Question 1

What is the Shannon index value for an area in which only a single species is present?
A) 0
B) 1
C) ‒1
D) Infinity

Accepted Answer

The Shannon index measures species diversity. If only one species is present, there is no diversity, resulting in a Shannon index value of 0.

Question 2

Four species of fish in a pond are found in equal abundance. The Shannon index of the fish community is therefore
A) -1 [4 (ln 4)].
B) -4 [0.25 (ln 0.25)].
C) -0.25 [0.25 (ln 4)].
D) -0.25 (ln 0.25).

Accepted Answer

The answer of Four species of fish in a pond...

Question 3

Suppose you wanted to determine whether you had adequately sampled the species richness of a given community. Which result would lead most strongly to the conclusion that the current sampling had adequately assessed the species diversity?
A) A high Shannon index value
B) A low Shannon index value
C) A linear species accumulation curve
D) A species accumulation curve that leveled off

Accepted Answer

A species accumulation curve that levels off indicates that additional sampling is not discovering new species, suggesting that the sampling has adequately captured the species richness of the community.

Question 4

In the study by Jennifer Hughes and colleagues, in which community did it appear that the species richness had been adequately sampled?
A) A plant community from a forest in Michigan
B) East Amazonian soil bacteria
C) Human oral bacteria
D) Costa Rican moths

Accepted Answer

The study by Jennifer Hughes and colleagues found that the species richness in a plant community from a forest in Michigan had been adequately sampled, indicating that the sampling effort was sufficient to capture the diversity present in that community.

Question 5

Which statement describes a limitation of a species accumulation curve in terms of its ability to determine whether species diversity has been adequately sampled?
A) It can be used only for a community of large spatial scale.
B) It can be used only for a community of small spatial scale.
C) It assumes that the sampling methods are consistent throughout the study.
D) It assumes a high Shannon index.

Accepted Answer

Species accumulation curves assume that the sampling methods are consistent throughout the study to accurately reflect the increase in species observed with additional sampling effort.

Question 6

Which of the following example emphasizes the importance of species composition?
A) Knowing that there are seven tree species in a particular forest
B) Determining that a particular forest is dominated by one or two species
C) Understanding the influence of the loss of a species of trees on a particular forest
D) Measuring the total abundance of all tree species in a forest

Accepted Answer

Understanding the influence of the loss of a species of trees on a particular forest emphasizes the importance of species composition, as it highlights how the presence or absence of specific species can impact the ecosystem.

Question 7

Cougars prey on both white-tailed deer and mule deer. Because of their shared predator, each deer's species abundance is affected by the presence of the other deer species. The white-tailed and mule deer are engaged in a(n)
A) direct interaction.
B) indirect interaction.
C) trophic facilitation.
D) predator-prey relationship.

Accepted Answer

The interaction between the two deer species is indirect because the presence of one species affects the abundance of the other through their shared predator, the cougar.

Question 8

Cougars prey on both white-tailed deer and mule deer. Because of their shared predator, each deer's species abundance is affected by the presence of the other deer species. The cougar and the mule deer are engaged in a(n)
A) direct interaction.
B) indirect interaction.
C) trophic facilitation.
D) trophic cascade.

Accepted Answer

The answer of Cougars prey on both white-tailed deer and...

Question 9

Refer to the figure.
 
-Research has suggested that in some cases, killer whales (Orcinus orca) have increased their predation on sea otters. This would have a(n) _______ effect on kelp.
A) direct positive
B) direct negative
C) indirect positive
D) indirect negative

Accepted Answer

Killer whales prey on sea otters, which in turn prey on sea urchins. Sea urchins graze on kelp, so a decrease in sea otters would lead to an increase in sea urchins, which would in turn lead to a decrease in kelp.

Question 10

Refer to the figure.

- If another predator were to begin competing with sea otters for the urchins, they would have a(n) _______ effect on otters and a(n) _______ effect on urchins.
A) direct negative; direct positive
B) direct negative; direct negative
C) direct negative; indirect negative
D) direct positive; direct negative

Accepted Answer

The answer of Refer to the figure.

- If another predator...

Question 11

Refer to the figure.
 Considering the figure, which of the following scenarios would be best described as trophic facilitation?
A) A wolf feeding on deer assists aspen trees in regeneration
B) Ravens, eagles, and vultures consuming an elk carcass left behind by the wolves that made the kill
C) Two species of squirrel each consuming the same type of nut, resulting in reduced numbers of germinating seeds
D) Three species of birds that directly compete with each other for similar resources, with no one species dominating any other

Accepted Answer

The answer of Refer to the figure.
 Considering the figure,...

Question 12

The presence of a mutualist spider in a certain area improves the survival of an herbaceous shrub by reducing the impact of herbivorous insects. These spiders are preyed on by lizards, and lizards are eaten by birds. The removal of birds from the area would most likely have a(n) _______ effect on spiders and a(n) _______ effect on the plant.
A) indirect positive; indirect positive
B) indirect negative; indirect positive
C) direct negative; direct negative
D) indirect negative; indirect negative

Accepted Answer

The answer of The presence of a mutualist spider in...

Question 13

In their studies of a salt marsh community, Sally Hacker and colleagues found that removing _______ led to a(n) _______.
A) Juncus; increase in the abundance of Iva
B) Iva; increase in the abundance of Juncus
C) Juncus; increase in the abundance of aphids through indirect effects
D) Juncus; decrease in the abundance of aphids through indirect effects

Accepted Answer

The answer of In their studies of a salt marsh...

