Question 1

In some circumstances, grasses that initially lose tissues from being consumed by animals such as elk or cattle regrow more than they would have otherwise, and benefit from the moderate levels of grazing. Which of the following terms would best describe such a plant-herbivore interaction?

Accepted Answer

A)   mutualism
B)   commensalism
C)   parasitism
D)   predation A

Question 2

Which of the following best describes the consequences of white-band disease in Caribbean coral reefs?

Accepted Answer

A)   Staghorn coral is decimated by the pathogen, and Elkhorn coral takes its place.
B)   Key habitat for lobsters, snappers, and other reef fishes improves.
C)   Algal species take the place of the dead coral, and the fish community is dominated by herbivores.
D)   Algal species take over and the overall reef diversity increases due to increases in primary productivity. C

Question 3

Use the graph to answer the following question.

What does the graph tell you about the effect of a keystone species?

Accepted Answer

A)   A keystone species has little interaction with other species in an environment.
B)   Removing a keystone species from the community drastically reduces species richness.
C)   Adding a keystone species to the community will make it more diverse.
D)   Removing a keystone species from the community will eventually allow for the invasion of a new species. B

Question 4

Bouchard and Brooks studied the effect of insect flight on dispersal and speciation in rain forest insects. They sampled all of the insects in the study area and found that 60 insect species are flightless and 19 are able to fly. What can you conclude so far about this study?
(P. Bouchard and D. R. Brooks. 2004. Effect of vagility potential on dispersal and speciation in rainforest insects. Journal of Evolutionary Biology 17:994-1006.)

Accepted Answer

A)   Flightless insects have a greater dispersal potential from this study area.
B)   Flightless insects are more numerous in the study area.
C)   Flightless insects have a higher species richness in the study area.
D)   Flightless insects are better suited for the tropics.

Question 5

Which of the following is a widely supported explanation for the tendency of tropical communities to have greater species diversity than temperate or polar communities?

Accepted Answer

A)   There are fewer parasites to negatively affect the health of tropical communities.
B)   Tropical communities are low in altitude, whereas temperate and polar communities are high in altitude.
C)   Tropical communities have higher sunlight and precipitation, and are generally older than temperate or polar communities.
D)   More competitive dominant species have evolved in temperate and polar communities.

Question 6

Use the following diagram of five islands formed at around the same time near a particular mainland, as well as MacArthur and Wilson's island equilibrium model principles to answer the question.

Imagine these are tropical islands. Which island would likely encounter the highest rate of species extinction if these islands were subject to unregulated, commercial logging in the rainforest?

Accepted Answer

A)   A
B)   B
C)   C
D)   E

Question 7

Use the figure to answer the following question.

The figure proposes a combination of a top-down and bottom-up model (a hypothesis) to describe the variable effects of biological control herbivores on the fitness (growth and reproduction) of an invasive, non-native plant, spotted knapweed (Centaurea stoebe). These herbivores include multiple insects that were first studied in the plant's native home range in eastern Europe, where the plant is not dominant in grassland communities and does not pose a problem to land managers and conservationists. Many insects there were found to consume the plant's tissues, including stems, leaves, and seeds, and some were very host specific and were not found to attack plants other than C. stoebe. Several insects were subsequently transported and released in an attempt to reduce densities of this non-native and problematic weed in the United States. The y-axis shows C. stoebe plant fitness, and the x-axis represents the intensity of herbivory by the insects, from low to high. As the vertical shaded bar is moved along the x-axis, the ultimate effect of herbivory (now A, B, andC) on plant fitness can change based on its intensity and also may depend on the other factors. The horizontal dashed line represents no predicted change in fitness under the effects of varying intensity of herbivory, plant competition, and soil resources available to the plant (such as nitrogen or water), while the three solid lines represent other possible outcomes.
(D)G. Knochel and T.R. Seastedt. 2011. Reconciling contradictory findings of herbivore impacts on spotted knapweed (Centaurea stoebe) growth and reproduction. Ecological Applications 20(7):1903-1912.
What portion of the model would be characterized as bottom-up?

Accepted Answer

A)   plant fitness
B)   resources available to the plant
C)   intensity of herbivory on the plant
D)   plant competition and fitness

Question 8

Based on the intermediate disturbance hypothesis, a community's species diversity is increased by

Accepted Answer

A)   frequent massive disturbance.
B)   stable conditions with no disturbance.
C)   moderate levels of disturbance.
D)   human intervention to eliminate disturbance.

