Question 1

How is facultative mutualism different from the relationship known as commensalism?

Accepted Answer

Facultative mutualism and commensalism are both types of symbiotic relationships that occur between different species living in close physical proximity. However, they differ significantly in terms of the benefits received by the organisms involved.

Facultative Mutualism:
In a facultative mutualistic relationship, both species involved benefit from the interaction, but unlike obligate mutualism, the interaction is not essential for the survival of either species. Each species can survive without the other, but they generally do better together. The benefits received are not strictly necessary for the life cycle of either organism, but they do provide an advantage that can enhance growth, reproduction, or survival.

For example, certain species of cleaner fish remove and eat parasites from the skin of larger fish. The cleaner fish receive a meal, and the larger fish benefit from parasite removal. Both species can survive without the other, but they have a better chance of thriving when the mutualistic relationship is in place.

Commensalism:
In a commensal relationship, one species benefits while the other is neither helped nor harmed. The commensal species receives some sort of benefit, such as food, shelter, or support, while the host species does not receive any significant benefit or detriment from the interaction.

An example of commensalism is the relationship between barnacles and whales. Barnacles attach themselves to the skin of whales, which provides them with a means of transportation into nutrient-rich waters. The whale, on the other hand, is largely unaffected by the presence of the barnacles; it neither benefits nor suffers significantly from the barnacles being there.

In summary, the key difference between facultative mutualism and commensalism lies in the benefits received by the organisms involved. In facultative mutualism, both species benefit from the interaction but do not depend on it for survival, whereas in commensalism, only one species benefits while the other is unaffected.

Question 2

Yucca moths typically lay about six eggs in a yucca flower. If a biologist were to experimentally add 12 moth eggs to a yucca flower, what would be the most likely result?

Accepted Answer

A)  More seeds would be dispersed by yucca moths. 
B)  The yucca plant would selectively abort that flower. 
C)  The yucca plant would stop fixing nitrogen from the atmosphere. 
D)  The yucca plant would receive more protection from herbivores. 
A)  More seeds would be dispersed by yucca moths. 
B)  The yucca plant would selectively abort that flower. 
C)  The yucca plant would stop fixing nitrogen from the atmosphere. 
D)  The yucca plant would receive more protection from herbivores. B

Question 3

In the mutualism between ants and trillium flowers, if the trillium stopped producing the elaiosome on its seeds, the ants would probably

Accepted Answer

A)  discard the seeds near their nest. 
B)  not carry the seeds to their nest. 
C)  protect the seeds from herbivores. 
D)  pollinate the trillium flowers. 
A)  discard the seeds near their nest. 
B)  not carry the seeds to their nest. 
C)  protect the seeds from herbivores. 
D)  pollinate the trillium flowers. B

Question 4

Which of the following benefits do acacia plants obtain from mutualisms with ants?
I. Ants kill herbivorous insects.
II. Ants keep competitive plants from growing nearby.
III. Ants spread antibacterial compounds on the plant.

Accepted Answer

A)  I only 
B)  II only 
C)  III only 
D)  I and III only 
E)  I, II, and III 
A)  I only 
B)  II only 
C)  III only 
D)  I and III only 
E)  I, II, and III

Question 5

When two species provide fitness benefits to each other but do not require each other to persist, they are

Accepted Answer

A)  obligate mutualists. 
B)  facultative mutualists. 
C)  parasites. 
D)  predators and prey. 
A)  obligate mutualists. 
B)  facultative mutualists. 
C)  parasites. 
D)  predators and prey.

Question 6

A small forest herb does not normally develop nectaries. However, when herbivorous insects attack it, the herb develops nectaries that attract ants to the plant. Explain why this plant develops nectaries only when attacked by herbivorous insects.

Accepted Answer

The development of nectaries in the smal

Question 7

What benefit do Rhizobium bacteria provide to plants that plants cannot provide for themselves?

