Exam 15: Mutualism and Commensalism

In desert environments, many larger plants serve as "nurse" plants for smaller species that grow beneath them and benefit from their shade. Which characteristic of this association suggests that coevolution is not a major factor?

Algae called zooxanthellae live in the tissues of corals. Their photosynthesis provides organic compounds that the corals use as food and the corals provide the algae with a safe place to live and with nutrients to use in photosynthesis. This relationship is best described as

Refer to the figure. In Grutter's studies in the Great Barrier Reef off of Australia, he measured the number of fish species and the number of individual fish on the parts of the reef where cleaner fish were present (controls) and where cleaner fish had been removed (experimental). Based on the figures, what is the best conclusion that can be drawn regarding the effects of cleaner fish on reef fish abundance and diversity?

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?

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)

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?

Refer to the figure. Leaf-cutter ant colonies, which farm fungi for food, are often infested with a specialized parasitic fungus called Escovopsis. Under normal conditions, the ants periodically "weed" their fungal gardens, removing unwanted materials and organisms. The figure illustrates results of an experiment showing what happens to weeding behavior when the ant colony is exposed to water, to Trichoderma (a generalist fungal parasite), and to Escovopsis. What does this figure suggest about the mutualism between leaf-cutter ants and the fungi they farm?

Refer to the table. The table contains data on the effects of a symbiosis between a bee (host) and a bacterium over many years. The table 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 1988 was a

In one interaction, a bird feeds on the seeds of a specific plant. Some of the seeds are digested, while others pass unharmed through its digestive tract and are deposited in new locations. In a second interaction, a bird digests all of the seeds from the plant and therefore, none of the seeds are dispersed. The plant is not damaged because the number of seeds eaten is relatively small. Which term best describes both of these interactions?

A wasp pollinating a plant in exchange for food is an example of

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 1990 was a

Leaf-cutter ants are part of a complex system of species associations. These include a(n) _______ with fungi, which they cultivate in gardens within their nests; a(n) _______ with a parasitic fungus (Escovopsis) that invades and destroys fungal gardens; and a(n) _______ with a bacterium living on the ant's body that produces a chemical that inhibits Escovopsis. These three associations are, respectively,

Refer to the figure. In the study by van der Heijden et al. of mycorrhizal fungi, the root biomass of the target plants (shown in the figure) was found to

Three examples of associations in nature include: 1) Sea anemones riding on the backs of hermit crabs where the two species protect each other from their different enemies; 2) Lactobacillus bacteria living inside the human gut, having a beneficial effect on human health; and 3) Leaf-cutting ants farming and feeding on specific fungi, which receive free food and protection. How can these three associations best be classified?

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?

Refer to the figure. The RNE (relative neighbor effect) measures growth of a target plant species in the presence and absence of neighboring species. The figure shows graphs of the RNE at eleven sites around the world. RNE was measured at high and at low elevations at each site. RNE values above zero (blue) indicate that neighboring plants increased the growth of target species; RNE values below zero (red) indicate that neighbors decreased target species growth. -What type of ecological interaction did plants show at high elevations and at low elevations, respectively?

When leaf-cutter ants encounter the parasitic fungus Escovopsis, they

Which criterion is most important in determining whether an ecological relationship is a symbiosis?

The interaction of fig trees and fig wasps is a very close obligate mutualism. In contrast, desert ironwood serves as a "nurse" species for seedlings of 165 different desert plants and shares a facultative mutualism with each. Compare and contrast these two types of relationships. What might cause the development of each?

Which factor in the association between figs and fig wasps, if true, indicates that they have gone and/or are undergoing coevolution?