Question 1

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?
A) Species A is a much better competitor than species B.
B) Species A is a slightly better competitor than species B, but there is a lot of variability.
C) Species B is a much better competitor than species A.
D) Species B is a slightly better competitor than species A, but there is a lot of variability.

Accepted Answer

The answer of Refer to the figure. 
 Suppose you...

Question 2

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.
- Based on the data, what would you expect that a newly colonized area in a natural pond would look like?
A) Species A would dominate species B, although species B would still occupy some space.
B) Species A and B would coexist at about equal proportions.
C) Species B would dominate species A, although species A would still occupy some space.
D) The predators in the natural ponds would cause both species A and species B populations to decrease significantly.

Accepted Answer

Species A would dominate species B, although species B would still occupy some space, as newly colonized areas often see one species initially outcompeting others before reaching a balance.

Question 3

Which human activity can bring about shifts in communities to alternative stable states?
A) Habitat destruction
B) Introduction of invasive species
C) Overexploitation of native species
D) All of the above

Accepted Answer

All of the listed activities can disrupt ecosystems and lead to shifts in communities to alternative stable states by altering species composition and ecosystem functions.

Question 4

Which statement about the amphibians that colonized the area around Mount St. Helens after the eruption is true?
A) The frog Rana cascadae was the most important animal ecosystem engineer in the community.
B) Frogs and salamanders started to colonize the area within the first few years of the eruption.
C) By the year 2000, the species diversity of amphibians had reached pre-eruption levels.
D) Both a and b

Accepted Answer

Frogs and salamanders began to colonize the area around Mount St. Helens within the first few years after the eruption, as they are often among the first animals to return to disturbed habitats.

Question 5

In the succession that followed the eruption of Mount St. Helens, which organism played an important role as an ecosystem engineer?
A) The toad Bufo boreas
B) The frog Rana cascadae
C) The pocket gopher Thomomys talpoides
D) The salamander Ambystoma gracile

Accepted Answer

The pocket gopher Thomomys talpoides played an important role as an ecosystem engineer by burrowing and mixing soil, which helped in the redistribution of nutrients and facilitated plant growth in the disturbed landscape after the eruption.

Question 6

Plants with bacterial symbionts that fix _______ are often important players in _______ stages of succession.
A) nitrogen; early
B) phosphorus; late
C) sulfur; early
D) phosphorus; early

Accepted Answer

Plants with bacterial symbionts that fix nitrogen are often important in early stages of succession because they enrich the soil with nitrogen, which is crucial for the establishment of other plant species.

Question 7

Which statement about plants with nitrogen-fixing bacteria is true?
A) They often play major roles in early succession.
B) They are often at a competitive disadvantage in late succession due to the energetic costs involved in maintaining their bacterial symbionts.
C) Only a few types of nitrogen-fixing bacteria are associated with plants.
D) Both a and b

Accepted Answer

Plants with nitrogen-fixing bacteria often play major roles in early succession because they can improve soil fertility by adding nitrogen. However, in late succession, they may be at a competitive disadvantage due to the energy costs of maintaining the symbiotic relationship.

Question 8

Refer to the figure.
Figure 1
  You are studying succession in an area affected by a volcanic eruption. Figure 1 shows the amount of volcanic activity over time, from no activity to high activity. Time periods with no activity indicate that the volcano is inactive and no disturbance is occurring; time periods with high activity indicate that the volcano is active and there are high levels of disturbance.Answer the following questions:
a) How would you describe the frequency of eruptions in terms of ecological timescales? Are eruptions common or rare in this area compared to the lifespan of organisms?
b) Using the frequency of eruptions, create a graph (this will be referred to as Figure 2) that shows where this type of event would be located on the plot of the spectrum of disturbance. Make the x-axis frequency (from low to high), and the y-axis intensity (from low to high).
c) Based on the frequency and intensity of the eruptions, what type of successional response would you predict for this area?

Accepted Answer

The answer of Refer to the figure.
Figure 1
  You...

Question 9

Refer to the figures.
Figure 1
  Figure 3
  You are studying two islands (Figure 3) that have recently experienced volcanic activity. Both were formerly forested with palm trees. On island 1, a heat wave resulting from the volcanic eruption leads to the destruction of all the above-ground vegetation (middle figure). On island 2, a lava flow resulting from the volcanic eruption (right figure) completely covers the island.Answer the following questions:
a) How have the resources, environmental conditions, and species communities likely changed on the two islands as a result of the volcanic eruption?
b) Assume that the frequency of eruptions on the islands follows the pattern shown in Figure 1. Using data from Figures 1 and 3, create a graph (this will be referred to as Figure 4) using the frequency of eruptions to show where island 1 and island 2 would be located on the spectrum of disturbance. The x-axis should be frequency and the y-axis should be intensity.
c) Based on the frequency and intensity of the eruptions you plotted in Figure 4, what type of successional response would you predict for each island?

