Question

Two chambered heart occurs in
A. Crocodiles
B. Fish
C. Aves
D. Amphibians

Answer 1

Hint:
Heart is divided into various chambers depending on the types of blood it contains like oxygenated blood or deoxygenated blood and it also has entry and exit points of the heart. Mammals and birds have four chambered hearts as left atrium, right atrium, left ventricle and right ventricle. Amphibians and most reptiles have three chambered hearts with two atriums and one ventricle. Two chambered hearts are the heart which have one atrium and one ventricle to pump the blood.

Complete answer:
Fish have two chambered hearts , one atrium and one ventricle to pump the blood throughout the body. Atrium and ventricle are defined as true chambers whereas others are considered as accessory chambers. There are four compartments in the fish; the first one is sinus venosus which is sac with thin walls which contain cardiac muscles which collect deoxygenated blood through incoming hepatic and cardinal veins. Atrium in the fish heart has thick walls that send the blood to ventricles. Ventricles then pump the blood into the outflow tract as it has thick and muscular walls. Shape of the ventricle in fish is tubular with an elongated body and has a triangular base in other organisms. Outflow tract consists of tubule shaped conus arteriosus, bulbus arteriosus and goes to ventral aorta.

Hence, the correct option is B. Fish.

Note:
Crocodiles are reptiles and have three chambered hearts along with the amphibians as they have two atriums and one ventricle. Aves and mammals have four chambered hearts as their heart consists of two atriums and two ventricles.