CBSE Class 10 Science 2020 · Paper 31/3/2 · Question 20

Three factors that could lead to speciation: (1) geographical isolation of a population, which stops gene flow between the separated groups; (2) genetic drift; (3) natural selection. (Mutations, severe changes in DNA, are also accepted; other correct factors earn credit.) Geographical isolation cannot be a major factor in the speciation of a self-pollinating plant species. In such a plant, pollination takes place within the same plant, so genes are not exchanged between plants even without a barrier; isolating the plants therefore cuts off no gene flow, and pollination within the same plant brings little new variation.