Bivalve is a term used to describe a group of aquatic animals that have two shells connected by a HINGE. This group includes oysters, cockles, scallops, clams, mussels, and other mollusks. All of these creatures have shells that are held together by a HINGE, allowing them to open and close. The shells also provide protection from predators and the environment. In addition, some bivalves use their shells to filter food from the water.