Hysteresis and the limits of homeostasis: From daisyworld to phototaxis

Abstract

All biological organisms must be able to regulate certain essential internal variables, e.g. core body temperature in mammals, in order to survive. Almost by definition, those that cannot are dead. Changes that result in a mammal being able to tolerate a wider range of core body temperatures make that organism more robust to external perturbations. In this paper we show that when internal variables are regulated via 'rein control' mechanisms, decreasing the range of tolerable values increases the area of observed hysteresis but does not decrease the limits of regulation. We present circumstances where increasing the range of tolerable values actually decreases robustness to external perturbation. © Springer-Verlag Berlin Heidelberg 2005.