Question 1

Which is an example of a trait-mediated indirect effect?

Accepted Answer

A trait-mediated indirect effect occurs when a predator alters the behavior or traits of a prey species, which then affects a third species or ecological process. In this example, the predator is indirectly affecting the amount of food available to the consumer by causing it to change its foraging pattern.

Question 2

Explain whether species would be limited more by resources or interspecific interactions in tropical rainforests (low latitude) or taiga (high latitude).

Accepted Answer

The answer of Explain whether species would be limited more...

Question 3

What most accurately describes a trophic cascade?

Accepted Answer

A trophic cascade is a top-down effect in which changes in the top predator population can impact the entire food chain all the way down to primary producers. This is often seen in ecosystems where the removal of top predators leads to an increase in their prey populations, which then leads to a decrease in the populations of the prey's food source.

Question 4

What is a reasonable explanation of the results in the figure?

Accepted Answer

The graph shows that as fertilizer is added, the height of the plants initially increases, but then levels off and begins to decrease. This suggests that some plants may be competing more successfully for the added fertilizer, shading out other plants and limiting their growth. The fact that adding more light does not result in increased growth supports the idea that the plants are already limited by competition for resources.

Question 5

What is a major distinction between direct and indirect effects in a community?

Accepted Answer

Indirect effects involve interactions that include more than two species, often through a chain of interactions, whereas direct effects occur between just two species without the involvement of a third party.

Question 6

Carbon dioxide with radioactive carbon was bubbled into an illuminated aquarium containing unfiltered pond water. In what order will radioactivity appear in various organisms in the aquarium?

Accepted Answer

Producers (such as algae and aquatic plants) will be the first to take up the radioactive carbon in the form of carbon dioxide during photosynthesis. Herbivores (such as zooplankton and snails) will then consume the producers and acquire the radioactivity. Finally, carnivores (such as fish) will consume the herbivores and acquire the radioactivity. Therefore, the order is producers, herbivores, carnivores.

Question 7

Keystone species

Accepted Answer

Keystone species have a disproportionately large effect on their environment relative to their abundance. They play a critical role in maintaining the structure of an ecological community, affecting many other organisms in the ecosystem and helping to determine the types and numbers of various other species in the community. This impact is not necessarily related to their biomass, trophic level, or whether they are invasive.

Question 8

Keystone species that are predators in a food web can increase species diversity by

Accepted Answer

Keystone species that are predators can increase species diversity by removing competitive dominants. This action prevents any single species from monopolizing resources, thereby maintaining a balance in the ecosystem and allowing a variety of species to coexist.

Question 9

What population trait allows a species to have high resilience to disturbance?

Accepted Answer

The answer of What population trait allows a species to...

Question 10

A researcher removed predatory starfish from sections of intertidal rock and found that the number of prey species decreased by 50 percent relative to control plots within a short time. This indicates that

Accepted Answer

Removing predatory starfish resulted in a decrease in prey species diversity, indicating that starfish predation actually contributes to maintaining or increasing prey diversity by possibly controlling dominant species that would otherwise outcompete others.

Question 11

The presence of fish has a positive effect on shoreline flowering plants. Which lines in the diagram reflect a negative direct effect?

Accepted Answer

The answer of  The presence of fish has a...

Question 12

Consider invertebrates such as starfish and mussels on a rocky intertidal habitat where tidal cycles cause the animals to move between exposure and submersion. Are these changing conditions considered a disturbance?

Accepted Answer

The answer of Consider invertebrates such as starfish and mussels...

Question 13

A trophic cascade is an example of _____ effect.

Accepted Answer

A trophic cascade is an indirect effect because it involves changes in the population of one species that affect other species across multiple trophic levels.

Question 14

Explain what the intermediate disturbance hypothesis predicts for the comparison of species richness in forests where fires have been suppressed versus those with unsuppressed natural fire.

Accepted Answer

The answer of Explain what the intermediate disturbance hypothesis predicts...

Question 15

When Hairston, Smith, and Slobodkin suggested that Earth is green because carnivores depress the populations of herbivores that would otherwise consume most vegetation, they were focusing on _____ control of community structure.

Accepted Answer

The hypothesis proposed by Hairston, Smith, and Slobodkin is an example of top-down control, where predators (carnivores) regulate the population of herbivores, thereby allowing vegetation to thrive.

Question 16

Which is an example of an ecosystem engineer?

Accepted Answer

Beavers are an example of an ecosystem engineer as they manipulate their environment by building dams which alters the flow of water and creates new habitats for other species. This has a significant impact on the surrounding ecosystem. The other options, though important in their own ecological roles, do not have the same level of impact on their environment as beavers do.

Question 17

What is the relation between habitat diversity and species diversity?

Accepted Answer

Habitat diversity positively affects species diversity. This is because a greater variety of habitats provides more niches for different species to occupy, leading to higher species richness and diversity.

Question 18

You have been keeping a list of the bird species that frequent your property. At the end of the year you have tallied eight seedeaters, one nectar sipper, three woodpeckers, six insectivores, two frugivores, four predators, and one carrion feeder. You have organized your tally according to

Accepted Answer

The tally of bird species on the property has been organized according to guild, which refers to the feeding roles or niches of the birds. Seedeaters, nectar sippers, woodpeckers, insectivores, frugivores, predators, and carrion feeders all have different feeding strategies, and organizing the data according to guild helps to understand the diversity and interactions among the bird species on the property. Habitat, community, and population refer to other aspects of ecological organization that are not reflected in this type of bird tally.

Question 19

Why are keystone species important in food webs?

Accepted Answer

The answer of Why are keystone species important in food...

Question 20

Which of the following is NOT an example of a trait-mediated indirect effect?

Accepted Answer

The presence of raptors causes squirrels to forage at night instead of during the day is not an example of a trait-mediated indirect effect because it is a direct effect of predation on squirrels.

Quiz 18: Community Structure