Reptiles 41-1 Origin & Evolution I. Arose from Amphibians around 359 mya. A. Small, four-legged, and had teeth adapted for eating insects. B. Became a dominant land vertebrate by the Permian (300-250 mya) C.End of Permian, Pangaea formed. 1. Interior of continents had a dry climate. II. Mesozoic Era (251-66 mya) A. Reptiles flourished due to: 1. abundance of food 2. dry climate 3. mass extinction of other species B. Became known as the “Age of Reptiles”, nearly all the large vertebrates were reptiles. C.Dinosaurs evolved from thecodonts - an extinct crocodile-like reptile D. Triassic Dinosaurs 1. near the end they became small and carnivorous, largely replacing the thecodonts. 2. Reasons they were successful: a. legs positioned under the body making them faster and agile. b. adapted to dry conditions. c. mass extinction (80%) at end of Triassic reducing competition. E. Jurassic “Golden Age of Dinosaurs” 1. Largest land animals ever was the giant sauropods. 2. Carnivorous Theropods appear at end of Jurassic. a. Bi-pedal, short arms, sharp teeth b. Were the dominant land predators until the end of the Cretaceous. F. Extinction (65 mya) 1. Asteroid Impact Theory – asteroid hit in the Yucatan Peninsula 2. Multiple Impact Theory – many impacts before the final one. 3. Along with other unfavorable environmental conditions, led to the decline. III. Success of Reptiles on Land A. The amniotic egg III. Success of Reptiles on Land A. The amniotic egg 1. Contains a large amount of yolk for embryo nourishment. 2. A leathery or hard shell surrounding embryo. 3. Several membranes which protect and provide gas and waste exchange. a. amnion – membrane with fluid in which embryo floats. b. yolk sac – food for developing embryo c. allantois – stores wastes and exchanges CO2 with O2. d. chorion – surrounds all membranes, helps protect embryo. e. albumen – fluid that contains protein and water for embryo. B. Watertight Skin – thick, dry, scaly skin that prevents water loss. 1. Keratin – tough protein that makes up scales, hair, and fingernails. C.Efficient respiration and excretion that help them conserve water. 1. Nitrogen waste – secreted in the form of uric acid, which reduces the amount of water loss in urine. Section 1 Origin and Evolution of Chapter 41 Reptiles Key Features of Reptiles 41-2 Characteristics of Reptiles I. Circulatory system – double looped A. Pulmonary loop – lungs B. Systemic loop - body C.Heart – 3 chambered. The single ventricle is partially divided by a wall of tissue called a septum. D.Can divert blood from the lungs back to the body to warm their bodies. E. Crocodiles have a 4 chambered heart. II. Respiratory sys. A. Large Lungs – lining of the lungs may be folded into small sacs called alveoli. 1. alveoli increases the surface area of the lungs B. Inflate lungs by expanding ribs. This lowers pressure in chest which draws air in. C.When ribs relax, air is forced out. III. Nervous System A. Brain size is similar to amphibians except: 1. the cerebrum is much larger. (controlling & integrating behavior) 2. well developed olfactory lobe. 3. large optic lobe. B. Senses 1. Sight - Reptiles have large, well- developed eyes. 2. Hearing - Sound waves strike the tympanum (eardrum) and are transmitted by the columella to the inner ear. 3. Smell - Snakes have a special structure called the Jacobson’s organ, located in the roof of the mouth, that also detects odors. 4. Vibrations - Snakes lack a tympanum and can sense only low-frequency sounds and ground vibrations. 5. Heat detection - Pit vipers have a heat- sensitive pit below each eye that detects prey. IV. Thermoregulation – controlling body temp. A. All reptiles are Ectotherms - warm their bodies by absorbing heat from their environment. 1. Advantage a. slow metabolism and require very little energy, one-tenth as much food as an endotherm of the same size. 2. Disadvantage a. cannot live in very cold climates. b. cannot provide enough energy for sustained exertion. Section 2 Characteristics of Reptiles Chapter 41 Changes in Lizard Body Temperature V. Reproduction A. Oviparity – eggs are layed B. Ovoviviparity – eggs with shells develop within the female’s body. C.Viviparity – eggs have NO shell, develop within female and is nourished by a placenta. VI. Parental Care A. Many species provide NO care. B. Some lizards and snakes guard and warm eggs until they hatch. C.Crocs & Alligator’s provide the most care. 1. build nest 2. guard nest 3. carry the hatched young to water 4. a mother croc may protect her young for a year or more. Section 2 Characteristics of Chapter 41 Reptiles External Structures of a Timber Rattlesnake Section 2 Characteristics of Chapter 41 Reptiles Internal Structures of a Timber Rattlesnake 41-3 Modern Reptiles I. Order Chelonia A. turtles – usually live in water. B. tortoise – usually live on land. C.shell – fused bony plates 1. carapace – top, or dorsal, part of shell 2. plastron – lower, or ventral, portion. 3. vertebrae and ribs are fused to the interior of the carapace. D. Lay eggs – digs hole on land, no parental care. II. Order Crocodilia (crocs, alligators, caimans, and gavials). Most closely related to Dinosaurs • All are carnivorous. • A valve in the oral cavity covers the esophagus and windpipe, allowing crocodilians to capture and swallow prey underwater. III. Order Squamata A. Lizards – most are small, fast, agile, and camouflaged. 1. Some lizards can detach their tail to distract predators. This is called autotomy. Alaina is desperate!! B. Snakes 1. Constriction – wrapping around prey and suffocating it. 2. Prey is swallowed whole. Jaws and skull are joined by ligaments that allow the mouth and head to stretch around prey. 3. Injecting venom a. grooved fangs at the back of mouth. b. Elapid snakes – inject through two small fixed fangs in the front of the mouth. (Cobras, Coral Snakes) c. Vipers – inject through large, hinged fangs in the front of the mouth. (rattlesnakes, copperheads, water moccasins) IV. Order Rhynchocephalia A. Tuataras – spiny crest that runs down the animal’s back..