Final answer:
Acclimatization is the adaptive process where organisms make physiological adjustments to environmental stresses such as temperature extremes, UV radiation, or high altitude to maintain stable internal conditions.
Step-by-step explanation:
The process of an organism making internal physiological changes in response to environmental stresses such as high or low temperatures, intense ultraviolet radiation from the sunlight, or high altitude is known as acclimatization. These changes enable an organism, such as a human, to maintain a set point in its physiological systems despite the external environment. For example, when migrating to a high altitude, the body may increase the number of red blood cells to cope with lower oxygen levels, or in response to cold temperatures, animals might develop a heavier coat to retain heat. Acute exposure to extreme UV radiation can suppress the immune system, while chronic exposure elicits an acclimative response.