A bat and a bird can fly yet they are different from each others . how?

Bats are the only mammals capable of flying, and they are widespread on every continent in the world except Antarctica. Some people consider bats to be scary creatures, while others see them as wonderful animals. The Spanish website Super CuriOSo said in a report that bats represent 20 percent of the mammalian species on the planet, given that there are more than 1,100 species of them.