evolution of heart in higher animalsthe

Question

Evolution of heart in higher animals

1. The circulatory system in higher animals has undergone several changes during evolution.
2. The heart has become totally muscular.
3. The heart has two chambers in fishes - one auricle and one ventricle. It is a branchial heart.
4. In amphibians like frog the heart is made up of three chambers 
5. It has two auricles and one ventricle.
6. In reptiles like lizards, the ventricle is incompletely divided.
7. So, it is an incompletely divided four chambered heart.
8. In birds and mammals, the heart is completely divided into four chambers with two auricles and two ventricles. It is a pulmonary heart.