What are the similarities between tadpoles and fish and amphibians?

The tadpole is similar in appearance and internal structure to a small fish. He, like fish, has a two-chambered heart, consisting of an atrium and a ventricle, one circle of blood circulation, a lateral line, and a tail. Breathes with gills.

Then the tadpole undergoes changes: first the hind limbs appear, then the front ones, the gills are gradually replaced by the lungs, the second circle of blood circulation is formed, the heart becomes three-chambered. The tail is shortened. The tadpole becomes like a frog.