Exam 2 - Regis

Principles of Ecology
BL / ENVS 402
Exam II
10-26-2011
Name:_________________________________________
There are three parts to this exam. Use your time wisely as you only have 50 minutes.
Part One: Circle the BEST answer. Each question is worth 2 points
1. Suppose a population of worms is variable at a genetic locus involved in foraging patterns. Individuals that
are FF or Ff are rovers, and will travel widely in pursuit of food. Individuals that are ff are sitters, and will not
travel as far. The frequency of the F allele is 0.75. Based on this information, rovers are what proportion of the
population?
a. 0.0625
b. 0.125
c. 0.25
d. 0.375
e. This question cannot be answered without further information.
2. Which of the following statements about genetic drift is false?
a. It affects allele frequencies the most when populations are small.
b. It can cause slightly deleterious alleles to be fixed in populations.
c. It tends to decrease genetic variation within populations.
d. It tends to decrease genetic differences among different populations.
e. All of the above are true; none is false.
3. The most recent mass extinction, which wiped out the dinosaurs, occurred approximately _______ million
years ago.
a. 505
b. 285
c. 145
d. 65
e. 25
4. As a habitat becomes fragmented, the population sizes of a species in the habitat should _______, effects of
genetic drift should _______, and genetic variation within populations of this species should _______.
a. increase; increase; increase
b. increase; increase; decrease
c. decrease; increase; decrease
d. decrease; decrease; increase
e. decrease; decrease; decrease
5. A species of turtle grows for several years before becoming sexually mature. It mates, reproduces, and dies
soon afterward. This species of turtle would best be described as
a. sporophytic.
b. gametophytic.
c. iteroparous.
d. semelparous.
e. scary
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6-7. Refer to the following two graphs. Seedlings of an annual plant were split into two equal treatment groups;
in one group, extra fertilizer was provided, and in the other group (the control group), no additional fertilizer
was added. The numbers of seeds and the average weight of the seeds from each individual plant were
monitored, and these data were plotted (each point represents an individual plant). The first graph represents the
number of seeds (x-axis) and the weights of those seeds (in micrograms) (y-axis) from the control group. The
second graph represents the number of seeds (x-axis) and the weights of those seeds (in micrograms) (y-axis)
from the with fertilizer group.
6. According to the graphs, fertilizer treatment _______ seed size and _______ seed number.
a. increased; had no effect on
b. increased; increased
c. had no effect on; decreased
d. had no effect on; increased
e. decreased; increased
7. Which of the following statements best describes the results of this study?
a. Trade-offs between seed size and seed number existed in both the control and the fertilizer groups, and these
trade-offs were of roughly equal magnitude.
b. Trade-offs between seed size and seed number existed in both the control and the fertilizer groups, but these
trade-offs were much larger in the fertilizer group.
c. A trade-off between seed size and seed number existed in the control group but not in the fertilizer group.
d. A trade-off between seed size and seed number existed in the fertilizer group but not in the control group.
e. Neither the fertilizer group nor the control group showed a trade-off between seed size and seed number.
8. If the population density of ocotillo in a desert is 15 per square kilometer, how many plants would be
expected in an area that is 5 km by 3 km?
a. 15
b. 45
c. 150
d. 225
e. 1,500
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9. An evolutionary ecologist is interested in studying the evolutionary change over the course of many years in
populations of lizards that reproduce via parthenogenesis. Which type of individual would be the most
appropriate focus of the study?
a. Genet
b. Ramet
c. Opuntia
d. Both a and b
e. ghost
10. Area-based methods often make use of sampling areas of a defined size called
a. transects.
b. quadrats.
c. mark and recapture.
d. ramets.
e. cemetaries.
11. Which of the following statements about population growth is true?
a. Exponential population growth is always faster than geometric population growth.
b. We use the term “exponential growth” when the individuals in the population reproduce in synchrony at
discrete individuals.
c. A population that has a of 0.88 should grow in size.
d. All of the above
e. None of the above
12. Which of the following would not be an example of density-dependent factors regulating population size?
a. The number of possible territories for robins is limited; thus when population sizes are high, a lower
proportion of individuals can produce offspring.
b. In conditions of overcrowding, some desert pupfish living in ponds will emigrate to other ponds if given the
opportunity.
c. In conditions of high density, mice are more susceptible to mortality from heat stress.
d. Predation on mosquitofish is high, regardless of population size.
e. All of the above are examples of density-dependent factors regulating population size.
13. Which of the following statements about logistic growth is true?
a. The carrying capacity is the maximum population size that can be supported by the environment indefinitely.
b. At low densities, logistic growth is similar to exponential growth.
c. At the carrying capacity, there is no population growth in the logistic model.
d. All of the above
e. None of the above
14. As of 2010, the human population was just under
a. 7 billion.
b. 700 million.
c. 3 billion.
d. 17 billion.
e. 30 billion, but most are zombies.