Accepted Answer

A)  a place to live 
B)  products of photosynthesis 
C)  conversion of atmospheric nitrogen to a form that plants can use 
D)  protection from herbivorous mammals 
A)  a place to live 
B)  products of photosynthesis 
C)  conversion of atmospheric nitrogen to a form that plants can use 
D)  protection from herbivorous mammals

Question 8

Several animal species have gone extinct on the islands of Mauritius. These extinct animals, including the dodo bird and tortoises, once ate the fruit of many plant species. As a result of the extinction of these animals,
I. the flowers of the plants can no longer be pollinated.
II. the parental plants are strongly competing with their offspring.
III. many plants are growing together in tight groups instead of being spread over the island.

Accepted Answer

A)  I only 
B)  II only 
C)  III only 
D)  I and III only 
E)  II and III only 
A)  I only 
B)  II only 
C)  III only 
D)  I and III only 
E)  II and III only

Question 9

Ants are often observed with aphids, small insects that feed on plants. The ants obtain nutritious nectar from the aphids. A biologist wants to test whether ants and aphids are mutualists. She removes ants from groups of aphids and compares them to controls. Which of the following outcomes is consistent with a mutualistic relationship between ants and aphids?

Accepted Answer

A)  Aphids consume more of the plant. 
B)  Plants with aphids produce fewer seeds. 
C)  More aphids are eaten by herbivores. 
D)  Fewer aphids are eaten by herbivores. 
A)  Aphids consume more of the plant. 
B)  Plants with aphids produce fewer seeds. 
C)  More aphids are eaten by herbivores. 
D)  Fewer aphids are eaten by herbivores.

Question 10

A shrub species lives in low-nutrient soil that contains mycorrhizal fungi. The plant provides sugars from photosynthesis to the fungi. The fungi provide the plants with nitrogen and phosphorus. If you add enough nitrogen and phosphorus fertilizer to the soil so that the plant can maximize its reproductive success without nutrients from the fungi, would you expect the mutualism to change? Why or why not?

Accepted Answer

Adding enough nitrogen and phosphorus fe

Question 11

Studies have shown that the herbaceous plant garlic mustard can impact forest growth of certain tree species. How does garlic mustard impact tree growth?

Accepted Answer

A)  by decreasing water uptake from the soil 
B)  by shading seedlings and saplings in the herbaceous layer 
C)  by preventing seed germination 
D)  by disrupting the colonization of mycorrhizal fungi in the soil 
A)  by decreasing water uptake from the soil 
B)  by shading seedlings and saplings in the herbaceous layer 
C)  by preventing seed germination 
D)  by disrupting the colonization of mycorrhizal fungi in the soil

Question 12

A plant may defend itself from herbivores through mutualism with fungi that produce chemicals that can repel insect herbivores. These fungi are called

Accepted Answer

A)  endophytic fungi. 
B)  arbuscular mycorrhizal fungi. 
C)  ectomycorrhizal fungi. 
D)  endomycorrhizal fungi. 
A)  endophytic fungi. 
B)  arbuscular mycorrhizal fungi. 
C)  ectomycorrhizal fungi. 
D)  endomycorrhizal fungi.

Question 13

The association between bees and flowering plants is a well-known mutualism. What benefit do flowers provide bees?

Accepted Answer

A)  Parasites are removed during the visits. 
B)  Bees are sheltered from predators in flowers. 
C)  Bees are fertilized by visiting flowers. 
D)  Bees obtain nutrients from the flowers. 
A)  Parasites are removed during the visits. 
B)  Bees are sheltered from predators in flowers. 
C)  Bees are fertilized by visiting flowers. 
D)  Bees obtain nutrients from the flowers.

Question 14

In the classic work of Dan Janzen and acacia trees, Janzen supported his contention that ants were critical to the survival and growth of acacia trees with a variety of data and observations. Which of the following was NOT evidence of Janzen's contention?

Accepted Answer

A)  Trees with ants had fewer herbaceous insects as compared to trees without ants. 
B)  Trees with ants tend to be heavier than trees without ants. 
C)  Trees with ants produced more flowers that lasted longer than trees without ants. 
D)  Trees with ants had higher comparative survival rates than trees without ants. 
A)  Trees with ants had fewer herbaceous insects as compared to trees without ants. 
B)  Trees with ants tend to be heavier than trees without ants. 
C)  Trees with ants produced more flowers that lasted longer than trees without ants. 
D)  Trees with ants had higher comparative survival rates than trees without ants.

