Sometimes it is hard for us to imagine that creatures which are so unlike us have organs very much like ours that function in the same way. Many people think that because a fish lives in the water and is cold-blooded it must lack various organs, or not have certain senses.

Actually, the anatomy of a fish is very much like that of higher warm-blooded animals. In fact, many scientists believe this similarity is evidence that life on land evolved from life in the sea!