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Questions and Answers
What is the characteristic feature of the body of a mollusk?
What is the characteristic feature of the body of a mollusk?
What is the function of the mantle in mollusks?
What is the function of the mantle in mollusks?
What is the name of the tongue-like structure bearing transverse rows of minute chitinous teeth in mollusks?
What is the name of the tongue-like structure bearing transverse rows of minute chitinous teeth in mollusks?
What is the outer layer of the shell of a mollusk composed of?
What is the outer layer of the shell of a mollusk composed of?
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What is the characteristic feature of the radula in mollusks?
What is the characteristic feature of the radula in mollusks?
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How many species of mollusks are known?
How many species of mollusks are known?
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What is the name of the phylum that includes mollusks?
What is the name of the phylum that includes mollusks?
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What is the function of the ctenidia in mollusks?
What is the function of the ctenidia in mollusks?
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What is the characteristic feature of the inner layer of the shell of a mollusk?
What is the characteristic feature of the inner layer of the shell of a mollusk?
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What is the term for the space between the mantle epithelium and the visceral mass body wall?
What is the term for the space between the mantle epithelium and the visceral mass body wall?
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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!
