Natural Selection Occurs Over Time

Genetic variation combined with natural selection allows species to survive by adapting to changes in the environment. If enough significant changes or adaptations occur in the inherited traits of a population, natural selection may result in a new species.

Over time, favorable traits are likely to increase within a population and unfavorable traits are likely to decrease. In this way, natural selection plays an important role in the way species evolve over time. When natural selection results in changes in a species, these changes generally develop gradually, over many generations, rather than suddenly.

The following are sources of genetic variation among living organisms.

· Mutations, or changes to an organism's genetic material, are a significant source of genetic variation.

· Sexual reproduction results in an offspring that has a combination of genetic material from its parents, which contributes to genetic variation.

· Meiosis is the process by which sexually-reproducing organisms produce unique gametes, or sex cells. The unique gamete of one parent can fuse with the unique gamete of another parent to produce a unique offspring, resulting in increased genetic variation.