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Reptiles

Reptiles. Origin and Evolution. History of Reptiles. Reptiles arose from amphibians Earliest fossils 359 m.y.a Small, four – legged vertebrates w/small teeth. Pangaea. Drier climate Mass extinction during Paleozoic era Diversified to fill niches left by extinct species

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Reptiles

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  1. Reptiles Origin and Evolution

  2. History of Reptiles • Reptiles arose from amphibians • Earliest fossils 359 m.y.a • Small, four – legged vertebrates w/small teeth

  3. Pangaea • Drier climate • Mass extinction during Paleozoic era • Diversified to fill niches left by extinct species • Mesozoic era “Age of Reptiles”

  4. Evolution of Dinosaurs • 235 m.y.a dinosaurs dominated the earth • Evolved from thecodonts • Extinct group of crocodile – like reptiles • Pangaea separated climates changed dinosaurs became extinct, while new species flourished

  5. Evolution of Dinosaurs (Triassic) • Oldest known fossils • Small carnivorous dinosaurs replaced thecodonts • Successful because • Legs directly under body • Good support, more agile, fast runners • Well adapted for dry conditions • Mass extinction of thecodonts and large amphibians reduce competition

  6. Extinction of Dinosaurs • Asteroid Impact Hypothesis • Multiple Impact Hypothesis

  7. Success of Reptiles • Four modern orders of reptiles • Chelonia (turtles and tortoises) • Squamata (lizards and snakes) • Crocodilia (crocodiles, alligators, caimans) • Rhynchocephalia (tuataras)

  8. Success of Reptiles • Watertight skin • Keratin • Respiration • Lungs • Excretion • Uric acid requires little water • Amniotic Egg

  9. Amniotic Egg • Reptiles considered the first terrestrial vertebrate • Amniotic egg • First evolved in reptiles but also found in mammals and birds • Protection from physical damage • Limits evaporation of water • Diffusion of O2 and CO2

  10. Internal Structure of Amniotic Egg • 4 specialized membranes • Amnion • Thin membrane encloses the fluid where embryo floats • Yolk sac • Encloses the yolk, fat – rich food supply for embryo • Allantois • Stores wastes produced by embryo • Chorion • Surrounds all other membranes • Albumen • Protein and water for embryo

  11. Body Systems of Reptiles • Circulatory System • Two loops • Heart structure and function • Two atria and a single ventricle (except crocodiles) • Divert blood from lungs when inactive • Conserves energy • May help raise body temp

  12. Respiratory system • Lungs are large • Divided into chambers (alveoli) • Increases surface area • Filled by expanding rib cage • Snakes right lung enlarged, left obsolete

  13. Nervous system • Brain • Sight detect light • Hearing • Tympanum (eardrum) and columella • Snakes lack tympanum (low frequency sounds)transmitted to the bones of the jaw • Jacobson’s organ • Roof of mouth in reptiles (crocodiles and most turtles) • Sensitive to odors • Pit Vipers

  14. Thermoregulation • Vertebrates regulate body heat in two ways • Ectotherm • Warms the body from the environment • Endotherm • Generates heat as needed to warm body • Behavior • Require little energy and 1/10th food as endotherms same size

  15. Reproduction and Parental Care • 3 patterns among reptiles • Differences based on how long the eggs remain within the female and how nutrition is provided to them

  16. Reproduction • Oviparity • Deposits egg in environment • Ovoviviparity • May be laid shortly before hatching or hatch inside female • Viviparity • Shell does not form around egg and young are retained within female

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