A central principle of evolution, natural selection is a non-random process that generates organisms well adapted to their environment by selectively reproducing beneﬁcial changes in their genotype (their genetic make-up). Selection itself can be based on several factors – including survivability, fertility, development speed and mating success among others – and mitigates the potentially harmful effects of random mutations by multiplying instances of those beneﬁcial and eliminating those that are not (ie an organism’s chance of descendents is reduced).
Combined or no, these factors result in a natural selection that directly affects an organism’s ability to reproduce and pass-on its genetic make-up to its offspring. Consequently, the process of natural selection improves the preservation rate of a group of organisms that are best adjusted to their environments, and reduces the preservation rate of those poorly adjusted. In addition, in many cases, natural selection serves to enhance an organism’s ability to survive too.
In simple analogy, natural selection undertakes roughly the same role as a human dog breeder, however instead of selecting dogs based on a subjective, sensory appearance, does so based on a genetic level and by factors that will have a beneﬁcial effect on its ability to adapt to, and survive in, its particular environment.