ABSTRACT
Robustness is the ability of a system to continue to function in the face of perturbations. Robustness is a very defining characteristic of biological systems. Unlike most engineered systems, which are often designed to be robust, biological systems are typically naturally and inherently robust. Biological systems exploit several key devices or mechanisms to achieve robustness; Kitano presents an excellent account of these mechanisms, also juxtaposing them with those observed in engineered human-made systems. A common and important device for robustness is redundancy, or the existence of multiple alternate components/fail-safe mechanisms to achieve a particular end. Another classic device for robustness is the existence of control mechanisms, which typically rely on feedback. Decoupling and buffering ensure that slight changes in stimuli, noise, and small genetic perturbations do not produce significant impacts on cellular phenotypes. This chapter discusses the concept of genotype spaces and genotype networks, which provide excellent insights into the robustness and evolvability of various biological systems.
