Robustness in biological systems

The systems approach to biology aims to address problems using a holistic approach that focuses on emergent properties, namely those that cannot be attributed to a single part of a biological system, but rather, arise from complex, collective processes at the molecular level. An important feature of these emergent properties is robustness— the emergent phenomena are, to a considerable extent, insensitive to changes in the parameters of the microscopic processes that give rise to the phenomena in the first place. In this paper, we examine the general features of robustness as it appears in biology. We also present a model for adaptation in bacterial chemotaxis as an example of how robustness can influence the process of understanding systems-level phenomena by model building.