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Chapter 41 Reptiles

Chapter 41 Reptiles. Section 1 Origin & Evolution of Reptiles. History of Reptiles. Fossils & comparative anatomy suggest that reptiles arose from amphibians Earliest reptiles date 359-299 million years ago Many insects during this time period which served as food. History of Reptiles.

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Chapter 41 Reptiles

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  1. Chapter 41Reptiles Section 1 Origin & Evolution of Reptiles

  2. History of Reptiles • Fossils & comparative anatomy suggest that reptiles arose from amphibians • Earliest reptiles date 359-299 million years ago • Many insects during this time period which served as food

  3. History of Reptiles • Around 299 to 251 million years ago- reptiles dominant land vertebrates • Pangaea- super continent • Interior of Pangaea was dry- suitable for reptiles- why? • End of Permian Period (299 MYA)- mass extinction

  4. History of Reptiles • Mesozoic era (251-66 MYA)- Age of the Reptiles • Nearly all large vertebrates were reptiles

  5. Evolution of Dinosaurs • 235 MYA- dinosaurs- group of extinct reptiles • Evolved from thecodonts- extinct group of crocodile-like reptiles • Evolution was affected by the break-up of Pangaea • Climates changed- some died, some flourished

  6. Thecodont

  7. Triassic Dinosaurs • 235 MYA- oldest dinosaur fossils- Triassic Period • Successful because- • 1. legs positioned under body provided support • 2. well-adapted to dry conditions • 3. Last mass extinction wiped out other animals

  8. Triassic Dinosaurs • Evidence suggests asteroid impacts contributed to mass extinction • Canada, France, Ukraine, and Minnesota have evidence to support this theory

  9. Jurassic & Cretaceous Dino • Jurassic- golden age of dinosaurs- variety and abundance • Sauropods- largest land animals of all time • Theropods- powerful legs and short arms (T. Rex)

  10. Dinosaur Diversity • Land dinosaurs • Mesozoic reptiles- pterosaurs- evolved the ability to fly • Ichthyosaurs & plesiosaurs- lived in the oceans- resembled bottle-nose dolphins

  11. Ichthyosaurs plesiosaurs

  12. Extinction of Dinosaurs • Scientists still have many questions, but they have some ideas and evidence as to why the dinosaurs are extinct

  13. Asteroid Impact Hypothesis • Asteroid impact hypothesis- suggests huge asteroid hit Earth and formed a crater on the Yucatan Peninsula in southern Mexico

  14. Asteroid Impact Hypothesis • Caused much dust that covered Earth and changed climate • Sediments during Cretaceous time- high iridium- very rare metal (abundant in asteroids)

  15. Multiple Impact Hypothesis • Proposes multiple asteroids hit Earth • Unfavorable environmental conditions because of this event • Paleontologist- Gerta Keller- provided evidence to support this hypothesis

  16. Success of Reptiles • Order Chelonia- turtles & tortoises • Order Squamata- lizards & snakes • Order Crocodilia- alligators & crocodiles • Order Rhynchocephalia- tuataras • Found on every continent except Antarctica

  17. Modern Reptiles • Turtles have changed very little in structure • Tuataras- lizard-like reptiles • Snakes & lizards- majority of reptiles • Crocodiles & alligators changed very little- decedents of thecodonts

  18. Modern Reptiles • Crocodiles resemble birds especially by looking at the structure of their heart (four-chambered) • Crocodiles take care of young • Scientists suggest birds are direct decedents of reptiles

  19. Amniotic Egg • Amniotic egg- encase embryo in a secure, self-contained aquatic environment • More secure than jelly-like amphibian eggs

  20. Amniotic Egg • Amnion- thin membrane enclosing the fluid in which the embryo floats • Yolk sac- encloses the yolk, fat-rich food supply for developing embryo • Allantois- stores nitrogenous wastes produced by embryo • Chorion- surrounds all other membranes and protects embryo

  21. Amniotic Egg • First occurred in reptiles, but also is found in birds and mammals • Strong evidence suggests that reptiles, birds, and mammals evolved from a common ancestor • The eggs of some reptiles & nearly all mammals lack shells & embryo develops in mother’s body

  22. Water-tight skin • What type of skin do amphibians have? Why do they have this type? • Reptiles have thick, dry, scaly skin that prevents water loss • Keratin- same protein that forms your fingernails & hair • Lipids & proteins in the skin help make it water-tight

  23. Respiration & Excretion • All reptiles have lungs for gas exchange • All reptiles have bodies adapted to conserve water • Tissues for gas exchange located in body- kept moist • Reptiles lose small amounts of water in urine (uric acid)

  24. REVIEW!!! • Explain the importance of iridium found in sediments from the end of the Cretaceous period. • Summarize the two asteroid impact hypotheses. • Describe three characteristics that contribute to the success of reptiles on land.

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