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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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)
Classification • Phylum: Chordata • Subphylum: Vertebrata • Superclass: Gnathostomata • Class: Amphibia • Order: Urodela (Salamanders) • Order: Anurans (Frogs and Toads) • Order: Apodans (Caecilians)
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
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
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
Order: Apodans • 150 species • Caecilians • Legless and blind • Mostly Tropical • __________ Fertilization • Usually give birth to live young. Internal
Conditions for Respiratory Surfaces • Large surface area • Thin • Moist
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
Respiratory Surfaces • Cutaneous Respiration • Gills • Tracheal Systems • Lungs
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)
Gills • Found in echino-derms, mollusks, annelids, arthropods, some vertebrates • Countercurrent Gas Exchange
Countercurrent Gas Exchange • Maintains gradient over the whole length of the capillaries • Extracts ____% of the oxygen from the water 80
Tracheal Systems • Found in arthropods • Tracheae • open tubes • Spiracles • openings • Tracheoles • contact with cells • Muscle • increase amount of Carbon Dioxide removed
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
Ventilation Lungs • Found in amphibians, reptiles, mammals and birds • Pharynx • Larynx • Trachea • Bronchi • Bronchioles • Alveoli
_______ 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
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)
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
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
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)
Reptile Radiation • Synapsids (therapsids) - led to mammals • Sauropsids • _________ (turtles) • _________ (all others) Anapsid Diapsid
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!)
Class: Testudines (Chelonia) teeth • No _____ • Most move legs to breathe • TDS (low:male high:female)
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?
Class: Squamata • Lizards • geckos, iguanas, skinks, chameleons • terrestrial, burrowing, aquatic, arboreal • moveable eyelids (in most) • Paired copulatory organs
Class: Squamata • Tongue usually not bifurcated • Lower jaw loosely connected to skull • TSD (female to male) • ______________ Parthenogenesis
Class: Squamata • Gila Monster – • One of two poisonous lizards • Protein in saliva studied to treat diabetes.
Class: Squamata • Snakes • Lack limbs • Lack moveable eyelids
Class: Squamata • Bifurcated tongue • _________ organ • Pit Vipers (Loreal Pits) Jacobson’s
Class: Squamata • Venom • Viperidae (Folding Fangs) • Rattlesnakes • Elapidae (Fixed Front Fangs) • Cobras, Sea Snakes, Coral Snakes • neurotoxic • hemotoxic
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