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Four Key Chordate Characteristics

Explore the four key chordate characteristics, invertebrate chordates, and the evolution of vertebrates through various classes and orders.

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Four Key Chordate Characteristics

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  1. Four Key Chordate Characteristics

  2. Invertebrate Chordates • Cephalochordata -Lancelets/Amphioxus • Urochordata • Tunicates/Sea Squirts • Vertebrates may have evolved from a sexually mature larval urochordate • Metamorphosis is eliminated

  3. Subphylum Cephalochordata: the Lancelet Branchiostoma

  4. Lancelet Anatomy

  5. Subphylum Urochordata Tunicate Anatomy

  6. Subphylum: Vertebrata • Cephalization (Craniates are chordates with a head) • Vertebrate skeleton • Brain protected by skull • Closed circulatory system • Gills or lungs • Kidneys for excretion

  7. Fish Fishes • Very successful vertebrates • Fast streamlined body plan • Excellent sensory organs, lateral line system • Highly developed organs for osmoregulation • Complex behavior • 2 chambered heart • Swim bladder

  8. A Sea Lamprey (Class Cephalospidomorphi)

  9. A Hagfish (Class Myxini)

  10. Hypothesis for the evolution of vertebrate jaws from two pairs of skeletal rods

  11. Gnathostomes Are Vertebrates That Have Jaws

  12. Class Chondrichthyes

  13. Ray-finned Fishes; Yellow Perch; Have thin bony spines connected by a layer of skin to form the fins

  14. Ray-finned Fishes (Class Actinopterygii): long-snouted sea horse

  15. A coelocanth (Class Actinistia), a Lobe-finned Fish, has rod-shaped bones and few bones in its fin bases

  16. Coelacanth at the Field Museum - Chicago

  17. Fossilized and modern coelocanths

  18. Problems: No support on land Gills stick together Ammonia no longer a good source of excretory waste Dehydration Sound/light /smell is perceived differently on land Solutions cartilage  bone Lungs Excrete concentrated urea  uric acid Skin and scales Adapt ability to perceive sound, smell and light differently Life on Land

  19. Skeleton of Acanthostega, a Devonian tetrapod fish

  20. Class Amphibia • Shoulder hip and girdles act to strengthen limbs for life on land • Heart with 3 chambers • They are not completely free from water • Reproduction • Dessication (skin must stay wet)

  21. Amphibian Orders: Newt (left) Order Urodela, frog (right) Order Anura

  22. Frogs

  23. “Dual life” of a frog (Rana temporaria)

  24. Class Reptilia • Completely free from water • Amniotic egg • Scaly skin • 3-4 chambered heart • Uric acid as nitrogenous waste • Ectothermic

  25. Extant Reptiles: Desert tortoise (top left), lizard (top right), king snake (bottom left), alligators (bottom right)

  26. Banded Gecko, Coleonyx varigatus

  27. Emerald Tree Boa

  28. Sea Turtle

  29. Archaeopteryx

  30. Archaeopteryx

  31. Cretaceous theropod dinosaurs with putative feathers from Chinese sediments: Caudipteryx

  32. Class Aves • Evolved from reptiles • Flying dinosaurs • Bones and feathers are adapted for flight • 4 chambered heart • Endothermic • Efficient 1 way lungs • Excrete uric acid

  33. A small sample of birds: Blue-footed boobies (top left), male peacock (top right), penguins (bottom left), perching bird (bottom right)

  34. Class Mammalia • Hair • Mammary glands • Placenta connects fetus to mom (missing in marsupials) • Diaphragm for ventilation of lungs • 4 chambered heart • Endothermic • Large brains • Diverged from reptilian ancestors earlier than the birds

  35. Major Groups of Mammals • Monotremes: • Platypuses, spiny anteater - lay eggs • Mixture of reptilian and mammalian traits • Marsupials • Non-placental – Kangaroo, opossum • Young born early and complete development within pouch • Placental Mammals – bats, dogs, us!

  36. Major Orders of Mammals (Monotremata-Sirenia)

  37. Major Orders of Mammals (Edentata-Primates)

  38. Major Orders of Mammals (Carnivora-Cetaceans)

  39. Major Orders of Mammals (Perissodactyla-Insectivora)

  40. Hypothetical Cladogram of Mammals

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