Question 1

What is the main difference between a disturbance and a disturbance regime?
A) A disturbance regime includes defining the predictable frequency and severity of the disturbance.
B) A disturbance regime includes defining the length of the disturbance.
C) A disturbance regime is a more specific type of disturbance.
D) They are essentially the same thing.

Accepted Answer

A disturbance refers to any physical or biotic event that causes a change in an ecosystem, whereas a disturbance regime refers to the patterns and characteristics of those disturbances over time. Therefore, the main difference between the two is that a disturbance regime includes defining the predictable frequency and severity of the disturbance, which is not included in the definition of a disturbance. Choices B, C, and D are all incorrect because they do not accurately describe the difference between a disturbance and a disturbance regime.

Question 2

According to bottom-up and top-down control models of community organization, which of the following expressions would imply that an increase in the size of a carnivore (C) population would negatively impact its prey (P) population, but not vice versa?
A) P ← C
B) P → C
C) C ↔ P
D) P ← C → P
E) C ← P →

Accepted Answer

The expression "P ← C" implies that the carnivore (C) population has a direct negative impact on its prey (P) population, but there is no indication that the prey population affects the carnivore population, which aligns with the scenario described.

Question 3

Which one of the following animals would most likely be defined as a keystone species?
A) sea otter
B) housefly
C) fathead minnow
D) nauplii (a species of zooplankton)

Accepted Answer

A keystone species is one that has a disproportionate effect on the ecosystem compared to its numerical abundance. Sea otters are considered a keystone species because they help maintain the health of kelp forests by keeping sea urchin populations in check. Without sea otters, sea urchins can overgraze kelp forests and destroy the habitat for many other species in the ecosystem.

Question 4

In a tide pool, 15 species of invertebrates were reduced to 8 after one species was removed. The species removed was likely a(n) ________.
A) pathogen
B) keystone species
C) herbivore
D) resource partitioner
E) mutualistic organism

Accepted Answer

A keystone species has a disproportionate effect on their ecosystem compared to their abundance. Removing a keystone species often leads to a domino effect causing a decrease in species diversity and a disruption in the ecological balance. The fact that 15 species were reduced to 8 after the removal of one species suggests that the removed species was a keystone species.

Question 5

Which of the following terms do ecologists use to describe the community interaction where one organism makes the environment more suitable for another organism?
A) parasitism
B) mutualism
C) inhibition
D) facilitation
E) commensalism

Accepted Answer

Facilitation is the community interaction where one organism makes the environment more suitable for another organism. This can include things like providing shelter, nutrients, or resources that the other organism needs to survive and thrive. Parasitism, mutualism, inhibition, and commensalism all describe different types of community interactions, but they do not specifically involve one organism making the environment more suitable for another.

Question 6

The symbols +, −, and 0 are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. 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.
-Recall that 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 we wished to test Gleason's hypothesis?
A) Identical plankton communities will develop in all ponds.
B) Similar plankton communities will develop in all ponds.
C) Different plankton communities will develop in all ponds.
D) Limited plankton communities will develop in all ponds.
E) Initially the number of species in each pond will be greater than the number normally found in similar environments.

Accepted Answer

If Gleason's view is correct, then individual species should operate independently and not be highly predictable or interrelated. Therefore, we would expect different plankton communities to develop in each pond due to chance factors and independent interactions among species. This would support Gleason's hypothesis.

Question 7

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?
A) Elephants exhibit a disproportionate influence on the structure of the community relative to their abundance.
B) Grazing animals depend upon the elephants to convert forests to grassland.
C) Elephants prevent drought in African grasslands.
D) Elephants are the biggest herbivore in this community.
E) Elephants help other populations survive by keeping out many of the large African predators.

Accepted Answer

Elephants are the keystone species because they have a disproportionate influence on the community structure relative to their abundance. Their uprooting of woody plants maintains the grassland habitat, which supports a greater diversity of species than forests or shrublands. Removing elephants would cause a drastic shift in the community structure and lead to a loss of biodiversity.

Question 8

The symbols +, −, and 0 are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. 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 does the graph in the accompanying figure tell you about the definition of a keystone species?
A) A keystone species has little interaction with other species in an environment.
B) Removing a keystone species from the community drastically reduces diversity.
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.

Accepted Answer

The graph shows that removing the keystone species (sea star) drastically reduces the diversity of the community, indicating that the keystone species plays a crucial role in maintaining species diversity. This supports the definition of a keystone species as a species that has a disproportionately large effect on the community relative to its abundance or biomass. Therefore, option B, "Removing a keystone species from the community drastically reduces diversity," is the best choice.

Question 9

The symbols +, −, and 0 are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. 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 a lion pride and a hyena pack?
A) +/+
B) +/0
C) +/−
D) 0/0
E) −/−

Accepted Answer

Both lion prides and hyena packs compete for the same prey, leading to negative interactions for both groups as they can harm each other or reduce each other's food availability.

Question 10

What is the main advantage of controlled burnings of forested areas? Controlled burnings ________.
A) eliminate the possibility of forest fires
B) clear forested areas for farmland
C) prevent the overgrowth of the underbrush
D) allow new species to form

Accepted Answer

Controlled burnings can prevent the overgrowth of the underbrush, which can become a potential fuel source for wildfires. It also helps to promote new growth of certain plant species and facilitates the release of nutrients back into the soil. It does not eliminate the possibility of forest fires nor clear forested areas for farmland, and it may or may not lead to the formation of new species depending on the specific ecological conditions.

Question 11

Which statement best describes the evolutionary significance of mutualism?
A) Mutualism offers more biodiversity to a community.
B) Individuals partaking in a mutualistic relationship are more resistant to parasites.
C) Interaction increases the survival and/or population growth rate(s) of mutualistic species.
D) Mutualistic interaction lessens competition in communities where it is present.
E) Mutualistic relationships allow organisms to synthesize and use energy more efficiently.

