According to Darwinism,
(i) Within any population, there is natural variation
(ii) In spite of reproduction, the population becomes fairly constant.
(iii)This is due to the struggle between the inpiduals of various species for food, space and mate.
(iv) Due to this struggle, only the better ones are selected by nature.
(v) The selected inpiduals pass on their favourable variations to their offsprings.
(vi) These variations when accumulated over a long period of time lead to origin of new species.
