Final answer:
Natural selection preserves favorable variations and rejects harmful variations in a population.
Step-by-step explanation:
Natural selection preserves favorable variations and rejects harmful variations in a population. Natural selection acts on the population's heritable traits, selecting for beneficial alleles that allow for environmental adaptation and increasing their frequency. It also selects against deleterious alleles, decreasing their frequency in the population.
Natural selection is a fundamental mechanism of evolution, first proposed by Charles Darwin and Alfred Russel Wallace in the mid-19th century. It is a process by which traits that enhance an organism's survival and reproductive success are passed on more frequently to future generations, leading to an increase in the prevalence of those advantageous traits in a population over time. Natural selection is a cornerstone of the theory of evolution and is a driving force behind the diversity and adaptation of life on Earth.