Biological effect

A biological function is the reason some object or process occurred in a system that evolved through a process of natural selection. That reason is typically that it achieves some result, such as that chlorophyll helps to capture the energy of sunlight in photosynthesis, and hence the organism is more likely to survive and reproduce.

In physiology, a function is an activity or process carried out by a system in an organism, such as sensation or locomotion in an animal. This concept of function as opposed to form (respectively Aristotle's ergon and morphê) was central in biological explanations in classical antiquity, and in more modern times formed part of the Cuvier–Geoffroy debate.

A functional characteristic is known in evolutionary biology as an adaptation, and the research strategy for investigating whether a character is adaptive is known as adaptationism. Although an assumption that a character is functional may be fruitful as a research method, some characteristics of organisms are non-functional, and may simply be spandrels, side effects of functional systems.

From the point of view of natural selection, biological functions exist to contribute to fitness, increasing the chance that an organism will survive to reproduce. For example, the function of chlorophyll in a plant is to capture the energy of sunlight for photosynthesis, which contributes to evolutionary success.

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