The evolutionary changes in pattern of heart among vertebrates are :

1. Fishe heart is two chambered, one auricle and one ventricle. In there is single circulation of blood. 

2. Amphibian heart : The heart of amphibians have 3 chambers i.e. two auricles and one ventricle. 

3. Reptilian heart : In reptiles heart is three chambered, but ventricle is also incompletely divided by incomplete interventricular septum. 

In crocodile, the heart is four chambered i.e. with wo auricles and two ventricles.

4. Avian and Mammalian heart : In avian and mammals, the heart is four chambered ie with two auricles and two ventricles and there is complete separation of pure and impure blood.