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15. Which of the following is most likely to lead to population cycles?
a. Demographic stochasticity
b. Genetic drift
c. Delayed density dependence
d. Habitat fragmentation
e. Logistic growth
16. Which of the following is a plausible consequence of delayed density dependence in a population that would
otherwise have logistic growth?
a. Increased environmental stochasticity
b. Dampened oscillations
c. Population cycles
d. Both a and b
e. Both b and c
17. According to May’s model, a population that experiences delayed density dependence can exhibit logistic
growth or dampened oscillations, or it can fluctuate forever in a stable limit cycle. Which two factors determine
the pattern that will result?
a. The population growth rate under ideal conditions and the starting population size
b. The population growth rate and the time lag
c. The starting population size and the time lag
d. The time lag and the degree of demographic stochasticity
e. The time lag and the carrying capacity
18. Suppose that a population of weevils that experiences logistic growth has an initial size of 1,563 and follows
the standard equation for delayed density dependence with a 5-week delay and an intrinsic growth rate of 0.15
per week. If these conditions remain constant and the population is tracked for a long time, what type of
population dynamics should it display? (The cutoff rτ value for dampened oscillations is 0.368, and the cutoff
for a stable limit cycle is 1.57.)
a. Exponential growth
b. Logistic growth
c. Dampened oscillations
d. A stable limit cycle
e. No change over time
19. Suppose that two species of Darwin’s finches live on the same island and eat seeds, but one species tends to
eat larger seeds than the other one does. Based on this observation, we can conclude that these species are
engaged in
a. resource partitioning.
b. allelopathy.
c. interference competition.
d. competitive exclusion.
e. character displacement.
20. Suppose that a species of moss cannot coexist with a superior competitor unless there is periodic
disturbance. This species is also a frequent disperser. Which of the following is most likely?
a. The moss is engaged in character displacement.
b. In a constant environment, the moss and its competitor have zero population growth isoclines that cross.
c. The moss is a fugitive species.
d. Both a and b
e. None of the above
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21. Many species of butterflies are noxious to predators. They also have bright red coloration that indicates to
the potential predators that they are unpleasant or even harmful to eat. This is an example of _______
coloration.
a. apomitic
b. aposematic
c. cryptic
d. induced
e. exploitative
22. Different species of marine snails that are preyed on by a shore crab differ in terms of how easily the crab
can crush their shells. Studies of these snails have provided evidence for
a. the value of “gene silencing” in ecological studies.
b. the principle of compensation.
c. the presence of trade-offs between different anti-predator adaptations.
d. the influence of exploitation in the distribution and abundance of food organisms.
e. the headless horseman.
23. Huge numbers of adult periodic cicadas emerge simultaneously from pupae at intervals of either 13 or 17
years. This phenomenon is most similar to which of the following?
a. Trick-or-treating
b. Compensation
c. Exploitation
d. Allelopathy
e. Masting
24. The caffeine produced by coffee beans to reduce herbivory are an example of a(n)
a. allelopathy
b. crypsis.
c. secondary compound.
d. candy corn.
e. compensatory agent.
Part Two: Short-answer questions. Please use ONLY the space provided. Answer all five questions, which
are worth six (6) points each.
25. Define genetic drift and gene flow and give an example of each.
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26. Contrast resource partitioning and character displacement. Give a brief example of each.
27. Draw and label the three main dispersal patterns organisms exhibit in nature. Give an example of each and
describe why it would show that pattern.
28. Draw the three types of life curves and give an example organism for each one. Be sure to label the axes.
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Part Three: Longer-answer questions. Answer both questions and please use only the space provided. These
questions are worth eleven (11) points each.
30. Suppose you are involved in a project constructing a life table for a population of a small perennial plant.
Currently, there are 650 plants that are less than a year old, 347 that are between 1 and 2 years of age, 123 that
are between 2 and 3 years old, and 55 that are older than 3 years. Based on previous work, the expected survival
rates of plants that are less than a year old, between 1 and 2, and between 2 and 3 are 0.4, 0.6, and 0.8,
respectively.
Set up the correct life table using Nx, Sx, and calculate lx (5 points).
Assuming that the expected survival rates remain the same, how many plants between 2 and 3 years of age
should you expect to see in 12 months? Show your work (3 points)
Assuming that the expected survival rates remain the same, how many plants between 2 and 3 years of age
should you expect to see in 24 months? Show your work (3 points)
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31. Draw directional, stabilizing and disruptive selection and remember to label the axes (6 points). Give a one
sentence biological example of these three types of selection (3 points).
What is your favorite Halloween candy and why? (2 points) ________________________________________
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