CBSE Class 10 Science 2022 · Paper 31(B)/6 · Question 3(b)

Variation is the occurrence of differences in characters among the individuals of a species - between parents and offspring, and among the offspring themselves. It arises during reproduction. Beneficial to the species: if the niche of a population changes drastically (for example, the water in which bacteria live becomes much warmer through global warming), a population of identical individuals could be wiped out. If some individuals carry variations suited to the new conditions (heat-resistant bacteria), they survive and reproduce, and the species continues. Variation thus helps a species to survive over time, and it is the basis for evolution. Not necessary for an individual: an individual can live and reproduce in its existing conditions without any new variation, and a particular variation may be useful, useless or even harmful to the individual that carries it. Its value to the species shows chiefly when the environment changes, through the survival of some individuals of the population over generations.