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Evolution PCB4674
Midterm exam2
Name:__________________________________
Mar 22 2005
ID:________________
For each multiple choice question select the single best answer. Answer questions 1 to 20 on
your scantron sheet. Answer the remaining questions in the space provided or on the figures.
Brevity is rewarded. Please print clearly. Each multiple choice question is worth 1 point.
For short answer questions, the number of points is indicated in parentheses at the end of
each question.
1
a)
b)
c)
d)
e)
A point mutation is:
a single allele substitution in DNA
a single base substitution in DNA
a single chromosome substitution in DNA
a single gene substitution in DNA
none of the above
b
2
What is the Red Queen hypothesis?
a) sexual selection is driven by female choice
b) organisms have to evolve as fast as they can just to keep pace with evolution of other
organisms around them
c) genetic diversity is maintained by natural selection
d) allele frequencies will not change generation after generation
e) none of the above
b
3
a)
b)
c)
d)
e)
An insertion or deletion of a base changes the codon reading sequence. This is knows as:
frameshift mutation
point mutation
chromosome inversion
transversion
none of the above
a
4
Given a low degree of heritability for a trait and a low selection differential, what would
be the predicted evolutionary response to selection? R=h2S
a) high
b) low
c) intermediate
d) any of the above
e) insufficient information to answer that question
b
5
The vast majority of mutations are:
a) strongly beneficial
b)
c)
d)
e)
neutral to slightly beneficial
neutral to slightly deleterious
strongly deleterious
lethal
a)
b)
c)
d)
e)
Genetic drift is most important in:
large populations
small populations
asexual populations
sexually reproducing populations
all of the above
a)
b)
c)
d)
e)
Random genetic drift will cause the average heterozygosity in a population to:
increase
decrease
remain stable
all of the above are possible
none of the above
c
6
b
7
b
8
If 2 groups compete for the same ecological niche, one will drive the other to extinction.
This is known as:
a) character displacement
b) community interaction
c) competitive exclusion
d) resource partitioning
e) none of the above
c
9
a)
b)
c)
d)
e)
Evolution above the species level is known as:
microevolution
gradualism
population genetics
saltation
none of the above
e
10
The rapid diversification of a small group of ancestral species into a large number of
descendant species that occupy a wide range of ecological niches is known as:
a) adaptive radiation
b) gradualism
c) migration
d) drift
e) sexual selection
a
11
Evolutionary changes that fluctuate around a mean value and give the overall appearance
of stasis are known as:
a) punctuated equilibrium
b) gradualism
c) selection
d) mutation
e) zigzag evolution
e
12
a)
b)
c)
d)
e)
What is a polymorphism?
a difference in the rate of evolutionary change
expression of different protein products from the same allele
multiple mutations in a single individual
more than 1 possible allele at a particular locus
none of the above
a)
b)
c)
d)
e)
What effect does inbreeding have on the frequency of homozygotes in a population?
increases homozygotes
decreases homozygotes
stabilizes frequency of homozygotes
all of the above are possible
none of the above
a)
b)
c)
d)
e)
In the realm of population genetics, evolution is defined as:
any violation of Hardy-Weinberg Equilibrium assumptions
the appearance of a new species
a change in allele frequencies across generations
all of the above
population genetics has nothing to do with evolution
a)
b)
c)
d)
e)
Which of the following are mechanisms of divergence that can lead to speciation?
genetic drift
sexual selection
natural selection
all of the above
none of the above
d
13
a
14
c
15
d
16
Define resource partitioning. (1)
Species minimize harmful effects of direct competition by using different aspects of their
common environment
17
List 2 assumptions required for Hardy-Weinberg Equilibrium. The requisite assumptions
for HWE are unrealistic and unlikely to be found in any population so what is the value of this
model? (3)
No selection, no mutation, no migration , no drift, no assortative mating
Allows us to quantify what will happen when each assumption is violated
18
Briefly describe Eldredge and Gould’s concept of punctuated equilibrium. What
derogatory term was applied to their concept? (3)
Evolution tends to be characterized by long periods of stasis punctuated by episodes of very fast
development of new forms
Evolution by jerks
19
Hardy-Weinberg equilibrium states that regardless of allele frequencies, genotype
frequencies will go to and remain at: (1)
p2 + 2pq + q2 = 1
20
Distinguish between allopatric and sympatric speciation. Give an example (real or
hypothetical) of allopatric speciation. (3)
allopatric speciation – populations evolve in geographic isolation
sympatric speciation – populations evolve in geographic proximity
21
Distinguish between Batesian and Muellerian mimicry. (3)
Batesian – 1 species mimics another
Muellerian – 2 species share similar aposematic coloration
22
Distinguish between coevolution and cospeciation. (3)
coevolution – evolutionary changes in 1+ species in response to changes in other species in the
same community
cospeciation – speciation process that occurs in 2 interacting species simultaneously
23
Label these selection modes. (3)
directional
24
disruptive
stabilizing
Label these two hypotheses for the evolution of different morphologies over time. (2)
saltation
gradualism
25
For a population of mice, the mean midparent value for tail length for the entire
population =18.3cm and mean midparent value for the one third of the population with the
longest tails =19.9cm. If the mean midoffspring value for the entire population =18.7 and the
mean midoffspring value for the offspring of the parents with the longest tails =20.1, what is the
heritability of the selected trait? Given a selection differential of 0.8, what is the predicted
evolutionary response (R)? (3)
O * -O R
=
P * -P S
heritability (h2) = 0.875
selection differential (R) = 0.7
26
You observe a field of wildflowers with the following genotype frequencies: AA: 144,
Aa: 100, aa: 81. i) What are the allele frequencies? ii) What are the expected genotype
frequencies under Hardy-Weinberg equilibrium assumptions? iii) Is this population in HardyWeinberg equilibrium (ie. is the observed genotype frequency close to the expected frequency)?
(6)
i) A: 0.5969; a: 0.4031
ii) AA: 0.3563; Aa: 0.4812; aa: 0.1625
iii) no, observed numbers are very different from expected
27
Given initial allele frequencies of A: 0.9 and a: 0.1, calculate the i) genotype frequencies
for a population of 1000 individuals ii) genotype frequencies after selection eliminates 40% of all
homozygotes and ii) final allele frequencies. Which conclusion(s) is violated. (6)
i) AA: 810; Aa: 180: aa: 10
ii) AA: 486; Aa: 180; aa: 6
iii) A: 0.8571; a: 0.1429
selection violates conclusion 1: allele frequencies in a population will not change, generation
after generation
28
Choose any one of the required chapters from The Origin of Species (Difficulties on
theory, Instinct, Hybridism, Geological record, Geological succession) and provide a brief
summary of the chapter including at least 2 examples mentioned by Darwin. (8)