Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift. Darwin’s grand idea of evolution by natural selection is simple but often misunderstood. To find out how it works, imagine a population of beetles where some are brown and some are green which gives variation in traits. However, since the environment can’t support an infinite population growth, not all individuals get to produce for the next generation. Since green beetles are mistaken to look like plants, more herbivore predators have been feeding on green beetles more often than brown beetles. Meaning that green beetles will survive to produce less offspring compared to the brown beetles; hence, there is differential reproduction. As a result, the surviving brown beetles produce more brown beetle offspring because this trait has a genetic basis and there is heredity involved over time. After multitudes of generations of each offspring, the beetle population will consist of only brown beetles because this trait had more chances of survival in an area where more predators would feed off of more green beetles than brown. Therefore, the saying ‘survival of the fittest’ is best fit for heredity that has been effected/not effected by environmental factors over time.

References:

Natural Selection. (n.d) Retrieved From April 12, 2017 from:

http://evolution.berkeley.edu/evolibrary/article/evo_25