Answer:
Natural selection refers the effect of selection pressure on the frequency of allele in the population.
Generally,natural selection increases the chances that certain allele will survive for long period of time, and therefore the chances of successive reproduction. Therefore organisms with these alleles with higher chances of reproduction have high selective advantages, and therefore better adapted to withstand the selective pressure and therefore undergo directional selection within the organisms in the population.
Consequently, they are better reproduced, and thus well populated.The r frequency of their traits is well expressed from generation to generation, and therefore naturally selected, and evolve over long period.
