The fundamental statement of natural selection is that heritable
traits which are beneficial will tend to become more numerous in
successive generations, while heritable traits which are harmful
will tend to become more scarce. The traits are defined to be
beneficial if they become more numerous in successive
generations. This principle is general, and applies to any
system of individuals which reproduce; it is most commonly
applied to systems of living organisms. It is sometimes
summarized by the slogan, survival of the fittest, where the
"fittest" are the organisms which leave the most offspring. This
means that "fitness" is determined by the environment; for
example, a penguin is very good at producing offspring when it
lives in Antarctica, but wouldn't be so good if it lived in the
Sahara. Natural selection will automatically take place in any
system which follows a certain set of rules. These rules are: -
There must be a set of individuals. - These individuals must
exhibit variation. - These individuals