Final answer:
Positive selection in natural selection is a powerful evolutionary force that promotes the survival of advantageous traits and increases their frequency in a population, contributing to adaptive evolution.
Step-by-step explanation:
We've learned that positive selection is a powerful force in natural selection, and it promotes the survival of advantageous traits. A correct choice that describes positive selection is that it: a) Promotes the survival of advantageous traits.
Positive selection acts at both the level of the individual and the population. It favors individuals with traits that are beneficial for survival and reproduction and thereby increases the frequency of these advantageous alleles in the population. This process is known as adaptive evolution. Unlike the predominantly negative view of natural selection in Darwin's time, we now understand that natural selection can have positive effects on a population by increasing its overall fitness and adaptation to the environment.
It is important to realize that evolution also includes other forces like genetic drift and gene flow, which may not always be adaptive but still contribute to changes in a population's genetic makeup over time. These evolutionary forces operate together to shape the genetic and phenotypic variance within populations.