Practice question

Acclimatization is a reversible phenotypic adjustment made by an individual after exposure to a changed natural environment. Moving to high altitude, for example, lowers oxygen availability and triggers increased ventilation, erythropoietin release, red-cell production, and altered tissue oxygen use over days to weeks. These responses improve performance without changing the individual’s inherited DNA sequence, and many diminish after return to low altitude. Adaptation, in the evolutionary sense, is a heritable population trait shaped by natural selection over generations. Evolution includes changes in allele frequencies, while speciation involves the formation of reproductively isolated lineages; neither is a temporary response by one organism. Acclimatization depends on phenotypic plasticity encoded by the genotype, so it has biological limits and may carry energetic costs. It should also be distinguished from short-term regulation, such as sweating within minutes, and from acclimation, a term often reserved for adjustment under controlled laboratory conditions. The defining clues are timescale and level of organization: acclimatization occurs during one lifetime, responds to environmental exposure, and is generally reversible rather than inherited as a newly evolved state.