Why is the cell know as the structural ad fuctioal unit of life ?

A cell is the smallest and basic membrane bound unit of which all living things are made and which is capable of surviving independently. Working through the tissues, the cells build up the body and carry on its different activities. They are recognized on this account as the units of structure and of function, and are the "individuals" in the body organization. Among the most important and interesting of the activities of the cells are those by which they build up the body, or cause it to grow.