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Reptiles

Reptiles . Jessica Brown Miila Hall. Characteristics. Cold-blooded Tetrapods , four appendages Considered as the first animals on land with the ability to live and multiply on land (amniotic egg)

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Reptiles

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  1. Reptiles Jessica Brown Miila Hall

  2. Characteristics • Cold-blooded • Tetrapods, four appendages • Considered as the first animals on land with the ability to live and multiply on land (amniotic egg) • Amniotic egg- a shelled, water-like sac that enables reptiles to complete their life cycles on dry land. • Dry skin with scales • 3-chambered hearts • No metamorphosis • Binocular vision • Well-developed brain and a central nervous system • Strong skeletal system with a rib cage

  3. Evolution and Relationships • Originated around 320-310 million years ago • During the Carboniferous period • Were called reptile-like amphibians because they could survive efficiently on land • Jacques Gauthier discovered a cladistic definition of the crown group known as turtles, lizards, and snakes and crocidiles share common ancestors.

  4. Order Testudines • Approx. 300 species of turtles • Bony shell, limbs internal to the ribs, and a keratinized beak. • Keratin is a resistant protein found in epidermally derived structures of amniotes • Dorsal side of the shell is the carapace, which forms the fusion of vertebrate, expanded ribs, and bones in the skin. • Long life spans- 14 or more years • Turtles vulnerable to extinction due to predation, hunting, and threatened at time of birth. • Types of turtles- sea turtles, green sea turtles, freshwater turtles

  5. Order Crocodylia • 21 species • Openings in the skull, triangular eye orbits, laterally compressed teeth • Snout is elongated to capture food by sweeping their head. • A flap of tissue near the back of the tongue forms a watertight seal so it can breathe without inhaling water into the mouth. • A secondary palate separates the nasal and mouth passageways. • Tail used for swimming, defense, and attacking • Oviparous and display parental care of hatchlings. • Include- alligators, crocodiles, gavials, and caimans

  6. Order Sphenodontida • Tuataras • Lizardlike reptiles from Mesozoic era • Two rows of teeth on the upper jaw and a single row in the lower jaw that can decapitate a small bird. • Only present in offshore islands • Oviparous • Feed on insects

  7. Order Squamata • Divided into three suborders: • Suborder Sauria- Lizards • 4,500 species • Two pairs of legs • Upper and lower jaw • Oviparous yet some are ovoviviparous or viviparous • Geckos, iguanas, chameleons • Geckos are nocturnal and have Clicking vocalizations • Adhesive disks allow them to cling to trees and walls • Iguania are robust with short necks and distinct heads • Flying dragons • Chameleons have the ability to change color in response to illumination, temperature, or their behavioral state

  8. Suborder Serpentes • 2,900 species • Around 300 are venomous • Elongate and lack limbs, joints that make snake flexible, two hundred vertebrate • Skull adaptations that allow the snake to swallow large amounts of prey • Oviparous • Reduction or loss of left lung an displacement of gall bladder, the right kidney, and often, the gonads. • Vipers, cobras, and boas

  9. Suborder Amphisbaenia • Worm lizards • 135 species • Specialized burrowers • Legless and skulls are wedge or shovel shaped • Skin has ringlike folds called annuli and loosely attaches to body wall • Feed on worms and small insects • Oviparous

  10. External Structure & Locomotion • Skin has no respiratory functions • Periodically shed the outer, epidermal layers of the skin called ecdysis • Movement of lymph between the inner and outer epidermal layers loosens the outer epidermis. • Chromatophores are primarily dermal in origin and function like those of amphibians. • Cyptic coloration, mimicry, and aposematic coloration occur. • Have a cervical vertebrate • Tail loss, or autotomy, is an adaptation that allows a lizard to escape from predators • The lizard regenerates the lost portion of the tail • Laterally move in a horizontal plane • Bipedal, meaning to walk on hindlimbs

  11. Nutrition & Digestive System • Most are carnivorous, although turtles can be herbivores • Some have sticky tongues to catch prey • Tongue extension in chameleons • Snakes have a loose jaw that spreads apart to ingest prey much larger than their normal head size. • After prey is captured, alternately the jaw thrusts forward and retracts • The glottis is far forward so the snake can breathe during swallowing

  12. Circulation, Gas Exchange, and Temperature • Blood must travel under higher pressures to reach body parts. • Two atria, turtles have a patch of cells that act as a pacemaker • Ventral aorta divide during development and become three major arteries • All reptiles breathe intermittently. • Exchange respiratory gases across the surface to avoid losing large quantities of water • Larynx is present; vocal cords are absent • To warm itself, a lizard may stand at an angle to the suns rays or press itself to warm surfaces. • To cool itself, seeks shade or burrows itself.

  13. Nervous and Sensory • Cerebral hemispheres are somewhat larger causing an improved sense of smell • Eyes swivel independently with binocular vision • Nictitating membrane and a blood sinus to protect and cleanse the eye • Possess a median, or parietal, eye can differentiate light and dark periods for the sun • Olfactory senses are better developed • Jacobson’s organs are pouches that open through the secondary palate into the mouth cavity. • Rattlesnakes and other vipers have pit organs that are used to detect objects with temperatures different from their surroundings.

  14. Excretion & Osmoregulation • Require kidneys to process wastes and little water loss. • Excrete uric acid • The behaviors to regulate temperature also help conserve water • Produce salt glands to rid the body of excess salt • Blood-filtering units are called nephrons

  15. Reproduction & Development • Internal fertilization and the amniotic egg • Tract of female before protective egg membranes are laid down around an egg • Male reptiles, except tuataras, possess an intromittent organ for introducing sperm into the female tract • Parthenogenesis can be present in some types of lizards • Courtship functions in sexual recognitions • Head-bobbing in males and revealing brightly colored patches of skin on the throat • Entwines his body around the female and runs his chin along the female • After egg is laid it is usually abandoned

  16. Amniotic Egg • Shell- sturdy and leathery for protection • Albumen- the “white” of the egg, contains protein • Chorion- outermost membrane surrounding the embryo of the reptile • Allantois- fetal membrane formed as an outgrowth of the embryo’s gut • Yolk Sac- membranous sac containing yolk attached to the embryo • Yolk- rich in protein and fat and nourishes the developing embryo • Amnion- the innermost membrane that encloses the embryo

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