Depending on the nature of variation different organism have different advantages
eg: bacteria variants which can tolerate heat have high survival chance than the non-variant bacteria that have no capacity to tolerate heat.
however not all variations are beneficial or useful.
Variations happen due to inaccuracies in DNA copying.Thus new organisms with variations may have survival advantages and can adapt to the new generations come there is more accumulation of variations which help in survival of such species.Such species have better chances of survival For example,in a bacteria population,new variants are formed.if the temperature of water in which they live is increased,the bacteria tolerant to heat that is the variants will survive while the normal bacteria dies...