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Phylum Chordata

Phylum Chordata . Class Reptilia. Amphibians vs Reptiles. Shell-less eggs and gill breathing larvae so their development is still tied to water The shelled egg freed the reptiles from dependence on aquatic environments. Amniotic Egg.

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Phylum Chordata

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  1. Phylum Chordata Class Reptilia

  2. Amphibians vs Reptiles • Shell-less eggs and gill breathing larvae so their development is still tied to water • The shelled egg freed the reptiles from dependence on aquatic environments

  3. Amniotic Egg • Amnion: membrane that encloses a fluid filled cavity (creating a “pond”) within which the developing embryo floats • Allontois: membranous sac that serves as both a respiratory surface and as a chamber for the storage of nitrogenous waste • Chorion: encloses other 2 membranes; oxygen and carbon dioxide freely pass

  4. Class Reptilia • First truly terrestrial vertebrate • Nearly 8000 species • The Age of Reptiles last for more than 165 million years, among which were the dinosaurs • Mass extinction during Mesozoic caused many reptilian lineages to go extinct • Today’s reptiles are survivors, which include the tuataras who are the sole survivors of a group that disappeared 100 million years ago

  5. Characteristics • Body covered with scales • 2 paired limbs, usually with 5 toes • Lungs for breathing (no gills) • Ectothermic • Internal fertilization • Eggs covered with calcareous or leathery shells • No aquatic larval stages

  6. Distinguished from Amphibians • Have tough, dry, scaly skin offering protection against dessication and injury • Chromatophores: color- bearing cells that give many lizards and snakes their beautiful colors • Scales are made of beta keratin • Osteoderms: bony plates located beneath the scales in the dermis of may crocs and lizards

  7. Shows overlapping, keratinized scales in the epidermis and bony osteoderms in the dermis

  8. Distinguished from Amphibians • Amniotic egg permits rapid development of large young in relatively dry environments • Jaws are efficiently designed for applying crushing or gripping force to prey • Have some form of copulatory organ, permitting internal fertilization • Efficient strategies for water conservation-uric acid

  9. Order Testudines-Turtles & Tortoises • Enclosed in shells consisting of a dorsal carapace and a ventral plastron • Lack teeth, but jaw has a touch, horny plate for gripping food • Brain is small- about only 1% or less of body weight

  10. Skeleton showing fusion of vertebrae and ribs with carapace Long neck allows turtle to withdraw it head into its shell for protection

  11. Snapping turtle showing absence of teeth

  12. Turtles and Totoises • Have a middle and inner ear, but perception of sound is poor • Virtually mute although many tortoises utter grunting or roaring sounds during mating • Good sense of smell, acute vision, and color perception as good as humans

  13. Turtles and Totoises • Oviparous-fertilization is internal, then they bury their shelled eggs in the ground (even marine species) • Female deserts eggs once buried • In some turtle families (and all croc and lizards), nest temp determines sex of hatchlings • In turtles, low temps produce males and high temps produce females

  14. Mating Galapagos tortoises: Male has a concave plastron that fits over the highly convex carapace of female, helping provide stability during mating

  15. Marine turtles • Leatherbacks are largest- attaining length of 2 meters • Green turtles (named for their greenish body fat) get to about 1 meter

  16. Alligator snapping turtle: Lures fish and other prey by a pink, wormlike protrusion form its tongue Any prey attempting to eat the bait is instantly captured in powerful jaw

  17. Order Squamata: Lizards, Snakes and worm lizards • Comprised of 95% of all known living reptiles • Suborder Sauria: Lizards • Includes geckos, iguanas, skinks, chameleons • Most have moveable eyelids (where as snakes eyes are permanently covered with a transparent cap) • Most have good vision in daylight and have an outer ear that snakes lack

  18. Geckos • Mostly nocturnal forms with adhesive toe pads that enable them to walk upside down and on vertical surfaces • Strongly vocal to announce territory and discourage approach of other males Tokay gecko of SE Asia has a true voice and in name after the repeated to-kay, to-kay call

  19. Gila Monster • Only venomous lizards known-painful to human but not fatal • Feed on birds’ eggs, nesting birds, mammals, and insects • Secretes venom from lands in its lower jaw • Store fat in their tails which they use during drought to provide energy and metabolic water

  20. Marine Iguanas • Feeds on algae underwater • Only marine lizard in the world-lives on Galapagos Islands • It can dive to depths exceeding 33 feet and remain submerged more than 30 minutes

  21. Chameleon • After cautiously edging close to its target, it lunges forward, anchoring its tail and feet to the branch • A split second later, it launches its sticky tipped, foot-long tongue • Eyes are swiveled forward to provide binocular vision and excellent depth perception

  22. Glass Lizard • SE US • Legless lizard feel stiff and brittle to the touch and has an extremely long, fragile tail that readily fractures when the animal is struck or seized • Distinguish from snakes by the deep, flexible groove running along each side of the body • Feed on worms, insects, spiders, birds’ eggs and small reptiles

  23. Worm lizard • Burrowing forms with a solidly constructed skull used as a digging tool • Widely distributed in S America • Move backward as effectively as forward • Eyes and ears are hidden under skin • One species found in Florida known as “graveyard snake”

