Biology
Evolution Solutions
Evolution: Natural Selection
1. How natural selection affects a population
1. Natural selections acts upon (circle one) genotypes I phenotypes.
TRUE OR FALSE. If you believe the following statement is True, write "T". If you believe it is False,
write "F".
2. Competition is a factor of natural selection.
3. Genetic variation is a factor of natural selection.
4. Individuals among a population that are better adapted to their environment leave more
offspring.
II. Natural selection's effect on the population's gene pool
The diagram at left represents a gene pool. Assume that each "X"
represents a gene with 2 alleles.
ttt
Xt.
X 7 X
Xxxx
5. How many alleles are in the population sample at left?
6. How many of these alleles are dashed?
7. How often does the dashed allele occur? (Divide the number of
times the dashed allele is present by the total number of alleles):
(this is the allelic frequency for that particular allele).
Suppose that a virus outbreak occurred within the population reflected above. The dashed allele codes
for a protein that is present on the cell membrane. The viruses cannot attach to this particular protein,
therefore the individuals with the dashed allele are more likely to survive the outbreak. Those that do not
possess the allele are more likely to die.
After the outbreak, all of those individuals that contain the dashed allele survived. Half of those that did
not contain the dashed allele died off.
8. How does this change the population?
9. How is this an example of natural selection?
10. Defend the following statement using the virus outbreak that occurred in the population as an
example: “Natural selection acts upon a population, not an individual"
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