Exam 17: Change in Communities

What type of disturbance regime is most likely to result in gradual changes in community composition?

Refer to the tables and the figure. Figure 10 You are studying succession and colonization at two sites, site 1 and site 2. You sample the abundance of two species at the sites and determine their percent cover at each site and time period. Your data are shown in Tables 1 and 2 and are graphed in Figure 10.Answer the following questions: a) Based on percent cover of species 1 and species 2 at each site, determine the percent of space that is both occupied and unoccupied at each site for each time period. Enter the data into Tables 1 and 2 to create two new tables (these will be referred to as Tables 3 and 4). b) Using the data in Tables 1 and 2, add lines to the graphs in Figure 10 to plot how the percent of unoccupied space changed over time at both sites (this will be referred to as Figure 11). c) Using the data in Figure 10, create a table (this will be referred to as Table 5) with summary data on each site. Answer each question for each site. • How much biomass was present at time 0? • Which species was the earlier colonist? • What type of succession occurred early in the study period? • Which species is dominant at time 8? • When is the total amount of available area fully utilized by the species at each site?

Suppose that a late succession plant that is surrounded by early succession plants grows at a rate of 0.5 cm per day. If the early succession plants are removed experimentally, the late succession plants are observed to grow at a rate of 0.9 cm per day. This experiment shows that the early succession plants have a _______ effect on the late succession plants, and this observation is most consistent with the _______ model of succession.

If Cowles is correct about succession, then

Suppose that you are in Glacier Bay, Alaska, and standing at a location that is dominated by Dryas. If you moved toward the edge of the glacier, you would most likely next encounter _______. If you moved in the opposite direction, away from the edge of the glacier, you would most likely next encounter _______.

You are in Glacier Bay. Starting at a location dominated by alders, you would most likely first run into the _______ stage if you travelled toward the glacier's edge and the _______ stage if you travelled away from the glacier's edge.

Refer to the figure. The figure shows examples of possible disturbance intensity (y-axis) and frequency (x-axis) combinations. - What type of succession occurs after the disturbance in C?

Which of the following is a biotic factor that can be an agent of change?

A mudslide kills a large fraction of a population of a flower species. The reduction in this flower population allows for an increase in the population size of a fern that competes with the flower. This is an example of

The regime shift from kelp forests to urchin barrens along the west coast of the United States illustrates how human actions have caused communities to shift to alternate states. This particular shift was caused because of a decline in sea otters, most likely due to hunting. Why would the reintroduction or protection of sea otters not return the system to its original state?

Bertness and Shumway's studies of high salt stress conditions in the middle intertidal regions of New England salt marshes led to which conclusion?

Which statement about change in communities is true?

Which statement about early primary succession is false?

In a hypothetical example of succession, the early succession plants produce toxins that hinder both the subsequent colonization of other early succession species and colonization by later succession plants. This scenario fits the _______ model of succession.

In their studies of succession in Glacier Bay, Alaska, Chapin and colleagues found that the survival rate of germinated spruce seeds was highest at the _______ stage.

Farrell's studies of algal succession on the Oregon coast showed that

Refer to the figure. In their work on aspen-fir interactions, Calder and St. Clair claim that aspens are facilitated by the presence of fir trees. From these data, what is the primary evidence for aspen being facilitated by fir?

Sousa's studies of intertidal zones in southern California showed that

Refer to the figure. Figure 9 You are studying disturbance and succession patterns, focusing on data you collect in area 1, area 2, and area 3. Part A of the figure shows how the community type changed across each year sampled, and part B shows how the abiotic conditions changed across study years (no specific condition specified or units listed). - According to the data in Figure 9, which area had the most stable community type in comparison to the changes in the abiotic conditions? Justify your answer.

Refer to the figure. Suppose you are studying succession patterns in two species, species A and species B, both small aquatic organisms that colonize bare surfaces underwater. You replicated Sutherland's experiments in this new system by placing bare tiles underwater in predator-protected areas and areas with predators. You collect data on the percent of cover for each species, as shown in the figure. - Without predation, which species is a better competitor?