acclimatization

Acclimatization or acclimation is the process of an organism adjusting to change in its environment, allowing it to survive changes in temperature, water and food availability, other stresses and often relates to seasonal weather changes. Acclimatization occurs in a short time, (days to weeks) and within one organism's lifetime (compare adaptation). This may be a discrete occurrence or may instead represent part of a periodic cycle, such as a mammal shedding heavy winter fur in favor of a lighter summer coat.^[1]

Plants

Many plants, such as maple trees, irises, and tomatoes, can survive freezing temperatures if the temperature gradually drops lower and lower each night over a period of days or weeks. The same drop might kill them if it occurred suddenly. This process is called hardening and involves several changes, such as a decrease in the water content and an increase in the sugar content of the plant, lowering the freezing point of sap.

Animals

Animals acclimatize in many ways. Sheep grow very thick wool in cold, damp climates. Fish are able to adjust only gradually to changes in water temperature and quality. Tropical fish sold at pet stores are often kept in acclimatization bags until this process is complete.

Humans

When humans move from a cool or temperate environment to a hot, dry desert environment or vice versa, they should spend up to seven days acclimatizing to the change in their environment. This lets the body make internal adjustments (see homeostasis) to compensate for the change in environmental conditions. If people do not acclimatize, then the person is at higher risk of heat related injuries (heat stroke, heat cramp, pneumonia). A heat acclimatized person will begin to sweat earlier and more intensely under heat, have a lower heart rate, and a lower skin temperature. The salt content of sweat also decreases as people acclimatize.^[2]

Acclimatization to high altitude continues for months or even years after initial ascent, and ultimately enables humans to survive in an environment that, without acclimatization, would kill them. Humans 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 in the air.^[3][4]

See also

• Altitude sickness
• Vostok Station
• Acclimatisation society

References

• World Book encyclopedia 1989
• US Army - Heat Acclimation Guide [1]

Footnotes

1. ^ Schmidt-Nielsen, Knut. Animal Physiology: adaptation and environment. 4th Ed. Cambridge ; New York : Cambridge University Press, 1990.
2. ^ "Heat acclimitization guide". US Army. http://www.usariem.army.mil/download/heatacclimatizationguide.pdf. Retrieved on 2009-07-02. 
3. ^ Muza, SR; Fulco, CS; Cymerman, A (2004). "Altitude Acclimatization Guide.". US Army Research Inst. of Environmental Medicine Thermal and Mountain Medicine Division Technical Report (USARIEM-TN-04-05). http://archive.rubicon-foundation.org/7616. Retrieved on 2009-03-05. 
4. ^ Kenneth Baillie and Alistair Simpson. "Altitude oxygen calculator". Apex (Altitude Physiology EXpeditions). http://www.altitude.org/calculators/oxygencalculator/oxygencalculator.htm. Retrieved on 2006-08-10.  - Altitude physiology model

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