Eli5: Why do birds and fish come in such a spectacular variety of colors and shapes compared to other animals?

Question

Eli5: Why do birds and fish come in such a spectacular variety of colors and shapes compared to other animals?

In: 81

Answer 1

This is not a complete answer, but in some species, bright colors help the males to attract females. This is true for various bird and fish species, however there are also plenty who don’t exhibit sexual dimorphism. Like I said, not a complete answer.