In the structure of which organs of amphibians there were complications in comparison with fish, which proves.

In amphibians, the skin-pulmonary type of respiration and, in connection with this, the lungs are developed, and the fish are able to breathe only with gills. Also, amphibians underwent changes in the circulatory system and in the heart. Now the circulatory system makes two circles of circulation, and the heart has become three-chambered. Fish have scales on their skin, while amphibians do not. Also, amphibians have a more developed brain than fish. All these changes indicate that amphibians are half adapted to life on land.