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Invertebrates

The Parazoa The Radiata The Acoelomates The Pseudocoelomates The Coelomates: Protostomes The Coelomates: Deuterostomes. 1,000,000+ species of animals 95% are invertebrates Most are aquatic. Invertebrates. The Parazoa. Sponges Sessile Lack muscles and nerves Suspension-feeders.

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Invertebrates

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  1. The Parazoa The Radiata The Acoelomates The Pseudocoelomates The Coelomates: Protostomes The Coelomates: Deuterostomes 1,000,000+ species of animals 95% are invertebrates Most are aquatic Invertebrates

  2. The Parazoa • Sponges • Sessile • Lack muscles and nerves • Suspension-feeders

  3. Cnidaria Corals, hydras, jellyfis Radial symmetry Diploblastic Gastrovascular cavity Cnidocytes Nerve net Ctenophora Comb jellies 100 species, all marine The Radiata

  4. The Acoelomates • Bilateral symmetry • Moderate cephalization • Triploblastic • Organs, organ systems and muscle • Still lack a body cavity (coelom) • Flatworms • Examples: planaria, liver flukes, tapeworms

  5. The Pseudocoelomates • Includes the phyla Rotifera and Nematoda • Complete digestive system • Fluid filled body cavity, acts as a hydrostatic skeleton

  6. Coelomates • Two major lines: Protostomes and Deuterostomes • Probably evolved to fill different ecological niches • Differ in cleavage patterns and fate of the blastopore

  7. The Protostomes • “mouth first” • Includes a number of phyla: nemertae, bryozoans, brachiopods, mollusks, annelids, and arthropods • Characterized by determinate cleavage • Formation of a mouth from the blastopore • Spiral cleavage

  8. The Deuterostomes • “mouth second” • Spiral cleavage • Blastopore forms the anus • Includes echinoderms and chordates • Indeterminate cleavage

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