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

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