Question

Shell of molluscs is derived from

• A. Foot
• B. Mantle
• C. Ctenidia
• D. Placoid

Answer 1

The correct option is B Mantle

The dorsal body wall covering the visceral mass of molluscs is known as mantle, which serves to form shell by the process of biomineralization. During the process, the epidermal shell glands of mantle concentrate calcium out of blood and crystallize it as calcium carbonate in form of two layers of calcite crystals. The calcite crystals are held together by conchin protein. Option A is incorrect as foot of molluscs is the organ of locomotion.

Ctenidia are gills present in mantle cavity and serve as respiratory organ by collecting the oxygenated hemolymph.

Option D is incorrect as placoid scales are characteristic feature of cartilaginous scale. Thus correct answer is option B.