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Chapter 42 Birds

Chapter 42 Birds. Section 1 Origin & Evolution of Birds. Characteristics. Feathers - composed of keratin, essential for flight, insulate body Wings - modified forelimbs, covered by feathers Lightweight, rigid skeleton- bones are thin & hollow Endothermic metabolism- high body temperature.

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Chapter 42 Birds

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  1. Chapter 42Birds Section 1 Origin & Evolution of Birds

  2. Characteristics • Feathers- composed of keratin, essential for flight, insulate body • Wings- modified forelimbs, covered by feathers • Lightweight, rigid skeleton- bones are thin & hollow • Endothermic metabolism- high body temperature

  3. Characteristics • Unique respiratory system- rapid metabolism, lungs connected to air sacs, oxygen-rich • Beak- no teeth, horny sheath made of keratin • Oviparity- lay amniotic eggs- eggs are incubated by both parents

  4. Evolution • Similarities between birds & dinosaurs • S-shaped neck, unique ankle joint, & hollow bones • Thought to have evolved from small, fast running dinosaurs • Archaeopteryx

  5. Archaeopteryx

  6. Archaeopteryx • Shapes of feathers are visible • Feathers cover wings, forelimbs, & its body and tail • Hollow bones & furcula- wishbone • Teeth, claws on forelimbs, long tail

  7. Origin of Flight • Hypothesis 1: ancestors of birds were tree-dwellers that lived in trees- glided and wings evolved • Hypothesis 2: ancestors of birds were land-dwellers- wings evolved to stabilize and protect against predators

  8. Evolution after Archaeopteryx • Only two of the modern orders of birds appeared after the mass extinction. • 40 million years ago, most modern orders of birds originated

  9. REVIEW!!! • List two unique features of a bird’s skeleton. • What are two functions of feathers? • Identify the characteristics that birds have in common with dinosaurs.

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