The field deals with all the physicochemical aspects of life.

A common accounts for the ability of all living matter to replicate itself exactly and to transmit genetic information from parent to offspring.

Furthermore, the mechanisms for that transmittal follow a pattern that is the same in all organisms. The phenomenon of diversity has had a long history of study because so many of the variations that exist in nature are visible to the eye.

The fact that organisms changed during prehistoric times and that new variations are constantly evolving can be verified by paleontological records as well as by breeding experiments in the laboratory.

Furthermore, since the action of any organism is determined by the manner in which its cells interact and since all cells interact in much the same way, the basic functioning of all organisms is also similar.

There is not only unity of basic living substance and functioning but also unity of origin of all living things.

According to a theory proposed in 1855 by German pathologist , “all living cells arise from pre-existing living cells.” That theory appears to be true for all living things at the present time under existing environmental conditions.

If, however, life originated on Earth more than once in the past, the fact that all organisms have a sameness of basic structure, composition, and function would seem to indicate that only one original type succeeded.

Before that time, the individual organism was studied as a whole in a field known as organismic biology; that area of research remains an important component of the biological sciences.

biology deals with groups or populations of organisms that inhabit a given area or region.

Included at that level are studies of the roles that specific kinds of plants and animals play in the complex and self-perpetuating interrelationships that exist between the living and the nonliving world, as well as studies of the built-in controls that maintain those relationships naturally.

Those broadly based levels—molecules, cells, whole organisms, and populations—may be further subdivided for study, giving rise to specializations such as and humans.