Cytology and Genetics - Chandan Sukumar - Bog

Cells even vary on the basis of their role in the living body. A cell is often called a structural and functional unit of life because of its capabilities of performing all the life process independently. It rarely rely upon any foreign agents for any kind of functional regulations. They simply get specialised in higher organisms for defining their specific role on the basis of their scope in the tissue system whith which they remain spepcialised. Such specialisations become materialised in due course of time during the process of development. It is even clear from various aspects of life process that a cell can vsuccessfully give birth to another cell of identical type through the process of equational division (mitosis). Organisms produce germ cells by the process of reductional cells division.

Size of a cell also varies from few microns to a metre. Some prokartotic cells of bacteria are the smallest ones.