Bivalvia is a class of marine and freshwater animals known for their two-part shells, which are hinged together. Common examples include clams, oysters, and mussels. These creatures are filter feeders, meaning they obtain their food by filtering plankton and other small particles from the water. They play a vital role in aquatic ecosystems by helping to maintain water quality. Bivalves have a soft body protected by their hard shells, which are made of calcium carbonate. They can be found in various habitats, from sandy beaches to deep ocean floors. Some bivalves, like oysters, are also important for human consumption and contribute to local economies.