Download Chapter 17: Evolution of Populations 1. Natural Selection a

Name: _______________________________________________________ Period: __________ Date: _______________
Chapter 17: Evolution of Populations
1. Natural Selection
a. Organisms that are best __________________________ to their
environment are more likely to
___________________________________ and
________________________________
b. Remember! Adaptation = helpful mutation
2. Artificial Selection
a. Humans
_________________________________________________
organisms for traits that are desirable
b. Examples:
1) Dogs
2) Plants
3. Natural Selection & Phenotype
a. Natural selection acts directly on the _________________________________ of an organism.
b. An organisms is best fit to survive in its environment based on its ___________________________
c. Best fit organisms passes its _______________________ down to more ______________________
4. Gene Pools & Allele Frequency
a. All of the genes within a population including the
different alleles for each gene make up the
______________________________
b. Scientists study gene pools by examining _____________________________________________or
how common a given alleles is in comparison with the total number of alleles for that gene.
5. Relationship to Evolution
a. Evolution involves a change in the frequency of particular alleles in a population over time.
b. Evolution works on ________________________________________ as a whole whereas natural
selection works on ________________________________________.
6. How do allele frequencies change?
1) For _______________________________________- natural selection can causes changes in
allele frequency and thus, change phenotype frequencies.
2) For _______________________________________ - natural selections affects the relative
fitness of phenotypes and therefore creates 3 possible selection patterns:
a) Directional selection
b) Stabilizing selection
c) Disruptive selection
a. Directional Selection
1) Occurs when organisms at
____________________________________________have_________________________________
than those in the middle or other end.
2) Curve shifts in the direction of the __________________________________________________
b. Stabilizing Selection
1) Individuals _____________________________________ of the
curve are best fit to survive
2) Curve _________________________________ and remains in the
__________________________
c. Disruptive Selection
1) _________________________ fit individuals are at the
_________________________ of the curve while
__________________________ fit individuals are on
__________________________.
2) Curve begins to separate and _____________________ fully separate into two distinct phenotypes.