Final answer:
Hardy-Weinberg describes conditions that would result in no evolution within a population. When allele frequencies do change, this reflects microevolution, which is the change in genetic structure within a population over time, contrasting with macroevolution that occurs on a larger scale.
Step-by-step explanation:
The Hardy-Weinberg principle describes the conditions under which allele frequencies in a population's gene pool remain constant, indicating a state of no evolution. When these frequencies do change due to factors such as natural selection, genetic drift, or gene flow, it leads to microevolution, which is the change in a population's genetic structure over time. On the other hand, macroevolution is a broader scale of evolutionary changes that are observed over paleontological time, often at or above the species level.
Thus, Hardy-Weinberg describes how allele frequencies change in populations through microevolution. This pertains to the evolution within a species or a population, not the emergence of new species, which would be categorized as macroevolution. It is important to understand that while populations may remain in Hardy-Weinberg equilibrium for certain periods, this is rare in nature. Evolutionary forces are frequently at play, leading to genetic variation and microevolutionary processes that shape the diversity of life we see today.