Question 1

Which of the following best describes the interaction between ants and antbirds, as shown in the images above, where ants stir up insects while hunting and antbirds follow to catch the insects?

Accepted Answer

Commensalism, because antbirds benefit while ants are neither helped nor harmed.

Question 2

In the context of community ecology, what is the main difference between a fundamental niche and a realized niche?

Accepted Answer

A fundamental niche is the set of resources a species could theoretically use, while a realized niche is the set of resources it actually uses when competition is present.

Question 3

Which of the following scenarios best illustrates the competitive exclusion principle?

Accepted Answer

Two species of Paramecium are grown together, and one species drives the other to extinction because they compete for the same resources.

Question 4

Which equation best represents logistic growth, which can result from density-dependent predation?

Accepted Answer

$$\frac{dN}{dt} = rN \left(1 - \frac{N}{K}\right)$$

Question 5

Which of the following is an example of an induced defense?

Accepted Answer

A plant producing toxic chemicals only after being grazed by herbivores.

Question 6

In the classic hare and lynx population cycles, which of the following statements is most accurate?

Accepted Answer

Both food availability for hares and predation by lynx interact to cause population cycles.

Question 7

Which of the following best describes character displacement?

Accepted Answer

An evolutionary change in a population’s traits in response to competition with another species.

Question 8

Which of the following is a key difference between ecosystem engineers and keystone species?

Accepted Answer

Ecosystem engineers have a large impact due to their abundance and physical modification of the environment, while keystone species have a large impact relative to their low abundance.

Question 9

Which of the following is an example of a top-down effect in a community?

Accepted Answer

The removal of wolves from Yellowstone leads to an increase in elk, which reduces the abundance of aspen trees.

Question 10

Which of the following best describes the concept of species evenness?

Accepted Answer

How similar the relative abundances of different species are in a community.

Question 11

Which of the following is NOT a type of consumptive interaction?

Accepted Answer

Mutualism

Question 12

Why might intraspecific competition be stronger than interspecific competition?

Accepted Answer

Individuals of the same species have identical ecological niches, leading to complete overlap in resource use.

Question 13

Which of the following is an example of mutualism?

Accepted Answer

A bee pollinating a flower while collecting nectar.

Question 14

Which of the following best explains why mutualisms are not considered altruistic?

Accepted Answer

Mutualisms evolve because both partners benefit by maximizing their own fitness, not from a desire to help the other.

Question 15

Which of the following is a plausible outcome when two species have partially overlapping niches?

Accepted Answer

The weaker competitor persists in the area of non-overlap, leading to competitive coexistence.

Question 16

Which of the following best describes a coevolutionary arms race?

Accepted Answer

A process where predators and prey evolve adaptations and counter-adaptations in response to each other.

Question 17

Which of the following is an example of an indirect effect in a food web?

Accepted Answer

A predator eats herbivores, which reduces the damage to plants.

Question 18

Which of the following is a bottom-up effect in a community?

Accepted Answer

An increase in nutrient availability leads to more plant growth, which supports more herbivores and predators.

Question 19

Which of the following is NOT a key attribute of community structure?

Accepted Answer

The genetic diversity within a single species.

Community Ecology: Species Interactions and Community Structure

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