ABSTRACT
The capacity for growth and replication distinguishes living organisms from nonliving matter. This capacity stems from the ability of the organism to selectively absorb relatively simple chemical substances from the environment and utilize them for the formation of an amazing variety of complex compounds in cells and tissues, while at the same time maintaining its uniqueness as well as its structural and functional integrity in the face of changes in the physicochemical environment. This is made possible by the versatility of the organism and its ability to maintain a dynamic equilibrium with the environment by the rigorous regulation of the entry and exit of substances into and from the cell and of the synthesis and catabolism of substances manufactured by the cell.