Question 15

(Figure 17.15) This figure indicates that yucca plants

Accepted Answer

A)  select for moths that pollinate their flowers. 
B)  select for moths that lay fewer eggs per flower. 
C)  select for moths that lay many eggs per flower. 
D)  do not select for any moth trait. 
A)  select for moths that pollinate their flowers. 
B)  select for moths that lay fewer eggs per flower. 
C)  select for moths that lay many eggs per flower. 
D)  do not select for any moth trait.

Question 16

Of the following types of mutualisms, which would likely have the largest impact on other species if one member of the mutualism went extinct?

Accepted Answer

A)  generalist obligate 
B)  generalist facultative 
C)  specialist obligate 
D)  specialist facultative 
A)  generalist obligate 
B)  generalist facultative 
C)  specialist obligate 
D)  specialist facultative

Question 17

Ants have a mutualism with the forest herb trillium. A plant structure known as an elaiosome is part of this mutualism. What does the elaiosome do?

Accepted Answer

A)  fixes atmospheric nitrogen 
B)  contains toxins that kill herbivores 
C)  provides proteins and lipids for the ants to eat 
D)  provides shelter for ants to nest in 
A)  fixes atmospheric nitrogen 
B)  contains toxins that kill herbivores 
C)  provides proteins and lipids for the ants to eat 
D)  provides shelter for ants to nest in

Question 18

Imagine that an acacia tree in the ant-plant mutualism is introduced to an island without ants. Over evolutionary time, natural selection from the lack of ants would probably lead to acacia trees that produce

Accepted Answer

A)  more nectar. 
B)  less nectar. 
C)  larger seeds. 
D)  smaller seeds. 
A)  more nectar. 
B)  less nectar. 
C)  larger seeds. 
D)  smaller seeds.

Question 19

Under which circumstance do we tend to NOT see mutualism?

Accepted Answer

A)  between animal species only 
B)  between plant species only 
C)  between plants and fungi 
D)  between plants and bacteria 
A)  between animal species only 
B)  between plant species only 
C)  between plants and fungi 
D)  between plants and bacteria

Question 20

A biologist is studying three species of small fish (sp 1, sp 2, and sp 3) that cling to the bodies of bigger fish and consume parasites on the larger fish. He conducts an experiment with three treatments. In each treatment, he removes a different one of the small fish species from a large fish and examines the number offspring produced by the large fish. Which of the following conclusions are supported by the data shown in the figure?

Accepted Answer

A)  Species 1 is a mutualist. 
B)  Species 2 is a mutualist. 
C)  Species 3 is a mutualist. 
D)  Species 1 and 2 are mutualists. 
E)  Species 2 and 3 are mutualists. 
A)  Species 1 is a mutualist. 
B)  Species 2 is a mutualist. 
C)  Species 3 is a mutualist. 
D)  Species 1 and 2 are mutualists. 
E)  Species 2 and 3 are mutualists.

How is facultative mutualism different from the relationship known as commensalism?

Yucca moths typically lay about six eggs in a yucca flower. If a biologist were to experimentally add 12 moth eggs to a yucca flower, what would be the most likely result?

In the mutualism between ants and trillium flowers, if the trillium stopped producing the elaiosome on its seeds, the ants would probably

Which of the following benefits do acacia plants obtain from mutualisms with ants? I. Ants kill herbivorous insects. II. Ants keep competitive plants from growing nearby. III. Ants spread antibacterial compounds on the plant.

When two species provide fitness benefits to each other but do not require each other to persist, they are

A small forest herb does not normally develop nectaries. However, when herbivorous insects attack it, the herb develops nectaries that attract ants to the plant. Explain why this plant develops nectaries only when attacked by herbivorous insects.

What benefit do Rhizobium bacteria provide to plants that plants cannot provide for themselves?

Studies have shown that the herbaceous plant garlic mustard can impact forest growth of certain tree species. How does garlic mustard impact tree growth?

