According to Darwin, natural selection is the process which brings about evolution of new species of plants and animals.
It consists of the following processes:
(i) He noted that the size of population tends to remain constant despite the fact that more offsprings are produced than needed.
(ii) Variations provide adaptations.
(iii) The best adopted survive in the changing environment (survival of the fittest).
(iv) Nature selects the best organisms with better adaptations and after many generations new species are formed (natural selection).