CBSE Class 10 Science 2017 · Paper 31/1 · Question 11

(1) It keeps the species going. Individuals die — of age, disease or accident — and reproduction produces new individuals of the same kind to take their place, so the species continues from one generation to the next. An individual does not need to reproduce to stay alive, but its kind does. (2) It passes on the DNA, and with it the body design. In reproduction DNA copied from the parent, or from both parents, passes to the offspring, so the offspring look very much like their parents. This consistency of DNA copying keeps the body-design features that let a population live in its particular place in the ecosystem, which is why reproduction is linked to the stability of populations. (3) It produces variation. DNA copying is not absolutely accurate, and sexual reproduction combines DNA from two parents, so offspring differ slightly. If the surroundings of a population change drastically, some of these variants may survive when others cannot, so variation is useful for the survival of species over time and is the basis of evolution.