It is true that all variations and mutations in species will not have equal chances to survive in the environment. According to 'Survival of the fittest, only the species which can adapt themselves to the environment can survive. Selection of the variants occurs by the different environmental factors.
The type of variation determines whether or not variants survive. Individuals stand a variety of possibilities. Evolutionary processes are based on the selection of variations by environmental variables. These differences may result in higher survival benefits for individuals as a result of positive trait adoption, or they may simply contribute to genetic drift.