The mantle that forms the shell in many mollusks is composed primarily of which substance?

The mantle that forms the shell in many mollusks is composed primarily of which substance?

• A. Calcium carbonate
• B. Silica
• C. Calcium phosphate
• D. Chitin

Answer: (A)

Mollusk shells are built by the mantle from calcium carbonate. The mantle deposits calcium carbonate crystals, usually in the forms of calcite or aragonite, often guided by an organic protein matrix that helps organize the layers and strengthen the shell. This mineral composition gives shells their rigidity and hardness. Silica appears in some other organisms’ structures, calcium phosphate is the mineral in bones and teeth of vertebrates, and chitin is a major component of many arthropod exoskeletons but not the primary material of mollusk shells. So the shell is primarily calcium carbonate.

Mollusk shells are built by the mantle from calcium carbonate. The mantle deposits calcium carbonate crystals, usually in the forms of calcite or aragonite, often guided by an organic protein matrix that helps organize the layers and strengthen the shell. This mineral composition gives shells their rigidity and hardness. Silica appears in some other organisms’ structures, calcium phosphate is the mineral in bones and teeth of vertebrates, and chitin is a major component of many arthropod exoskeletons but not the primary material of mollusk shells. So the shell is primarily calcium carbonate.