Question 1

Which one of the following animals would most likely be defined as a keystone species?

Accepted Answer

A keystone species is one whose impact on an ecosystem is disproportionately large relative to its biomass or abundance. Sea otters are considered a keystone species because they control the population of sea urchins, which in turn graze on kelp. Therefore, without sea otters, the population of sea urchins would explode, leading to overgrazing of kelp forests and subsequent loss of habitat for a variety of other species.

Question 2

During succession, tall canopies of maple trees form allowing chipmunks to be better hidden against hawks. This is an example of

Accepted Answer

Facilitation occurs when one species benefits from the presence or actions of another species. In this case, the tall canopies of maple trees provide a benefit to chipmunks by allowing them to be better hidden from predators.

Question 3

Figure 52.7
-Clements's view of biological communities is that of a highly predictable and interrelated structure, while Gleason's view of biological communities is that individual species operate independently. If we set up many identical sterilized ponds in the same area and allowed them to be colonized, what should we predict if Gleason's hypothesis is the one we believe is correct?

Accepted Answer

According to Gleason's hypothesis, individual species operate independently and are affected by chance events. Therefore, we would predict that different plankton communities would develop in each of the sterilized ponds due to the random nature of colonization and chance events that would occur in each pond.

Question 4

Figure 52.9
-In the figure above, which community has the highest species richness?

Accepted Answer

The answer of  Figure 52.9
-In the figure above, which...

Question 5

Figure 52.9
-In the figure above, which community has the highest species diversity?

Accepted Answer

Community 2 has the highest species diversity because it has the greatest number of species and the most even distribution of individuals among those species when compared to the other communities.

Question 6

What is the main difference between a disturbance and a disturbance regime?

Accepted Answer

A disturbance refers to any event that disrupts or alters an ecosystem, while a disturbance regime specifically includes information about the frequency and severity of these events. Disturbance regimes can provide important information for understanding and managing ecological systems.

Question 7

Figure 52.6
-Treehoppers a type of insect) produce honeydew, which ants use for food. Treehoppers have a major predator, the jumping spider. Researchers hypothesized that the ants would protect the treehoppers from the spiders. In an experiment, researchers followed study plots with ants removed from the system and compared them to a control plot. In the figure above, what can you conclude?

Accepted Answer

The figure shows that in the control plot, where ants are present, there are fewer spider attacks on the treehoppers compared to the plot where ants were removed. This suggests that the presence of ants does somehow protect the treehoppers from spiders.

Question 8

Which of the following is not an example of a mutualism?

Accepted Answer

This is an example of commensalism, where the birds benefit from the insects disturbed by the army ants, but the ants are not affected by the birds' presence. All the other options are examples of mutualism, where both species involved benefit from the interaction.

Question 9

Figure 52.7
-What does the graph in the figure above tell you about the definition of a keystone species?

Accepted Answer

The graph shows that the removal of the keystone species (represented by the black bars) causes a significant decrease in the diversity and abundance of other species in the community. This supports the idea that keystone species have a crucial role in maintaining the structure and stability of ecosystems, and their removal can have drastic effects. Choices A and B are incorrect because they do not accurately reflect the information presented in the graph. Choice D is also incorrect because a keystone species has a specific definition and cannot be any species.

Question 10

Figure 52.11
-Which of the following statements regarding the figure above is true?

Accepted Answer

The figure shows that species richness increases with island size and proximity to the mainland. Therefore, species richness should be higher on larger islands close to the mainland (D). Choice A is incorrect because the graph does not provide data on extinction rates. Choice B is incorrect because the graph only shows species richness, not overall diversity (which would also include genetic and ecosystem diversity). Choice C is also incorrect because immigration rates are not shown in the graph.

Question 11

Elephants are not the most dominant species in African grasslands, yet they influence community structure. The grasslands contain scattered woody plants, but they are kept in check by the uprooting activities of the elephants. Take away the elephants, and the grasslands convert to forests or to shrublands. The newly growing forests support fewer species than the previous grasslands. Which of the following describes why elephants are the keystone species in this scenario?

