Animal Kingdom - Notes | Class 11 | Part 9: Mollusca

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4. ANIMAL KINGDOM

PHYLUM MOLLUSCA (SOFT BODIED ANIMALS): GENERAL CHARACTERS

Mollusca is the second largest phylum.

  1. Grades of organization:
    • Organ system.
  2. Symmetry:
    • Bilateral symmetry.
  3. Germ layers:
    • Triploblastic.
  4. Coelom:
    • Coelomate.
  5. Habit and habitat:       
    • Aquatic.
    • Few are terrestrial.
  6. Digestive system:          
    • Complete.
  7. Respiratory system:
    • Gills in aq. forms and pulmonary sac in terrestrial forms.
  8. Circulatory system:
    • Open type.
  9. Reproduction:
    • Dioecious.
    • Oviparous.
    • Development is direct or indirect.
  10. Unique features:
    • Body has head, visceral hump & muscular foot.  
    • Head has sensory tentacles.
    • Calcareous shell.
    • Mantle: The membrane which covers visceral mass. 
    • Space between the hump and mantle is called mantle cavity. It contains feather-like gills for respiration & excretion.
    • Radula: File-like rasping organ present in the mouth. It is used for feeding.
  11. Examples:
    • Pila (Apple Snail)
    • Pinctada (Pearl Oyster)
    • Sepia (Cuttlefish)
    • Loligo (Squid)
    • Octopus (Devil fish)
    • Aplysia (Sea Hare)
    • Dentalium (Tusk shell)
    • Chaetopleura (Chiton)

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