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Animals: The Vertebrates

Animals: The Vertebrates. Chapter 26. Something Old, Something New. Every animal is a combination of traits Some traits are conserved from remote ancestors Other traits are unique to its branch of the family tree. Chordate Features. Deuterostomes All share four features:

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Animals: The Vertebrates

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  1. Animals: The Vertebrates Chapter 26

  2. Something Old, Something New • Every animal is a combination of traits • Some traits are conserved from remote ancestors • Other traits are unique to its branch of the family tree

  3. Chordate Features • Deuterostomes • All share four features: • Notochord supports body • Nervous system develops from dorsal nerve cord • Embryos have pharynx with slits • Embryos have tail that extends past anus

  4. Chordate Groups • Urochordata • Salps and tunicates • Cephalochordata • Lancelets • Craniates • Fishes, amphibians, reptiles, birds, mammals

  5. Tunicates (Urochordates) • Larva is free-swimming • Adult is sessile and baglike with no coelom • Both stages are filter feeders • Pharynx serves in both feeding and respiration

  6. oral opening Tunicate Life History atrial opening Larva undergoes metamorphosis to adult form pharynx with gill slits Tunicate adult nerve cord notochord pharynx gut Figure 26.3Page 446 Tunicate larva

  7. Lancelets (Cephalochordates) • Fish-shaped filter feeders • Simple brain • Segmented muscles • Chordate characteristics of adult: • Notochord lies under dorsal nerve cord • Pharynx has gill slits • Tail extends past anus

  8. Lancelet Body Plan pharynx with gill slits dorsal, tubular nerve cord tail extending past anus notochord pore of atrial cavity segmented muscles aorta gonad anus tentaclelike structures around mouth midgut hindgut Figure 26.4aPage 447

  9. Early Craniates • Brain inside chamber of cartilage or bone • Arose before 530 million years ago • Resemble lancelets, lamprey larva Do not post on Internet Reconstruction of one of the earliest known craniates Figure 26.4Page 447

  10. Trends in the Evolution of Vertebrates • Shift from notochord to vertebral column • Nerve cord expanded into brain • Evolution of jaws • Paired fins evolved, gave rise to limbs • Gills evolved, gave rise to lungs

  11. supporting structures Evolution of Jaws Early jawless fish (agnathan) • First fishes lacked jaws • Jaws are modifications of anterior gill supports gill slit Early jawed fish (placoderm) jaw jaw support spiracle Modern jawed fish (shark) Figure 26.5Page 448 jaw

  12. Existing Jawless Fishes • Cylindrical body • Cartilaginous skeleton • No paired fins Hagfish tentacles gill slits (twelve pairs) mucous glands Lamprey gill openings (seven pairs)

  13. Jawed Fishes • Most diverse and numerous group of vertebrates • Two classes: • Chondrichthyes (cartilaginous fishes) • Osteichthyes (bony fishes)

  14. Cartilaginous Fishes: Class Chondrichthyes • Most are marine predators • Cartilaginous skeleton • Main groups: • Skates and rays • Sharks • Chimaeras (ratfishes)

  15. Bony Fishes: Class Osteichthyes • Includes 96 percent of living fish species • Three subclasses: • Ray-finned fishes • Lobe-finned fishes • Lung fishes

  16. Body Plan of a Bony Fish fin supports muscle segments brain olfactory bulb urinary bladder heart liver anus gallbladder kidney stomach Figure 26.9bPage 451 swim bladder intestine

  17. Lobe-Finned Fishes • Coelocanths • Lunglike sacs do not function in gas exchange

  18. Lungfishes • Have gills and one lung or a pair • Must surface to gulp air Do not post on Internet Figure 26.9fPage 451

  19. Early Amphibians • Fishlike skull and tail • Four limbs with digits • Short neck Ichthyostega Acanthostega Do not post on Internet Figure 26.10aPage 452

  20. Modern Amphibians • All require water at some stage in the life cycle; most lay eggs in water • Lungs are less efficient than those of other vertebrates • Skin serves as respiratory organ

  21. From Fins to Limbs • Genetic enhancer controls genes involved in formation of digits on limb bones • Change in a single master gene can drastically alter morphology

  22. Living Amphibian Groups • Frogs and toads • Salamanders • Caecilians

  23. Rise of Amniotes • Arose during Carboniferous • Adaptations to life on land • Tough, scaly skin • Internal fertilization • Amniote eggs • Water-conserving kidneys

  24. Adaptive Radiation • Produced numerous lineages • Extinct groups include: • Therapsids (ancestors of mammals) • Marine plesiosaurs & ichthyosaurs • Dinosaurs and pterosaurs

