Practice question

Acclimatization takes place within an individual organism as its physiology or morphology adjusts to a changed natural environment. The response may require hours, days, or weeks, depending on the system. At high altitude, altered breathing begins quickly, while increased red-cell mass develops more slowly; seasonal mammals may change coat thickness or metabolic settings over months. These changes arise through gene regulation, hormonal signalling, tissue remodelling, and phenotypic plasticity, not through a shift in population allele frequencies. Natural selection operates across differential reproduction over generations and produces evolutionary adaptation, whereas acclimatization does not require reproduction. It is also not restricted to a laboratory. In common usage, adjustment under controlled experimental conditions is called acclimation, while acclimatization refers to multifactorial change in nature, although some texts use the terms interchangeably. Because the same individual can often reverse the response when conditions return to normal, acclimatization is distinct from genetically fixed local adaptation. The organism’s genotype determines the range of possible plastic responses, but the particular adjusted phenotype is induced by environmental exposure during its lifetime.