Answer:
Natural selection is an adaptative mechanism that modifies gene frequencies (allele frequencies) in the whole population across generations
Step-by-step explanation:
According to the evolutionary theory proposed by Darwin, natural selection is the main process that leads to evolution. Natural selection can be defined as a mechanism through which populations adapt and change. The organisms better adapted to their environment will have more chances to survive and reproduce, and therefore they will pass their genes (and favorable traits) to the next generation. This process is able to modify the allele frequencies in the whole population, thereby changing and adapting (i.e., evolving) across generations.