Exam 56: Communities

As global temperatures rise, warm seasons lengthen.Flowering dates for some flowers are now about 10 days earlier than in the recent past.For pollination to occur, pollinators depend on flowers to bloom at specific times.Pollinators also alter their seasons-for example, insects emerge earlier.But these alterations do not necessarily coincide with changes in flowering.What is the most likely near-term consequence of these mismatches in flowering and pollinator readiness?

Following disturbance to a community, succession-characterized by a change in community structure over time-can eventually result in a relatively stable stage called a

The plants that grow best on recently formed moraines at Glacier Bay are those that

Organisms most likely to tolerate harsh abiotic conditions are found

Two species of protozoa are competing in a laboratory environment.A third species is introduced, with no other changes made to the experimental conditions.The population size of the third species gradually decreases for several days, and then it eventually goes extinct.What is the most likely reason this species went extinct?

Keystone species and foundation species are sometimes also ecosystem engineers, which change the environment and provide habitat for a variety of species.In the process, they have a profound effect on community structure.Which of the following would be considered members of keystone or foundation species but not ecosystem engineers?

Refer to the figure. Compare the samples of frogs in the two communities.Assume that frogs that appear different are separate species.Compared to pond A, pond B has

Two areas in similar climates undergo disturbance.Area X is completely destroyed; nothing living is visible.Area Y is heavily damaged, but a few plants and animals remain.The area that will recover most rapidly is area _______.

The Hawaiian Islands were formed by volcanic activity, and the original lava and soil substrate was deficient in nutrients, particularly nitrogen.This suggests that many of the earliest plants to become established on the islands were probably

Scientists reported that the reintroduction of wolves into Yellowstone National Park initiated a trophic cascade.Which factual statement best supports this conclusion?

In which case would secondary, rather than primary, succession occur?

Tilman's experiments showed that increasing species richness enhanced the stability of plant production in the plots because

Two communities are analyzed using the Shannon index of species diversity.Community A has an H value of 1.5.Community B has an H value of 3.0.What is the strongest conclusion that can be drawn about the species diversity of these two communities?

The reintroduction of wolves into Yellowstone Park in 1995 had a(n) _______ effect on aspen and _______ effect on elk.

Explain the concept of "filters" in determining which species become members of a community.Describe the three major filters determining community structure.

Which concept would a community ecologist be most likely to study?

A farmer has routinely planted soybeans, a nitrogen-fixing crop, in her fields, alternating it with corn, which requires high amounts of nitrogen.Then, for several years, she stops planting soybeans and plants only corn.Her corn crops decline more every year.This indicates that the interactor species (soybeans) has a (positive/negative) _______ interaction with the target species (corn).

The Shannon index of species diversity is calculated using this equation: Habitat A has a total of 100 birds, with the following numbers of individuals per species: 20, 25, 20, 15, and 20.Habitat B also has 100 birds, with the following numbers of individuals per species: 80, 5, 5, 5, and 5.Based on the Shannon indices for habitats A and B, which habitat (if either) has a higher species diversity?

An area is undergoing secondary succession.Early in the process, facilitating species such as nitrogen fixers and decomposers predominate.Later in succession, there are more inhibiting species, such as competitors.What is a major reason that facilitating species outnumber inhibiting species early in succession?

The intermediate disturbance hypothesis states that a community experiencing an intermediate level of disturbance will have higher species diversity than it would with low or high disturbance.What is a major justification for this hypothesis?