Oxygenated blood enters the right and left atrium.
5. They have incomplete double circulation because of the mixing of oxygenated and deoxygenated blood of blood in the single ventricle.
6. So, the blood comes into the heart by two different routes but leaves through the single route.

Explanation of the incorrect incorrect options:

Option A:

1. Fishes have a single circulatory system.
2. The deoxygenated blood is pumped to the gills, from there the oxygenated blood is pumped to the rest of the body.
3. They have a single atrium and ventricle.

Option C:

1. Birds have a closed circulatory system.
2. They have two atria (left and right) and two ventricles (left and right).
3. They have a four-chambered heart.
4. The right side of the heart receives deoxygenated blood from the whole body.
5. The deoxygenated blood is pressurized by the pulmonary circulation/
6. The left side of the heart receives the oxygenated blood from the lungs and the left ventricle pressurizes the systemic circulation.

Option D:

1. Mammals have complete double circulation.
2. They have a four-chambered heart.
3. Deoxygenated blood is received by the right atrium by the vena cava.
4. The superior vena cava carries the deoxygenated blood from the upper part of the body (head, neck, arms, chest, etc.), while the inferior vena cava carries the deoxygenated blood from the lower part of the body such as the legs, feet, organs, etc.
5. Then they have pumped to the heart by the right ventricle.
6. The oxygenated blood from the heart enters the left atrium via pulmonary veins.
7. The right atrium pumps the oxygen into the aorta for the rest of the body for systemic circulation.

Final answer: Incomplete double circulation is seen in amphibians.