Exam 56: Communities

The figure shows 200 years of succession as glaciers recede in Glacier Bay, Alaska.In terms of succession, what is the significance of the climax (spruce forest) at the right of the top diagram? What can you infer about the nature of the climax forest, based on the graph?

As a community's species richness increases, its community function generally _______.

Communities can be defined based on all of the following except

Many species are introduced outside their normal ranges deliberately, for specific purposes.Some of these (such as the honey bee) integrate into natural communities; others (such as the gypsy moth) reproduce out of control, become pests, and are defined as "invasive." Which of the following could be a difference in the way these two categories of introduced species changed a community's structure?

According to the intermediate disturbance hypothesis, species diversity might be low under conditions of low disturbance or stress because there may be high levels of

A group of species in a community all feed on similar resources, and they are all approximately equal in their ability to obtain these resources.Species diversity in this group is likely maintained by

What is the major distinction, if any, between a food web and an interaction web?

Which trophic interaction in a community is an indirect interaction?

In a coastal aquaculture operation, mussels and seaweed are introduced to use the nutrients contained in the waste produced by salmon.This reduces salmon waste in the system by up to 60 percent.This is an example of a _______ system that is most likely _______ stable compared with a traditional system, in which salmon are farmed alone.

The succession occurring on the glacial moraines of Glacier Bay, Alaska, and behind other retreating glaciers is considered primary succession.What aspect of this process defines it as primary, rather than secondary, succession?

Many biotic factors have the potential to affect community structure.Such biotic factors include all of the following except

In which situation would primary succession occur?

An ecologist studying the community within the canopy of a rainforest tree constructs a food web of the canopy community.By simply observing the connections in this food web, the ecologist will gain insight into which aspect of the community?

Ecologists want to understand ecological changes as a forested area is cut and then begins to recover.They measure the number and evenness of species present at the beginning (before cutting) and at different times after cutting.They are measuring changes in which ecological characteristic?

In 1988, fires in Yellowstone National Park affected over 36 percent of its area.Where the fires burned hottest, most plants, including forest trees, were killed.Where the fires were less severe, forest trees survived and only smaller plants were killed.What is most likely to happen in terms of succession in situations like this?

A scientist removes one species from a community and observes how the abundance of a second "target" species is affected.The scientist is measuring the _______ between the two species.

An ecologist wants to better understand the evolutionary relationships of organisms making up a community.She would most likely define the community based on its

After a volcanic eruption, weathering, rain, and other natural forces help break down the volcanic rock and ash, releasing its nutrients.This helps pioneer plant species to colonize.As succeeding generations of plants develop on the volcanic landscape, how (if at all) will the plant community be likely to change?

A saguaro cactus in the Sonoran Desert takes 80 years to become mature and begin flowering.During that time, woodpeckers drill cavities into the cactus and provide nesting sites for up to 30 bird species.After it begins to flower, the cactus also provides nectar for bats, bees, and doves, and fruit for various other birds and insects.Based on these interactions, the saguaro cactus could best be described as a

Formation of an alternative state of succession is probably least likely to occur under which conditions?