Powered flight has evolved three times among vertebrates in the history of life on Earth.
The first to achieve the feat were flying reptiles known as pterosaurs. They first appeared roughly 220 million years ago but died along with the dinosaurs 65 million years ago when an asteroid slammed into Earth.
Scientists think birds descended from small, feathered dinosaurs roughly 150 million years ago. They survived the asteroid impact.
Bats, which generally are nocturnal, are the only mammals to have developed powered flight — some like flying squirrels glide but do not fly. Bats arose about 50 million years ago.
The wing structure of bats and birds differs. Birds have feathers projecting back from lightweight, fused arm and hand bones. Bats have flexible, relatively short wings with membranes stretched between elongated fingers.
While birds can open their feathers like a Venetian blind, bats have developed a twisting wing path that increases the lift during the upstroke.
There are about 1,000 species of bats, accounting for about 20 percent of mammal species. Most catch insects.
Human, Bird, and Bat Bone Comparison
From the outside human arms, bird wings, and bats wings look very different. Humans are covered in skin, birds are covered in feathers, and bats are covered in hair. But on the inside there are many similarities among human, bird, and bat forearms. Did you know that humans, birds, and bats have the exact same types of bones in their forearm? These organisms share the same forearm bones because they all evolved from a common ancestor.
Human, bird, and bat forearm bones include the humerus, ulna, radius, carpals, metacarpals, and phalanges.
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