Question 1

Which of the following best describes the outcome of Gause’s experiment with Paramecium aurelia and Paramecium caudatum when cultured together?

Accepted Answer

P. aurelia outcompeted P. caudatum, leading to the local extinction of P. caudatum.

Question 2

Which of the following is an example of exploitation competition?

Accepted Answer

Plants in a forest absorbing nutrients from the soil more efficiently than others, reducing availability for competitors.

Question 3

According to the Lotka-Volterra competition equations, what does the competition coefficient $$\alpha$$ represent?

Accepted Answer

The effect of one individual of Species 2 on the population growth rate of Species 1.

Question 4

Which of the following scenarios best illustrates apparent competition?

Accepted Answer

An increase in rabbit population leads to an increase in foxes, which then causes a decline in pheasant population.

Question 5

If the zero-growth isocline for Species 1 is always above the zero-growth isocline for Species 2 on a phase plane, what is the predicted outcome?

Accepted Answer

Species 1 will outcompete Species 2 and drive it to extinction.

Question 6

Which of the following is NOT a mechanism by which competition occurs, as described in the study materials?

Accepted Answer

Mutualistic competition

Question 7

In the context of the Lotka-Volterra competition equations, what does the term $$K_1$$ - $$N_1$$ - \alpha $$N_2$$ represent?

Accepted Answer

The effective carrying capacity for Species 1 after accounting for both intraspecific and interspecific competition.

Question 8

Which of the following best explains why Chthamalus barnacles have a smaller realized niche than their fundamental niche in the intertidal zone?

Accepted Answer

They are excluded from lower intertidal zones by competition with Semibalanus.

Question 9

Which of the following experimental results would provide the strongest evidence for competition between two species?

Accepted Answer

Removal of one species leads to a significant increase in the abundance of the other.

Question 10

Which of the following is a real-world example of resource partitioning?

Accepted Answer

Two species of finches evolving different beak sizes to specialize on different seed sizes.

Question 11

Given the Lotka-Volterra competition equation for Species 1:

$$\displaystyle \frac{dN_1$}{dt} = r_1$ N_1$ \left( \frac{K_1$ - N_1$ - \alpha N_2$}{K_1$} \right)$$

What happens to the population of Species 1 when $$N_1$$ = $$K_1$$ - \alpha $$N_2$$?

Accepted Answer

Species 1 population growth rate is zero (population is stable).

Question 12

Which of the following factors would NOT facilitate coexistence of two competing species?

Accepted Answer

Identical niches with no resource partitioning.

Question 13

A researcher observes that when two species of rodents are present together, their population sizes are lower than when each is alone. When one species is removed, the other’s population increases. What ecological principle does this experiment best illustrate?

Accepted Answer

Competition for shared resources

Question 14

Which of the following equations correctly represents the zero-growth isocline for Species 2 in the Lotka-Volterra competition model?

Accepted Answer

$$N_2$$ = $$K_2$$ - \beta $$N_1$$

Question 15

Which of the following best describes the difference between a fundamental niche and a realized niche?

Accepted Answer

A realized niche is the actual area occupied by a species, while a fundamental niche is the potential area it could occupy in the absence of competition.

Question 16

Which of the following is a direct interaction between organisms?

Accepted Answer

Two male lions fighting over territory.

Question 17

If the competition coefficient $$\beta is $$much greater than 1, what does this imply about the effect of Species 1 on Species 2?

Accepted Answer

Each individual of Species 1 has a strong negative effect on the population growth of Species 2.

Question 18

Which of the following best describes the competitive exclusion principle?

Accepted Answer

Two species with identical niches cannot coexist; one will outcompete the other.

Question 19

A population of birds is observed to increase when below its zero-growth isocline and decrease when above it. What does this indicate about the population dynamics?

Accepted Answer

The population is regulated by both intra- and interspecific competition.

Question 20

Which of the following is an example of asymmetrical competition?

Accepted Answer

One plant species consistently outcompetes another, reducing its abundance more than its own.

5.3 Competition and Interspecific Interactions in Ecology

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