Deck 17: Mutualism

Question 1

(Figure 17.9) Two species of ant that live on acacia are Pseudomyrmex ferruginea and P. gracilis. The figure shows how the presence or absence of each species of ant affects the abundance of pathogenic bacteria on acacia leaves. What conclusion can you draw from this figure?

A) Neither ant is mutualistic with acacia.
B) Only P. ferruginea is mutualistic with acacia.
C) Only P. gracilis is mutualistic with acacia.
D) Both ant species are mutualistic with acacia.

Answer 1

B

Question 2

Which of the following three interactions are mutualisms? I: Wasp and butterfly larvae. The wasp lays its eggs inside the body of a butterfly larva. The eggs hatch and the wasp larvae feed on the body of the butterfly larva. By the time the wasp larvae metamorphose from the butterfly larva, the butterfly larva is killed.
II: Fig and fig wasp: The adult wasps crawl into the cluster of fig flowers to lay eggs. By moving around, the adult wasp pollinates the fig flowers, allowing them to produce fruit and seeds. As the fig fruit develops, it provides shelter for the wasp larvae.
III: Ants and acacias: Acacia plants develop hollow thorns that provide shelter for ant colonies and produce nectaries on their leaves that provide food for ants. The ants defend the acacia plant from herbivores.

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

Answer 2

E

Question 3

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

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

Answer 3

C

Question 4

Cattle egrets are birds that often follow herds of mammals. As the mammals walk through vegetation, insects fly into the air, where the egrets catch them. Is the relationship between cattle egrets and mammals a mutualism? Explain your answer.

Question 5

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

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

Question 6

Which of the following are specialists that form a mutualism?
I) Honeybees pollinate many species of flower.
II) The crayfish snake eats only crayfish.
III) The yucca plant is pollinated by a single species of moth.

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

Question 7

Which of the following are benefits that many mutualists provide one another?
I) shelter
II) protection from predators
III) nutrients

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

Question 8

A mutualist that interacts with many other species is a

A) generalist.
B) specialist.
C) mutualist.
D) parasite.

Question 9

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?

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.

Question 10

A specialist is a mutualist that

A) interacts with many other species.
B) interacts with one of a few closely related species.
C) provides fitness benefits to another species.
D) receives fitness benefits from another species.

Question 11

What benefit do Pseudomyrmex ants obtain from their mutualism with acacia trees?
I) shelter in hollow thorns
II) food from nectaries
III) nitrogen from atmospheric sources

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

Question 12

If oxpecker birds went extinct, what would be the most likely consequence?

A) Acacia plants would no longer be protected by ants.
B) Plants would no longer be able to fix atmospheric nitrogen.
C) Large African mammals would have more parasites.
D) Large African mammals would have fewer parasites.

Question 13

Coral and zooxanthellae algae have a mutualism in which coral provide shelter for algae. What do algae provide for coral?

A) reduced fitness
B) protection from enemies
C) water
D) nutrients

Question 14

If you removed mutualistic ants from acacia trees, there would be

A) fewer herbivorous insects on the acacia.
B) more herbivorous insects on the acacia.
C) less atmospheric nitrogen available to acacia.
D) more atmospheric nitrogen available to acacia.

Question 15

Endophytic fungi

A) live within a plant's tissue.
B) provide shelter to ants.
C) fix atmospheric nitrogen.
D) are removed from mammals by oxpecker birds.

Question 16

What condition of large mammals do oxpecker birds seek out?

A) thin skin
B) thick skin
C) many parasites
D) few parasites

Question 17

Consider a species of fig tree that is pollinated by a single species of wasp. Without the wasp, the fig tree will not produce seeds. Without the fig tree, the wasp will not produce offspring. The relationship between these species is an example of

A) parasitism.
B) obligate mutualism.
C) facultative mutualism.
D) negative interaction.

Question 18

A gardener grows pea plants in two pots. One pot has a low amount of ammonia in the soil, while the other pot has normal levels of ammonia. Which group of pea plants would benefit the most from the addition of Rhizobium bacteria to the soil? Explain your answer.

Question 19

Which of the following statements about the hyphae of ectomycorrhizal fungi are correct?
I) They provide plants with minerals and water from the soil.
II) They obtain sugars that plants produce by photosynthesis.
III) They grow between root cells.

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

Question 20

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.

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

Question 21

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

A) Bees spread pollen from one flower to the next.
B) Bees lay eggs on the flowers.
C) Bees disperse the plant's seeds.
D) Bees allow plants to fix nitrogen.

Question 22

Whitebark pine seeds are dispersed through a mutualism with Clark's nutcracker birds. If Clark's nutcracker went extinct, what is the most likely immediate outcome for pines?

