Which mollusk class includes snails and slugs?

• A. Bivalvia
• B. Gastropoda
• C. Cephalopoda
• D. Polyplacophora

Answer: (B)

Gastropoda is the class that includes snails and slugs. This group is characterized by a single, usually spiraled shell in many species and a broad, muscular foot used for crawling; many gastropods also show torsion during development, which twists the body so the mantle cavity moves over the head. Slugs are basically gastropods that have lost or greatly reduced their shells. The other mollusk groups differ: bivalves like clams have two hinged shells, cephalopods like octopus and squid are active predators with tentacles, and polyplacophorans (chitons) have eight dorsal plates.