Practice question

Acclimation is commonly defined as a reversible physiological adjustment by an individual to one controlled environmental variable in the laboratory. For example, animals maintained at a new experimental temperature may alter enzyme expression, membrane lipid composition, metabolic rate, or thermal tolerance over days or weeks. Acclimatization usually refers to a comparable adjustment under natural conditions, where temperature, humidity, oxygen, and other variables may change together. Both processes occur within a lifetime and depend on phenotypic plasticity; neither requires a new mutation or a change in population allele frequencies. Evolutionary change, by contrast, is inherited across generations. Summer dormancy is aestivation, a specific behavioural and physiological strategy, not the general definition of acclimation. Terminology is not perfectly uniform—some authors use acclimation and acclimatization interchangeably—so the controlled-versus-natural distinction should be stated when precision matters. Acclimation can reveal the capacity and limits of a genotype’s plastic response and is central to experimental physiology. If conditions return to their original state, many induced changes reverse, distinguishing them from genetically fixed local adaptations produced by selection.