The Eight Mechanisms of Natural Selection

Natural selection is the driving force of evolution. For any adaptations or evolution to occur, the population’s genes need to go in a certain direction. The processes listed in our introduction to evolution do not change the overall makeup of a population or move it in any one direction, that is natural selection’s role. This means that some alleles must become more common and others must become less common. Natural selection occurs when the environment favors one trait over another and causes traits to increase or decrease in a population. A trait is selected for when individuals with it are better suited to survive past reproductive age and produce offspring with that trait. Since those with the favored trait are reproducing, that favored trait becomes more common in a population.


The eight mechanisms of natural selection are:

1. All species are capable of producing offspring at a faster rate than food supplies increase.
2. There is a biological variation within all species.
3. In each generation more offspring are produced than survive, and because of limited resources, there is competition among individuals.
4. Individuals who possess favorable variations or traits have an advantage over those who don't have them.
5. The environment context determines whether or not a trait is beneficial. What is favorable in one setting may be a liability in another.
6. Traits are inherited and passed on to the next generation because individuals who possess favorable traits contribute more offspring to the next generation than others do. Over time those favorable traits become more common in the population while less favorable characteristics are less common and become weeded out.
7. Over long periods of time, successful variations accumulate in a population, so that later generations may be distinct from ancestral ones. Thus, in time, a new species may appear.
8. Geographical isolation also contributes to the formation of new species. As populations of a species become geographically isolated from one another, they begin to adapt to different environments. Over time, as populations continue to respond to different selective pressures, they may become distinct species.