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Reptiles

Reptiles. Reptilia. Reptiles are the evolutionary base for the rest of the tetrapods . Early divergence of mammals from reptilian ancestor . Early reptiles arose from amphibian ancestor and were small, lizard-like insectivores. Characteristics. Scales Amniotic egg Ectothermic

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Reptiles

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  1. Reptiles

  2. Reptilia • Reptiles are the evolutionary base for the rest of the tetrapods. • Early divergence of mammals from reptilian ancestor. • Early reptiles arose from amphibian ancestor and were small, lizard-like insectivores.

  3. Characteristics • Scales • Amniotic egg • Ectothermic • Must live in favorable conditions or hibernate. • Being ectothermic enables an organism to survive on much less food than an endothermic organism. • Three chambered heart • Alligators have 4 • Claws

  4. Characteristics • Positioning of legs more directly under animal (more support). • Paired limbs with five toes. • Adapted for running, climbing, swimming. • Absent in snakes.

  5. Characteristics • Body covered with horny epidermal scales made from protein keratin. • Scales serve to reduce water loss and provide protection. • Reptiles molt as they grow. • Brain = first cerebral cortex (capable of reasoning, planning, perception)

  6. Respiration • All reptiles breathe using lungs. • Aquatic turtles have developed more permeable skin. • Some species have modified their cloaca to increase the area for gas exchange.

  7. Circulation • Most reptiles have a 3-chambered heart with a partially divided ventricle. • No mixing of blood from lungs with deoxygenated blood. • Crocodiles have 4 chambers and a unique feature: cog teeth. CogTeeth

  8. Digestion/Excretion • Excretory waste = uric acid • Lack structures in nephrons to reabsorb water, so water absorption happens in the colon.

  9. Reproduction • Internal fertilization: gametes not subject to desiccation (drying out). • Amniote egg = significant evolutionary breakthrough. • Egg covered by tough, water-resistant, leathery or calcerous shell. • Extra embryonic membranes compartmentalize the interior for several functions – keep fetal homeostasis http://www.youtube.com/watch?v=t1kFiehGh9s

  10. Amniotic Egg • Chorion = hard covering permeable to respiratory gases but not water. • Allantois = functions in gas exchange and a storage reservoir for metabolic waste. • Amnion = fluid-filled sac acts as cushion for embryo and prevents desiccation. • Yolk sac = food for embryo; eliminates need for larval stage.

  11. Orders • Crocodilia = crocodiles, alligators • Testudines = turtles and tortoises • Sphenodonta = tuatara • Squamata = lizards, snakes (largest group)

  12. Order Crocodilia • 23 species of crocodiles, alligators, & caimans • Largest of the living reptiles • Amphibious carnivores • Live in tropics/subtropics • Lizard-like body with short legs, clawed/webbed toes, massive tail • Flat head with nostrils at tip • Powerful jaws • Dorsal side armored with dermal plates

  13. Order Testudines • 260 species of turtles/tortoises • Oldest group of reptiles (225 mya) • Only reptile with shell • Only reptile WITHOUT TEETH • All lay eggs on land. • Third eyelid = nictitating membrane. • Longest living vertebrates (100+years in wild)!

  14. Order Testudines • Protective body shell • Encases vital organs • Provides some protection to head/limbs • Composed of bony plates covered by horny epidermal scales • 2 parts: upper carapace, lower plastron • Loss of body-wall muscles • Ribs/trunk vertebrae fused to carapace

  15. Order Squamata • 4675+ species of lizard • 2700+ species of snakes • 140 species of amphisbaenians • Limbless, burrowing animals • Vestigial eyes under skin • Most successful, diversified of living reptiles. • Occur in most habitats of world amphisbaenians

  16. Snakes • Elongated derivative of lizard (increased vertebrae, not lengthening of segments) • Lack limbs, eyelids, ear openings • Jaw bones are loosely united to allow swallowing of large prey • Throat and windpipe are at separate ends of mouth to allow breathing while eating • Can be venomous (hemotoxin/neurotoxin) • Tongue to smell, some have heat pits to sense body heat

  17. Snakes • No legs • No external ears • Jacobson’s organ • Sense smell with aid of tongue • Cornea of eye protected with a spectacle • transparent membrane • Skull bones loose • Swallow large prey 17

  18. Snakes • An extrasensory organ in the roof of a snake's mouth • Sharpens its sense of smell. • Two hollow, highly sensitive saclike structures • Allows it to track both prey and potential mates

  19. Snakes • “Pit" organ located between the eye and the nostril on each side of the head. • Detects heat given off by warm-blooded prey

  20. Lizards • Legs, eyelids, ear openings • Halves of lower jaw united • Small lizards - Adhesive toe pads • Color is variable • Slender body • Small scales • Self amputation to escape predators • Can’t regrow • Costly; lose muscle/stored fat http://www.youtube.com/watch?v=GgB4u6Mgy2M

  21. Chameleon • How are chameleons able to change color? • Special cells called CROMATOPHORES http://science.howstuffworks.com/zoology/28369-fooled-by-nature-chameleon-colors-video.htm Insane in the Chromatophore: http://www.youtube.com/watch?v=G-OVrI9x8Zs

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