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

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

8. Archaeopteryx

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

11. 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

13. 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

14. 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.