Final answer:
Natural selection describes the process by which advantageous alleles become more common in a population over many generations, leading to the adaptation of the population to its environment. It acts on the phenotype of organisms, affecting their survival and reproductive success.
Step-by-step explanation:
The correct statements that describe the process of natural selection are that it:
Results in the adaptation of a population to its environment through increased frequency of beneficial alleles and decreased frequency of deleterious alleles.
Acts on the phenotype of an organism, as natural selection can only increase or decrease the frequency of alleles within a population if those alleles affect the organism's phenotype in a way that impacts survival and reproduction.
Requires genetic variation in a population and operates over many generations, not causing the immediate change in allele frequency but rather a gradual change that can lead to evolution.