Exam 56: Communities

Three species of kangaroo rats and five species of mice live in the same geographic region.All of these species are competitors, feeding on grains or seeds.These eight species belong to the same

A woodland was felled, stripped of its existing vegetation, and left to undergo secondary succession.Which factor in this situation is different from primary succession and ensures that secondary succession occurs more rapidly than primary succession does?

Lottery, or neutral, models are most appropriately used for which types of communities?

Rising ocean temperatures are affecting coral reefs around the world.When temperatures become too high, the corals undergo bleaching; that is, the algae living inside them leave.Corals depend on these algae for 90 percent of their energy.What will most likely happen if temperatures remain higher than the corals' preferred range for an extended time period?

The presence of soil fauna increases the likelihood that many plants will be established during succession.This is an example of

When Mount St.Helens erupted, three relatively distinct zones of destruction resulted: the Pumice Plain, which was essentially sterilized and had no remaining life; the Blowdown Zone on the mountain slopes, where downed trees and vegetation were covered with mud and ash; and farther down, forests that remained standing but were also covered with mud and ash.Based on these levels of destruction, what would the likely rate of recovery be for these zones?

In a study in China, several different varieties of rice were planted in the same field.Crop yields increased by 89 percent compared with fields with a single variety of rice.This occurred because there was a dramatic decrease in disease and the fields remained stable without using pesticides.In addition, the system increased local biodiversity.This is an example of a(n) _______ showing greater productivity and stability than a(n) _______.

A researcher wants to understand the fitness of a population of butterflies, in order to better understand its place in the community.The researcher would most likely carry out a study of the

A survey of a pond community identified 57 different species that made up the community.This number can best be described as a measure of the community's

Low levels of chemical pesticides occur in water supplies such as ponds and lakes, which provide habitats for many fish species.This results in death of some fish fry (first-year fish), loss of some insects and invertebrates that serve as fish food, and depleted oxygen concentrations due to decomposition of algae killed by herbicides.These effects suggest that the presence of low-level pesticide residues in water supplies acts as a _______ to fish populations.

In the Shannon index, the mathematical calculation of species diversity, H, incorporates measurements of

An ecologist constructs a diagram to describe the structure of a city park community.The diagram includes the trophic levels connecting park organisms.It also includes information on which pollinators pollinate various plants and on major competitors in the community.This diagram could best be described as a(n) _______.

Dryas and alders in Glacier Bay, and dwarf lupines on the Pumice Plain of Mount St.Helens, all have root nodules containing nitrogen-fixing bacteria.Why were these plants important to the development of communities on these two primary succession sites?

Charles Darwin observed the following interactions among plants and animals in his region of England: Bees pollinate flowers and make seed production possible.Field mice prey on bee combs and nests.Cats eat field mice.From these observations, he concluded that cats could control the populations of certain flowers.On what did he base this conclusion?

A community ecologist is studying all the pollinators in a prairie community.This researcher has chosen to subdivide the community on the basis of

Which condition in an ecosystem would be considered a disturbance, as opposed to a stress?

In a pasture, several types of animals (cattle, rabbits, grasshoppers, and geese) all graze on grass.According to ecologists, these organisms are all members of the same

Goldenrod and thistles exude chemicals from their roots that deter the germination and growth of potential competitor plants within their community.This is an example of

Which factor is characteristic of disturbances within a community?

During the process of succession, early species tend to be facilitators, while many later species compete with each other and act more as inhibitors.Yet, species diversity tends to increase as succession continues.How is it possible for high species diversity to coexist with inhibitory interactions in mature communities?