Different classes of mollusk eat in various ways, depending on their body structure, environment and physical capabilities. Most mollusks have a tongue-like organ, called a radula (which is rough like sandpaper), that they use to rasp away at food. The different classes of mollusks include monoplacophora, polyplacophora, aplacophora, gastropoda, scaphapoda, bivalvia and cephalopoda.
Scallops are considered bivalves, which contain two shells. These include oysters, mussels and clams. They eat by filtering food particles that live in the water. This class of mollusk does not have a radula, since they filter their food from the water rather than scratching it off rock surfaces. As water passes through the bivalve's gills, the food particles stick to a mucous coating.
Chitons forage for food by scraping algae off of rocks using their radula. The radula contain tiny "teeth" that are really strong and can remove even coraline algae from rocks.
Cephalopods have extremely good eyesight, which help them to find food. They have a mouth just below their arms, which they use to grab their prey. They also have "beaks," which allow them to bite into their prey. Some cephalopods, such as the Blue-Ringed octopus, use powerful lethal venom. This venom is even lethal to humans, although octopods do not easily or typically attack humans.