Which phylum includes snails, clams, and squids?

Which phylum includes snails, clams, and squids?

• A. Arthropoda
• B. Mollusca
• C. Echinodermata
• D. Chordata

Answer: (B)

All three organisms fit into Mollusca, a group of invertebrates known for a soft body, often a calcium carbonate shell, a muscular foot for movement, and a mantle that can secrete the shell. In mollusks, the major body regions include a visceral mass containing the organs, and many have a feeding structure called a radula (though not all, like many bivalves). Squids are cephalopods, snails are gastropods, and clams are bivalves — all classes within the same phylum. This shared plan distinguishes them from other groups: arthropods have segmented bodies and exoskeletons, echinoderms show radial symmetry and a water vascular system, and chordates have a dorsal nerve cord and notochord. So snails, clams, and squids are classified together because they all belong to Mollusca.

All three organisms fit into Mollusca, a group of invertebrates known for a soft body, often a calcium carbonate shell, a muscular foot for movement, and a mantle that can secrete the shell. In mollusks, the major body regions include a visceral mass containing the organs, and many have a feeding structure called a radula (though not all, like many bivalves). Squids are cephalopods, snails are gastropods, and clams are bivalves — all classes within the same phylum. This shared plan distinguishes them from other groups: arthropods have segmented bodies and exoskeletons, echinoderms show radial symmetry and a water vascular system, and chordates have a dorsal nerve cord and notochord. So snails, clams, and squids are classified together because they all belong to Mollusca.