Abstract
Variability in the environment defines the structure and dynamics of all living systems. Organisms have evolved traits and strategies that allow them to detect, exploit and predict the changing environment. Organisms maintain steady internal conditions required for physiological functioning through feedback mechanisms that allow internal conditions to remain at or near a set point despite a fluctuating environment. In addition to feedback, many organisms use feedforward processes, which allow them to adjust in anticipation of an expected future state of the environment. Daily, seasonal and multi-year cycles provide cues that organisms may use to anticipate regular changes in physiologically-relevant environmental conditions. Using feedforward mechanisms, organisms can exploit correlations in environmental variables and act, based on information acquired in the present, to prepare for anticipated future changes. All living systems exploit the information in variable, auto-correlated, and cross-correlated environmental conditions to reduce their uncertainty about the environment. Strategies to obtain, store and act on information about the conditional nature of future events are advantageous and are evidenced in widespread phenotypes such as circadian clocks, social behaviour, diapause, and migrations. Here we provide a framework describing how feedback and feedforward mechanisms operate across scales of organization, and how they allow living systems to persist in fluctuating environments. Humans are altering the ways in which the environment fluctuates, causing correlations between environmental variables to become decoupled, decreasing the reliability of cues. Human-induced environmental change is also altering sensory environments and the ability of organisms to detect cues. Recognizing that living systems combine feedback and feedforward processes is essential to understanding their responses to current and future regimes of environmental fluctuations.