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Chapter 13
1. Which of the following statements about damselfish on Jamaican reefs is false?
a) Damselfish engage in both intraspecific and interspecific competition.
b) Damselfish compete for territories they use for feeding.
c) Damselfish attack intruders threatening their young.
d) Damselfish without territories die.
e) Competition in damselfish is “interference” competition.
Answer: D
2. Intraspecific competition for limited resources can play a key role in slowing
population growth at high densities.
Answer: T
3. In plants, “self-thinning” refers to reduction in
a) the biomass of an individual in response to competition.
b) the total biomass of a population in response to competition.
c) both population density and population biomass in response to competition.
d) population density in response to competition, as population biomass increases.
e) population density due to grazing by herbivores.
Answer: D
4. When the average mass of individual plants in a stand is plotted against stand density
(log-transformed), the slope of the relationship is very often around
a) -1/2.
b) –1.
c) -3/2.
d) +1/2.
e) +3/2.
Answer: C
5. Intraspecific competition among planthoppers
a) results in reduced survivorship.
b) results in increased development time.
c) occurs via resources rather than interference.
d) occurs because plants exploited by planthoppers have less protein and less moisture.
e) all of the above
Answer: E
6. Experiments with terrestrial isopods demonstrate that competition can occur only when
food resources are limiting.
Answer: F
7. Which statement about organisms’ “niches” is false?
a) The niche summarizes environmental factors influencing growth, survival, and
reproduction of a species.
b) The niche concept was developed by Joseph Grinnell and Charles Elton.
c) The “fundamental” niche refers to physical, but not biological aspects of the
environment.
d) Interactions such as competition and parasitism may restrict the size of an organism’s
niche.
e) In the laboratory, two species with identical niches are especially easy to maintain in a
mixed culture.
Answer: E
8. Gause’s “competitive exclusion principle” states that
a) when two species occur together, competition is always prevented by some behavioral
adjustment.
b) no two species can coexist indefinitely.
c) no two competing species can coexist indefinitely.
d) no two species with identical niches can coexist indefinitely.
e) none of the above
Answer: D
9. Within a species, all individuals have identical niches.
Answer: F
10. During droughts in the Galápagos Islands, the ground finches most likely to survive
are those with
a) smaller bodies.
b) smaller bills.
c) earlier maturation.
d) larger bills.
e) larger territories.
Answer: B
11. When a new species arises through hybridization followed by doubling of
chromosome number, the process is called _____________.
Answer: allopolyploidy
12. Which of the following does NOT contribute to determining the niche of the saltmarsh grass Spartina anglica?
a) the height of tidal fluctuations
b) the fetch of the estuary
c) latitude
d) temperature
e) rainfall frequency
Answer: E
13. In the Lotka-Volterra competition equations, the parameter α12 relates to the
a) population growth rate.
b) carrying capacity in the absence of competition.
c) carrying capacity in the presence of competition.
d) effect OF species 2 ON population growth rate OF species 1.
e) effect OF species 1 ON population growth rate OF species 2.
Answer: D
14. In the Lotka-Volterra competition equations, if α21 > 1, then
a) the population growth rate of species 2 is reduced more by each individual of species 1
than by each individual of species 2.
b) the population growth rate of species 2 is reduced more by each individual of species 2
than by each individual of species 1.
c) the population growth rate of species 2 is reduced equally by individuals of either
species 1 or species 2.
d) we would also have to know the value of K2 to decide which of the above is true.
e) we cannot tell from the parameters of the equation which of the above is true.
Answer: A
15. In the Lotka-Volterra competition model, the intersection of two isoclines of zero
population growth always indicates stable coexistence of two competitors.
Answer: F
16. Analysis of the Lotka-Volterra competition model implies that two competitors can
coexist only when
a) interspecific competition is stronger than intraspecific competition.
b) intraspecific competition is stronger than interspecific competition.
c) intraspecific and interspecific competition are equally strong.
d) predation or parasitism is stronger than interspecific competition.
e) Actually, the model implies that two competitors can never coexist.
Answer: B
17. In Thomas Park’s experiments with Tribolium beetles, which of the following was
true?
a) T. confusum and T. castaneum had identical niches.
b) T. confusum and T. castaneum always coexisted when cultured together.
c) T. confusum and T. castaneum never coexisted when cultured together.
d) T. confusum and T. castaneum could coexist under some environmental conditions, but
not all.
e) T. confusum and T. castaneum proved to be unsuitable species for laboratory
experimentation.
Answer: D
18. Joseph Connell discovered that Balanus barnacles were excluded from the upper
intertidal zone by ____________, while Chthalamus barnacles were excluded from the
middle intertidal zone by ___________.
a) competition from mussels, prolonged immersion in water
b) competition from mussels, competition with Balanus
c) prolonged exposure to air, competition with Balanus
d) prolonged exposure to air, competition with algae
e) predation by wading birds, predation by starfish
Answer: C
19. Rodents that feed primarily on seeds are called ____________.
Answer: granivores
20. Evolution of distinct niches in the presence of competition is called _____________.
Answer: character displacement
21. Two species occurring together in the same place are said to be
a) competitors.
b) precocial.
c) mutualists.
d) allopatric.
e) sympatric.
Answer: E
22. Field experiments differ from laboratory experiments in that
a) laboratory experiments include controls, but field experiments need not.
b) field experiments can be more easily replicated than laboratory experiments.
c) laboratory experiments allow variables not of direct interest to be controlled, while in
field experiments these typically vary.
d) field experiments can teach us about ecological systems, but laboratory experiments
cannot.
e) field experiments are often used by ecologists, but laboratory experiments never are.
Answer: C