All populations show . It can be seen in an individual's . DNA varies through and .

There will always be for resources in .

Charles created the theory of natural based on observations of .

Organisms with the most beneficial traits survive and reproduce more .

The advantages or disadvantages of a trait is determined by the in which the organism lives in. Beneficial traits are called .

Darwin's idea was that today, all species are from older types. All species are to each other in a family .

Adaptation is a that improves an organism's ability to and/or . is the process in which organisms change overtime.

Natural selection is the process in which organisms better to the survives.

If an organism is born with that help it or attract , it will produce offspring than individuals that do have these traits. Over long periods of , these traits will spread throughout the .

Evolution is a from which species have from ancestral species while accumulating for their environment.

Natural selection occurs in steps. Natural selection changes a species to help it .

Step 1: A species lives in a particular . Individuals compete for resources such as , water, space, and . Some show variation in their traits.

Step 2: A occurs in their environment. The change can be (living) like a new or food source. The change could also be abiotic (). Climate changes, change in pH, or more acidic water or soil are some examples of changes.

Step 3: An individual born with a that somehow one of its traits. The change allows this particular individual to survive , and therefore, more often. The individual produces more offspring to others.

Over many generations, individuals possessing the "" adaptation will become more . Individuals without the better reproduce less. They can't with the adapted individuals and get less resources. The species has now and the adaptation can be seen .