Robustness in Biological Systems - A Provisional Taxonomy

Biology is a domain of tension: on the one hand, biology is concerned with transformation and the generation of diversity; on the other hand, biology is concerned with the persistence of improbable structural regularities. Robustness, as a research program, aims to uncover those evolved mechanisms promoting the persistence of regularities. Here I organize mechanisms of robustness into a phenomenological taxonomy, grouping biological mechanisms into principles of robust organization. These include: Redundancy, Purging, Feedback, Modularity, Spatial Compartmentalization, Distributed Processing, and the Extended Phenotype. I review studies in which mechanisms representative of each principle are described.