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Chapter 29

Chapter 29. The Animal Kingdom: The Protostomes. Characteristics of protostome coelomates Spiral cleavage Determinate cleavage Development of the mouth from the blastosphore. Characteristics of protostome coelomates, cont. Coelom is a fluid-filled cavity lined with mesoderm

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Chapter 29

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  1. Chapter 29 The Animal Kingdom: The Protostomes

  2. Characteristics of protostome coelomates • Spiral cleavage • Determinate cleavage • Development of the mouth from the blastosphore

  3. Characteristics of protostome coelomates, cont. • Coelom is a fluid-filled cavity lined with mesoderm • Evolution of the coelom permitted many innovations, including • Tube-within-a-tube body plan • Hydrostatic skeleton

  4. Characteristics of protostome coelomates, cont. • Coelom provides space for development of internal organs and gonads • Coelom helps transport materials and protects internal organs

  5. Protostome coelomates include two main branches • Lophotrochozoa • Ecdysozoa

  6. Lophotrochozoa • Platyhelminthes • Nemerteans • Mollusks • Annelids • Lophophorate phyla • Rotifers

  7. Longitudinal section of rotifer

  8. Ecdysozoa • Nematodes • Arthropods

  9. Characteristics of phylum Nemertea • Proboscis • Reduced coelom: rhynchocoel • Tube-within-a-tube body plan • Complete digestive tract • Mouth with anus

  10. Lateral view of a typical nemertean

  11. Characteristics of phylum Platyhelminthes • Acoelomate • Bilateral symmetry • Cephalization • Three definite tissue layers

  12. Characteristics of phylum Platyhelminthes, cont. • Well-developed organs • Many are hermaphrodites • Ladder-type nervous system • Ganglia • Protonephridia

  13. Phylum platyhelminthes • Turbellaria • Free-living flatworms including planarians • Trematoda and Monogenea • Parasitic flukes • Cestoda • Parasitic tapeworms

  14. The common planarian, Dugesia Internal structure LM of a living planarian, Dugesia dorotocephala

  15. Parasitic flukes and tapeworms typically have • Suckers or hooks • Complicated life cycles with intermediate hosts • Large numbers of eggs

  16. Life cycle of the blood fluke

  17. Adaptive advantages of cephalization • Beginnings of cephalization, increases the effectiveness of a bilateral animal to find food and detect enemies

  18. Distinguishing characteristics of phylum Mollusca • Soft bodied animals usually covered by a shell • Ventral foot for locomotion • Mantle covering the visceral mass

  19. Distinguishing characteristics of phylum Mollusca, cont. • Open circulatory system (except cephalopods) • Metanephridia • Radula • Ciliated trochophore larva

  20. Four classes of Phylum Mollusca • Polyplacophora • Gastropoda • Bivalvia • Cephalopoda

  21. Class Polyplacophora • Shells consist of eight overlapping plates • Chitons

  22. Class Polyplacophora

  23. Class Gastropoda • Body undergoes torsion • Snails • Slugs • Relatives

  24. Class Gastropoda

  25. Embryonic torsion in a gastropod

  26. Class Bivalvia • two-part, dorsally-hinged shell encloses body • Aquatic clams • Scallops • Oysters

  27. Class Bivalvia

  28. Class Cephalopoda • Active, predatory swimmers • Tentacles surround the mouth located in the large head • Squids • Octopods • Nautilus

  29. Class Cephalopoda

  30. Distinguishing characteristics of phylum Annelida • Segmented worms • Aquatic worms • Earthworms • Leeches

  31. Distinguishing characteristics of phylum Annelida, cont. • Conspicuously long bodies • Internal and external segmentation • Large compartmentalized coelom serves as a hydrostatic skeleton

  32. Phylum Annelida has three classes • Polychaeta • Oligochaeta • Hirudinea

  33. Class Polychaeta • Marine worms with • Parapodia for locomotion and gas exchange • Setae on the parapodia

  34. Class Oligochaeta • Earthworms • A few short setae per segment • Body is divided into more than 100 segments separated internally by septa

  35. Body plan of an earthworm

  36. Class Hirudinea • Leeches • No setae • No appendages • Parasitic leeches have suckers for holding onto their host

  37. Distinguishing characteristics of phylum Nematoda • Pseudocoelomates • Bilateral symmetry • Three tissue layers • Complete digestive tract • Body covered by cuticle

  38. Parasitic nematodes in humans • Ascaris • Hookworms • Trichina worms • Pinworms

  39. The roundworm Ascaris • Longitudinal section • (b) Cross section (b) (a)

  40. Distinguishing characteristics of phylum Arthropoda • Segmented animals with • Paired, jointed appendages • Armor-like exoskeleton of chitin • Molting is necessary for growth

  41. Distinguishing characteristics of phylum Arthropoda, cont. • Open circulatory system • Dorsal heart that pumps hemolymph

  42. Distinguishing characteristics of phylum Arthropoda, cont. • Aquatic forms have gills • Terrestrial forms have either tracheae or book lungs • Trilobites are extinct marine arthropods covered by a hard, segmented shell

  43. Subphylum Myriapoda • Unbranched appendages and a single pair of antennae • Class Chilopoda • Class Diplopoda

  44. Trilobite Dorsal view Ventral view

  45. Subphylum Chelicerata • Body consists of a cephalothorax and abdomen, with six pairs of jointed appendages, four pairs of which serve as legs • Merostomes • Arachnids

  46. Subphylum Chelicerata, cont. • First pair of appendages are chelicerae • Second pair are pedipalps • No antennae • No mandibles

  47. Subphylum Crustacea • Lobsters • Crabs • Shrimp • Pillbugs • Barnacles

  48. Anatomy of the lobster

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