Explain Charles Darwin's Theory of Evolution by Natural Selection.

Natural Selection is a theory of evolution based on the
premise that organisms which have genetic traits that make it easier for them to survive
in an environment and more attractive to the opposite sex are more likely to pass on
their gene pool to future generations. This makes future generations acquire their
genetic characteristics and alters the genetic pool of the
species.

Natural selection works in two ways, the first
being that the genetic traits make it easier for some organisms of a species to survive
in an environment. Examples of this could be genetic traits that make the color of some
insects such that they blend in easily with the surrounding and this saves them from
predators. Insects which do not have this trait are easily hunted which reduces the
number of organisms with alternate genetic traits.

The
second is that the genetic traits of some organisms make it easier for them to attract
the opposite sex and mate. They are in this way able to pass on the genetic traits which
make them look more attractive.

Usually the gene pool that
results in genetic traits making organisms of a species more attractive is also the one
which increase their ability to survive in the environment. For example, the most
brightly colored birds are also the ones which are the strongest and can easily find
food. This makes the opposite sex attracted to them and they have a higher probability
of passing on their gene pool to future
generations.

Natural selection in this way changes the
genetic traits of a species over time by selecting the gene pool of the organisms which
have features more suitable for survival in an environment.