Download AP Biology - TeacherWeb

AP Biology
Evolution – Note packet
N. Cunningham
Population Genetics
A. The birth of population genetics
1. What does population genetics add to Darwin’s
theory of evolution?
B. A population’s gene pool is defined by its allele
frequencies
1. Definition of population =
2. Definition of species =
3. Definition of gene pool =
4. Example of allele frequencies in a population’s
gene pool:
Let R = red flowers
r =white flowers
In a population of 500 flowers, 20 flowering
plants are white (rr) and 480 have red flowers
(RR and Rr)
Suppose that of the 480 red flowers, 320 are
RR and 160 are Rr.
What is the frequency of the R allele? (Show
how to figure this out)
What is the frequency of the r allele (Show
work)?
5. If the values for these allelic frequencies exist
today, but were to change in the future, what
assumption can we make?
C. The Hardy-Weinberg Theorem describes a nonevolving population.
1. What does this theorem state?
2. How does this theory prove evolution?
3. The Hardy-Weinberg Theory states that populations
will not evolve and allelic genotypic frequencies will
not change if….
a.
b.
c.
d.
e.
4. A detailed look at Hardy-Weinberg conditions:
a. Why is population size a factor in influencing
evolutionary changes?
Genetic drift =
b. How can gene flow influence evolution?
c. How can mutations have an impact on
evolution?
d. If mating is not random, why will evolution
presumably occur?
e. Why must there be an absence of natural
selection if there is to be no evolution?
5. Mathematical Hardy-Weinberg:
P2 + 2pq + q2 = 1
where p + q = 1
What does each part of the equation
represent?
P2 =
2pq =
q2 =
p=
q=
6. Back to the flower example……
a. If the frequency of the R allele was calculated
to be 0. 8, what part of the Hardy-Weinberg
equation is this value?
b. If the frequency of the r allele was calculated to
be 0.2, what part of the Hardy-Weinberg
equation is this value?
c. Knowing this, determine the percent of the
population that is homozygous dominant,
heterozygous and homozygous recessive for
flower color. Show work below.
Homozygous dominant =
Heterozygous =
Homozygous recessive =
d. Another example using the Hardy-Weinberg
equation and pku.
Given info: 1 in 10,000 babies are born with
pku due to a recessive allele.
What part of the Hardy-Weinberg equation
does this represent? _____________
What is this value in decimal form?
____________
Calculate the number of heterozygous carriers
of pku in the population given this information.
Show work below:
D. A Closer Look at the Hardy-Weinberg Conditions
1. What four factors can alter allele frequencies in a
population?
a.
b.
c.
d.
2. What effect does natural selection have on the
evolution of a population?
3. What is GENETIC DRIFT?
4. Genetic drift at small populations occurs as a result
of two situations: ____________________ and
_______________
5. Why are allelic frequencies subject to change in
small rather than large populations?
6. What is “The Bottleneck Effect”?
7. Give an example of how the bottleneck effect is an
important concept in conserving endangered
species.
8. What is “The Founder Effect”?
9. Explain how natural selection is clearly a violation
of keeping Hardy-Weinberg equilibrium.
10. What is GENE FLOW?
11. Give an example of gene flow.
12. What does gene flow do to variation in the
population? Explain why.
13. What is a mutation? How does it relate to the
evolutionary process?
E. Where does genetic variation come from?
1. What type of variation can be subject to evolution?
2. Examples of inherited variation include….
a. Polymorphism (give definition and example)
b. What is an example of variation that exists on
the molecular level?
c. Geographic variation-
d. A “cline” is a specific type of geographic
variation (give definition and example)
F. Mutation and sexual recombination generate genetic
variation
1. What kind of mutations are the source of
evolutionary change?
2. How does meiosis and sexual reproduction
facilitate the evolutionary process?
G. Diploidy and balanced polymorphism preserve
variation
1. Why does “diploidy” preserve variation?
2. What is meant by the term “heterozygote
advantage”?
3. Give an example (ie. Sickle cell anemia) of how
heterozygote advantage can maintain genetic
diversity in a population.
H. Evolutionary fitness is the relative contribution that
an individual makes to the gene pool of the next
generation.
1. The term “fitness” does not mean how in shape you
are physically. What does it mean?
I. The effect on selection on a varying characteristic can
be directional, diversifying or stabilizing.
1. Directional selection-
2. Diversifying selection –
3. Stabilizing selection – (defined? Example?)
J. Sexual selection may lead to pronounced secondary
differences between the sexes.
1. How do differences in males and females exhibit the
idea of “sexual dimorphism”
2. What is “intrasexual selection”?
K. Natural selection cannot fashion perfect organisms.
Why is this true? Explain the following….
1. Evolution is limited by historical compromises.
2. Adaptations are often compromises.
3. Not all adaptation is adaptive.
4. Selection can only edit existing variations.