what is a mollusc

Mollusks, also spelled molluscs, are soft-bodied invertebrates that are part of the phylum Mollusca. They are the second-largest phylum of invertebrate animals, after Arthropoda, with around 76,000 extant species recognized. Mollusks are highly diverse, not just in size and anatomical structure, but also in behavior and habitat. They are found in almost every ecosystem in the world, ranging in distribution from terrestrial mountain tops to the hot vents and cold seeps of the deep sea. Mollusks can be found in marine, freshwater, brackish waters, or land environments. They are typically divided into 7 or 8 taxonomic classes, of which two are entirely extinct. Some examples of mollusks include snails, clams, octopuses, and squid. Mollusks are of general importance within food chains and as members of ecosystems, and certain species are of direct or indirect commercial and even medical importance to humans.