1. (used with a sing. verb) A theory that explains the global distribution of geological phenomena such as seismicity, volcanism, continental drift, and mountain building in terms of the formation, destruction, movement, and interaction of the earth's lithospheric plates. 2. (used with a sing. or pl. verb) The dynamics of plate movement.
Despite the fact that mollusks are very susceptible to changes in their environment because of their permeable skin and soft body (often with an exoskeleton in the form of a shell), they have adapted to all of the main environments of our planetâmarine, freshwater, and terrestrial. With 41% of the 736 documented extinctions of all animal species, the number of mollusks exceeds that of any other major taxonomic group 3. 2  Most documented endangered mollusk species are non marine (they live in freshwater or terrestrial environments) 5.
Characteristics of Mollusks. Mollusks are soft-bodied invertebrates with bilateral symmetry and usually one or two shells. Their organs are in a fluid-filled cavity; the word mollusks in Latin means soft.Most of the mollusks live in water but some live on land. There are more than 110,000 species that have been identified.A theoretical, idealized mollusk would crawl on a single flat, muscular foot, and the body would have at least a suggestion of a head at one end and an anus at the other.ost of the mollusks live in water but some live on land. There are more than 110,000 species that have been identified. A theoretical, idealized mollusk would crawl on a single flat, muscular foot, and the body would have at least a suggestion of a head at one end and an anus at the other.