Functional language is ubiquitous in ecology, mainly in the researches about biodiversity and ecosystem function. However, it has not been adequately investigated by ecologists or philosophers of ecology. In the contemporary philosophy of ecology we can recognize a kind of implicit consensus about this issue: while the etiological approaches cannot offer a good concept of function in ecology, Cummins’ systemic approach can. Here we propose to go beyond this implicit consensus, because we think these approaches are not adequate for ecology. (...) We argue that a sound epistemological framework to function in ecology is to be found in organizational approaches. In this line, we define function in ecology as a precise effect of a given constraint on the ecosystem flow of matter and energy performed by a given item of biodiversity, within a closure of constraints. We elaborate on this definition by developing a case study of a bromeliad ecosystem. (shrink)