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Chapter 42 Birds
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Feathers-evolved from scales
Bird Characteristics Feathers-evolved from scales
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Wings-a bird’s forelimbs are modified into a pair of wings
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Lightweight, Rigid Skeleton-Bones are thin-walled and hollow
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Endothermic metabolism-a bird’s rapid metabolism supplies the energy needed for flight
Hummingbirds Eagle
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Bird Characteristics Unique respiratory system-The lungs are connected to several sets of air sacs Bird breathing Breathing
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Beak-no modern bird has teeth
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Oviparity-lay amniotic eggs encased in a hard, calcium-containing shell
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Evolution Scientific evidence suggests that birds arose from dinosaurs
Dinosaur Chickens
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Similarities between birds and dinosaurs:
Flexible, S-shaped neck Unique ankle joint Hollow bones
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Evolution The earliest flying vertebrates were dinosaurs.
The oldest known bird fossils are Archaeopteryx.
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Had hollow bones and a furcula-fused pair of collarbones; “wishbone”
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Feathers Feathers-modified scales Serve two primary functions:
Provide lift for flight Conserve body heat Took the place of scales as the body covering of birds.
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Preening-birds use their beaks to rub their feathers with oil secreted by a preen gland.
Bird Preening
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Bones Skeleton is: Composed of thin, hollow bones.
Composed of many fused bones. More rigid than a reptile’s.
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Sternum-breastbone-attachment point for flight muscles
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Pygostyle-fused terminal vertebrae of the spine, supports the tail feathers, adds lift, and aids in steering and braking
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Metabolism Birds are endothermic.
Cannot go for long periods without eating Bird eating
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Digestion Birds do not have teeth, and are not able to chew food.
Crop-temporarily stores food. Gizzard-grinds food.
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Have a four-chambered heart
Circulatory System Have a four-chambered heart
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Respiratory System Bird respiration is very efficient because a system of air sacs permits birds to have oxygenated air in their lungs during both inhalation and exhalation. Syrinx-produces songs Lyre bird
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Nervous System and Sense Organs
Relative to their size, birds have large brains Have keen, strong, color vision that aids them in finding food
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Eggs are encased in a hard shell.
Reproduction Eggs are encased in a hard shell.
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Migration Migration-the seasonal movement of animals from one habitat to another Bird migration
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