Question

Scoliodon has a _____________ heart.
a. 2-chambered heart
b. 3-chambered heart
c. 4-chambered heart
d. 1-chambered heart

Answer 1

Hint: Fishes have only two chambers like the simplest vertebrate heart, an atrium and a ventricle which is known as a single circulatory system.

Complete solution:
> Option A is correct. Scoliodon belongs to a category of cold-blooded fishes. Scoliodon has two chambered hearts (contains one ventricle and an atrium) that cannot stop blood mixing. Blood mixing causes the animals' blood to become cold.

> Option B is incorrect. Reptiles like Salamander being an amphibian have a chambered heart of three. The 3 chambered heart contains only one ventricle in which weak oxygen and rich oxygen mingle but not completely. The pulmonary respiration is increased in amphibians, since they also absorb oxygen through the skin.

> Option C is incorrect. Birds and mammals like dolphins have 4 chambered hearts. Blood reaches the right atrium and traverses the right ventricle. The right ventricle pumps the blood to the lungs where oxygenation occurs. Pulmonary veins entering the left atrium bring the blood oxygenated back to the heart. Blood rushes from the left atrium toward the left ventricle. The left ventricle pumps the blood towards the aorta which distributes the oxygenated blood to all parts of the body.

> Option D is incorrect. The left ventricle pumps the blood to the aorta which will carry the oxygenated blood to all areas of the body. The larger, more complex crustaceans, like lobsters, have developed arterial-like arteries that force blood across their bodies, and the more active mollusks, such as squids, have formed a closed circulatory system and are able to travel quickly to capture prey.

So, the correct answer is Option A.

Note: Closed circulatory systems are a hallmark of vertebrates; nevertheless, due to adaptation through evolution and related variations in anatomy, there are major differences in the configuration of the heart and blood supply between the various vertebrate classes.