How do clams and bivalves vary from other mollusks within the phylum Mollusca?

Clams and bivalves are part of the class Bivalvia within the phylum Mollusca, distinguished by their two-part hinged shells and lack of a distinct head and radula, which are characteristic of other mollusks like gastropods and cephalopods. While other mollusks often exhibit complex behaviors and advanced nervous systems, bivalves are primarily filter feeders with a simpler anatomy. Additionally, bivalves are mostly sessile or burrowing, whereas many other mollusks are mobile and exhibit more diverse habitats and lifestyles.