What does evolution primarily refer to in biological contexts?

Evolution primarily refers to the change in allele frequency over time within a population. This definition is fundamental to understanding evolutionary biology because it encapsulates the genetic and heritable changes that occur in populations across generations. As alleles—the different versions of genes—shift in frequency, the genetic structure of the population evolves, leading to adaptation to changing environments, speciation, or changes in traits.

This concept is rooted in the principles of population genetics and is central to mechanisms like natural selection, genetic drift, mutation, and gene flow, all of which influence allele frequencies. Changes in these frequencies can drive the evolution of new traits and ultimately the divergence of species.

While changes in behavior, environmental conditions, or species distribution may occur as a result of evolutionary processes, they do not encompass the primary mechanism of evolution itself, which is embodied in the changes occurring at the genetic level within populations over time. Recognizing that evolution is fundamentally about genetic change helps clarify many aspects of biological diversity and the history of life on Earth.