A) increased competition between seedlings and parents
B) increased photosynthesis by pines
C) reduced pollination of pines
D) reduced benefits from mycorrhizal fungi

Question 23

Which of the following situations is/are likely to cause a mutualistic relationship to change to a parasitic or predatory relationship?
I) A damselfish has no parasites for a cleaner fish to eat.
II) Acacia plants provide nectar to ants living in their thorns.
III) A plant and its mycorrhizal fungi are living in nutrient-rich soil.

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

Question 24

Which of the plots would be consistent with cleaner fish switching from a mutualistic to a parasitic relationship with damselfish when the cleaner fish does not obtain fitness benefits?

A) panel a
B) panel b
C) panel c
D) panel d

Question 25

In the interaction between yucca plants and yucca moths, yucca moths pollinate flowers and lay eggs in the flowers. If many eggs are laid in a flower, the yucca moth caterpillar will eat all the seeds. Explain why the relationship is considered a mutualism, even though the caterpillars eat the seeds. Be sure to discuss how both the yucca and yucca moth gain fitness benefits from this interaction.

Question 26

Oxpeckers are African birds that fly around large mammals and pick at both ticks and wounds on the animals. Scientists have debated whether oxpeckers are parasites or mutualists with large mammals. Draw bar graphs in the blank figures to show the relationships if oxpeckers are mutualists with large mammals. Plot a should show the abundance of ticks on large mammals in two conditions: if oxpeckers are present and if oxpeckers are absent. Plot b should show the number of offspring produced by oxpeckers if they are nesting near mammals with many ticks or nesting near mammals with few ticks. Explain why your drawings are consistent with mutualism.

Question 27

Many animals disperse seeds away from parent plants. What benefits do animals gain from this mutualism? Give a specific example.

Question 28

What benefit do mammals and birds provide to a plant when they eat its fruit?

A) They disperse the seeds in the fruit to new areas.
B) They allow the seeds to fix atmospheric nitrogen.
C) They provide the seeds with defense against herbivores.
D) They provide seeds with sugars produced by photosynthesis.

Question 29

The seeds of plants are moved to new areas by many animals, including birds, mammals, and insects. What benefit do animals gain from the plant in this mutualism?

A) defense against predators
B) food
C) shelter from the elements
D) removal of parasites

Question 30

You are studying a plant species that has a fungus growing in its roots. You remove the fungus and evaluate what happens to the plant. Which outcome indicates a mutualistic relationship?

A) The plant becomes toxic to herbivores.
B) There is no change in the toxicity of the plant.
C) The plant becomes less toxic to herbivores.
D) The plant can acquire atmospheric nitrogen.

Question 31

A group of biologists are studying an interaction between coral and three species of crab (crab 1, crab 2, and crab 3). They discover that all three species of crab benefit from the coral by feeding on lipid-rich coral mucus. They conduct an experiment in which they remove each species of crab from the coral and then measure the extent to which the coral were overgrown by noxious algae. Based on the data in the figure, explain whether or not each of the three crab species is a mutualist with coral.

Question 32

The yucca moth

A) provides shelter to the yucca plant.
B) protects the yucca flowers from herbivores.
C) improves yucca photosynthesis.
D) pollinates yucca flowers.

Question 33

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?

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.

Question 34

In the interaction between damselfish and cleaner fish, if a damselfish has few parasites, the cleaner fish will

A) add parasites.
B) ignore the damselfish.
C) feed on parts of the damselfish.
D) not change its behavior toward the damselfish.

Question 35

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

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 36

(Figure 17.15) This figure indicates that yucca plants

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 37

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

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

Question 38

Which of the following statements about the mutualism between the yucca plant and the yucca moth is/are accurate?
I) This is an obligate mutualism.
II) Yucca moth caterpillars eat yucca seeds.
III) Yucca moths pollinate yucca flowers.

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

Question 39

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?

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 40

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?

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 41

When two species have evolved a mutualistic relationship, if one species begins to provide less of a benefit, we predict that the other species will

A) evolve to provide more of a benefit.
B) not change the benefit it provides.
C) evolve to provide less of a benefit.
D) increase its population size.

Question 42

Garlic mustard is a plant that has been introduced to North America. It produces a chemical that kills mycorrhizal fungi in the forest where it grows. How would killing mycorrhizal fungi affect native trees in the forest?

A) Tree seeds will not be dispersed.
B) Tree flowers will not be pollinated.
C) Trees will be more vulnerable to herbivores.
D) Tree growth will be reduced.

Question 43

Consider a simple food web consisting of plants, aphids, ants, and ladybird beetles. Aphids are herbivores that consume the plants, and ladybird beetles are a predator that eats aphids. The ants obtain nutritious honeydew from the aphids, and in return the ants protect the aphids from predatory insects. What is likely to happen to the ladybird beetles, aphids, and plants if the ants go extinct?

Question 44

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?