Accepted Answer

The answer of Refer to the figures.
Figure 1
  Figure...

Question 10

Refer to the figures.
Figure 5
  Figure 6
  Figure 7
  You are studying the impacts of a volcanic eruption that produces a lava flow that covers part of a grassland (Figure 5). You begin taking samples as soon as the area is safe to work in-about one year after the main eruption has ended. You set up a transect (beginning at "Transect start" in Figure 5), and then collect data on how several abiotic and biotic factors vary across it (Figures 6 and 7).
-Answer the following questions:
a) According to the data in Figure 6, what was the effect of the eruption on the percent of organic material in the soil along the transect?
b) Based on Figure 5, predict how the eruption would have changed the amount of UV reaching ground level along the transect. Graph your prediction (this will be referred to as Figure 8).
c) Based on the available resources, what type of succession would you expect along the transect? In both the blast zone and lava flow areas, how extreme are the conditions faced by the colonizer species? How would you expect the extent of extreme conditions to limit the species that could potentially colonize the areas?

Accepted Answer

The answer of Refer to the figures.
Figure 5
  Figure...

Question 11

Refer to the figures.
Figure 5
  Figure 6
  Figure 7
  You are studying the impacts of a volcanic eruption that produces a lava flow that covers part of a grassland (Figure 5). You begin taking samples as soon as the area is safe to work in-about one year after the main eruption has ended. You set up a transect (beginning at "Transect start" in Figure 5), and then collect data on how several abiotic and biotic factors vary across it (Figures 6 and 7). 
-As part of your long-term research, you look into the succession patterns along the transect. Would a space for time substitution allow you to predict succession patterns in the lava flow area based on succession you observe in the blast zone? Why or why not? How is this situation similar or different from other situations that use space for time substitutions?

Accepted Answer

The answer of Refer to the figures.
Figure 5
  Figure...

Question 12

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).
-Answer the following questions:
a) According to the data in in Figure 9, when did the disturbance occur?
b) Which years would provide baseline data for these communities? Why is baseline data important?
c) How many years did it take the abiotic conditions to return to levels similar to their original conditions?
d) How many years did it take for the biotic communities in areas 1, 2, and 3 to return to their original conditions?

Accepted Answer

The answer of Refer to the figure.
Figure 9
  You...

Question 13

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.

Accepted Answer

The answer of Refer to the figure.
Figure 9
  You...

Question 14

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).
- Evaluate the successional paths for all three areas to answer the following questions:
a) What is hysteresis?
b) Which area shows evidence for this condition? Explain your answer.

Accepted Answer

The answer of Refer to the figure.
Figure 9
  You...

Question 15

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?

Accepted Answer

The answer of Refer to the tables and the figure.
...

Question 16

Refer to 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. Based on the data in Figure 10, does either site show evidence for facilitation? Why or why not?

Accepted Answer

The answer of Refer to the figure.
Figure 10  
...

Question 17

Refer to 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. Use the data in Figure 10 and your knowledge of the different successional paths that communities can follow to answer the following questions:
a) Are the patterns of changes in abundance of species 1 and 2 consistent across the two sites?
b) Based on the consistency of abundances of species 1 and 2 across the sites, how would you describe the successional patterns observed at sites 1 and 2? What might be driving this pattern?

Accepted Answer

The answer of Refer to the figure.
Figure 10
  You...

Question 18

Refer to the tables and the figure.
  Figure 11
  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.Answer the following questions:
a) When are the sites most vulnerable to colonization by an invasive species? Justify your answer. 
b) By time 8, which site is least vulnerable to colonization by an invasive species? Why?

Accepted Answer

The answer of Refer to the tables and the figure.
...

Question 19

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
A) stress.
B) primary succession.
C) disturbance.
D) facilitation.

Accepted Answer

A disturbance is an event that changes the structure of a community, such as a mudslide, which reduces the flower population and indirectly benefits the competing fern population.

Question 20

What type of disturbance regime is most likely to result in gradual changes in community composition?
A) Intense, infrequent disturbance
B) Intense, frequent disturbance
C) Weak, infrequence disturbance
D) Weak, frequent disturbance

Accepted Answer

The answer of What type of disturbance regime is most...

Quiz 17: Change in Communities

Which human activity can bring about shifts in communities to alternative stable states?

Which statement about the amphibians that colonized the area around Mount St. Helens after the eruption is true?

In the succession that followed the eruption of Mount St. Helens, which organism played an important role as an ecosystem engineer?

Plants with bacterial symbionts that fix _ are often important players in _ stages of succession.

Which statement about plants with nitrogen-fixing bacteria is true?

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

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