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Reptiles Chapter 41 Origin & Evolution of Reptiles Section 41.1 History of Reptiles • 350 million years old • Reptiles arose from amphibians • “Age of Reptiles” = Mesozoic era • Reptile means “to crawl” • Herpetology: study of reptiles & amphibians Evolution of Dinosaurs • Dinosaurs: group of extinct reptiles that dominated life 235 mya • Triassic dinosaurs: small, carnivorous • Jurassic dinosaurs: large, carnivorous • Cretaceous dinosaurs: large, herbivorous Extinction of Dinosaurs • 66 million years ago 1. Asteroid-impact hypothesis: huge asteroid hit the earth, creating lots of dust that reduced the amount of sunlight causing massive climatic changes 2. Multiple-impact hypothesis: multiple asteroid impacts Success of Reptiles • Only 4 orders of reptiles survived the mass extinction – Squamata, Chelonia, Crocodilia, & Rhynchocephalia • First totally terrestrial vertebrate Amniotic Egg • Egg that encases the embryo in a secure, self-contained aquatic environment Draw this picture! Parts of the Egg • Amnion: membrane enclosing the fluid where the embryo floats • Yolk sac: encloses the yolk (fat-rich food supply) • Allantois: stores wastes produced by embryo • Chorion: protects the embryo • Albumen: stores protein & water for embryo Characteristics of Reptiles Section 41.2 Watertight Skin • Thick, dry skin with keratin: – protein found in the outer surface cells • Lipids & protein barrier • Protects from water loss, infections, & injuries Respiration & Excretion • Efficient systems to help conserve water – Little water loss in urine • Lungs to breathe Circulatory System • Composed of two loops: 1. Pulmonary loop: deoxygenated blood from heart to lungs, oxygenated blood from lungs to heart 2. Systemic loop: oxygenated blood to body, deoxygenated blood to heart Heart Structure & Function • Most have a 3 chambered heart: – 2 atria & 1 ventricle (partially divided) • Crocodiles have a 4 chambered heart: – 2 atria & 2 ventricles – Ventricle divided by septum tissue • Reptiles can reroute blood flow away from lungs – Conserves energy – Raises body temperature quickly Crocodile Heart Septum Respiration • Large, several chambered lungs with small sacs called alveoli – Increases surface area for diffusion • First vertebrae group to breath by expanding & contracting their chest – Air pressure gradient between outside and the thoracic cavity Nervous System • Sight is very important thus big eyes • Hearing is also important though snakes lack a tympanum – Detect ground vibrations via jaw bones • Jacobson’s organ: detects odor (smell), on roof of mouth • Heat sensitive pits below eyes of some snakes Thermoregulation • Definition: control of body temperature • Ectotherm: warms body by absorbing heat from the surroundings – Fish, reptiles, amphibians • Endotherm: generates heat from within – Birds, mammals Advantages & Limitations of Ectothermy • Advantages: – Slow metabolism – Less food needed • Limitations: – Cannot live in cold climates (become dormant in winter) – No sustained exertion Reproduction & Parental Care 1. Oviparity: egg surrounded by tough protective shell, no parental care 2. Ovoviviparity: eggs stored within female until just before hatching, limited parental care 3. Viviparity: eggs stored with female and receives nutrients from the placenta, most parental care Welcome to the world! Modern Reptiles Section 41.3 Order Chelonia • Examples: turtles (water dwelling) & tortoises (land dwelling) • Body covered by a 2 part shell: carapace (dorsal) & plastron (ventral) • Vertebrae & ribs fused to carapace – Cannot leave shell! • Sharp beak with no teeth • Lay eggs (oviparity) Two parts of the shell Some Ohio turtles on the next few slides….. Eastern Box Turtle Stinkpot Musk Turtle Soft-shelled Turtle Blanding’s Turtle Spotted Turtle Snapping Turtle Painted Turtles Tasha, Daisy, & Bowser – in the Maroons’ house! Order Crocodilia • Examples: crocodiles & alligators • Closest relatives to dinosaurs • All are carnivores – Eat turtles, fish, etc. Order Squamata • Examples: lizards & snakes • Autotomy: the ability to detach a body part often when a predatory is near • Snakes swallow prey whole – Detachable jaw Types of Snakes • Constrictors: wrap body around prey and suffocate by increasing pressure – Boas, pythons, anacondas • Elapsid: inject venom through two small, fixed fangs in front of mouth – Cobras, coral snakes • Vipers: inject venom through large, mobile fangs in the front of mouth – Rattlesnakes, copperheads, water moccasins Order Rhynchoephalia • Example: tuatara • Meaning “spiny crest” • Only two modern species • Live in New Zealand 4 Order Note Cards • Front Side: – Name of order – Picture (in color) of animal • Back Side: – – – – – Example organisms Where on Earth?/habitat Unique characteristics Feeding patterns Reproductive behavior