Question

There has been an increase in the number of chambers in heart during evolution of vertebrates. Give the names of the class of vertebrates having two, three or four-chambered heart.

Answer 1

Heart has evolved from two chambered in fishes to three chambered in amphibians and reptiles (except crocodiles) to completely four chambered in birds and mammals.

Number of chambers	Class
Two-chambered	Osteichthyes and Chondrichthyes
Three-chambered	Amphibia, Reptilia (except crocodiles)
Four-chambered heart	Aves and Mammalia