A plant may defend itself from herbivores through mutualism with fungi that produce chemicals that can repel insect herbivores. These fungi are called

The association between bees and flowering plants is a well-known mutualism. What benefit do flowers provide bees?

In the classic work of Dan Janzen and acacia trees, Janzen supported his contention that ants were critical to the survival and growth of acacia trees with a variety of data and observations. Which of the following was NOT evidence of Janzen's contention?

(Figure 17.15) This figure indicates that yucca plants

Of the following types of mutualisms, which would likely have the largest impact on other species if one member of the mutualism went extinct?

Ants have a mutualism with the forest herb trillium. A plant structure known as an elaiosome is part of this mutualism. What does the elaiosome do?

Imagine that an acacia tree in the ant-plant mutualism is introduced to an island without ants. Over evolutionary time, natural selection from the lack of ants would probably lead to acacia trees that produce

Under which circumstance do we tend to NOT see mutualism?

Introduction: Ecology, Evolution, and the Scientific Method

Adaptations to Aquatic Environments

Adaptations to Terrestrial Environments

Adaptations to Variable Environments

Climates and Soils

Terrestrial and Aquatic Biomes

Evolution and Adaptation

Life Histories

Reproductive Strategies

Social Behaviors

Population Distributions

Population Growth and Regulation

Population Dynamics Over Space and Time

Predation and Herbivory

Parasitism and Infectious Diseases

Competition

Community Structure

Community Succession

Movement of Energy in Ecosystems

Movement of Elements in Ecosystems

Landscape Ecology and Global Biodiversity

Global Conservation of Biodiversity

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Exam 17: Mutualism

How is facultative mutualism different from the relationship known as commensalism?

Yucca moths typically lay about six eggs in a yucca flower. If a biologist were to experimentally add 12 moth eggs to a yucca flower, what would be the most likely result?

In the mutualism between ants and trillium flowers, if the trillium stopped producing the elaiosome on its seeds, the ants would probably

Which of the following benefits do acacia plants obtain from mutualisms with ants? I. Ants kill herbivorous insects. II. Ants keep competitive plants from growing nearby. III. Ants spread antibacterial compounds on the plant.

When two species provide fitness benefits to each other but do not require each other to persist, they are

A small forest herb does not normally develop nectaries. However, when herbivorous insects attack it, the herb develops nectaries that attract ants to the plant. Explain why this plant develops nectaries only when attacked by herbivorous insects.

What benefit do Rhizobium bacteria provide to plants that plants cannot provide for themselves?

Studies have shown that the herbaceous plant garlic mustard can impact forest growth of certain tree species. How does garlic mustard impact tree growth?

A plant may defend itself from herbivores through mutualism with fungi that produce chemicals that can repel insect herbivores. These fungi are called

The association between bees and flowering plants is a well-known mutualism. What benefit do flowers provide bees?

In the classic work of Dan Janzen and acacia trees, Janzen supported his contention that ants were critical to the survival and growth of acacia trees with a variety of data and observations. Which of the following was NOT evidence of Janzen's contention?

(Figure 17.15) This figure indicates that yucca plants

Of the following types of mutualisms, which would likely have the largest impact on other species if one member of the mutualism went extinct?

Ants have a mutualism with the forest herb trillium. A plant structure known as an elaiosome is part of this mutualism. What does the elaiosome do?

Imagine that an acacia tree in the ant-plant mutualism is introduced to an island without ants. Over evolutionary time, natural selection from the lack of ants would probably lead to acacia trees that produce

Under which circumstance do we tend to NOT see mutualism?

Introduction: Ecology, Evolution, and the Scientific Method

Adaptations to Aquatic Environments

Adaptations to Terrestrial Environments

Adaptations to Variable Environments

Climates and Soils

Terrestrial and Aquatic Biomes

Evolution and Adaptation

Life Histories

Reproductive Strategies

Social Behaviors

Population Distributions

Population Growth and Regulation

Population Dynamics Over Space and Time

Predation and Herbivory

Parasitism and Infectious Diseases

Competition

Community Structure

Community Succession

Movement of Energy in Ecosystems

Movement of Elements in Ecosystems

Landscape Ecology and Global Biodiversity

Global Conservation of Biodiversity

Filters