Dear student
In nature, variations occur during sexual reproduction. If this variation is beneficial to the species, it is selected and remains in the population. This is because the variant species are more adapted. Therefore, they can survive better and reproduce to pass the genes to the offsprings.
Variations are very important for organisms to survive because if there were no variations among living organisms there would have been no evolution or change and natural conditions do not remain constant they keep on changing. If variations stops then we would not be able to adapt to the changing conditions and can prove catastrophic to us.
Regards