The discussion of mechanisms in biology and philosophy of biology has been influenced by four features of many machines built by humans: they are (1) enduring structures that are readily differentiated from their environment that (2) consist of spatially localized and enduring parts, which (3) perform specific operations and (4) are organized so that whenever their start-up conditions are realized they produce the desired product. By considering examples of biological mechanisms whose behavior depends on concentrations, not discrete parts, and whose constitution changes dynamically as they operate, we push for expanding the conception of biological mechanisms to include mechanisms that are less machine-like than those that have been the focus. We appeal to the way biologists diagram mechanisms to emphasize departures from the machine-like framework and argue that, while not machine-like, these systems are still treated as mechanisms by scientists and preserve major features of philosophical accounts of mechanisms. One significant place the differences show up, though, is in the strategies that researchers use to discover, investigate, and evaluate non-machine-like accounts of biological mechanisms.