End Show Slide 1 of 53 Copyright Pearson Prentice Hall 31-2 Birds

End Show 31-2 Birds Slide 2 of 53 Copyright Pearson Prentice Hall What Is a Bird? Birds are reptilelike animals that maintain a constant internal body temperature. Birds have an outer covering of feathers; two legs that are covered with scales and are used for walking or perching; and front limbs modified into wings.

End Show 31-2 Birds Slide 3 of 53 Copyright Pearson Prentice Hall What Is a Bird? Feathers are made mostly of protein and develop from pits in the birds' skin. Feathers help birds fly and also keep them warm. The two main types of feathers are contour and down.

End Show 31-2 Birds Slide 4 of 53 Copyright Pearson Prentice Hall What Is a Bird? Feathers Contour feather: Contour feathers provide the lifting force and balance needed for flight. Down feather: Down feathers trap air close to the body and keep the bird warm. Barbule: The hooks on each barbule fit together, holding them flat. Barb

End Show 31-2 Birds Slide 5 of 53 Copyright Pearson Prentice Hall Evolution of Birds Paleontologists agree that birds evolved from extinct reptiles. Embryos of birds and reptiles develop within amniotic eggs. Both excrete nitrogenous wastes as uric acid. Bones that support the limbs, and other skeleton parts, are similar in both groups.

End Show 31-2 Birds Slide 6 of 53 Copyright Pearson Prentice Hall Evolution of Birds Archaeopteryx was the first birdlike fossil discovered. Archaeopteryx looked like a dinosaur, but it had feathers. It had teeth in its beak, a bony tail, and toes and claws on its wings. It may be a transitional species between dinosaurs and birds.

End Show 31-2 Birds Slide 7 of 53 Copyright Pearson Prentice Hall Evolution of Birds Other fossil evidence leads some to hypothesize that birds and dinosaurs both evolved from an earlier common ancestor. The origin of birds is still not completely resolved. New fossils of ancient birds are being found all the time.

End Show 31-2 Birds Slide 8 of 53 Copyright Pearson Prentice Hall Evolution of Birds Modern reptiles Ornithischia (bird-hipped dinosaurs) Saurischia (lizard-hipped dinosaurs) Archaeopteryx Modern birds Dinosaurs Ancestor of dinosaurs Reptile ancestor

End Show 31-2 Birds Slide 9 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Birds have a number of adaptations that enable them to fly, including: highly efficient digestive, respiratory, and circulatory systems aerodynamic feathers and wings strong, lightweight bones strong chest muscles

End Show 31-2 Birds Slide 10 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Body Temperature Control Birds generate their own body heat and are called endotherms. Endotherms have a high rate of metabolism. Metabolism produces heat. Feathers insulate a bird enough to conserve most of its metabolic energy, allowing it to keep warm.

End Show 31-2 Birds Slide 11 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Air flows in a single direction. The one-way flow of air: constantly exposes the lungs to oxygen-rich air. maintains a high metabolic rate. provides efficient extraction of oxygen, which enables birds to fly at high altitudes where the air is thin.

End Show 31-2 Birds Slide 12 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Excretion Excretion in birds is similar to that of most living reptiles. Nitrogenous wastes are removed from the blood by the kidneys, converted to uric acid, and deposited in the cloaca. Most of the water is reabsorbed, leaving uric acid crystals in a white, pasty form.

End Show 31-2 Birds Slide 13 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Skeletal System of a Bird Strut Air space Vertebra Skull Rib cage Sternum Pectoral griddle Collarbone (wishbone) Pelvic girdle Tailbone

End Show 31-2 Birds Slide 14 of 53 Copyright Pearson Prentice Hall Form, Function, and Flight Bones are strengthened by struts. Air spaces make bones lightweight.

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