biologicalfunction

Biological function refers to the role a component of an organism plays in its biology, contributing to survival, reproduction, or the propagation of its genes. In philosophy and biology, two main accounts describe function. The etiological (historical) account ties function to evolutionary history: a trait has a function if it was favored by natural selection because it improved fitness. The causal-role account defines function by the current contribution of a trait within a system, regardless of history. Many discussions blend these views, and function is often treated as a pragmatic description rather than a hard boundary.

Examples illustrate the distinction between function and mechanism. The heart’s function is to pump blood, sustaining circulation; bones provide structural support; wings in birds function for flight but can also serve other roles. The eye’s light-detection mechanism is not the same as its function, which relates to vision. Some traits are vestigial, having unclear or diminished current function, yet they may retain historical explanations. Exaptation describes features that acquire new functions during evolution.

Researchers study function through comparative anatomy, physiology, genetics, and experiments that measure effects on fitness. Understanding function informs fields from ecology to medicine, including drug targeting and the interpretation of evolutionary adaptations. The concept is distinct from teleology or purpose, and debates continue about how best to define and measure function across diverse organisms and levels of organization.