Especially directed consequence of action, as considered in terms of the acts of organisms.
So defined behavior would be limited to the action of animals, and this is a reasonable narrowing of the concept. The term behavior is not always defined that narrowly, however, and also can be applied to systems that are other than individual organisms.
No matter how defined, though, a behavior is some kind of body-intended modification in body activity – even if this modification is avoidance of doing something – and also is something that takes place over relatively short time scales.
Just how short a timescale a behavior must be over, to still be a behavior, is an important consideration that in part can be used to distinguish between more narrow versus broader definitions of just what constitutes a behavior. E.g., is a plant growing towards the a behavior? Strictly, no, but less strictly defined perhaps yes.
Behavior is a consequence of the physiology of organisms, that is, a consequence of how organism bodies work. Behavior also contributes to physiology, giving rise to various aspects contributing to as well as reproduction.
Natural selection does its best to favor the production of codes guaranteeing behavior that increases fitness. fitness. A behavior program that guarantees instantaneous correct reaction to a potential , to a potential , or to a potential will certainly give greater fitness in the Darwinian sense than a program that lacks these properties. Again, a behavior program that allows for appropriate learning and the improvement of behavior reactions by various types of gives greater likelihood of than a program that lacks these properties.
See also ultimate causation versus proximate causation.