The Cell

Abstract

The fundamental structural and functional unit of every organism is the cell (Fig. 2.1). The human body is composed of cells and intercellular material formed by cells. In primitive organisms, as in primitive human societies, each individual cell (person) performs all of the several activities basic to survival and function. In more complex organisms (societies) different cells (persons) are responsible for performing one or a few of these basic functions for the entire organism (society). Through evolution, specialization and dependence on the specialization of others have reached a level such that it is difficult to find a cell (person) capable of surviving isolated from its organism (society). Thus it is probably impossible to find in the complex human body a generalized or typical cell whose description would fit a universal definition of cell, and no definition is general enough to include all cells.