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The Deuterostomes: Echinoderms, Hemichordates, Acorn Worms, and Chordates

Explore the main branches of deuterostomes, including echinoderms, hemichordates, and chordates. Learn about the characteristics of echinoderms, their different classes like crinoidea, asteroidea, ophiuroidea, and echinoidea, as well as the unique features of chordates. Discover the evolutionary relationships of vertebrates, from jawless fishes to modern reptiles, and the transition to terrestrial life.

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The Deuterostomes: Echinoderms, Hemichordates, Acorn Worms, and Chordates

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  1. Chapter 30 The Animal Kingdom: The Deuterostomes

  2. Main branches of deuterostomes • Echinoderms • Hemichordates (marine deuterostomes with three-part body, including proboscis, collar, trunk) • Acorn worms • Chordates

  3. Characteristics of echinoderms • Spiny “skin” • Water vascular system • Tube feet • Endoskeleton • Larvae • Bilateral symmetry • Adults • Pentaradial symmetry

  4. Class Crinoidea • Oral surface is turned upward • Some crinoids are sessile • Class includes • Sea lilies • Feather stars

  5. Crinoidea:feather star

  6. Class Asteroidea • Central disk with five or more arms • Tube feet for location • Members are sea stars

  7. Class Ophiuroidea • Longer, more slender arms than members of Asteroidea • Arms are used for locomotion • No suckers on tube feet • Members are brittle stars

  8. Ophiuroidea: daisy brittle star

  9. Class Echinoidea • No arms • Solid shell • Covered with spines • Members are • Sea urchins • Sand dollars

  10. Echinoidea: sand dollar

  11. Class Holothuroidea • Mouth is surrounded by a circle of modified tube feet that serve as tentacles • Members are sea cucumbers

  12. Holothuroidea: sea cucumber

  13. Phylum Chordata • At some time in their life cycle, all chordates have • Notochord • Dorsal, tubular nerve chord • Pharyngeal slits • Postanal tail

  14. Generalized chordate body plan

  15. Subphyla of phylum Chordata • Urochordata • Cephalochordata • Vertebrata

  16. Invertebrate chordates • Tunicates (subphylum Urochordata) • Are suspension-feeding marine animals with tunics • Larvae have typical chordate characteristics and are free-swimming

  17. Tunicates (subphylum Urochordata), cont. • Adults of most groups are sessile suspension feeders

  18. Tunicate body plan:lateral view of an adult tunicate

  19. Tunicate body plan:internal structure ofa larval tunicate(lateral view)

  20. Invertebrate chordates • Lancelets (subphylum Cephalochordata) • Small • Segmented • Fishlike • Exhibit chordate characteristics

  21. Cephalochordate body plan: lancelet

  22. Evolution of chordates • Tunicates were probably first to evolve • Subphyla Cephalochordata and Vertebrata considered sister taxa by some • Common ancestor probably resembled tunicate larva

  23. Evolutionary relationships of vertebrates

  24. Shared derived characters of vertebrates • Verytebral column • Cranium • Neural crest cells • Pronounced cephalization • Muscles attached to endoskeleton

  25. Major groups of jawless fishes • Ostracoderms (extinct) • Agnathans • Hagfishes (class Cephalaspidomorphi) • Lamprey (class Myxini) • or Craniates • Vertebrates • Hagfishes (systematist designation referring to invertebrate character of hagfishes)

  26. Three lampreys attached to a carp Suction-cup mouth of adult lamprey

  27. Evolution of jawed fishes and amphibians • Class Chondrichthyes • Jaws • Two pairs of fins • Placoid scales

  28. Structure of a placoid scale

  29. Class Chondrichthyes, cont. • Sharks • Many species ovoviparous • Some species oviparous • Few species vivaparous • Rays • Skates • Oviparous

  30. Internal structure of a shark

  31. Bony fishes • Class Actinopterygii • Ray-finned fishes • Class Actinistia • Coelacanths • Class Dipnoi • Lungfishes

  32. Perch, a representative bony fish

  33. During the Devonian, bony fishes gave rise to • Actinopterygii • Lungs modified as a swim bladder • Evolved into modern bony fishes • Sarcopterygii evolved into • Lungfishes • Coelacanths

  34. Sarcopterygii, cont. • Coelacanths and lungfishes apparently preadapted for life on land • Lungfish may have given rise to tetrapods • First successful tetrapods labyrinthodonts (ancestors of frogs and salamanders)

  35. Diver swimming with coelacanth

  36. An artist’s conception of labyrinthodonts

  37. Class Amphibia • Use moist skin as well as lungs for gas exchange • Three-chambered heart • Systemic and pulmonary circulations • Most return to water to reproduce

  38. Class Amphibia, cont. • Salamanders • Frogs (tadpoles undergo metamorphosis) • Toads • Caecilians

  39. Modern reptiles: Chelonia mydas

  40. Vertebrate adaptations to terrestrial life • Amniotic egg: amnion forms fluid-filled sac around embryo • Body covering that retards water loss • Physiological mechanisms to conserve water

  41. Modern reptiles: Crocodilia niloticus

  42. Class Reptilia is paraphyletic • Dinosaurs • Turtles • Lizards • Snakes • Alligators • Birds sometimes included

  43. Modern reptiles: Basiliscus plumifrons

  44. Reptiles • Internal fertilization • Most secrete a protective shell around egg • Embryo develops protective membranes, including amnion, to retain moisture

  45. Reptiles, cont. • Dry skin with horny scales • Lungs with many changers • Three-chambered heart with some separation of oxygen-rich and oxygen-poor blood

  46. Paleontological discovery of feathered dinosaurs • Many biologists consider birds to be feathered dinosaurs; they classify as diapsids • Birds • Most reptiles

  47. Caudipteryx (headless)

  48. Reconstruction of Archaeopteryx

  49. Birds: adaptations for powered flight • Feathers • Wings • Light, hollow bones with air spaces • Four-chambered heart • Very efficient lungs

  50. Birds: adaptations for powered flight, cont. • High metabolic rate • Constant body temperature • Excrete solid metabolic wastes • Well-developed nervous system • Excellent vision and hearing

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