Accepted Answer

Elephants are the keystone species in this scenario because they exhibit a disproportionate influence on the structure of the community relative to their abundance. Despite not being the most dominant species in the African grasslands, their uprooting activities keep woody plants in check, preventing the grasslands from converting into less diverse forests or shrublands. Without elephants, the community structure would be drastically altered, and the number of species would decrease.

Question 12

During a one year study, researchers found no difference in treehopper populations in any of their control and experimental groups. What could they measure during the second year to gain information about why this might have occurred?

Accepted Answer

Measuring the relative abundance of jumping spiders could provide insight into predation pressure, which might explain the lack of difference in treehopper populations.

Question 13

Which are the only two interaction types to depend on density and effective defence to determine the short- term impact?

Accepted Answer

Consumption and parasitism are the only two interaction types where density and effective defence determine the short-term impact. In competition, the strength of the impact depends on resource availability and the abilities of the competitors rather than on density and defence. In mutualism and commensalism, both species benefit and are not affected negatively by density or defence, so these factors do not determine their short-term impact. In parasitism, the parasite benefits while the host is harmed, but the strength of the impact is primarily determined by the parasite's ability to infect and exploit the host, not by the host's density or defence. Therefore, the only two interaction types that depend on density and effective defence to determine short-term impact are consumption and parasitism.

Question 14

Figure 52.8
-Clements's view of biological communities is that of a highly predictable and interrelated structure, while Gleason's view of biological communities is that individual species operate independently. Looking at the results in the figure above, which hypothesis by Clements or Gleason) is supported by the data?

Accepted Answer

The answer of  Figure 52.8
-Clements's view of biological communities...

Question 15

A measure of how much a community is affected by a disturbance is termed

Accepted Answer

The answer of A measure of how much a community...

Question 16

Figure 52.11
-According to Figure 52.11, a species has the highest chance of extinction when

Accepted Answer

According to Figure 52.11, the highest chance of extinction for a species is when the island is small and remote. This can be seen by the intersection of the two curves, which shows that as island size decreases and isolation increases, the extinction rate of species increases rapidly. A small and remote island has a smaller gene pool and is more vulnerable to environmental perturbations, making it difficult for species to adapt and survive.

Question 17

Figure 52.10
-In figure above, what can be stated about species diversity and latitude?

Accepted Answer

The figure shows a graph with latitude on the x-axis and species diversity on the y-axis. As latitude increases, species diversity decreases. Therefore, the best choice is B, "As latitude increases, diversity decreases."

Question 18

In a particular case of secondary succession, three species of wild grass all invaded a field. By the second season, a single species dominated the field. What is a possible factor in this secondary succession?

Accepted Answer

Inhibition occurs when one species hinders the establishment and growth of another. In this scenario, the dominance of one grass species over the others could be due to its ability to inhibit the growth or establishment of the other species, leading to its dominance in the field.

Quiz 52: Community Ecology

Which one of the following animals would most likely be defined as a keystone species?

During succession, tall canopies of maple trees form allowing chipmunks to be better hidden against hawks. This is an example of

Figure 52.9 -In the figure above, which community has the highest species richness?

Figure 52.9 -In the figure above, which community has the highest species diversity?

What is the main difference between a disturbance and a disturbance regime?

Which of the following is not an example of a mutualism?

Figure 52.7 -What does the graph in the figure above tell you about the definition of a keystone species?

Figure 52.11 -Which of the following statements regarding the figure above is true?

During a one year study, researchers found no difference in treehopper populations in any of their control and experimental groups. What could they measure during the second year to gain information about why this might have occurred?

Which are the only two interaction types to depend on density and effective defence to determine the short- term impact?

A measure of how much a community is affected by a disturbance is termed

Figure 52.11 -According to Figure 52.11, a species has the highest chance of extinction when

Figure 52.10 -In figure above, what can be stated about species diversity and latitude?

In a particular case of secondary succession, three species of wild grass all invaded a field. By the second season, a single species dominated the field. What is a possible factor in this secondary succession?