Variation is the degree by which organisms differ from their parents. No living organisms are alike and they vary appreciably in many structural and functional aspects. These differences between individual organisms are called variations. The advantages of variations are: (a) Variations in a species may confer survival advantage. It is the genetic key to survival. (b) They enable the organism to adapt themselves to the changing environment. (c) They form raw material for evolution and development of new species. Example: Industrial melanism: When the growth of Lichen decreased due to industrial pollution, dark-coloured peppered moths were provided with a survival benefit through camouflage on trees as white coloured peppered moths were picked up by birds as food. Black color phenotype increased in frequency and the other variety became extinct.