Exam 15: Mutualism and Commensalism

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

Refer to the table. The table contains data on the effects of symbiosis between a fly (host) and a fungus over many years. It shows the upper and lower bounds for the effects of the association; positive numbers denote net benefits and negative numbers denote net costs. (If zero is between the upper and lower bounds, consider the effect to be zero, since it is statistically indistinguishable from zero.) -According to the table, the relationship between the fungus and the fly in 1996 was a

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?

Based on Grutter's studies, we can conclude that the presence of cleaner fish

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

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?

In comparing agriculture practiced by humans and by leaf-cutter ants, which of these statements is the least correct?

A bird species nests in a specific kind of tree. The tree is not harmed by the bird building its nest in the tree's branches, but the bird benefits from the shelter provided by the tree and is better able to successfully raise young. This is an example of

Suppose a fish species lives in an environment where both food and safe living space are hard to find. How would the development of mutualistic associations benefit this fish species? Would trophic or habitat mutualisms, or both, be most beneficial? Can you think of situations in nature where such associations occur?

Refer to the figure. What is the best description of the relationship identified by van der Heijden et al. between the average shoot biomass of the target plants and the number of mycorrhizal fungal species associated with them?

A bear accidentally carries the seeds of a weedy plant in its fur. Transporting the seeds neither helps nor harms the bear, but is beneficial to the plant. This is an example of a(n)

Which species has been documented as imposing penalties on individuals of its mutualistic partner that are engaged in overexploitation?

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

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

Many people think leaf-cutter ant colonies provide a large benefit to rainforest ecosystems. Which of these statements does not provide evidence to support this assumption?

Would positive associations be expected to change ecosystem processes in any way, other than effects on species diversity? For example, could mutualisms or commensalisms affect nutrient cycling, photosynthesis, or other key processes? If so, explain how this might happen, with examples.

In Daniel Janzen's study of the ant-acacia association, which question was Janzen attempting to answer?

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?

Which of these scenarios represents an example of habitat mutualism?

All other factors being equal, which scenario is least likely to involve coevolution?