Mollusca is a taxonomic phylum that includes a large and diverse group of invertebrate animals. It is derived from the Latin word "molluscus," meaning soft-bodied, which aptly describes the characteristic feature of these animals. With over 100,000 known species, Mollusca is the second-largest phylum in the animal kingdom, encompassing a wide range of organisms, including snails, clams, squids, and octopuses.
The defining anatomical feature of mollusks is the presence of a soft and unsegmented body, often protected by a calcareous shell. This shell, composed of calcium carbonate, can be found in various forms and sizes, or may be absent altogether in some species. Mollusks typically possess a muscular foot used for locomotion, a head with sensory organs, and a mantle that secretes the shell.
The group exhibits a remarkable diversity in terms of ecological adaptations, habitats, and feeding strategies. Mollusks have successfully colonized marine, freshwater, and terrestrial environments, occupying niches ranging from bottom dwellers to active swimmers. Some mollusks are herbivorous, feeding on algae and plants, while others are predators or filter feeders.
Due to their ecological importance and economic value, mollusks are extensively studied by biologists and ecologists. They play essential roles in various ecosystems as decomposers, ecosystem engineers, and keystone species. Additionally, mollusks have notable economic significance as a food source for both humans and other animals, as well as in the production of pearls, dyes, and pharmaceutical compounds.
