Natural selection is the natural process by which heritable traits are passed generation to generation. In natural selection, the traits that enable survival and reproduction are the ones that are passed on. It is the traits that enable the survival that then enable the reproduction and therefore future generations survive.
Mean Girls exemplifies survival of the fittest or Natural Selection in high school. The Queen Bee and her posse believe that if you’re not pretty enough or social adept enough to survive high school, you really don’t belong and therefore we should take you down socially.