Question

Two-chambered heart occurs in

• A. Crocodiles
• B. Fish
• C. Aves
• D. Amphibians

Answer 1

The correct option is B

Fish

The correct option is B.

Explanation of the correct option:

1. To pump blood throughout the body, fishes have two-chambered hearts, one atrium, and one ventricle.
2. The atrium and ventricle are genuine chambers, whereas the others are auxiliary chambers.
3. The fish has four compartments.
4. The first is the sinus venosus, which is a sac with thin walls that contains cardiac muscles that collect deoxygenated blood from entering hepatic and cardinal veins.
5. The thick walls of the atrium of the fish heart transport blood to the ventricles.

Explanation of the incorrect option:

Option A:

1. The heart of a crocodile differs from that of other reptiles in that it contains four chambers, similar to that of birds and mammals.
2. The right ventricle sends blood to the lungs for gas exchange, and the left ventricle pumps blood to the body.

Option C:

1. In birds, the heart is split into four chambers: right and left atria and right and left ventricle.
2. The existence of septa separates the left and right halves, preventing oxygenated blood from mixing with impure or deoxygenated blood.
3. This produces a very effective mechanism for supplying oxygenated blood to all regions of the body while ensuring double circulation.

Option D:

1. Amphibian hearts contain three chambers because they have slower metabolisms and they use less oxygen per liter of blood.
2. A frog's heart is made up of three chambers: one ventricle and two atria.
3. A heart with three chambers is perfect for amphibians, who can absorb oxygen via their skin when wet.

Hence, a two-chambered heart occurs in fish.