Question 45

Ants are often associated with aphids, small insects that feed on plants. The ants obtain nutritious honeydew from the aphids, and in return the ants protect the aphids from predatory insects. If the mutualism between aphids and ants broke down such that the ants no longer protected the aphids,

A) aphids would produce more honeydew.
B) aphids would have higher fitness.
C) plants would be damaged more by the aphids.
D) plants would be damaged less by the aphids.

Question 46

Why is the relationship between termites and the gut protozoans considered mutualism?

A) Protozoans fix nitrogen from the atmosphere for the termites to use.
B) Termites defecate into holes in wood and the protozoans in the fecal material are provided a safe area to live.
C) Protozoans are able to photosynthesize, providing energy to termites.
D) Protozoans are able to break down the lignin and cellulose that compose wood.

Question 47

If Rhizobium bacteria were to go extinct, plants would

A) not be able to obtain atmospheric nitrogen.
B) be more damaged by herbivory.
C) not be able to obtain energy from photosynthesis.
D) not be able to survive drought.

Question 48

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

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.

Question 49

If yucca plants did not selectively abort flowers with many yucca moth eggs, over several generations the frequency of moths that lay many eggs will likely

A) increase.
B) not change.
C) decrease.
D) fluctuate.

Question 50

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

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

Question 51

(Figure 17.22) Researchers manipulated the number of species of mycorrhizal fungi living in the soil and measured the effects on plant biomass and phosphorus uptake. Their results are shown in the figure. Based on their results, the most likely way the extinction of mycorrhizal fungi species would affect the ecosystem is to

A) reduce plant growth.
B) increase plant growth.
C) reduce plant extinction.
D) increase plant extinction.

Question 52

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.

Question 53

Under which circumstance do we tend to NOT see mutualism?

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

Question 54

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.

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

Question 55

(Figure 17.20) Researchers experimentally removed cleaner fish from some coral reef communities and left cleaner fish present in other communities. Their results are shown in the figure. Based on these results, extinction of cleaner fish would result in _____ fish species, and each species would be _____ abundant.

A) fewer; more
B) more; more
C) fewer; less
D) more; less

Question 56

If cleaner fish went extinct, damselfish would

A) become more abundant.
B) carry more parasites.
C) be less susceptible to predators.
D) be healthier.

Question 57

(Figure 17.18) A group of researchers grew plants so that half of their roots were in soil with a fungus that provides benefits to the plants and the other half were in soil with a fungus that did not provide benefits to the plants. After 9 weeks of growth, they provided the plants with carbon dioxide containing a rare isotope of carbon. For four days, they evaluated how much of the carbon went to the beneficial fungus and how much of the carbon went to the nonbeneficial fungus. Some of their results are presented in the figure. Which statement(s) about this experiment is/are CORRECT?
I) At the experiment's start, the nonbeneficial fungus was taking resources from the plant.
II) After 4 days, the plant provided more resources to the beneficial fungus.
III) This is an example of how species can prevent cheating in mutualisms.

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

Question 58

Which would be a reason to use a Mann-Whitney rank sum test rather than a t-test to compare two groups?

A) You are measuring fish.
B) Your data are normally distributed.
C) Your data are not normally distributed.
D) Your data can be arranged in ranks.

Question 59

Biologists have recently introduced wild turkeys and Aldabra tortoises to the islands of Mauritius. How have these introductions affected native plants of Mauritius?

A) Plants are now growing more closely together.
B) Plants are being damaged by herbivory from turkeys and tortoises.
C) The seeds have better rates of germination.
D) Plant diseases have become more common.

Question 60

In Palmer's experimental manipulation of large herbivore abundance on acacia trees, he found that exclusion of large herbivores often caused the ant species Crematogaster mimosa to abandon acacia trees and the ant species C. sjostedti to move into acacia trees. What were the effects of the shift from C. mimosa to C. sjostedti on the acacia trees?

Question 61

Some mutualists are said to be generalists, while other mutualists are said to be specialists. Discuss the advantages and disadvantages of being a generalist versus a specialist.

Question 62

The difference between ectomycorrhizal fungi and endomycorrhizal fungi has to do with

A) whether the fungal hyphae are connected to the plant above ground or below ground.
B) whether the fungal hyphae of the fungi penetrate the root cells of the plants involved.
C) whether the fungal hyphae provide the plant with minerals or sugars.
D) whether the fungal hyphae are specific to a single plant or generalized to many plants.

Question 63

Describe why the relationship between the pitcher plant (Nepenthes lowii) on the island of Borneo and the mountain tree shrew is considered to be an example of mutualism.

Question 64

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

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

Question 65

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) 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 66

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

Question 67

Plants like beans, peas, and alfalfa (legumes) form a mutualistic relationship with

A) fungi.
B) bacteria.
C) ants.
D) protozoans.

Question 68

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?

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.