Ecology 15

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 _______.

+/+; +/-

How can positive interactions affect the distribution and abundance of species?

All of the above

Ants form mutualisms with treehoppers. Which is true about this interaction

Ants protect treehoppers from predators.

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

Both groups have been practicing farming for about the same length of time

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?

High: mutualists; low: competitors

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 ____.

commensalism

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 _____.

commensalism

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 _____.

high-elevation sites

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 ____.

host‒parasite interaction.

Both competition and facilitation are important in

plant species that interact at high and low mountain elevations.

How can a facilitator increase species richness in communities?

A facilitator can benefit a dominant species that, in turn, benefits other species.

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

A facultative interaction in which the two parties are from different kingdoms

What is the difference between mutualism and commensalism?

Mutualism is a mutually beneficial interaction whereas commensalism is an interaction in which one species benefits and the other species does not benefit and is not harmed.

Why is there a conflict of interest between the partners in a mutualism?

Natural selection favors cheaters but also penalizes for overexploiting a partner.

Which of the following characterizes mutualisms?

One partner can provide food and the other can provide habitat.

What type of mutualistic interaction has been shown to have effects on nutrient cycling?

Plants and mycorrhizal fungi

In which of the following cases could positive interactions evolve over time?

The benefits of the interaction consistently outweigh its costs.

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

The degree of physical proximity between the two parties