Chaos : Its significance and detection in biology

Chaos is a mechanism which can generate random‐looking time series from simple deterministic systems. We outline the idea of deterministic chaos and discuss some biological examples where chaos is believed to play a part. The benefits that biological systems may gain from exhibiting chaotic dynamics are discussed. Establishing whether a system exhibits chaotic dynamics by examining a time series consisting of observations of a single variable is not an easy task. Several sophisticated techniques are examined, including dimensional analysis, estimation of Lyapunov exponents and nonlinear forecasting. There are many difficulties in applying these techniques; often the data requirements are large and noise in the data can give misleading results. We discuss the method of surrogate data, which can help avoid fallacious results.