Bats are the only mammals that can fly. There are over 1,300 species of bats, and they are found on every continent except Antarctica. Birds are also vertebrates that can fly, and there are over 10,000 species of birds in the world. Bats and birds use different anatomical structures to fly. Bats use their wings, which are made of skin and supported by bones, to fly. Birds use their feathers to fly. Feathers are lightweight and aerodynamic, and they help birds to achieve lift and thrust. Bats and birds are both important members of the ecosystem. Bats help to control insect populations by eating them, and birds help to spread seeds and pollinate plants.