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Class Amphibia

Class Amphibia. Fred Searcy ZOO2010. Early Tetrapods. Movement from water to land Oxygen content 210 ml/l atmosphere 3-9 ml/l in water Density Water 1000x as dense Buoyancy Skeletal system Stability Temperature extremes High specific heat of water Variety of Terrestrial environments

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Class Amphibia

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  1. Class Amphibia Fred Searcy ZOO2010

  2. Early Tetrapods • Movement from water to land • Oxygen content • 210 ml/l atmosphere • 3-9 ml/l in water • Density • Water 1000x as dense • Buoyancy • Skeletal system • Stability • Temperature extremes • High specific heat of water • Variety of Terrestrial environments • Humidity • Environmental effects on • Abundance of water • Abundance of food

  3. Early Tetrapods • Evolved from Osteichthyes • Legs with should and hip girdles • Devonian – mild temperatures, fluctuations of flood and drought. Conducive to • Lungs • Limbs • Acanthostega probably first tetrapod – still totally aquatic • Belief is tetrapod limbs evolved in water before movement to land

  4. Ichthyostega • Probably first tetrapod to have terrestrial existence • Still retained some aquatic features and thus tied to aquatic environment

  5. What is the first tetrapod to have a terrestrial existence? • A. amblistoma • B. icthyostegea • C. leptospondillia • D. none of the above • E. all of the above

  6. Frogs & Toads Anthracosauria Amniota Salamanders Lepospondyli Caecillians Lissamphibians Ichthyostega Dipneusti Only frogs, salamanders and caecilians survived Temnospondyl Groups Sarcopterygian Ancestor Rhipidistians Coelacanth Devonian400 mya Carboniferous 360 mya Permian286 mya Paleozoic 540-245 mya Mesozoic225 mya Cenozoic65 mya

  7. Amphibia(L from the Gr amphi = around, on both sides) • Capable of living both in or out of water • Most must return to water for reproduction • Classification • Class Amphibia • Order Gymnophiona (Caecilians) • Order Caudata (Salamanders) • Order Anura (Frogs, Toads)

  8. Characteristics • Bony skeleton, varying #s of vertebrae, ribs present or absent, notochord does not persist, no exoskeleton • Usually tetrapods, some legless, webbed feet often present, no true claws or nails • Smooth, moist skin with glands (some poisonous), chromatophores, no scales except for some concealed dermal forms • Small teeth in upper jaws, nostrils open to interior of mouth • Respiration usually by lungs & integument, some have gills in larval stage, some have persistent gills • Three chambered heart (2 atria, 1 ventricle) • Ectothermal • Mesonephric kidney, urea main nitrogenous waste • Ten pairs of craninal nerves • Sexes separate, internal (spermatophore) fertilization in salamanders and caecilians, external in frogs & toads, metamorphosis occurs, telolecithal eggs

  9. Caecilians • Native to tropical forests of South American, Africa, and Southeast Asia • Burrowing or aquatic • Approximately 160 species • Dermal scales may be present under the skin • Many vertebrae, long ribs, no limbs • Eyes small and many blind as adults • Terminal anus • Internal fertilization (male has protrusible copulatory organ) • Vivparous • Diet is worms, small insects

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