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.
â¢ Respiration â Most mollusks respire with gills, which are located in the mantle cavity. The mantle cavity is a space between the mantle and the visceral mass. â Mollusk gills extract 50% or more of the dissolved oxygen from the water that passes over them.â Most terrestrial snails have no gills.dditions and changes to the original content are the responsibility of the instructor. Mollusks and Annelids continued â¢ Marine Worms â Marine segmented worms are members of the class Polychaeta, the largest group of annelids.