Answer:
The environment is not in the control of the organism. According to the species, changes in the environment can impact the organism drastically. If the the reproductive population we're all to be configured for the exact same environment, changes in the surroundings could adversely impact their life. If some variation was introduced to the species then there would be some chance for the survival of the species (in the case of some severe environmental changes like asteroid impact, climate change etc.)
Thus variation is important in the process of reproduction and is linked to the stability of of the population of the species.
