Mollusca

•  Second largest phylum
• May be Aquatic ( Marine,Fresh Water) and Terrestrial 
• Symmetry : Bilateral
• Triploblastic and Coelomate Animal 
• Organ-System level of body organisation
• Body is covered by Calcareous shell 
• Body is unsegmented with Distinct Head, Muscular foot and Visceral hump
• Head: Contain sense organ like eyes and sensory tentacles
• Visceral Hump: Containing all visceral organs of body.
• Muscular Foot : Locomotion

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1.  Soft and spongy layer of skins form a mantle over visceral hump.

2. The Space between hump and mantle is called mantle cavity.

3. Mantle Usually Secrates an external calcareous shell.Shell is made up of Calcium carbonate and Concheolin proteins

4. Digestive Tract is complete and Buccal cavity contains a file-like rasping organ called Radula

5. Anus opens into mantle cavity

6. Respiration usually by feather like gills located in mantle cavity which also helps in excretion 

7. Circulatory system is of open type 

8. Examples of Mollusca 

• Pila (Apple Snail)
• Pinctada (Pearl Oyster )
• Sepia (Cuttle Fish)
• Loligo (Squid)
• Octopus (Devil fish)
• Aplysia (Sea Hare)
• Dentalium (Tusk shell)
• Chaetopleura (Chiton )

Pila (Apple Snail)

Octopus (Devil Fish)

Pearl Oyster(Pinctada)

Sepia (Cuttle Fish)