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Evolution of the Tetrapods. Evolution of the Tetrapods. Vertebrates. The Origin of Tetrapods. The first vertebrates on land were amphibians in the Devonian (400 mya) Arose from the rhipidistian (a family of lobed finned fish) (based on morhpology) or a lungfish (DNA). Origin of Tetrapods.

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Evolution of the Tetrapods


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    1. Evolution of the Tetrapods

    2. Evolution of the Tetrapods

    3. Vertebrates

    4. The Origin of Tetrapods • The first vertebrates on land were amphibians in the Devonian (400 mya) • Arose from the rhipidistian (a family of lobed finned fish) (based on morhpology) or a lungfish (DNA)

    5. Origin of Tetrapods

    6. Origin of Tetrapods

    7. Classification • Phylum: Chordata • Subphylum: Vertebrata • Superclass: Gnathostomata • Class: Amphibia • Order: Urodela (Salamanders) • Order: Anurans (Frogs and Toads) • Order: Apodans (Caecilians)

    8. Class: Amphibia • Two lives • refers to metamorphosis of many frogs • Skin smooth and moist (cutaneous respiration) • _____ chambered heart with a double circulation system • Mesolecithal eggs with jelly-like membrane 3

    9. Order: Urodela • 400 species • Salamanders • Retain their tail as adults • Limbs are at right angles to the body • Carnivorous • Most have internal fertilization using a _____________ • Axolotl - paedomorphosis Spermatophore

    10. Order: Anurans • 3500 species • Frogs and Toads • Lose their tail as adults • Hind limbs are adapted for jumping • Tongue connected to front of mouth • Secrete mucus • __________ Fertilization External

    11. Order: Apodans • 150 species • Caecilians • Legless and blind • Mostly Tropical • __________ Fertilization • Usually give birth to live young. Internal

    12. Gas Exchange

    13. Conditions for Respiratory Surfaces • Large surface area • Thin • Moist

    14. Less than ____% oxygen Oxygen amounts decrease as the temperature increases Aquatic animals use large amounts of energy to obtain oxygen (____%) About _____% oxygen Developed invaginations to increase surface area and decrease evaporation Terrestrial animals may use only 1% - 2% of its energy to obtain oxygen Aquatic vs. Terrestrial 1 21 20

    15. Respiratory Surfaces • Cutaneous Respiration • Gills • Tracheal Systems • Lungs

    16. Cutaneous Respiration • Direct diffusion of gases between the organism and the environment • Found in Porifera, Cnidarians, Platyhelminthes, nematodes, Annelids, and some Amphibians • Supplements other organisms (amphibians)

    17. Gills • Found in echino-derms, mollusks, annelids, arthropods, some vertebrates • Countercurrent Gas Exchange

    18. Countercurrent Gas Exchange • Maintains gradient over the whole length of the capillaries • Extracts ____% of the oxygen from the water 80

    19. Tracheal Systems • Found in arthropods • Tracheae • open tubes • Spiracles • openings • Tracheoles • contact with cells • Muscle • increase amount of Carbon Dioxide removed

    20. Tracheal Systems

    21. Diffusion Lungs • Found in invertebrates • Gas moved primarily by diffusion • may be increased by body movement • Modifications • snails - cavity with gill modified into lung • scorpions and spiders - invaginations of the abdomen

    22. Ventilation Lungs • Found in amphibians, reptiles, mammals and birds • Pharynx • Larynx • Trachea • Bronchi • Bronchioles • Alveoli

    23. Alveoli

    24. _______ Pressure Breathing pushes air down trachea seen in frogs and other amphibians ________ Pressure Breathing suction created by diaphragm seen in mammals Ventilating The Lungs Negative Positive

    25. Negative Pressure Breathing

    26. Evolution of the _________ Egg Amniotic • Allows animals to complete their entire life cycle on land • Has shell that retains water (or is lost when kept inside mammals) • Specialized extraembryonic membranes (not part of the animal)

    27. The Amniotic Egg

    28. Evolution of the Amniotic Egg • Amnion - Protects from dehydration and mechanical shock • Yolk Sac - Nutrient storage • Albumin (egg white) - Nutrient storage • Allantois - stores waste, gas exchange • Chorion - gas exchange

    29. Amniotes

    30. Amniotes

    31. Tough, dry skin Amniotic egg Crushing or gripping jaws Copulatory organs More efficient circulatory system with a higher blood pressure More developed lungs (thoracic breathing) Better water conservation Better body support and limbs Better nervous system How Reptiles differ from Amphibians

    32. Classification • Phylum: Chordata • Subphylum: Vertebrata • Superclass: Gnathostomata • Class: Reptilia (not real) • Class: Testudines (Turtles and Tortoises) • Class: Spenodontia (Tuataras) • Class: Squamata (Lizards and Snakes) • Class: Crocodilia (Crocodiles and Alligators)

    33. Reptile Radiation • Synapsids (therapsids) - led to mammals • Sauropsids • _________ (turtles) • _________ (all others) Anapsid Diapsid

    34. Class: Testudines (Chelonia) • Protective Shell • Carapace (top) • Plastron (bottom) • Land and Sea -Evolved on land and returned to water (lay eggs on land) Largest, Leatherback Sea Turtle (2,000 lbs!)

    35. Class: Testudines (Chelonia) teeth • No _____ • Most move legs to breathe • TDS (low:male high:female)

    36. Class: Sphenodontia Tuataras • ___________ • Two living species (New Zealand) • Not a True Lizard (no external ears, different teeth) • Very Primitive (similar to mesozoic reptiles • Well developed eye below skin?

    37. Class: Squamata • Lizards • geckos, iguanas, skinks, chameleons • terrestrial, burrowing, aquatic, arboreal • moveable eyelids (in most) • Paired copulatory organs

    38. Class: Squamata • Tongue usually not bifurcated • Lower jaw loosely connected to skull • TSD (female to male) • ______________ Parthenogenesis

    39. Class: Squamata

    40. Class: Squamata

    41. Class: Squamata

    42. Class: Squamata • Gila Monster – • One of two poisonous lizards • Protein in saliva studied to treat diabetes.

    43. Class: Squamata • Snakes • Lack limbs • Lack moveable eyelids

    44. Class: Squamata • Bifurcated tongue • _________ organ • Pit Vipers (Loreal Pits) Jacobson’s

    45. Class: Squamata • Venom • Viperidae (Folding Fangs) • Rattlesnakes • Elapidae (Fixed Front Fangs) • Cobras, Sea Snakes, Coral Snakes • neurotoxic • hemotoxic

    46. Class: Squamata

    47. Class: Squamata

    48. Class: Squamata

    49. Feeding Adaptations • Teeth curved and pointed inward • Hinged __________ bone • Bones of jaw are attached by muscles and ligaments • Moveable palate • Elastic skin • No sternum Quadrate