Taxonomy Chapter 20 Reptiles Kingdom - Animalia Phylum - Chordata Class Reptilia Order Testudines - turtles Order Crocodylia - crocodiles, alligators Order Sphenodontida - tuataras Order Squamata - snakes and lizards I. Evolution Evolutionary success due to the amniotic egg Dry scaly skin, limits water loss More powerful jaws Internal fertilization Advanced circulatory, respiratory, excretory and nervous systems Ectothermic Evolutionary Development Diagram Synapsids Mammals Paleozoic Era development of Amniotic Egg Diapsids Other reptiles and birds Anapsids Turtles 1
II. Order Testudines (Chelonia) Tortoises and turtles Shell is their main defense and is a part of the skeleton Carapace - dorsal part of shell Plastron - ventral part of shell Shell is moveable and can close the turtle inside Lack teeth Found on land, freshwater and marine environments Must lay eggs on land Oviparous III. Order Sphenodontida (Rhynocephalia) Tuatara Only two species in existence Live on protected islands off the coast of New Zealand Oviparous and share burrows with ground-nesting seabirds Parietal eye - concealed under a layer of scales. Photosensitive 2
IV. Order Squamata Lizards, snakes, worm lizards Comprise 95% of all reptiles First seen about 150 million years ago A. Suborder Sauria Lizards Body forms are adapted for walking, running, climbing, swimming, and burrowing Distinguished from snakes by typically having 2 pairs of legs Moveable eye lids External ears No fangs Some species have developed venom glands Gila monsters & Mexican bearded lizard B. Suborder Amphisbaenia Worm lizards Sometimes referred to as the two headed snake Legless lizards that burrow into the ground Are able to move forward and backward with extreme ease C. Suborder Serpentes Snakes Limbless, elongated body Upper and lower jaws are hinged and can move independently of one another Swallows prey whole and can still breathe because it will push its trachea into its throat 3
Jacobson s organ - smells gathered by the tongue are collected in two pits on the roof of the mouth Killing Prey Constrictors - boas, pythons, anacondas Venom - elapids, vipers, rear fangs Hemotoxic venom - attack the circulatory system, disrupt the clotting process Neurotoxic venom - attack the nervous system, disrupt the brains ability to tell the heart to beat Snake movement Lateral undulation - moves its head side to side causing a S-shaped movement down the body Rectilinear movement - applies muscular force on the belly and uses its scutes to inch across the ground like a caterpillar Sidewinding - move sideways not forward. Slings head side to side and the whiplike motion yanks along the rest of its body. Desert snakes Concertina - used for climbing. Pushes head forward and grips with scutes on ventral surface and moves the rest of the body with it Reproduction Most are oviparous Some are ovoviviparous - female carries the eggs in her body throughout development and the young are born alive 4
D. Order Crocodylia http:// video.nationalgeogr aphic.com/video/ index.html Crocodiles, alligators, caimans, gavials Adapted for carnivorous, semi-aquatic life Large heavy skull, provides powerful crushing jaws Have a secondary palate that allows them to breathe when the mouth is full of water (separates the nasal and mouth passages) Swallow rocks as abrasives to help break down food in the stomach 4 chambered heart Oviparous and display Parental care Mother builds a nest of mud and debris Hollows out the center and deposits her eggs there Temperature determines the sex Below 31.5 celsius = females Between 32.5 and 33 celsius = males At 32 celsius = mixture of both Mom stays with the nest to protect it from predators Hatchlings will call to mom and she will free them from the nest and carry them to water in her mouth V. The Amniotic Egg Egg with protective membrane and porous shell enclosing the developing embryo 4 specialized membranes Amnion Yolk sac Allantois Chorion The shell is waterproof but does allow for gas exchange 5
Amnion - thin membrane enclosing the fluid that the embryo floats in Yolk sac - contains the yolk which is the food supply for the embryo Allantois - stores waste from embryo until it hatches Chorion - lines the outer shell and regulates oxygen and carbon dioxide exchange between the egg and outside 6