Leah S. Taylor W. Chelsea S.

1. Leah, Taylor, Chelsea

2. “I have called this principle, by which, each slight
variation, if useful, is preserved, by the term of Natural
Selection.”–Charles Darwin

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

4. • Natural Selection determines the traits
that allow organism to multiply and survive
• Evolution often occurs as a result of this
process

5. 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

6. Factors
• Factors that encourage natural selection
are…
• Mutation
• Migration
• Random Genetic Drift

7. 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

8. 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.

9. Adaptations

10. Example: Humming Birds
Hummingbirds’ beak sizes
vary. Eventually there will only
be birds with long beaks.

11. Natural Selection

12. Affecting natural selection.
Humans can also affect natural selection.

13. Natural Selection &Evolution
• Without natural selection there wouldn’t be
any evolution.
• Passing on certain traits and leaving
others is how animals evolve

14. Citations
“natural selection.quot; Encyclopedia Britannica. 2009. Encyclopedia Britannica
Online.
14 Apr. 2009 <http://search.eb.com/eb/article-9055046>.
quot;adaptation.quot; Encyclopedia Britannica. 2009. Encyclopedia Britannica Online.
14 Apr. 2009 <http://search.eb.com/eb/article-9003688>.