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Mollusk Anatomy and Characteristics
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Mollusk Anatomy and Characteristics

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Questions and Answers

What is the characteristic feature of the body of a mollusk?

  • It has a bilateral symmetry (correct)
  • It has a segmented body
  • It has a appendages
  • It has a exoskeleton
  • What is the function of the mantle in mollusks?

  • It is responsible for circulation
  • It is responsible for movement
  • It is responsible for shell formation and gas exchange (correct)
  • It is responsible for digestion
  • What is the name of the tongue-like structure bearing transverse rows of minute chitinous teeth in mollusks?

  • Haemocoel
  • Mantle
  • Radula (correct)
  • Ctenidia
  • What is the outer layer of the shell of a mollusk composed of?

    <p>Protein</p> Signup and view all the answers

    What is the characteristic feature of the radula in mollusks?

    <p>It is a region of firm rows of teeth</p> Signup and view all the answers

    How many species of mollusks are known?

    <p>100,000</p> Signup and view all the answers

    What is the name of the phylum that includes mollusks?

    <p>Mollusca</p> Signup and view all the answers

    What is the function of the ctenidia in mollusks?

    <p>It is responsible for respiration</p> Signup and view all the answers

    What is the characteristic feature of the inner layer of the shell of a mollusk?

    <p>It is composed of nacre</p> Signup and view all the answers

    What is the term for the space between the mantle epithelium and the visceral mass body wall?

    <p>Mantle cavity</p> Signup and view all the answers

    Study Notes

    Phylum Mollusca

    • Highly diverse group of animals, with some members having no sense organs or brains, while others have advanced features like the octopus
    • Approximately 100,000 known species
    • Characteristics: bilateral symmetry, cephalization, triploblastic, coelomate, cells organized into tissues, tissues into organs, and organs into organ systems

    Body Structure

    • Body consists of an anterior head, ventral foot, and a dorsal visceral mass
    • Covered by a fleshy outgrowth of the body wall called a mantle
    • Mantle is responsible for shell formation and gas exchange
    • Mantle cavity is the space between the mantle epithelium and the visceral mass body wall

    Shell

    • Highly variable, secreted, and lined by the mantle
    • Composed of three layers: outer periostracum (protein), middle prismatic layer (ostracum), and inner nacreous layer (hypostracum)

    Radula

    • A tongue-like structure bearing transverse rows of minute chitinous teeth
    • Used for feeding, with the chitinous "teeth" moved forwards and backwards to break off small pieces of food

    Classes of Mollusca

    Polyplacophora (Chitons)

    • Marine
    • Shells have 8 plates
    • Foot is broad and ventral
    • Radula present
    • Head is poorly developed
    • Mantle is thick and fleshy, extending beneath the plates
    • Many bipectinate gills (6-80 pairs) and one pair of nephridia

    Bivalvia (Pelecypoda)

    • Body enclosed in a two-lobed large mantle
    • Shell consists of two lateral valves of variable size and form, with a dorsal hinge
    • Head is rudimentary
    • Mouth has labial palp, but no radula or cephalic eyes
    • Gills are plate-like
    • Posterior mantle margin forms siphons
    • All are suspension filter-feeders

    Gastropoda (Slugs and Snails)

    • Largest and most varied class of mollusks, with over 75,000 extant species and 15,000 fossil forms
    • Move using a muscular foot
    • Can be terrestrial (snails and slugs), freshwater, or marine
    • Shell varies greatly, from spired helical coiled to planispirals or cap-like
    • Head is well-developed with a mouth, tentacles, eyes, and other sense organs
    • All young gastropods undergo torsion during embryonic development

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    Description

    This quiz covers the characteristic features of mollusks, including their circulatory, respiratory, and coelomic systems. Test your knowledge of these unique features!

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