  24. Suborder Serpentes: Snakes • Limbless and usually lack both pectoral and pelvic girdles (vestigial in pythons and boas) • Numerous vertebrae that are shorter and wider than other tetrapods allows for quick lateral undulations through rough terrain

  25. Snakes • Unlike lizard jaws, the 2 halves of the lower jaw are joined only by muscles and skin allowing them to spread widely apart

  26. Snakes • No external ears or tympanic membrane • Do have internal ears, and are not totally deaf as many people believe • Sensitive to vibrations • The cornea of the snake’s eye is permanently protected with a transparent membrane called a spectacle • Gives them an unblinking stare • Relatively poor vision

  27. Snakes • Most snakes use chemical senses and not vision or hearing to hunt prey • Also use olfactory areas in nose and Jacobson’s organs: a pair of pit organs in the roof of the mouth (lined with chemosensory cells) • Forked tongue picks up scent molecules and conveys them to the mouth and then past the Jacobson’s organ for identification Blacktail Rattlesnake

  28. Snake Movement • Lateral undulation: movement in an S-shaped path, propelling itself by exerting lateral force against the surface • Fast and efficient • Concertina movement: enables a snake to move in a narrow passage, extending forward while bracing S-shaped loops against the sides of the passage

  29. Snake Movement • Rectilinear movement: advance in a straight line when staking prey (slow) • Side-winding: enable desert vipers to move with surprising speed across loose sandy surfaces with minimum surface contact

  30. Parrot snake adapted for sliding along branches without weighing them down (Central American tree snake)

  31. Snake feeding • Most capture prey by grasping it with their mouth and swallowing it while still alive • Some first kill their prey by constriction-usually if they specialize in large mammal prey • The largest constrictors are able to kill and swallow prey as large as deep, leopards, and crocodilians

  32. Non-venomous African house snake

  33. Snake feeding • Other snakes kell their prey before swallowing by injecting venom • Less than 20% of all snakes are venomous, although venomous species outnumber non-venomous species 4 to 1 in Australia • Venomous snakes are divided into 5 families based in part of type of fangs

  34. Venomous Snakes 1. Vipers: • Highly developed, moveable, tubular fangs at fron of mouth • Includes pit vipers, which lack facial heat-sensing pits • Cobras, mambas, coral snakes, and kraits • Sea snakes

  35. Spectacles, or Indian, cobra Cobras erect the front of the body and flatten the neck as a threat display and before attacking Although a cobra’s strike range is limited, all cobras are dangerous because of the extreme toxicity of their venom

  36. Pit vipers • Cottonmouths, copperheads, and several species of rattelsnakes • Possess special heat-sensitive pit organs on their head, located between their nostrils and their eyes • Sensitive to hear emitted by warm-bodied birds and mammals • Can distinguish temp differences of only .003 degrees celcius

  37. Bite • All vipers have a pair of teeth on the maxillary bones modified as fangs • Immediately release prey after the bite and wait for paralyzation

  38. Venom • 2 types: • Neurotoxic: acts mainly on nervous system, affecting optic nerves causing blindness, and phrenic nerve of diaphragm, causing paralysis of breathing • Hemorrhagin: breaks down red blood cells and blood vessels to produce extensive hemorhaging of blood into tissue spaces

  39. Dangerous Snakes • Mostly deadly drop for drop of venom is Australian tiger snake and some sea snakes • King cobra is largest and perhaps most dangerous of all venomous snakes • Worldwide, about 50,000 to 60,000 people die from snake bites each year • Mostly India, Pakistan where Russell’s viper, saw-scaled viper, and several species of cobra live

  40. Reproduction • Most are oviparous that lay shelled eggs beneath rotten logs, under rocks or in holes in the ground • American pit vipers give birth to well-formed young (ovoviviparous)

  41. Order Sphenodonta: Tuataras • Only 2 living species • Sole survivors of their lineage which radiated in the Age of Reptiles • Live in New Zealand

  42. Has a well developed third “eye” on top of its head complete with retina, lens and nervous connections to brain Although covered with scales, the third eye is sensitive to light (might have been an important sense organ in early reptiles)

  43. Order Crocodilia • Same lineage that gave rise to dinosaurs and birds • Have remained mostly unchanged for 200 million years • Divided into 3 families: alligators, caimans, and crocodiles and gavials

  44. Crocodilians • Elongate, robust, well-reinforced skull with massive jaw musculature arranged to provide a wide gape and rapid powerful closure • Teeth are in sockets • Have a second palate to be able to breath while their mouth is filled with water and food • 4 chambered heart

  45. Crocodiles • Estuarine crocodile in southern Asia and Nile crocodile grow to great size weighing up to 1000 kg • Can attack animals as large as cattle, deer, and people Nile Croc- 4th tooth of lower jaw fits outside the slender upper jaw (alligators lack this feature)

  46. Alligators • Usually less aggressive than croc and far less dangerous to humans • Only species of alligator in US is Alligator mississippiensis and the only species of croc is Crocodylus acutus which is restricted to extreme southern florida American alligator

  47. Alligators • Can make definite vocalizations • Give lout bellows during mating • Are oviparous-usually 20-50 eggs are laid in a mass of dead vegetations and guarded by the mother • The mother hears vocalizations from hatching young and responds by opening the nest allowing the hatchlings to escape • Incubation temperatures determine sex of hatchlings, but low temps produce females

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