End Show Slide 1 of 53 Copyright Pearson Prentice Hall 31-2 Birds.
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Transcript of End Show Slide 1 of 53 Copyright Pearson Prentice Hall 31-2 Birds.
End Show
Slide 1 of 53
Copyright Pearson Prentice Hall
31-2 Birds
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31-2 Birds
Slide 2 of 53
Copyright Pearson Prentice Hall
What Is a Bird?
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.
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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.
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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
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31-2 Birds
Slide 5 of 53
Copyright Pearson Prentice Hall
Evolution of Birds
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.
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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.
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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.
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31-2 Birds
Slide 8 of 53
Copyright Pearson Prentice Hall
Evolution of Birds
Evolution of Birds
Modern reptiles
Ornithischia (bird-hipped dinosaurs)
Saurischia (lizard-hipped dinosaurs)
Archaeopteryx
Modern birds
Dinosaurs
Ancestor of dinosaurs
Reptile ancestor
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31-2 Birds
Slide 9 of 53
Copyright Pearson Prentice Hall
Form, Function, and Flight
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
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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.
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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.
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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.
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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
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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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