CBSE Class 10 Science 2019 · Paper 31/5/2 · Question 13

Variation means that the individuals of a species differ from one another; it arises during reproduction. Depending on the nature of their variations, different individuals have different kinds of advantages. If the surroundings (niche) of the species change drastically, the individuals whose variations suit the new conditions survive, reproduce and pass on those variations, while the others die. So the species is not wiped out: variation is useful for the survival of species over time. Example: Suppose a population of bacteria lives in temperate waters. If the water temperature rises because of global warming, most of the bacteria die, but a few variants that are resistant to heat survive and grow further. The species survives because of this variation. (Any other relevant example earns credit.)