Question 1

Refer to the figure.
 The figure shows the RNE (relative neighbor effect) correlated to summer temperatures in alpine plants. Higher summer temperatures indicate communities at lower elevations, where plants are less stressed. The RNE is one measurement of the degree of mutualism in a community-the higher the RNE, the stronger the mutualistic interaction. Based on the data in this figure, which conclusion can be drawn about the importance of mutualism in this community?

Accepted Answer

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

Question 2

A bacterium provides essential amino acids to an aphid, which in turn provides sugars to the bacterium. Assuming that each partner is benefiting from the interaction, this would be an example of which type of mutualism?

Accepted Answer

This is an example of trophic mutualism, where each organism provides a nutritional benefit to the other.

Question 3

A fungus increases the ability of a plant to grow under high-salt conditions. For the plant, this association is which type of mutualism?

Accepted Answer

The answer of A fungus increases the ability of a...

Question 4

Because leaf-cutter ants and fungi help each other overcome plant defenses, the leaf-cutter ant-fungus mutualism can be described as which type of mutualism?

Accepted Answer

The answer of Because leaf-cutter ants and fungi help each...

Question 5

Which of these scenarios represents an example of habitat mutualism?

Accepted Answer

The answer of Which of these scenarios represents an example...

Question 6

Refer to the figure. 
 Medicago truncatula, or barrelclover, is a clover-like legume that has a mutualistic association with mycorrhizal fungi. In the experiment illustrated in the figure, fungi in contact with Medicago had access to either no phosphorus, or to either 35 or 700 ?M of phosphorus. According to the figure, how did Medicago alter the amount of carbohydrate it transferred to the fungi in response to the change in fungal phosphorus levels?

Accepted Answer

The answer of Refer to the figure. 
 Medicago truncatula,...

Question 7

In a plant-pollinator interaction, the plant expends energy to produce colors and scents that attract the pollinator. This energy is therefore not available to use in the plant's growth and reproduction. This interaction provides evidence in favor of which statement?

Accepted Answer

Mutualisms may impose costs on the partners, as seen in the energy expenditure by the plant to attract pollinators, which could otherwise be used for growth and reproduction.

Question 8

For an ecological interaction to be a mutualism, the net benefits must

Accepted Answer

In mutualism, both partners benefit from the interaction, meaning the benefits must outweigh the costs for both parties involved.

Question 9

From the act of pollinating flowers, a bee population gains the benefit of a 0.06 growth rate increase per month. However, the costs imposed by the flower (bees occasionally getting stuck, time spent pollinating the flower instead of pollinating other species, etc.) is a 0.02 reduction in growth rate per month. The flower gains benefits from the pollination that enhance its population growth rate by 0.05 per month, but it incurs costs (feeding the bees, damage done by the bees) that reduce its growth rate by 0.05 per month. In this situation, what is the best description of the relationship between the bees and the flowers?

Accepted Answer

The answer of From the act of pollinating flowers, a...

Question 10

The studies by Pellmyr and Huth on yuccas and yucca moths showed that

Accepted Answer

The studies by Pellmyr and Huth demonstrated that yucca plants can impose penalties on moths that lay too many eggs, such as aborting flowers, to maintain a balance in the mutualistic relationship.

Question 11

Yucca plants retain 62% of the flowers that contain up to six moth eggs, but only 11% of the flowers containing nine or more eggs. The yucca aborts these flowers before the moth eggs hatch. This process is only effective for reducing exploitation by moths if

Accepted Answer

The process of aborting flowers is effective in reducing exploitation by moths only if the moth larvae in an aborted flower all die, preventing them from maturing and exploiting the plant.

Question 12

An insect removes nectar from a flower without pollinating it. This is an example of

Accepted Answer

The insect is benefiting by taking nectar without providing the pollination service, which is considered cheating in mutualistic interactions.

Question 13

Refer to the figure.
 The fruit fly Drosophila neotestacea carries a bacterial symbiont; the fly can also be infected by a nematode worm. The figure shows the number of eggs produced by female flies that are or are not infected by the nematode and that have or do not have the bacterial symbiont.
- Assuming that the nematode benefits by being inside the fly, the fly?nematode relationship, when there is no bacterial symbiont, is best described as a(n)

Accepted Answer

In a host-parasite relationship, the parasite benefits at the expense of the host. Here, the nematode benefits by being inside the fly, indicating a parasitic relationship.

Question 14

Refer to the figure.
 The fruit fly Drosophila neotestacea carries a bacterial symbiont; the fly can also be infected by a nematode worm. The figure shows the number of eggs produced by female flies that are or are not infected by the nematode and that have or do not have the bacterial symbiont. 
-According to the figure, the bacterial symbiont

Accepted Answer

The bacterial symbiont increases the fecundity of female flies infected by the nematode, suggesting a beneficial role in counteracting the negative effects of the nematode infection.

Question 15

Acacia plants often have ants of the genus Pseudomymex associated with them. Removal of ant colonies from individuals of the bullhorn acacia species results in which change in the acacias?

Accepted Answer

The ants protect the acacia plants from herbivores and competitors, so removing them results in stunted growth due to increased damage and competition.

Question 16

When Daniel Janzen studied the ant-acacia system by removing ant colonies from some acacias, he found much lower growth rates in the acacia after ants were removed. Which other changes were seen in the responses of the acacia to ant removal?

Accepted Answer

The removal of ants led to lower survival rates and increased susceptibility to insect herbivores, as ants provide protection to the acacias.

Question 17

What characteristics are found in Pseudomyrmex ants that depend on acacias, compared to species of Pseudomyrmex that are not associated with acacias?

Accepted Answer

Pseudomyrmex ants that depend on acacias are more active and aggressive as they defend the acacia trees from herbivores and competing plants in exchange for food and shelter provided by the acacias.

Question 18

Refer to the figure.
 In the study by van der Heijden and colleagues comparing the effects of differing numbers of mycorrhizal species (0?-14) on the same 15 plant species, the shoot biomass of the target plants was found to

Accepted Answer

The answer of Refer to the figure.
 In the study...

Question 19

Which statement describes the most likely reason that a fish associated with a cleaner fish like Labroides dimidiatus does not eat the cleaner fish, even when the cleaner fish is in its mouth?

Accepted Answer

The mutualistic relationship provides a greater benefit to the fish by having parasites removed than the immediate gain from eating the cleaner fish.

Question 20

Grutter tested the effect of cleaner fish on species diversity in the Great Barrier Reef by

Accepted Answer

Grutter's experiment involved the removal of cleaner fish from certain reefs to observe the impact on species diversity, rather than adding them or manipulating other fish behaviors.

Quiz 15: Mutualism and Commensalism