Phylum Mollusca (Soft Bodied Animals): General Characters
Mollusca is the second largest phylum.
- Grades of Organization: Organ system.
- Symmetry: Bilateral symmetry.
- Germ Layers: Triploblastic.
- Coelom: Coelomate.
- Habit and Habitat:
- Aquatic.
- Few are terrestrial.
- Digestive System: Complete.
- Respiratory System: Gills in aquatic forms and pulmonary sac in terrestrial forms.
- Circulatory System: Open type.
- Reproduction:
- Dioecious.
- Oviparous.
- Development is direct or indirect.
- 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.
- Examples:
- Pila (Apple Snail)
- Pinctada (Pearl Oyster)
- Sepia (Cuttlefish)
- Loligo (Squid)
- Octopus (Devil fish)
- Aplysia (Sea Hare)
- Dentalium (Tusk shell)
- Chaetopleura (Chiton)
Well explained and good notes
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