Leah, Taylor, Chelsea

“I have called this principle, by which, each slight variation, if useful, is preserved, by the term of Natural

Selection.”–Charles Darwin

Natural Selection

• Definition: process that results in the adaptation of an organism to its environment by means of selectively reproducing changes in its

genotype

• Natural Selection determines the traits that allow organism to multiply and survive

• Evolution often occurs as a result of this process

Why does it happen?• Natural selection may

occur because of many different reasons

• All such differences result in natural selection and affect the number of offspring an organism leaves

Factors• Factors that encourage natural selection

are…

• Mutation

• Migration

• Random Genetic Drift

Natural selection changes the messed up effects of these processes because it multiplies the helpful mutations over the generations and

removes harmful ones, since carriers leave few or no offspring

Natural selection improves protection of a group of organisms that are best adjusted to the conditions of

their environment and may also result in their improvement

Sexual Selection

• Darwin posed a theory of “sexual selection.”

• Sexual selection: theory in postulating that the evolution of certain obvious physical traits may grant the possessors of these traits greater success in obtaining mates.

Adaptations

Example: Humming Birds

Hummingbirds’ beak sizes vary. Eventually there will only

be birds with long beaks.

Natural Selection

Humans can also affect natural selection.

Affecting natural selection.

Natural Selection &Evolution

• Without natural selection there wouldn’t be any evolution.

• Passing on certain traits and leaving others is how animals evolve

Citations

“natural selection." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online.

14  Apr.  2009  <http://search.eb.com/eb/article-9055046>.  

"adaptation." Encyclopedia Britannica. 2009. Encyclopedia Britannica Online. 14  Apr.  2009  <http://search.eb.com/eb/article-9003688>.