1 / 35

Class Reptilia

Class Reptilia. Fred Searcy ZOO2010. Class Reptilia (L. repto = to creep). Movement to Terrestrial Existence Greatest innovation is the shelled egg Shelled egg maintains aquatic environment Leathery or Hard Embryos of reptiles birds and mammals have four extraembryonic membranes

minh
Download Presentation

Class Reptilia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Class Reptilia Fred Searcy ZOO2010

  2. Class Reptilia(L. repto = to creep) • Movement to Terrestrial Existence • Greatest innovation is the shelled egg • Shelled egg maintains aquatic environment • Leathery or • Hard • Embryos of reptiles birds and mammals have four extraembryonic membranes • Amnion • Yolk sac • Chorion • allantois

  3. Amnion • Surrounds embryo • Amniotic fluid • Yolk sac • Yolk a mixture of proteins and lipoproteins • Chorion • Involved in gas exchange • Membrane next to shell • Shell porous to gases • In mammals, chorion forms placenta • Allantois • Holds metabolic wastes as uric acid • As embryo develops, also aids in gas exchange with chorion

  4. Class Reptilia • Dinosaurs – reptiles or birds? • Mass extinctions of many reptiles at end of Mesozoic • 8,000 extant terrestrially and aquatic • Adaptations of reptiles • Shelled egg • Tough, dry, keratinized skin • Powerful jaw enclosure • Internal fertilization • Ability to conserve water

  5. Reptile Ancestors • Ancestors had extraembryonic membranes • Called amniotes • Three lineages from amniotes • Anapsids – no openings in temple behind eye sockets – gave rise to turtles • Diapsids – two pair openings in temple behind eye sockets – gave rise to other reptiles and birds • Synapsids – one pair openings – gave rise to mammals

  6. Scales • Skin is especially adapted to prevent water loss • Epidermis (thick) • Hydrophobic lipids to retard water loss • Scales (composed of β-keratin) • Alligators keep scales their lifetime • Crocodilians and some lizards may have bony plates beneath scales in dermis - osteoderms • Dermis (thicker) • chromatophores

  7. Jaws • Skulls are better adapted for muscle attachment at foramina of skull • Allows stronger and better grip • Reptiles can hold closure very long times

  8. Internal Fertilization • Reptiles have a hemipenis • Evagination of cloacal wall which protrudes when engorged with blood

  9. Circulatory System • Two functional, separate systems • Pulmonary • Systemic • Heart • Right atrium has deoxygenated blood • Left atrium oxygenated • Ventricle partly partitioned to prevent mixing • Crocodilians have two ventricles (4 chambered heart) • Allows blood to flow even when oxygen not entering lungs during • Aestivation or • Swimming underwater • Higher blood pressure than amphibians • Ectothermic but with some behavioral thermoregulation

  10. Gas Exchange • Lungs (increased emphasis) • Skin (reduced importance) • Air brought in by muscles associated with rib cage to expand thoracic cavity or by • Movement of internal organs • Cutaneous respiration may occur through cloacal or pharyngeal membranes in aquatic turtles

  11. Osmoregulation & Excretion • Paired metanephros kidneys • No loop of Henle to concentrate solutes in urine in reptiles • Salt glands take over this function • Nose • Tongue • Eye • Uric acid

  12. Support & Locomotion • Strong endoskeleton • Limbs thrown outward • Abdomen closer to surface • Five toes • Limbs adapted for • Climbing • Running • Paddling • Some snakes & lizards are limbless • One occipital condyle to attach to the atlas (humans have two)

  13. Nervous & Sensory System • Cerebrum largest part of brain – more complex behaviors • Well developed • Sight • Infrared detection • Olfactory • Jacobson’s organ • 12 cranial nerves

  14. Order Testudines(Chelonia) • Turtles • Generally aquatic • Tortoises • Generally land dwellers • Little changed since Triassic (200 mya) • Shell 

  15. Shell • Two parts • Dorsal carapace • Ventral plastron • Composed of • outer keratinized layer and • inner bony layer • Fused ribs, vertebrae and other bony substances in skeleton • Limbs & girdles are found within the rib cage (no other vertebrate) • No teeth (jaws of keratinized bone)

  16. Shell continued • Individual plates which make up shell are named according to their location

  17. Gas Exchange • Turtles cannot expand chest to breathe • Abdominal and pectoral muscles pull air in like diaphragm • Exhalation when animal pulls his anterior portion of body back into the shell (walking also aids in this) • Aquatic species have membranes rich in blood vessels in • Mouth • Cloaca

  18. Senses • Middle and Inner ear • Not especially good for sound detection • Excellent • Smell • Vision with color perception

  19. Reproduction • Oviparous • Internal fertilization • Males have modified indention in shell to allow him to mount female • Females bury eggs and desert nest • Vertical distribution of eggs plays role in sex determination • Cooler (deeper) = males • Due to no sex chromosomes

  20. Aquatic and Terrestrial • Leatherbacks larges marine species (2 m and 725 kg) • Giant tortoises of Galapagos 150 years old

  21. Order SquamataSuborder Sauria - Lizards • Tetrapods or legless • Geckos, iguanas, skinks, chameleons, glass snakes • Most have moveable eyelids • Color vision excellent • External ears but doesn’t necessarily rely on hearing (most lizards are non-vocal) • Ectothermic and behavioral thermoregulation • Stilting • Dew nap

  22. Gila monster only poisonous lizard in US • Food reserves in tail

  23. Order Squamata Suborder Amphisabenia – Worm Lizards • Legless • Name of order means they can move backwards or forwards equally fast

  24. Order SquamataSuborder Serpentes - Snakes • Limbless • Pythons & boas have pectoral and pelvic girdles • Organs reduced and/or shifted • Capable of disarticulation of jaws • No external ears • Most with poor vision (except arboreal species) • Have fovea rich in cone cells.

  25. Infrared Vision • Some snakes “see” using infrared • Pit vipers • Facial pits rich in temperature receptors

  26. Oviparous but some Ovoviviparous & Viviparous • Egg tooth

  27. Identification • Shape of head & body • Arrangement, number & type of scales • Keeled • Unkeeled • Anal plate • Divided • Undivided

  28. Poisonous Snakes U.S. Image courtesy of http://www.agassiztrading.com/contact.htm • 4 poisonous species • Rattlesnake • Cotton mouth • Copperhead • Coral snake Coral snake, cottonmouth courtesy of www.brevardanimalservices.com.

  29. Poisonous Snakes • Two basic toxins • Neurotoxins • Hemorrhagins • Some toxins are body region specific • Effects based on • Size of prey • Size of snake • Amount delivered, etc. • LD50 indicates Australian tiger snake and some sea snakes are most deadly. Based on size and amount delivered, King Cobra most dangerous.

  30. Order Spenodonta(Tuataras) • Specific islands off coast of New Zealand • Most closely resembles extinct Mesozoan species • Third eye (parietal eyeon top of head) • Detects light • Has lens, retina and connections to brain • Covered by scales

  31. Order CrocodiliaCrocodiles, Alligators, Caimans (Caymans), Gavials • Only survivors of Mesozoic reptiles • Unchanged for 200 million years • Caimans & alligators are New World • Crocodiles worldwide • Gavial restricted to India and Burma

  32. Alligator mississippiensis in U.S. • American Crocodile Crocodylus acutus

  33. Order Crocodilia • Jaw muscles • Wide gape • Quick closure • Little force necessary to keep closed • Teeth in sockets (thecodont dentition) • Bulls vocal in mating season • Hatchlings vocal and heard by mother • Low nest temperatures = females, higher temperatures = males

More Related