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Phylogeny of Extant Phyla

Phylogeny of Extant Phyla. Phylum Porifera. Sponges Sole member of the Parazoa Lack true tissues, Simplest of Animals, no nerves or muscles Choanocytes (collar cells)  “Unique flagellated cells that ingest bacteria and tiny food particles” Choanocytes look a lot like Choanoflagellates

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Phylogeny of Extant Phyla

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  1. Phylogeny of Extant Phyla

  2. Phylum Porifera

  3. Sponges • Sole member of the Parazoa • Lack true tissues, Simplest of Animals, no nerves or muscles • Choanocytes (collar cells)  “Unique flagellated cells that ingest bacteria and tiny food particles” • Choanocytes look a lot like Choanoflagellates • Amoebocytes transfer food to rest of cells • Adults sessile, larvae non-sessile • “Cells tend to be totipotent (retain zygote’s ability to form the whole animal)” Porifera Characteristics

  4. Choanocytes

  5. Amoebocytes

  6. Anatomy of Simple Sponge

  7. A More Complex Sponge

  8. Phylum Cnidaria

  9. Cnidaria Characteristics • Hydras, Jellies, Sea Anenomies, Corals • One member of the Radiata (also Ctenophora) • Diploblastic, Carnivorous, Tentacled • Lack true muscles (since no mesoderm) • Possess nerve net • Cnidocytes Cells that shoot stinging or grasping threads at potential prey • Grastrovascular cavity (only one opening) = Hydrostatic Skeleton • Polyps vs. Medusa

  10. Cnidocytes

  11. Cnidaria Anatomy

  12. Class Hydrozoa

  13. Class Scyphozoa

  14. Class Anthozoa

  15. A Cnidarian Life Cycle (Obelia)

  16. Phylum Platyhelminthes

  17. Flatworms (including Flukes and Tapeworms) • Bilaterally symmetrical acoelomates • Flat, unsegmented, single opening to gastrovascular cavity • Eyespots, flaps on head involved in sense of smell • No circulatory system (instead diffusion) • Tapeworms have no digestive system • Use ventral cilia to locomote across surfaces (but some can swim) • Cephalized, have nervous system Platyhelminth Characteristics

  18. Planarian Anatomy Class Turbellaria

  19. Fluke Lifecycle Class Trematoda

  20. Tapeworm Anatomy Class Cestoidea

  21. Phylum Rotifera

  22. Rotifer Characteristics • Rotifers • Very small animals • Possess complete digestive tract • Pseudocoelomates • Aquatic, essentially serve as animals that approximate the protozoan niche

  23. Phylum Nematoda

  24. Nematode Characteristics • Round worms (including pinworms & hookworms) • Pseudocoelamates, complete digestive tracts • There are many free-living nematodes as well as some parasitic nemotodes • Includes Caenorhabitis elegans, a very important research organism to developmental biology

  25. A Roundworm

  26. Phylum Mollusca

  27. Mollusk Characteristics • Snails, Slugs, Clams, Squids, Octopi, etc. • Class Gastropoda, Class Bivalvia, Class Cephalopoda, etc. • Protostomes • Basic body plan built around a muscular foot, a visceral mass, and a mantle • Not all mollusks have a shell • Mollusks lack segmentation • Most have OpenCirculatory System • Some (cephalopods) have Closed Circulatory System

  28. Class Polyplacophora (chitons)

  29. Class Gastropoda

  30. Class Bivalvia

  31. Class Bivalvia

  32. Class Cephalopoda

  33. Closed vs. Open Circulation

  34. Phylum Annelida

  35. Annelid Characteristics • Segmented worms (earth, marine, leeches) • Class Oligochaeta (I.e., earth worms), Class Polychaeta (e.g., clam worms), Class Hirudinea (I.e., leeches) • Protostomes, Body segments, Closed circulatory system

  36. Class Oligochaeta

  37. Class Polychaeta

  38. Class Hirudinea

  39. Phylum Arthropoda

  40. Arthropod Characteristics • Insects, Crustaceans, Spiders, Scorpions, Horseshoe crabs, Millipedes, Centipedes, Ticks, Mites, etc. • Protostomes with segmented bodies, jointed appendages, and hard (chitinous) exoskeletons • Also have well-developed senses and open circulation • Note that the taxonomy of the arthropods is in some turmoil and we will try to split the difference by describing “phylum” Arthopoda as a Superphylum… • …What previously were subphyla as phyla…

  41. Phylum Trilobita

  42. Phylum Chelicerata

  43. Phylum Uniramia

  44. Phylum Crustacea

  45. Phylum Echinodermata

  46. Echinoderm Characteristics • Sea stars, brittle stars, sea urchin, sea lilies, sea cucumbers • Coelomates, Deuterostomes • Multiple arms, tube feet, water vascular system, calciferous endoskeleton • Radial symmetry, but radial symmetry likely derived (i.e., not radiata) • Larvae are bilaterally symmetrical

  47. All 7,000 or so species of echinoderms are marine. • Examples are: • sea stars • brittle stars • sea urchins • sea lilies and feather stars • sea cucumbers • sea daisies • sand dollars

  48. Starfish Anatomy

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