CBSE Class 10 Science 2017 · Paper 31/1/2 · Question 14

Natural selection: The individuals of a population show variations, which arise during reproduction. Nature favours the variations that suit the environment: individuals having them survive better and reproduce more, so over generations these variations become common and the population changes. For example, green beetles hidden from crows on green bushes increase in number over red ones. Speciation: When a population is split into sub-populations that cannot interbreed, for example by geographical isolation, gene flow between them stops. Each sub-population changes in its own way by natural selection (and genetic drift). Over many generations the changes accumulate until the members of the two groups can no longer reproduce with each other, and a new species is formed. Thus natural selection changes populations over time and speciation gives rise to new species; together they produce the gradual change and the diversity of living organisms, which is evolution. Hence the statement is justified.