Question

Which among the following is the second largest animal phylum ?

• A. Phylum Arthropoda
• B. Phylum Annelida
• C. Phylum Mollusca
• D. Phylum Chordata

Answer 1

Answer:

C. Phylum Mollusca

Phylum Mollusca:

• This is the second largest animal phylum 
• Molluscs are terrestrial or aquatic (marine or fresh water) 
• It has organ-system level of organisation. 
• They are bilaterally symmetrical, triploblastic and coelomate animals. 
• Body is covered by a calcareous shell
• Body is unsegmented with a distinct head, muscular foot and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.
• The space between the hump and the mantle is called the mantle cavity in which feather like gills are present. They have respiratory and excretory functions.
• The anterior head region has sensory tentacles.
• The mouth contains a file-like rasping organ for feeding, called radula 
• They are usually dioecious and oviparous with indirect development

Examples: 

• Pila (Apple snail)
• Pinctada (Pearl oyster)
• Sepia (Cuttlefish)
• Loligo (Squid) 
• Octopus (Devil fish)
• Aplysia (Seahare)
• Dentalium (Tusk shell) 
• Chaetopleura (Chiton)

Phylum Mollusca:

• This is the second largest animal phylum 
• Molluscs are terrestrial or aquatic (marine or fresh water) 
• It has organ-system level of organisation. 
• They are bilaterally symmetrical, triploblastic and coelomate animals. 
• Body is covered by a calcareous shell
• Body is unsegmented with a distinct head, muscular foot and visceral hump.
• A soft and spongy layer of skin forms a mantle over the visceral hump.
• The space between the hump and the mantle is called the mantle cavity in which feather like gills are present. They have respiratory and excretory functions.