As mentioned before, many species of bivalvia are filter feeders. This means that water is drawn into the body and through their gills. At this time, food particles are caught in the gill mucus; they eat through their gills.
Bivalves tend to have different lifestyles. Both mussels and oysters spend their lives attached to a substrate. Clams however, are usually found burried in the ground. Scallops on the other hand, are able to swim and live on the ocean bottom.