Evolution of Amniotes: Reptiles, Birds, and Mammals

1. A closer look at AAnmiotes

2. Amniotes 26-1

3. KEY CONCEPT Reptiles, birds, and mammals are amniotes.

4. Amniote embryos develop in a fluid-filled sac. • The amniotic sac contains everything an embryo needs to grow. • some develop inside mother’s body • some develop inside a tough, semipermeable shell

5. AllantoisHolds waste materialsas the embryo grows Embryo AmnionProtects andsurrounds theembryo Yolk sac Contains the nutrient supply for the growing embryo Chorion Allows gas exchange with outside environment • The amniotic egg allowed vertebrates to reproduce on land.

6. Anatomy and circulation differ among amniotes. • The first animals walked in a sprawl. • Other amniotes, including dinosaurs, evolved a more upright stance.

7. All amniotes have two circuits of blood vessels. • pulmonary circuit moves blood from the heart to the lungs • systemic circuit moves blood from the heart to the rest of the body

8. THREE-CHAMBERED HEART FOUR-CHAMBERED HEART • Amniotes have a three- or four-chambered heart. • reptiles hearts have three chambers • birds and mammals hearts have four chambers

9. Amniotes can be ectothermic or endothermic. • Amniotes manage body heat in different ways. • Ectotherms have body temperatures determined by the surrounding environment. • Endotherms use metabolic heat to keep tissues warm. • Endotherms can live in a wider range of climates than ectotherms.

10. Reptiles

11. KEY CONCEPT Reptiles were the first amniotes.

12. Reptiles are a diverse group of amniotes. • Reptiles share several characteristics. • ectotherms • covered with dry scales • reproduce by laying or retaining amniotic eggs • three-chambered heart • cloaca

13. Reptiles have two reproductive strategies. • Oviparous reptiles deposit eggs into an external nest. • Viviparous reptiles retain eggs and give birth to live offspring.

14. Reptiles have been evolving for millions of years. • Over time, amniotes evolved into three different groups. • synapsids • anapsids • diapsids

15. The diversity of ancient reptiles led to the evolution of modern reptiles, birds, and mammals.

16. There are four modern groups of reptiles. • Turtles, tortoises, and terrapins are the remaining anapsids. • bony shell encases body • 200 species

17. Sphenodonts are closely related to lizards. • diapsids • primitive characteristics • two species

18. brain Jacobson’s organ tongue • Snakes and lizards are very closely related and share a number of features. • diapsids • shed skin at regular intervals • flexible skull • Jacobson’s organ

19. Crocodilians are more closely related to birds than other diapsids. • diapsids • semi-aquatic predators • 23 species

20. KEY CONCEPT Birds have many adaptations for flight.

21. Birds

22. Birds evolved from theropod dinosaurs. • Birds and many theropods share anatomical features. • hollow bones • fused collarbones that form V-shaped wishbone • rearranged muscles in the hips and legs • “hands” that have lost their fourth and fifth fingers • feathers

23. The oldest undisputed fossilized bird is Archaeopteryx.

24. lung gizzard kidney crop small intestine pectoral muscle large intestine cloaca sternum(keel) liver heart A bird’s body is specialized for flight. • Birds have several unique features that allow them to fly. • wings to produce flight • strong flight muscles to move the wings • active metabolism that provides energy to the muscles • hollow bone structure to minimize weight • gonads active during only part of year

25. Wings are structures that enable birds to fly. • airfoil shape • covered with feathers

26. Air sacs help a bird meet its oxygen demand during flight.

27. Birds have spread to many ecological niches. • The shape of a bird’s wing reflects the way it flies. • short and broad • long and narrow

28. lung gizzard kidney crop small intestine pectoral muscle large intestine cloaca sternum(keel) liver heart • The shape of a bird’s wing reflects the way it flies. • stout and tapered • wide and broad

29. Bald eagle green woodpecker blue-footed booby • Differences in the shape of a bird’s beak reflects how it eats. • spearlike • hooked • chisel-shaped

30. blue-footed booby bald eagle green woodpecker • Birds show great diversity in their foot shape. • webbed • heavy claws • different toe location

31. Mammals

32. KEY CONCEPT Evolutionary adaptations allowed mammals to succeed dinosaurs as a dominant terrestrial vertebrate.

33. All mammals share several common characteristics. • Mammals are active, large-brained, endotherms with complex social, feeding, and reproductive behaviors.

34. All mammals share four anatomical characteristics. • hair to retain heat • mammary glands to produce milk

35. All mammals share four anatomical characteristics. • a middle ear with three bones to hear higher-pitched sounds • chewing jaw to break up food quicker

36. A set of adaptations in the mammalian jaw makes chewing possible. • secondary palate closes off air passages • muscles move jaw side-to-side

37. Modern mammals are divided into three main groups. • Monotremes lay eggs. • duck-billed platypus • echidna

38. Marsupials give birth to live young that grow to maturity inside a pouch. • opossum • kangaroo • wombat • koala

39. Eutherians give birth to live young that have completed fetal development. • most familiar mammals • humans • Eutherians filled many niches after the extinction of the dinosaurs.