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.
There are almost 100,000 species of mollusks around the world, and many tens of thousands more undiscovered. Most mollusk species only live in the ocean, but some live in freshwater or on land. In Michigan there are about 300 species of mollusks known, with more to be found. There are three main groups of mollusks. Snails ( Gastropoda ) are the most diverse group, there are tens of thousands of species.