Question

How many chambers are there in a fish heart?
A. Two
B. Three
C. Four
D. One

Answer 1

Hint:- Fishes belong to the class of Pisces and belong to the group of vertebrates having gill slits. Fishes are poikilothermic that are cold-blooded which means that they cannot regulate their body temperature, unlike humans. Fishes have a closed circulatory system in which the blood flows inside the body in closed vessels.

Complete Answer:-Fishes have a two-chambered heart. The heart consists of an atrium and a single ventricle. The atrium receives blood and the ventricle is responsible for pumping it. The circulation in fishes is also a single circulation in a single direction - unidirectional flow. This is in contrast to the bidirectional double circulation in humans occurring in four-chambered hearts. Fishes only have systemic circulation and not pulmonary circulation.
The ventricles pump blood to the gills where gaseous exchange occurs and blood is oxygenated. The gills function as lungs. After oxygenation, blood from the gills reaches the rest of the body. Deoxygenated blood from the body reaches the heart and fills it. This deoxygenated blood is again pumped by the ventricles to the gills where it is oxygenated and the cycle goes on.
Thus, the correct answer is Option (A) - Two.

Note:- A fish’s heart is also known as a venous heart because it is filled with deoxygenated blood. This type of single circulation present in fishes is known as simple circulation. Instead of pulmonary circulation, the fishes have gill circulation in which the ventricles pump out deoxygenated blood to the gills for oxygenation.