Explain Class Bivalvia in animal kingdom?
This name of this Class reflects the group's most distinguishing feature. Clams, oysters, scallops and mussels all have two shells that are held together by a hinge ligament at the back. One or two muscles (adductor muscles) are used to pull the shells together, forming a tight seal. Scallops are able to "swim" through the water by "clapping" their shells together rhythmically. The mantle secretes the material that makes up the shell. Another bivalve characteristic is a powerful, muscular foot that can be extended great lengths to help them move about or burrow into the sand or mud.
There are other features that distinguish bivalves from the gastropods or cephalopods. Bivalves do not have an anterior head region, and because they filter the water for food, they also lack a rasping radula. Siphons formed by the mantle provide for the circulation of water past the gills for gas exchange and filter feeding. Although most species of bivalves are marine in distribution, many species do live in fresh water.