Natural Selection: The process that drives evolution. Often described as "Survival of the Fittest". Natural Selection works on the natural variation in a population. Where does that natural variation come from? Either mutations or from sexual reproduction. A species that reproduces asexually will evolve more slowly than one that reproduces sexually. Why? A species that reproduces asexually will have less variation between individuals, because asexual reproduction produces identical offspring. With less variation, it is less likely that a species will adapt to a changing environment and more likely that the species may go extinct in a changing environment.

misconceptions_beavers.gif This cartoon illustrates the idea that many people have misconceptions when it comes to natural selection. Organisms do not simply get what they need from natural selection, natural selection merely works on the natural variation within a species. We know that beavers can't grow chainsaws for hands, but one organism may have a slightly different tooth shape that makes him/her more efficient at cutting trees, and that trait may become more abundant in future generations.

Over-Production: Many more individuals are produced than will survive. It is more likley to pass on your genes if you produce many children. Why you ask? Well I'll tell you..... There is variation amongst the offspring, and natural selection will weed out the ones that are "not fit", and hopefully the best will survive to carry on the species. Over a long period of time the individuals with favorable traits will become more abundant, and the ones with less favorable traits will diminish.