Acclimatization

Acclimatization refers to any of the numerous gradual, long-term responses [blank] an organism to changes in its environment. Such responses are more or less habitual and reversible should environmental conditions revert [blank] an earlier state. The numerous sudden changes that evoke rapid and short-term responses via the nervous and hormonal systems are not examples of acclimatization. An individual organism can regulate its internal processes rapidly to sustain itself [blank] the usual range of environmental changes that it encounters hourly or daily. But this rapid regulation, or homeostasis, [blank] limited in its operation to a small range of environmental variations. Homeostatic regulations usually cannot meet effectively large environmental changes such as those that would allow a plant or animal living in the warmth of summer to function in the cold of winter. As summer wanes, organisms change [blank] substance and their habits in seeming anticipation of the coming winter. This gradual adjustment to conditions is acclimatization.