Question 9

Character displacement differs from resource partitioning because character displacement ________.

Accepted Answer

A)   is a fundamental difference in feeding behaviors of individuals
B)   is directly linked to the evolution of genotypes that have allowed alternate resource use
C)   is a difference in the niche within a habitat that is preferred to be used by a species
D)   is not the result of competition

Question 10

Why is a pathogen generally more virulent in a new habitat?

Accepted Answer

A)   Intermediate host species are more motile and transport pathogens to new areas.
B)   Pathogens evolve more efficient forms of reproduction in new environments.
C)   Hosts in new environments have not had a chance to become resistant to the pathogen through natural selection.
D)   New environments are almost always smaller in area so that transmission of pathogens is easily accomplished between hosts.

Question 11

The oak tree fungal pathogen, Phytophthora ramorum, has migrated 800 kilometers in 15 years. West Nile virus spread from New York State to 46 other states in 5 years. The difference in the rate of spread is probably related to ________.

Accepted Answer

A)   the lethality of each pathogen
B)   the mobility of their hosts
C)   the fact that viruses are very small
D)   innate resistance

Question 12

Use the figures to answer the following question.

In the hypothesis that Chthamalus stellatus (a species of barnacle) is competitively excluded from the lower intertidal zone by Balanus balanoides (another species of barnacle), what could be concluded about the two species?

Accepted Answer

A)   The fundamental and realized niches of B. balanoides and C. stellatus are identical.
B)   The fundamental and realized niches of B. balanoides and C. stellatus are different.
C)   The fundamental and realized niches of B. balanoides are different, but the fundamental and realized niches of C. stellatus are identical.
D)   The fundamental and realized niches of B. balanoides are identical, but the fundamental and realized niches of C. stellatus are different.

Question 13

The principle of competitive exclusion states that

Accepted Answer

A)   two species cannot coexist in the same habitat.
B)   competition between two species always causes extinction or emigration of one species.
C)   two species that have exactly the same niche cannot coexist in a community.
D)   two species will stop reproducing until one species leaves the habitat.

Question 14

The symbols +, -, and 0 are to be used to show the results of interactions between individuals and groups of individuals. The symbol + denotes a positive interaction, - denotes a negative interaction, and 0 denotes where individuals are not affected by interacting. The first symbol refers to the first organism mentioned. What interactions exist between cellulose-digesting organisms in the gut of a termite and the termite?

Accepted Answer

A)   +/+
B)   +/0
C)   +/-
D)   0/0

Question 15

One plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that ________.

Accepted Answer

A)   tropical communities are younger
B)   tropical regions generally have more available water and higher levels of solar radiation
C)   higher temperatures cause more rapid speciation
D)   tropical regions have very high rates of immigration and very low rates of extinction

Question 16

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that

Accepted Answer

A)   tropical communities are younger.
B)   tropical regions generally have more available water and higher levels of solar radiation.
C)   higher temperatures cause more rapid speciation.
D)   diversity increases as evapotranspiration decreases.

Question 17

The symbols +, -, and 0 are used to show the results of interactions between individuals and groups of individuals. The symbol + denotes a positive interaction, - denotes a negative interaction, and 0 denotes interactions in which individuals are not affected. The first symbol refers to the first organism mentioned. Which fact is correct when describing species interactions?

Accepted Answer

A)   +/0 will always remain such.
B)   A +/- interaction could shift to +/0 or +/+ over time, depending on other factors such as competition, population density, or environmental changes.
C)   Species interactions occur in isolation and cannot affect the structure of ecological communities.
D)   A -/- interaction benefits both of the species in the relationship.

Question 18

Resource partitioning would be most likely to occur between ________.

Accepted Answer

A)   sympatric populations of species with similar ecological niches
B)   sympatric populations of a flowering plant and its specialized insect pollinator
C)   allopatric populations of the same animal species
D)   allopatric populations of species with similar ecological niches

Question 19

According to the island equilibrium model, species richness would be lowest on an island that is ________.

Accepted Answer

A)   large and close to a mainland
B)   large and remote
C)   small and remote
D)   small and close to a mainland

Question 20

Dwarf mistletoes are flowering plants that grow on certain forest trees. They obtain nutrients and water from the vascular tissues of the trees. The trees derive no known benefits from the dwarf mistletoes, nor are they negatively affected by this interaction. Which of the following best describes the interactions between dwarf mistletoes and trees?

Accepted Answer

A)   mutualism
B)   commensalism
C)   competition
D)   facilitation

Exam 54: Community Ecology