Function (biology)

In evolutionary biology, function is the reason some object or process occurred in a system that evolved through natural selection.

That reason is typically that it achieves some result, such as that chlorophyll helps to capture the energy of sunlight in photosynthesis.

In the philosophy of biology, talk of function inevitably suggests some kind of teleological purpose, even though natural selection operates without any goal for the future.

[1] This concept of function as opposed to form (respectively Aristotle's ergon and morphê[2]) was central in biological explanations in classical antiquity.

[3][4][5] Function can be defined in a variety of ways,[6][7] including as adaptation,[8] as contributing to evolutionary fitness,[9] in animal behaviour,[10] and, as discussed below, also as some kind of causal role or goal in the philosophy of biology.

[8] 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.

[14] The ethologist Niko Tinbergen named four questions, based on Aristotle's Four Causes,[10] that a biologist could ask to help explain a behaviour, though they have been generalised to a wider scope.

[15][16][17][18] Function is not the same as purpose in the teleological sense, that is, possessing conscious mental intention to achieve a goal.

[22] Causal role theories of biological function trace their origin back to a 1975 paper by Robert Cummins.