Accepted Answer

Mutualism involves a mutually beneficial relationship between two species, allowing them to interact in a way that increases their individual fitness and population growth rates. This leads to the expansion of both species, which can be seen as an evolutionary advantage. Mutualistic relationships can also improve the survival rates of both species, especially as they can work together to resist parasites and other harmful agents.

Question 12

Looking at the results in the accompanying figure, which hypothesis (by Clements or Gleason) is supported by the data?
I. Clements
II. Gleason
A) only I
B) only II
C) both I and II
D) neither I nor II

Accepted Answer

The answer of  Looking at the results in the...

Question 13

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?
A) Measure the number of ant females.
B) Measure the relative sizes of the treehoppers.
C) Measure the relative abundance of jumping spiders.
D) Measure the relative sizes of different ant species.

Accepted Answer

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

Question 14

Which of the following would be most significant in understanding the structure of an ecological community?
I. determining how many species are present overall
II. determining which particular species are present
III. determining the kinds of interactions that occur among organisms of different species
IV. determining the relative abundance of species
A) only I and III
B) only II and IV
C) only I, II, and III
D) only II, III, and IV
E) I, II, III, and IV

Accepted Answer

Understanding the structure of an ecological community involves knowing how many species are present (I), which particular species are present (II), the kinds of interactions that occur among organisms of different species (III), and the relative abundance of species (IV). Each of these aspects provides crucial information for a comprehensive understanding of community structure.

Question 15

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 shown, what can you conclude?
A) Ants do somehow protect the treehoppers from spiders.
B) Ants eat the honeydew produced by treehoppers.
C) Ants reduce the numbers of treehoppers.
D) No specific conclusions can be drawn from this figure.
E) Treehoppers do not produce honeydew in July and are not protected by the ants.

Accepted Answer

The figure shows that the number of treehoppers is higher in the plot with ants present compared to the plot without ants. This suggests that the presence of ants somehow protects the treehoppers from predators like jumping spiders.

Question 16

Which of the following are responsible for generating successional pathways?
I. species interactions
II. historical and environmental context
III. species traits
A) I only
B) II only
C) III only
D) II and III only
E) I, II, and III

Accepted Answer

Successional pathways are influenced by species interactions (such as competition, predation, and facilitation), the historical and environmental context (which includes past disturbances, climate, and soil conditions), and species traits (such as dispersal mechanisms, life span, and growth rate). These factors collectively determine the direction and rate of succession in ecosystems.

Question 17

People with at least one copy of the HLA-B53 gene are better able to beat back malarial infections before the infection progresses. If this is a coevolutionary arms race between Plasmodium and humans, what would the next step in this race be?
A) to see humans with more than one copy of the HLA-B53 gene
B) to see humans without the HLA-B53 gene
C) to see Plasmodium populations that counter the HLA-B53 gene
D) to see Plasmodium populations that have the HLA-B53 gene
E) to see a mutation in the HLA-B53 gene that makes it more effective against malarial infections

Accepted Answer

If this is a coevolutionary arms race between Plasmodium and humans, Plasmodium populations that can counter the HLA-B53 gene would be the next step in this race. It is important to note that this answer is based on the assumption that the arms race is ongoing and not at its end, as the question does not specify the timing or duration of the race.

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. A possible factor in this secondary succession was ________.
A) equilibrium
B) facilitation
C) immigration
D) inhibition
E) parasitism

Accepted Answer

Inhibition is the best choice as it refers to the process where a species that arrives first in a particular area will prevent the growth of other species by occupying the space, consuming resources, and emitting toxins from their metabolic processes. This process may have occurred in the field, where the initial three species might have equally occupied the space and resources. However, in the following season, one of the species might have outcompeted the others and inhibited their growth and development, leading to the dominance of a single species.

Question 19

The symbols +, −, and 0 are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. 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 a tick on a dog and the dog?
A) +/+
B) +/0
C) +/−
D) 0/0
E) −/−

Accepted Answer

A tick on a dog benefits (+) from feeding on the dog's blood, while the dog is harmed (−) by the parasitic feeding of the tick. Therefore, the interaction is +/−.

Question 20

Why do moderate levels of disturbance result in an increase in community diversity?
A) Habitats are opened up for less competitive species.
B) Competitively dominant species infrequently exclude less competitive species after a moderate disturbance.
C) The environmental conditions become optimal.
D) The resulting uniform habitat supports stability, which in turn supports diversity.
E) Less-competitive species evolve strategies to compete with dominant species.

Accepted Answer

The answer of Why do moderate levels of disturbance result...

Quiz 52: Community Ecology

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

According to bottom-up and top-down control models of community organization, which of the following expressions would imply that an increase in the size of a carnivore (C) population would negatively impact its prey (P) population, but not vice versa?

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

In a tide pool, 15 species of invertebrates were reduced to 8 after one species was removed. The species removed was likely a(n) ________.

Which of the following terms do ecologists use to describe the community interaction where one organism makes the environment more suitable for another organism?

What is the main advantage of controlled burnings of forested areas? Controlled burnings ________.

Which statement best describes the evolutionary significance of mutualism?

Looking at the results in the accompanying figure, which hypothesis (by Clements or Gleason) is supported by the data? I. Clements II. Gleason

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 of the following are responsible for generating successional pathways? I. species interactions II. historical and environmental context III. species traits

People with at least one copy of the HLA-B53 gene are better able to beat back malarial infections before the infection progresses. If this is a coevolutionary arms race between Plasmodium and humans, what would the next step in this race be?

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. A possible factor in this secondary succession was ________.

Why do moderate levels of disturbance result in an increase in community diversity?