Question 1

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

Accepted Answer

Humans have been practicing agriculture for about 10,000 years, whereas leaf-cutter ants have been farming fungi for millions of years, making the statement about the same length of time incorrect.

Question 2

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

Accepted Answer

This is an example of commensalism, where one species benefits (the bird) and the other is neither helped nor harmed (the tree).

Question 3

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?

Accepted Answer

B

Question 4

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?

Accepted Answer

All three associations involve two species living in close association, with one species benefiting from the relationship and the other species neither benefiting nor being harmed. This is the definition of commensalism.

Question 5

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

Accepted Answer

Symbiosis is defined by the close physical proximity and interaction between two different species, regardless of whether the relationship is beneficial, harmful, or neutral to the parties involved.

Question 6

The loss of mycorrhizae-plant associations, in both angiosperms and gymnosperms, would have which effect on the plants?

Accepted Answer

Mycorrhizae are symbiotic associations between fungi and plant roots that enhance the plant's ability to absorb water and nutrients, particularly phosphorus, from the soil. Without these associations, plants would struggle to extract sufficient water and nutrients.

Question 7

A mycorrhizal-associated fungus grows between the cells of the root of a plant, forming a mantle around the exterior of the root. This is an example of which type of association?

Accepted Answer

Ectomycorrhizal fungi form a sheath or mantle around the roots and grow between root cells, unlike endomycorrhizal fungi, which penetrate the root cells.

Question 8

Which statement describes the critical distinction between arbuscular mycorrhizae and ectomycorrhizae?

Accepted Answer

Arbuscular mycorrhizae penetrate root cells, forming structures called arbuscules, while ectomycorrhizae form a sheath around roots and grow between root cells without penetrating them.

Question 9

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

Accepted Answer

The relationship is mutualistic because both the algae and the corals benefit from each other.

Question 10

Cord grass is a major plant in saltmarshes in southeastern United States. It provides habitat for many saltmarsh species, such as snails, crabs, conch, and mullet. Within these species, cord grass could best be described as a

Accepted Answer

Cord grass is considered a foundation species because it plays a critical role in creating and maintaining the structure of the saltmarsh ecosystem, providing habitat and resources for other species.

Question 11

An ant colony maintains and farms a species of fungus on which it feeds. The fungus, in turn, is parasitized by a bacterium. The ant/fungus interaction is _______ and the fungus/bacterium is _______.

Accepted Answer

The ant/fungus interaction is mutualistic (+/+) because both benefit: ants get food, and the fungus gets a place to grow. The fungus/bacterium interaction is parasitic (+/-) because the bacterium benefits at the expense of the fungus.

Question 12

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

Accepted Answer

In 1990, the relationship between the fungus and the fly was described as a host-parasite interaction, where the fungus benefits at the expense of the fly.

Question 13

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

Accepted Answer

The answer of Refer to the table.
 The table contains...

Question 14

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, in what year did the relationship between the fungus and the fly first become a mutualism?

Accepted Answer

The answer of Refer to the table.
 The table contains...

Question 15

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

Accepted Answer

Coevolution involves reciprocal evolutionary changes between interacting species. If wasp reproductive behavior is highly specialized to benefit figs, it suggests that both species have evolved traits in response to each other, indicating coevolution.

Question 16

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?

Accepted Answer

The answer of In desert environments, many larger plants serve...

Question 17

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

Accepted Answer

Coevolution is less likely in facultative interactions because the relationship is not essential for the survival of either party, reducing the selective pressure for reciprocal evolutionary changes.

Question 18

Refer to the figure.
 The figure shows the influence of soil temperature on the interaction between two wetland plants, forget-me-nots and cattails. Cattails have extensive air channels for transporting oxygen in their leaves, stems, and roots. Forget-me-nots lack air channels. Based on the figure, as soil temperature increased, the influence of cattails on the growth of forget-me-nots changed from

Accepted Answer

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

Question 19

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. 
-This study showed that the presence of neighboring plants most often benefited the target plants at

Accepted Answer

High-elevation sites often have harsher environmental conditions, where the presence of neighboring plants can provide benefits such as protection from wind and cold, leading to a positive effect on target plants.

Question 20

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?

Accepted Answer

At high elevations, plants often engage in mutualistic interactions to survive harsh conditions, while at low elevations, they may compete for resources.

Quiz 15: Mutualism and Commensalism