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Vertebrates Old and New • Every animal is a combination of traits • Some traits come from ancestors • Other traits are unique Chordate Characteristics • All share four features: – Notochord -> vertebrae – Dorsal tubular nerve cord – Pharynx with gill slits – Post-anal tail LE 17-30 Muscle segments Notochord Dorsal, hollow nerve cord Brain Mouth Anus Post-anal tail Pharyngeal slits Invertebrate Chordates • Two subphyla • Sea squirts – Larval stage • Lancelet – All characteristics Figure 17.31 LE 17-32 Chordates Vertebrates Tetrapods Amniotes 0 65 145 200 251 299 Hair and mammary glands Amniotic egg 359 Four legs 416 444 Lungs or lung derivatives 488 Jaws Vertebrae 542 Ancestral chordate Fishes • Lampreys • Cartilaginous fishes • Bony fishes Lampreys • Jawless • Blood suckers • 2 paired fins • Few remaining species Hagfish tentacles gill slits (twelve pairs) mucous glands Do not post photos on Internet Figure 26.6 Page 449 Slide 9 Evolution of Jaws supporting structures Early jawless fish (agnathan) gill slit • Modifications of gill supports Early jawed fish (placoderm) jaw spiracle jaw support Modern jawed fish (shark) jaw Jawed Fishes • Large diverse group – Powerful tails – Streamlined body – Swimbladder • Two classes: – Cartilaginous fishes (Chondrichthyes) – Bony fishes (Osteichthyes) Cartilaginous Fishes: (Chondrichthyes) • Most are marine predators • Cartilaginous skeleton • Streamline body • Powerful tail • Lateral line system Cartilaginous Fishes Bony Fishes: (Osteichthyes) • 96% of living fish species • Operculum covers gills • Swim bladder • Good sense of smell • Good eyesight Body Plan of a Bony Fish fin supports muscle segments brain olfactory bulb urinary bladder heart anus kidney swim bladder liver gallbladder stomach intestine Ray-finned Fishes Unarmored Stickleback - Endangered Green Sunfish • • • • Lobe-Finned Fishes Lung fish Coelocanths Lunglike sacs “Walk” on fins Lungfishes • Have gills and one lungs • Surface to gulp air Invasion of Land • Water availability • Temperature Variation • Skeletal support • New habitats • Food Invasion of Land Lobe-finned fish Early amphibian Amphibians • Require water; most lay eggs in water • Lungs are inefficient • Skin works as respiratory organ Amphibian Groups Reptiles Amniotes: Amniotic egg • No more water – Tough, scaly skin – Internal fertilization – Water-conserving kidneys • Ectotherms Evolutionary History of Amniotes snakes lizards stem reptiles tuataras ichthyosaurs pterosaurs birds dinosaurs plesiosaurs archosaurs crocodilians turtles anapsids therapsids synapsids Carboniferous Paleozoic era (mammals) Permian Triassic Jurassic Mesozoic era Cretaceous Turtles • Armorlike shell • Horny plates instead of teeth • Lay eggs on land Lizards and Snakes Coast Horned Lizard Crocodilians Birds • Evolved from reptiles • Endotherms • Feathers – Derived from reptilian scales – Serve in insulation and flight Adapted for Flight • Four-chambered heart • Highly efficient respiratory system • Lightweight bones with air spaces • Powerful muscles attach to the keel Adapted for Flight Birds Mammals: (Mammalia) • Hair • Mammary glands • Distinctive teeth • Highly developed brain • Extended care for the young Three Mammalian Lineages • Monotremes – Egg-laying mammals • Marsupials – Pouched mammals • Eutherians – Placental mammals Role of Geologic Change PLACENTAL MAMMALS EVOLVE; ADAPTIVE RADIATIONS BEGIN Isolation of the early monotremes, marsupials on this land mass Between 100 million and 85 million years ago, during the Cretaceous Figure 26.20b Monotremes • Three species – Duck-billed platypus – Two kinds of spiny anteater • Lay eggs and suckle Marsupials • Development in a permanent pouch Placental Mammals • Young develop in mother’s uterus • Placenta composed of maternal and fetal tissues • Placental mammals develop more quickly than marsupials Placental Mammals Trends in the Evolution of Vertebrates • Shift from notochord to vertebral column • Nerve cord expanded into brain • Cranium • Evolution of jaws • Paired fins evolved, gave rise to limbs • Gills evolved, gave rise to lungs
