Transcript Chapter 34
Chapter 34 ~ Vertebrate Evolution and Diversity Chordates Notochord: longitudinal, flexible rod located between the digestive and the nerve cord Dorsal, hollow nerve cord; eventually develops into the brain and spinal cord Pharyngeal slits; become modified for gas exchange, jaw support, and/or hearing Muscular, postanal tail deuterostomes hollow dorsal nerve cord becomes brain & spinal cord pharyngeal pouches becomes gills or Eustachian tube postanal tail becomes tail or tailbone notochord becomes vertebrae Subphylum: Vertebrata Retain chordate characteristics with specializations…. Neural crest: group of embryonic cells near dorsal margins of closing neural tube Pronounced cephalization: concentration of sensory and neural equipment in the head Cranium and vertebral column Closed circulatory system with a ventral chambered heart Vertebrate diversity Phy: Chordata Subphy: Vertebrata Superclass: Agnatha~ jawless vertebrates (hagfish, lampreys) Superclass: Gnathostomata~ jawed vertebrates with 2 sets of paired appendages; including tetrapods (‘4-footed’) and amniotes (shelled egg) Superclass Agnatha Jawless vertebrates Most primitive, living vertebrates Ostracoderms (extinct); lamprey and hagfish (extant) Lack paired appendages; cartilaginous skeleton; notochord throughout life; rasping mouth Class Chondrichthyes Class: Chondrichthyes~ Sharks, skates, rays Cartilaginous fishes; well developed jaws and paired fins; continual water flow over gills (gas exchange); lateral line system (water pressure changes) Life cycles: Oviparous- eggs hatch outside mother’s body Ovoviviparous- retain fertilized eggs; nourished by egg yolk; young born live Viviparous- young develop within uterus; nourished by placenta Class Osteichthyes Class: Osteichthyes Ossified (bony) endoskeleton; scales operculum (gill covering); swim bladder (buoyancy) Most numerous vertebrate Ray-fined (fins supported by long, flexible rays): bass, trout, perch, tuna, herring Lobe-finned (fins supported by body skeleton extensions): coelocanth Lungfishes (gills and lungs): Australian lungfish (estivation) Transition to Land Evolution of tetrapods Humerus Femur Tibia Ulna Pelvis Shoulder Radius Fibula Pelvis Lobe-finned fish Femur Humerus Tibia Fibula Ulna Shoulder Radius Early amphibian Jump to first page Class Amphibia Class: Amphibia 350 mya 1st tetrapods on land Frogs, toads, salamanders, body structure body function legs (tetrapods) moist skin lungs (positive pressure) & diffusion through skin for gas exchange three-chambered heart; veins from lungs back to heart ectotherms reproduction external fertilization external development in aquatic egg metamorphosis (tadpole to adult Class Aves Class: Aves 150 mya Birds body structure feathers & wings thin, hollow bone; flight skeleton body function very efficient lungs & air sacs four-chambered heart endotherms reproduction internal fertilization external development in amniotic egg trachea lung anterior air sacs posterior air sacs Class Reptila Class: Reptilia 250 mya Lizards, snakes, turtles, and crocodilians body structure dry skin, scales, armor body function lungs for gas exchange thoracic breathing; negative pressure three-chambered heart ectotherms reproduction internal fertilization external development in amniotic egg Amniotic Egg Jump to first page Class Mammalia Class: Mammalia 65 mya body structure hair specialized teeth body function lungs, diaphragm; negative pressure four-chambered heart endotherms reproduction internal fertilization internal development in uterus • nourishment through placenta birth live young mammary glands make milk Vertebrates: Mammals Sub-groups monotremes egg-laying mammals lack placenta & true nipples duckbilled platypus, echidna marsupials pouched mammals • offspring feed from nipples in pouch short-lived placenta koala, kangaroo, opossum placental true placenta • nutrient & waste filter shrews, bats, whales, humans Jump to first page