Question 1

Which statement was supported by Stomp and colleagues' study of the partitioning of resources between two species of Baltic Sea cyanobacteria?

Accepted Answer

Stomp and colleagues' study found that the two species of cyanobacteria partition resources by utilizing different wavelengths of light efficiently, with one species using short wavelengths and the other using longer wavelengths.

Question 2

Suppose that, instead of the results actually obtained in Brown and Davidson's experiments, the number of rodents in the ant-excluded treatment was roughly the same as the number of rodents in the control group, and the number of ants in the rodent-excluded treatment was roughly the same as the number of ants in the control group. Which of the following would you then conclude?

Accepted Answer

If the numbers of rodents and ants in the exclusion treatments are similar to the control groups, it suggests that the two species are not significantly affecting each other's populations, indicating reduced competition possibly through resource partitioning.

Question 3

Suppose that two species of Darwin's finches live on the same island and eat seeds, but one species tends to eat larger seeds than the other one does. Based on this observation, we can conclude that these species are engaged in

Accepted Answer

Resource partitioning occurs when species divide a niche to avoid competition for resources, as seen with the finches eating different sizes of seeds.

Question 4

Two similar rodent species are consistently more different from each other when they occupy the same habitat than when they live separately. What is the most likely explanation for the increased divergence when they live together?

Accepted Answer

Character displacement occurs when similar species that compete for the same resources evolve differences in traits to minimize competition when they coexist in the same habitat.

Question 5

Refer to the figure.
 The figure shows the relationship between the growth rates (on a log scale) of individual fish and the similarity of the fish to their competitors. Assuming that populations with faster growth rates are more likely to have greater population growth, which principle or concept does the figure support?

Accepted Answer

The answer of Refer to the figure.
 The figure shows...

Question 6

Character displacement is likely to _______ the competition coefficients in two competing species and to _______ resource partitioning.

Accepted Answer

The answer of Character displacement is likely to _______ the...

Question 7

Two species of Drosophila have been competing in the lab for a long time. A researcher notes that over the course of time, the competition coefficients of these species have become smaller. What is the most likely explanation of this change?

Accepted Answer

Character displacement occurs when species evolve differences to reduce competition, leading to smaller competition coefficients over time.

Question 8

A population of Drosophila melanogaster with 10,000 individuals and a carrying capacity of 20,000 follows the logistic growth equation. Suppose that 5,000 individuals of a competitor species, Drosophila simulans, are added to the population, and that this species has an α of 0.5. One would predict that this number of competitive individuals will decrease the D. melanogaster population growth rate by the same amount as the addition of _______ D. melanogaster individuals would.

Accepted Answer

The competitive effect of D. simulans on D. melanogaster is equivalent to adding 0.5 D. melanogaster individuals for each D. simulans individual. Therefore, 5,000 D. simulans individuals are equivalent to 0.5 * 5,000 = 2,500 D. melanogaster individuals.

Question 9

Two species of sparrows are competing, and these species behave according to the Lotka‒Volterra equations. If each individual sparrow reduces the population growth rate of its own species by 0.02 per year, and it reduces the population growth rate of the other species by 0.005 per year, then the competition coefficient is

Accepted Answer

The competition coefficient is calculated as the effect of one species on the other divided by the effect of the species on itself. Here, the effect of one species on the other is 0.005, and the effect on itself is 0.02. Thus, the competition coefficient is 0.005 / 0.02 = 0.25.

Question 10

Two species of flour beetles, Tribolium castaneum and Tribolium freemani, are competing according to the Lotka‒Volterra equations. If the α of T. freemani on T. castaneum is 1.5, the addition of 150 T. freemani individuals would depress the T. castaneum population growth rate by the same amount as the addition of _______ T. castaneum individuals would.

Accepted Answer

The competition coefficient α of 1.5 means that each individual of T. freemani has the same competitive effect as 1.5 individuals of T. castaneum. Therefore, 150 T. freemani individuals would have the same effect as 150 * 1.5 = 225 T. castaneum individuals.

Question 11

A population at the zero population growth isocline is

Accepted Answer

A population at the zero population growth isocline is stable in size because the birth rate equals the death rate, resulting in no net change in population size.

Question 12

The competition coefficient of one species towards itself is, by definition,

Accepted Answer

The competition coefficient of a species towards itself is +1, as it represents the effect of an individual on its own population, which is always equal to itself.

Question 13

A population of white oak trees with 500 individuals and a carrying capacity of 1,500 follows logistic growth. Under ideal low-density conditions, its growth rate is 0.15 per year, but it faces competition from a population of 1,000 Chapman oaks with an α of 0.5. What is the expected growth of the population of white oaks in the next year?

Accepted Answer

The logistic growth equation is used: dN/dt = rN(1 - (N + αC)/K). Here, N = 500, K = 1500, r = 0.15, α = 0.5, and C = 1000. Plugging in these values: dN/dt = 0.15 * 500 * (1 - (500 + 0.5*1000)/1500) = 0.15 * 500 * (1 - 1000/1500) = 0.15 * 500 * (1 - 0.6667) = 0.15 * 500 * 0.3333 = 25.

Question 14

By pitting two species of worms against each other at varying densities, researchers have determined that the zero growth isocline of species A is always above that of species B. This means that

Accepted Answer

The zero growth isocline of species A being above that of species B indicates that species A has a competitive advantage and will always exclude species B.

Question 15

Which statement about zero population growth isoclines of two competing species is true?

Accepted Answer

Species coexistence requires that the two isoclines cross, indicating that each species limits its own growth more than it limits the growth of the other species.

Question 16

Refer to the figure.
 Based on the figure, what is the expected outcome of the competition between species 1 and species 2?

Accepted Answer

The answer of Refer to the figure.
 Based on the...

Question 17

Dragonfly species A (with a carrying capacity of 1,000) and species B (with a carrying capacity of 400) are competing. The competition coefficient of species A on species B is 0.25, and the competition coefficient of species B on species A is 0.5. Dragonfly species C (with a carrying capacity of 5,000) and species D (with a carrying capacity of 10,000) are also competing. The competition coefficient of species C on species D is 0.1, and the competition coefficient of species D on species C is 0.2. Based on the Lotka‒Volterra equation, which of these pairs of species can coexist?

Accepted Answer

Both pairs of species can coexist because the competition coefficients are less than 1, indicating that interspecific competition is less intense than intraspecific competition, allowing for coexistence according to the Lotka-Volterra model.

Question 18

Based on the Lotka‒Volterra equations, which statement about carrying capacity and species coexistence is most likely true?

Accepted Answer

The answer of Based on the Lotka‒Volterra equations, which statement...

Question 19

There are two pairs of competing species of ferns. Species A and species B have carrying capacities of 10,000 and 6,000, respectively. The competition coefficient of species A on species B is 0.25 and the competition coefficient of species B on species A is 2.5. Species C and species D have carrying capacities of 8,000 and 14,000, respectively. The competition coefficient of species C on species D is 0.1 and the competition coefficient of species D on species C is 0.2. Based on the Lotka‒Volterra equation, which of these pairs of species can coexist?

Accepted Answer

Species C and D can coexist because the competition coefficients are less than 1, indicating that interspecific competition is less intense than intraspecific competition.

Question 20

Two species of ground crickets compete in the eastern United States. In colder areas, Allonemobius fasciatus outcompetes Allonemobius socius, but in warm areas, A. socius outcompetes A. fasciatus. This is an example of

Accepted Answer

This scenario is an example of a competitive reversal, where the competitive advantage between two species changes depending on environmental conditions, such as temperature.

Quiz 14: Competition