  25. Living Reptiles Not a monophyletic group Crocodilians Turtles Tuataras Snakes and lizards

  26. Evolutionary History of Amniotes snakes lizards stem reptiles tuataras ichthyosaurs pterosaurs birds dinosaurs plesiosaurs archosaurs crocodilians turtles anapsids therapsids synapsids (mammals) Figure 26.14Page 455 Carboniferous Permian Triassic Jurassic Cretaceous Mesozoic era Paleozoic era

  27. Crocodile Body Plan olfactory lobe vertebral column hindbrain, midbrain, forebrain gonad spinal cord snout kidney heart stomach cloaca esophagus liver intestine Figure 26.13cPage 454

  28. Turtles • Armorlike shell • Horny plates instead of teeth • Lay eggs on land Figure 26.15Page 456

  29. Lizards and Snakes • Largest order (95 percent of living reptiles) • Most lizards are insectivores with small peglike teeth • All snakes are carnivores with highly movable jaws venom gland hollow fang Figure 26.15dPage 457

  30. Tuataras • Only two living species • Live on islands off coast of New Zealand • Look like lizards, but resemble amphibians in some aspects of their brain and in their way of walking

  31. Birds • Diverged from small theropod dinosaurs during the Mesozoic • Feathers are a unique trait • Derived from reptilian scales • Serve in insulation and flight

  32. Amniote Egg yolk sac embryo amnion allantois chorion albumin hardened shell Figure 26.16aPage 458

  33. Adapted for Flight • Four-chambered heart • Highly efficient respiratory system • Lightweight bones with air spaces • Powerful muscles attach to the keel Figure 26.17Page 458

  34. Mammals: Phylum Mammalia • Hair • Mammary glands • Distinctive teeth • Highly developed brain • Extended care for the young Figure 26.19cPage 460

  35. Mammal Origins & Radiation • During Triassic, synapsids gave rise to therapsids (ancestors of mammals) • By Jurassic, mouselike therians had evolved • Therians coexisted with dinosaurs through Cretaceous • Radiated after dinosaur extinction

  36. Three Mammalian Lineages • Monotremes • Egg-laying mammals • Marsupials • Pouched mammals • Eutherians • Placental mammals

  37. Role of Geologic Change • Monotremes and marsupials evolved while Pangea was intact • Placental mammals evolved after what would become Australia had split off • No placental mammals in Australia • Elsewhere, placental mammals replaced most marsupials

  38. Living Monotremes • Three species • Duck-billed platypus • Two kinds of spiny anteater • All lay eggs

  39. Living Marsupials • Most of the 260 species are native to Australia and nearby islands • Only the opossums are found in North America • Young are born in an undeveloped state and complete development in a permanent pouch on mother

  40. Living Placental Mammals • Most diverse mammalian group • Young develop in mother’s uterus • Placenta composed of maternal and fetal tissues; nourishes fetus, delivers oxygen, and removes wastes • Placental mammals develop more quickly than marsupials

  41. Earliest Primates • Primates evolved more than 60 million years ago during the Paleocene • First primates resembled tree shrews • Long snouts • Poor daytime vision

  42. From Primates to Humans “Uniquely” human traits evolved through modification of traits that evolved earlier, in ancestral forms

  43. Hominoids • Apes, humans, and extinct species of their lineages • In biochemistry and body form, humans are closer to apes than to monkeys • Hominids • Subgroup that includes humans and extinct humanlike species

  44. Trends in Lineage Leading to Humans • Less reliance on smell, more on vision • Skeletal changes to allow bipedalism • Modifications of hand allow fine movements • Bow-shaped jaw and smaller teeth • Longer lifespan and period of dependency

  45. Adaptations to anArboreal Lifestyle • Better daytime vision • Shorter snout • Larger brain • Forward-directed eyes • Capacity for grasping motions

  46. The First Hominoids • Appeared during Miocene • Arose in Central Africa • Spread through Africa, Asia, Europe • Climate was changing, becoming cooler and drier

  47. The First Hominids • Sahelanthropus tchadensis arose 6-7 million years ago • Bipedal australopiths evolved during Miocene into Pliocene • Exact relationships are not known A. anamensis A. afarensis A. africanus A. garhi A. boisei A. robustus

  48. Homo Habilis1.9-1.6 million years ago • May have been the first member of genus • Lived in woodlands of eastern and southern Africa Do not post on Internet H. habilis Figure 26.31Page 468

  49. Homo erectus2million-53,000? years ago • Evolved in Africa • Migrated into Europe and Asia • Larger brain than H. habilis • Creative toolmaker • Built fires and used furs for clothing

  50. Homo sapiens • Modern man evolved by 100,000 years ago • Compared to Homo erectus: • Smaller teeth and jaws • Chin • Smaller facial bones • Larger-volume brain case

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