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Vertebrates Which of these is most closely related to you? Which of these is most closely related to you? Vertebrates Echinoderms and Chordates are the only two phyla of deuterostomes. Chordata fish, amphibians, reptiles, birds, mammals Deuterostome coelomates Notochord serves as axis of body Dorsal, hollow nerve cord Tails. Human coccyx is vestigial tail. Birds & mammals = homeotherms (constant body temperature) All others are poikilotherms (cold-blooded) though some reptiles are endothermic. Mammals class Nurse their young with milk Have hair or fur made of keratin Homeotherms • Placental = develops in womb • Marsupial = born early, develops in pouch • Monotreme = egg-laying (duck-billed platypus and spiny anteater). Primates order Hands with opposable thumbs Claws have become nails Eyes are in front and close together for binocular vision Nurture their young for a long time. Chordate Characteristics Chordate Characteristics Notochord •A flexible rod between the nerve cord and the digestive tube •All chordates have this as embryos •Most develop later into complex, jointed skeleton. Chordate Characteristics Dorsal, hollow nerve cord •Develops from a plate of ectoderm that rolls into a tube •Unique to chordates. (Other phyla have solid, ventral nerve cords) •Develops into central nervous system, spinal cord, and brain. Chordate Characteristics Pharyngeal slits or clefts •Just posterior to the mouth •Used for suspension feeding and gas exchange (gills) •In land animals, they develop into parts of the ear. Chordate Characteristics Muscular, post-anal tail •Lost during embryonic development in many species •Provides propulsion for many aquatic species. Classes of Chordates Classes of Chordates Tunicates Classes of Chordates Tunicates Classes of Chordates Tunicates Classes of Chordates Tunicates Classes of Chordates Lancelets Classes of Chordates Lancelets Classes of Chordates Hagfish •Craniate (has brain and skull) •No jaws •No vertebrae Classes of Chordates Hagfish Classes of Chordates Hagfish Classes of Chordates Hagfish Classes of Chordates Lamprey •Vertebrate (has backbone) •Still no jaws Classes of Chordates Lamprey Classes of Chordates Lamprey Classes of Chordates Lamprey Classes of Chordates Sharks and Rays •Gnathostomes (“jaw-mouths”) •Bones have some mineralization but are still mostly cartilage •Acute senses (lateral line, nostrils, black-and-white vision) •Oviparous, ovoviviparous, or viviparous. Classes of Chordates Sharks and Rays Classes of Chordates Sharks and Rays Classes of Chordates Sharks and Rays Classes of Chordates Ray-Finned Fishes Classes of Chordates Lobe-Finned Fishes Classes of Chordates Lungfishes Tetrapods Classes of Tetrapods Amphibians Urodela (“tailed ones”) Salamanders Anura (“tailless ones”) Frogs and toads Apoda (“legless ones”) Caecilians Classes of Tetrapods Amphibians Adaptations: •Camouflage •Poison •Metamorphosis / paedomorphosis •Complex social behavior •Eggs lack shells, dehydrate quickly •Gas exchange through moist skin Amniotes Amniotes •Amniotic egg may be laid on land. •Contains extra-embryonic membrane •May be calcified (birds) or leathery (reptiles) or may implant in the uterus (mammals) Phylogeny of Amniotes Synapsidia Anapsidia Ancestral amniote Diapsidia Phylogeny of Amniotes Synapsidia Mammals Anapsidia Turtles Lizards & Snakes Ancestral amniote Crocodiles Diapsidia Dinosaurs Birds Phylogeny of Amniotes Synapsidia Mammals Anapsidia Turtles Lizards & Snakes Ancestral amniote Crocodiles Diapsidia Dinosaurs Birds Reptiles Adaptations: •Keratinized skin •Lungs •Leathery shells on eggs •Ectotherms. Birds began as feathered reptiles Adaptations: •Feathers •Honeycombed bones •Missing some organs •Gizzard instead of teeth •Endothermic •Four-chambered heart •Good vision •Relatively large brains. Mammals diversified in the wake of the Cretaceous extinctions Adaptations: •Mammary glands •Hair •Four-chambered heart •Endothermic •Placenta / live birth •Large brains •Differentiated teeth. Primates and Human Evolution Adaptations: •Brain size •Jaw shape •Bipedal posture •Size difference between sexes •Long-term pair bonding •Long-term infant dependency. Multiregional Hypothesis African European Asian interbreeding 1-2 million years ago Homo erectus In Africa Austalasian Replacement Hypothesis African European Asian 100,000 years ago 1-2 million years ago Homo erectus In Africa Austalasian
