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acclimatization

(acclimation, acclimatation, acclimatisation) A process in which an individual organism adjusts to a change in its environment such as altitude, temperature, humidity, photoperiod, or pH, allowing it to maintain fitness across a range of environmental conditions. Organisms can adjust their morphological, behavioral, physical, and/or biochemical traits in response to changes in their environment. (Mechanisms) • In response to changes in temperature, organisms can change the cell membranes more fluid in cold temperatures and less fluid in warm temperatures by increasing the number of membrane proteins. • Heat shock proteins act as molecular chaperones and reduce denaturation by guiding folding and refolding of proteins in response to stress caused by change of temperatures. (Examples) • The salt content of sweat and urine decreases as people acclimatize to hot conditions. Plasma volume, heart rate, and capillary activation are also affected. • Mountaineers acclimate to high altitude over hours or days. • People who migrate permanently to a higher altitude naturally acclimatize to their new environment by developing an increase in the number of red blood cells to increase the oxygen carrying capacity of the blood, in order to compensate for lower levels of oxygen intake. • A mammal shedding heavy winter fur in favor of a lighter summer coat. (Comparison) • acclimatization: Occurs in a short period of time, hours to weeks, and within the lifetime. • adaptation: An evolution, taking place over many generations.