Functional significance of biological variability.

Abstract

The variability of biological matter contributes to both its adaptability and reliability. To represent the structure of this variability we treat a complete biological system (e.g. community and environment) as a system with sets of states and certain (unknown) probabilities governing the state to state transitions. Adaptability (defined operationally in terms of the maximum tolerable uncertainty of the environment) consists of behavioral uncertainty, ability to anticipate the environment, and indifference to the environment. It may also be decomposed into components associated with genetic, organismic, population, and community levels of organization. Considerations of adequate design suggest that adaptability tends to fall to its lowest allowable value in the course of evolution. This means that any change in adaptability associated with one level or unit of organization tends to be compensated by opposite changes in the adaptability associated with other levels or units, or by opposite changes in the indifference to the environment. The analysis shows that the adaptability is not independent of reliability, and that each functionally distinct state consists of: (1) finer states which mediate the processing of information about the environment; (2) redundant sets of such states; and (3) informationally equivalent states associated with macroscopically equivalent microdescriptions.