Exam 56: Communities

Refer to the figure. The process illustrated in the figure is known as

Lottery models of natural communities are considered neutral because they assume that

Lawn A was planted with a single species of grass, which covers 90 percent of the lawn.The other plant species there include five species of weeds, each covering 2 percent of the lawn.Lawn B has the same six species, but with percentages of 75 percent grass and 5 percent for each of the five weeds.How do species richness and species evenness of the two lawns compare?

During succession, two plant species become established at different times.Species A is a perennial with roots that secrete chemicals to maintain a distance between members of the species and similar species.Species B is a low-growing annual with nitrogen-fixing bacteria in its root nodules.Which (if either) of these two species most likely appears first during succession, and why?

Refer to the graph. According to the graph, which statement best describes the relationship between total plant cover (a measure of productivity) and number of species (species richness) in test plots?

The eruption of Mount St.Helens in 1980 gave scientists the opportunity to study all natural situations except

The greatest noticeable change in the community structure of a natural community would most likely occur as a result of

The initial cause that is triggering the loss of polar bears, and the resulting change in Arctic communities, is

In the traditional definition of succession (which may not always be achieved), a climax community is characterized by

A volcanic eruption occurs.Which resulting condition would likely be considered a stress, rather than a disturbance?

Which of these is a biotic factor that can affect community structure?

A new herbivore species is introduced into a community and appears to be well adapted to the environmental conditions.However, it fails to compete well with existing herbivores and, after several years of low reproductive success, it dies out.This species was excluded through the process of _______.

Refer to the figure, showing the soil food web. Based on this food web, which organisms are members of the detritivore/decomposer level of the web?

Two species of gobies (small fish) live on a coral reef.The two species use similar habitats and compete equally for vacant corals.The "winner" is the goby that arrives first.Juveniles and adults of the two species have the same relative abundance.When one species is removed experimentally, either species can colonize the vacant coral.These factors indicate that the presence of the two species on the reef can best be described by a model called the

Approximately once every century, a coastal region suffers a severe flood that inundates freshwater marshes, swamps, and low-lying fields with salt water for an extended time period.After each of these floods, the communities undergo secondary succession, eventually returning to climax states.Will these communities always return to the same climax states, with the same species compositions? If so, why? If not, what factors can cause them to attain alternative states?

Kudzu originated in Asia and was introduced to the southern United States for uses including cattle fodder and erosion control.Kudzu grows extremely rapidly, obtains resources very quickly, and absorbs nitrogen from the air.Its rapid growth smothers plants, including whole trees, and covers buildings and other structures.These characteristics suggest that kudzu would have what effect on community structure?

Beginning about 500 million years ago, plants began to colonize land.One factor that made this colonization possible was the presence of an atmosphere with high concentrations of carbon dioxide, which was necessary for photosynthesis.This suggests that before colonization, the green aquatic algae that eventually evolved into plants were prevented from forming land communities by

The aspect of community structure that measures both the number of species in a community and how evenly they are apportioned is the _______ of the community.

An ecologist is studying two competing snail species in a woodland habitat.She hypothesizes that one species, the interactor, is controlling the population size of the other, the target species.She designs an experiment to determine the interaction strength between the two species.What should she manipulate and measure?

A scientist analyzes genetic differences in all the frog species in a pond.She also determines the total number of frog species in the community and calculates the Shannon diversity index.She is measuring which aspect(s) of biodiversity?