Question

The animals with two-chambered heart belong to
(a) Amphibia
(b) Protozoa
(c) Pisces
(d) Aves

Answer 1

Hint: The animals that belong to this superclass are usually having streamlined bodies and are mainly found in fresh, marine, and brackish water. They have two sets of paired fins named the pectoral and the pelvic fins. Other than these two fins they also bear dorsal fins, caudal fins, and the anal fins present in the middle.

Correct answer:
The animals with two-chambered hearts belong to superclass Pisces which includes fishes. The heart of fish is a two-chambered structure, the upper chamber is called the atrium whereas the lower chamber is called the ventricle. In the atrium the deoxygenated blood is carried from the body, then from here the blood is transported to the ventricle and then from the ventricle to the gills where the exchange of gases takes place and the blood becomes oxygenated. The oxygenated blood continues to flow throughout the body and before arriving back to the atrium collects the carbon dioxide and becomes deoxygenated.

Additional Information:
-For the circulation of blood, the heart is the pump that generates the driving pressure for it.
-In the heart of fish, two more chambers are also found namely the sinus venosus and the bulbus arteriosus.
-The sinus venosus is a thin-walled sac that is responsible for the collection of blood from the veins of fish before entering the atrium.
-The bulbus arteriosus is a large tube that receives blood from the ventricle and then the blood moves out of the heart.
-In the amphibians the three chambered hearts are found having two atriums and one ventricle.
-Aves have four chambered hearts with two atriums and two ventricles.
-Protozoa is a unicellular organism having a nucleus enclosed within a membrane. The organelles of Protozoa perform functions similar to the organs of higher animals.

So, the correct answer is,' Pisces'.

Note:
-The fishes have the simplest circulatory system where the blood flows only in one direction from the two-chambered heart through the gills and then the rest of the body.
-The oxygenated blood passing through the heart supplies oxygen to the heart itself.
-The blood flows to the gills for oxygenation through the aorta which connects the bulbus arteriosus.