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Phylum Mollusca

Phylum Mollusca. - From mollus meaning “ soft ”. Characteristics. Eucoelomate - True body cavity Hollow body cavity, Lined with peritonium (endodermis) Bilateral symmetry Most have Mantle Secretes shell - grows with organism Site of Respiration in terrestrial mollusks

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Phylum Mollusca

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  1. Phylum Mollusca - From mollus meaning “soft”

  2. Characteristics • Eucoelomate - True body cavity • Hollow body cavity, Lined with peritonium (endodermis) • Bilateral symmetry • Most have Mantle • Secretes shell - grows with organism • Site of Respiration in terrestrial mollusks • Tripoblastic - 3 tissue layers • Many Organ systems - well-defined circulatory, respiratory, excretory, and digestive systems

  3. Characteristics (Contd’)Digestion • Complete digestive tract • Separate mouth and anus • Radula • Rasping “file” with hundreds of tooth like structures • Feeding Patterns - filter feeders, herbivores, carnivores

  4. Characteristics (Contd’)Circulation • Some - Open Circulatory System • Ex. Gastropoda and bivalvia • Some - Closed circulatory system • Ex. Cephalopoda • All have hearts

  5. Characteristics (Contd’) Cephalization • Brain with nervous system • Gastropoda and Cephalopoda • Exception Bivalvia no head=no brain • Sensory cells • All have - Touch, smell, taste, balance • Some have - True eyes • Cephalopoda and some Gastropoda

  6. Classification Phylum- Mollusca • 5 classes: • Gastropoda • Bivalvia • Cephalopoda • Polyplacophora • Scaphopoda

  7. Class- Gastropoda -“stomach foot” • Has one shell or none • Ex. Snails, slugs, sea slugs Snail Conch Slug Whelk Abalone

  8. 2. Class Bivalvia - “Two Shells” • Ex. Clams, mussels, oysters, scallops Mussel Clam Oyster Scallop

  9. 3. Class Cephalapoda -“head foot” • No shell or one • Ex. Squid, octopus, nautilus, cuttlefish Nautilus Octopus Squid

  10. 4. Class Polyplacophora -“many plates” • Mantle made of 8 dorsal plates • Ex. Chitons

  11. 5. Class Scaphopoda • Ex. Tooth shell ( aka. Tusk shell)

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