Final answer:
Natural selection is the process that increases the frequency of gene variations beneficial to an organism's survival and reproduction, leading to adaptive evolution. It consists of selecting for beneficial traits and increasing their allele frequency within the population.
Step-by-step explanation:
The increase in frequency of genes that produce phenotypes contributing to an organism's survival and reproduction is known as natural selection. This process of adaptive evolution works by favoring individuals with beneficial traits, which are passed down through generations, thus increasing the allele frequency of those advantageous traits in the population. Adaptive evolution involves both increasing the frequency of beneficial alleles and decreasing the frequency of deleterious ones, through mechanisms such as directional selection, stabilizing selection, and diversifying selection.
For example, if a gene mutation results in a phenotype with better running speed that allows a predator to catch prey more efficiently, individuals with this trait are more likely to survive, reproduce, and pass the beneficial allele on to their offspring. Over time, the frequency of this advantageous allele in the population will rise through natural selection a process evident in many aspects of the animal kingdom, from the variation in finch beaks to the development of webbed feet in aquatic animals.