Question 14

Which statement about the difference between a competitive network and a competitive hierarchy is true?
A) A competitive network comprises more species than interaction networks.
B) In a competitive hierarchy, one species dominates the interaction; in an interaction network, no one species dominates the interaction.
C) The interactions are stronger in a competitive network than in interaction networks.
D) In a competitive hierarchy, indirect species interactions always buffer strong competition; in interaction networks, they do not.

Accepted Answer

In a competitive hierarchy, one species tends to dominate the interactions, whereas in a competitive network, interactions are more evenly distributed among species, preventing any single species from dominating.

Question 15

Which conclusion was the primary finding of Buss and Jackson's study of coral-associated invertebrates and algae in Jamaica?
A) Competitive networks can be circular.
B) Environmental context can change the outcome of species interactions.
C) Diversity is maintained due to the existence of keystone species.
D) Species diversity estimates vary with sampling effort.

Accepted Answer

Buss and Jackson's study primarily found that competitive networks among coral-associated invertebrates and algae can be circular, meaning that no single species is dominant over all others, allowing for coexistence and maintaining diversity.

Question 16

Menge and colleagues performed experiments in which they exposed some populations of mussels to sea stars and excluded sea stars from other mussel populations. Suppose two populations of mussels are the same size prior to treatment, and after treatment there are 600 mussels in the treatment without sea stars and 200 mussels in the treatment with sea stars. Suppose further that the sea star population consists of 10 individuals. What is the per capita interaction strength of sea stars on mussels?
A) ln (3/10)
B) (ln 600)/(ln 200)
C) ln (0.33/10)
D) ln (0.33/200)

Accepted Answer

The answer of Menge and colleagues performed experiments in which...

Question 17

Suppose two populations of Anolis lizards are of equal size at the beginning of an experiment. One population (the experimental group) is exposed to a predator (16 predatory lizards), and the other (the control) is not. The final size of the experimental population is 50, and the final size of the control population is 200. What is the per capita interaction strength of predatory lizards on Anolis lizards?
A) ln (4/16)
B) ln (4/50)
C) ln (16/4)
D) ln (16/50)

Accepted Answer

The per capita interaction strength is calculated as the natural log of the ratio of the final population sizes of the control and experimental groups divided by the number of predators: ln(200/50) / 16 = ln(4/16).

Question 18

When wolves were returned to Yellowstone National Park in 1995, some of the effects noted were increasing levels of berries available to black bears, stabilization of stream banks, increased nesting habitat for birds, and increasing beaver numbers as a result of rejuvenating aspen trees. These were later determined to be the results of reduced numbers and altered feeding behavior of elk as they were preyed upon by the wolves. Given this information, which of the following best describes wolves in Yellowstone National Park?
A) They are a primary consumer.
B) They are an ecosystem engineer.
C) They are a foundation species.
D) They are a keystone species.

Accepted Answer

Wolves are considered a keystone species because their presence and predation on elk led to significant changes in the ecosystem, affecting various other species and ecological processes.

Question 19

Refer to the figure.

- Where would a keystone species most likely be located in the figure?
A) Position A
B) Position B
C) Position D
D) Position E

Accepted Answer

A keystone species is a species that has a disproportionately large effect on its ecosystem relative to its abundance. In the figure, the keystone species is most likely to be located at position A, which is the top of the food chain. This is because the species at position A has the greatest impact on the ecosystem, as it is the predator that controls the populations of the other species.

Question 20

Refer to the figure.

- Where would a foundation species most likely be located in the figure?
A) Position A
B) Position B
C) Position C
D) Position D

Accepted Answer

The answer of Refer to the figure.

- Where would a...

Quiz 16: The Nature of Communities

What is the Shannon index value for an area in which only a single species is present?

Four species of fish in a pond are found in equal abundance. The Shannon index of the fish community is therefore

Suppose you wanted to determine whether you had adequately sampled the species richness of a given community. Which result would lead most strongly to the conclusion that the current sampling had adequately assessed the species diversity?

In the study by Jennifer Hughes and colleagues, in which community did it appear that the species richness had been adequately sampled?

Which statement describes a limitation of a species accumulation curve in terms of its ability to determine whether species diversity has been adequately sampled?

Which of the following example emphasizes the importance of species composition?

Cougars prey on both white-tailed deer and mule deer. Because of their shared predator, each deer's species abundance is affected by the presence of the other deer species. The white-tailed and mule deer are engaged in a(n)

Cougars prey on both white-tailed deer and mule deer. Because of their shared predator, each deer's species abundance is affected by the presence of the other deer species. The cougar and the mule deer are engaged in a(n)

Refer to the figure. -Research has suggested that in some cases, killer whales (Orcinus orca) have increased their predation on sea otters. This would have a(n) _______ effect on kelp.

Refer to the figure. - If another predator were to begin competing with sea otters for the urchins, they would have a(n) _ effect on otters and a(n) _ effect on urchins.

Refer to the figure. Considering the figure, which of the following scenarios would be best described as trophic facilitation?

In their studies of a salt marsh community, Sally Hacker and colleagues found that removing _ led to a(n) _.

Which statement about the difference between a competitive network and a competitive hierarchy is true?

Which conclusion was the primary finding of Buss and Jackson's study of coral-associated invertebrates and algae in Jamaica?

Refer to the figure. - Where would a keystone species most likely be located in the figure?

Refer to the figure. - Where would a foundation species most likely be located in the figure?