Features of the structure of fish and frogs, their adaptation to the environment, the direction of evolution.

Fish and amphibians had common ancestors, so they have similar stages of development. Fish live in the aquatic environment. They have special bodies for this. Such organs include gills, fins, and more. Frogs live in a terrestrial-air environment, although they can submerge in water for a long time. Adult frogs breathe using their lungs and skin. But frog heads have gills and fins, since frogs develop in an aquatic environment. Only in the course of development do the lungs appear at the head, and the gills overgrow.