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INVERTEBRATES I - shell 4 Bivalves – loss of the...

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INVERTEBRATES I- SESSILE SUSPENSION I. Cnidarians: A. Major Groups 1. Anthozoans (corals, anemones, and kin) -polyp only 2. Hydrozoans (hydroids, Hydra, man-o-war, fire coral) -often with both polyps (dominant) and small medusae 3. Scyphozoans and Cubozoans (large jellyfish) -large medusae and small polyps B. Characteristics: 1. Diploblastic 2. Mouth and no anus 3. Gastrovascular cavity (GVC) 4. Radial symmetry in rmets 5. Mostly colonial polyp stage or a solitary medusoid stage or both C. Synapomorphies 1. Cnidocytes 2. Plnula larva 3. (Mesoglea)? makes up jelly D. Cnidocytes -produce the ultimate organelle – the nematocyst (toxic structure fired at the target animal) Cnidocytes are 1. Derived from totipotent cells 2. Migrate to place of acion 3. Die after their organelle (nematocyst) is fired II. Molluscs A. Major Groups 1. Polyplacophorans -chitons -8 plates 2. Gastropods -snails, slugs, limpets -+/- 1 shell, often coiled 3. Cephalopods – highly derived -octopuses, squids, cuttlefish -8+ arms, muscular mantle
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Unformatted text preview: -+/- shell 4. Bivalves – loss of the radula-clams, scallops, mussels, oysters-2 valves B. Characteristics Visceral mass (soft body) Exoskeleton of 1,2, or 8 parts Reduced coelom, large hemocoel C. Synapomorphies Radula Mantle/Mantle cavity Muscular foot Calcareous secretions from mantle III. Cephalopods A. Mantle locomotion Circular and radial muscles Fixed length and variable diameter B. Tentacles and arms Circular and longitudinal muscles Variable length and fixed volume C. Suckers Circular and radial muscles IV. Muscles A. The concept of muscle antagonists B. The concept of muscular hydrostats-Cephalopods mostly small, some big Move with propulsion due to circular muscle contractions Muscular Hydrostats: Squid Tentacles V. Bryozoans A. Characteristics 1. All colonial 2. Ramets are all small (<5mm) 3. U-shaped gut, anus near mouth B. Synapomorphies 1. Retractable lophophore...
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  • Spring '08
  • WALCOTT
  • Cnidaria, C. Synapomorphies Radula, A. Major Groups, C. Synapomorphies Cnidocytes Plnula, radial muscles Muscles

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