Figure 1.

Diagrammatic summary of the formally defined relationships between time and physiological responses to environmental change. Acute responses are those that occur essentially instantaneously with the environmental change. Adjustments requiring some fraction of the organism’s lifetime (from minutes, to hours, to days to reach a new steady state) are termed “acclimatory responses” or “acclimations”. In the North American literature, the response is termed an “acclimatization” if it occurs naturally (in which parameters other than the one of interest cannot be controlled fully). Only acute and acclimatory responses are possible within a given generation. However, all components of the cascade (from sensing and signal transduction to acclimatory response) can change through evolutionary time, a process defined in the literature as “phylogenetic adaptation” (17, 35, 42).