Evolution of Birds from Feathered Dinosaurs

1. Class Aves 1

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3. Caudipteryx zoui Microraptor gui Sinornithosaurus millenii The Origin of Birds • Most paleontologists agree that the common ancestor of all existing birds was a type of small, feathered dinosaur. • Recent fossil discoveries of feathered dinosaurs in China support this hypothesis. 3

4. Caudipteryx • Feathered dinosaur • Flightless • Transitional fossil • Dinosaur arms • Dinosaur teeth • Only front of upper jaw • Bird feathers 4

5. Archaeopteryx • Represents an animal that lived about 150 million years ago. • Unlike modern birds, Archaeopteryx had clawed forelimbs, teeth, and a long tail with vertebrae—all reptilian characteristics. • In fact, if the feathers had not been preserved in the fossil, Archaeopteryx probably would have been identified as a small dinosaur. 5

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7. A Separate Taxon? • Molecular and fossil evidence has convinced most biologists that birds are actually reptiles. • The evidence indicates that crocodilians and birds are more closely related to each other than either one of them is to snakes and lizards. 7

8. Class Aves • Feathers • No teeth • Flexible long neck • Scales on legs • Bones with air spaces • Endothermic • Four chambered heart 8

9. Characteristics of Birds • Bony beak, no teeth • Large muscular stomach • Bipedal – walk on two legs • Large, yolked, hard-shelled, amniotic eggs • The parent bird provides extensive care of the young until it is grown • Strong, lightweight skeleton • Specialized adaptations for flight: • Keratinous feathers (modified scales) that function in both flight and insulation • Specialized wing shape that produces lift • Numerous weight-reducing features 9

10. Internal Anatomy

11. Adaptations for Flight • Honey combed bones • Air cavities • Less weight 11

12. Adaptations for Flight • Reduce body weight • No teeth • No urinary bladder 12

13. Light Weight Skeleton • Frigate bird • 7 foot wing span • 4 ounce skeleton 13

14. Wings • Most birds have airfoil-shaped wings. • Wing shape is closely related to wing function. 14

15. Adaptations for Flight • Wing • lift 15

16. Adaptations for Flight • Feathers • Light weight • Strong 16

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18. Adaptations for Flight • Enlarged sternum • Flight muscle attachment • Long neck • balance 18

19. Skull • Most bones fused • Much lighter than reptile or mammal skull 19

20. Flying Styles • Different styles of flying: • Cardinals and finches rapidly change altitude as they fly, a behavior that helps them avoid predators. • Falcons and albatrosses are hunting birds that soar, using their wings to gain altitude and then gliding on air currents without flapping. • Hummingbirds flap their wings as many as 80 times per second, enabling them to hover. • Penguins are flightless diving birds that use the same basic flight stroke to swim. • Chickens belong to a group of birds that can fly short distances, but are incapable of long flights. • Ostriches, emus, and kiwis cannot fly at all. 20

21. High Metabolic Rate • Birds have a system of branching airsacs that function with their lungs in respiration. • The system of air sacs supplies the high levels of oxygen needed to support a high rate of metabolism for the hard-working flight muscles. • This high metabolic activity also provides heat for endothermy. 21

22. Respiratory System • Nine air sacs • Connect to lungs and centers of bones • Cools the bird • Fresh air always moving • No dead ends as in mammals • Each wing beat moves air • Never run out of air 22

23. Circulatory System • Bird circulatory systems efficiently deliver oxygen to cells. • Like amphibians and reptiles, birds have two pathways of blood flow: one from the heart to the lungs and back, and the other from the heart to the rest of the body and back. • Unlike amphibians and most reptiles, birds have a four-chambered heart with two separate ventricles that keep oxygen-rich blood from the lungs separate from the oxygen-depleted blood that passes through the heart. 23

24. Digestive System • Crop • Storage • Enzymes • Gizzard • Grind food • Cloaca • Waste • Reproduction 24

25. Vision • Up to 8 times keener than human vision • Each eye moves indendtantly 25

26. Chicks • Altricial • No feathers • Cannot walk or see • Cannot feed themselves Precocial • Down feathers • Can walk and see • Can feed themselves 26

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28. Beak Adaptations • Also called “bills” • Made of keratin • Nostrils function in breathing • Variety of beak shapes reflects a wide range of functions • Beaks are not used for chewing, though some are used to break food into smaller pieces 28

29. Beak Adaptations • Ripping flesh 29

30. Beak Adaptations • Eating seeds 30

31. Beak Adaptations • Sucking nectar from flowers 31

32. Beak Adaptations • Drilling wood 32

33. Beak Adaptations • Catching fish 33

34. Beak Adaptations • Basket-like bill to hold fish caught under water 34

35. Beak Adaptations • Filtering 35

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37. Foot Adaptations • Various birds use their feet for walking, perching on branches, wading, paddling through water, grasping food, in defense, and in some courtship rituals • Most bird feet are covered in scales • Most birds have four toes on each foot, though the arrangement varies from species to species 37

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39. Fastest Animal • Peregrine falcon • Strikes prey at 180 mph 39

40. Bird Classification • 28 orders • 9600 species 40