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Class Reptilia 1
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History 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
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Class Reptilia Scales Amniotic egg One occipital condyle Ectothermic
Three chambered heart Alligators have 4 Claws 4
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Ectothermic 5
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Common Features Positioning of legs more directly under animal (more support). Paired limbs with five toes. Adapted for running, climbing, swimming. Absent in snakes. 6
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Common Features Body covered with horny epidermal scales made from protein keratin. Scales serve to reduce water loss and provide protection. Reptiles molt as they grow. Jaws adapted to biting/tearing. 7
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Fig. 26.3 8
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Common features Respiration through internally protected and moistened (a moist cloacal surface in some turtles). 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. 9
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Common features Excretory waste = uric acid (doesn’t waste water)
Brain = first cerebral cortex (capable of reasoning, planning, perception) Still ectothermic Must live in favorable conditions or hibernate. Being ectothermic enables an organism to survive on much less food than an endothermic organism. 10
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Reproduction Internal fertilization: gametes not subject to desiccation. Amniote egg = significant evolutionary breakthrough. Egg covered by tough, water-resistant, leathery or calcerous shell. Extraembryonic membranes compartmentalize the interior for several functions. 11
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Amniote Egg 12
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Amniote 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. 13
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Reptile Skulls Except for turtles, all reptiles have two temporal openings in the skull. These openings have allowed for attachment and expansion of the jaw muscles. 14
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Reptile Skulls Anapsid Synapsid Diapsid Euryapsid No opening
One opening Diapsid Two openings Euryapsid One small opening 15
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Fig. 26.5 16
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Subclass Anapsida Order Testudines
260 species of turtles/tortoises Oldest group of reptiles (225 mya) 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 17
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Primitive features Loss of body-wall muscles
Ribs/trunk vertebrae fused to carapace Lack teeth; hard beak grab and tear food
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Subclass Anapsida Order Testudines
All lay eggs on land. Third eyelid = nictitating membrane. Longest living vertebrates (100+years in wild)! 19
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TURTLES & TORTOISES Only reptile with shell Only reptile WITHOUT TEETH
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Turtle Shell Carapace Plastron 21
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Box Turtle Terrapene Adapted to live on land Feet not webbed
High domed shell Safe 23
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Red-Eared Slider Trachemys
Red stripe behind eye Live in or near water Ponds Slow moving water Pets Carry Salmonella 24
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Snapping Turtle Chelydra
Live in water Lay eggs on land Long tail Muscular limbs 25
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Fig. 26.7 26
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Giant Tortoise Lifespan 150 Years
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Leatherback Sea Turtle
6 feet long 1,400 pounds 28
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Diapsids Dinosaurs Snakes Lizards Crocodilians Birds 29
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Subclass Diapsida Superorder Lepidosauria Order Squamata
4675+ species of lizard 2700+ species of snakes 140 species of amphisbaenians Limbless, burrowing animals Vestigial eyes under skin 30
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Order Rhynchocephalia
2 species of Tuatara Solitary, nocturnal, burrowing animal
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Order Squamata Kinetic skull Movable joints Lizards Snakes Dinosaurs
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Order Squamata Most successful, diversified of living reptiles.
Occur in most habitats of world. Lizards: Legs, eyelids, ear openings Halves of lower jaw united 33
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Geckos Small lizards Adhesive toe pads 34
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Gecko Toe Pads Fig 35
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Wall Lizard Lacerta Color is variable Slender body Small scales 36
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AUTOTOMY Self amputation to escape predators Can’t regrow
Costly; lose muscle/stored fat 37
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Texas Horned Lizard Spines for protection Eats ants Endangered species
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Gila Monster Poisonous lizard Not very aggressive 39
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Green Iguana Ornamental crest Five feet long Tropical rainforest
Mexico South America Omnivores 40
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Chameleons Arboreal - live in trees Africa and Madagascar
Catch insects with tongue 41
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Komodo Dragon Attack and eat humans 10 feet long 300 pounds Indonesia
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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
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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 44
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JACOBSON’s ORGAN Sharpens its sense of smell.
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 45
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HEAT SENSING ORGAN “Pit" organ located between the eye and the nostril on each side of the head. Detects heat given off by warm-blooded prey 46
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Swallow Prey 47
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Constrictors Wrap around prey and kill by suffocation
Constrictors Wrap around prey and kill by suffocation Ex: Boa constrictors 49
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VIPERS Inject venom with large movable fangs
Ex: rattlesnakes, copperheads, water moccasins 50 Images from:
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ELAPIDS Inject venom with small fixed (non-movable) fangs
Ex: cobras, kraits, coral snakes 51
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Snake Venom 53
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Copperhead Agkistrodon
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Cottonmouth or Water Moccasin Agkistrodon
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Western Diamond Backed Rattlesnake Crotalus
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Prairie Rattlesnake Crotalus
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Timber Rattlesnake Crotalus
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Black Rat Snake 59
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Diamond Backed Watersnake Nerodia
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Green Snake 61
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Coral Snake 62
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Superorder Archosauria
Includes extinct dinosaurs/pterosaurs and birds 23 species of crocodiles, alligators, & caimans Largest of the living reptiles Amphibious carnivores Live in tropics/subtropics 63
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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
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Dinosaurs Dominate animals in Mesozoic Era 65
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Euryapsid Extinct Ichthyosaurs 66
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Synapsids Pelycosaurs Dimetrodon Mammal like reptile 67
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Order Crocodilia Crocodiles Caimans Alligators Gavials Elongated skull
Four chambered heart 68
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Alligator 69
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Caiman Elevated eyes 70
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Gavial 71
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Alligator Caiman Crocodile Gavial 72
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The End Fig 73
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