Question

questions 1 through 3 refer to the following.
number of plant species
1 mark for review
based on the data shown in the graph, which of the following best describes how ecologists could determine when this ecosystem is approaching a climax community?
a determine if the keystone species in the ecosystem is present two years after the volcanic eruption
b measure the biomass of the pioneer species present before and after the volcanic eruption
c record the number and type of producers present every year after the eruption
d calculate the net primary productivity of a specific indicator species every year after the eruption

Explanation:

A climax community is a stable, mature ecological community that has reached a long - term equilibrium. In ecological succession studies, one way to determine if an ecosystem is approaching a climax community is by observing the species composition over time. If the number of plant species (as shown in the graph) stabilizes (after initial changes due to the eruption), it can be an indication. Measuring biomass of pioneer species (Option B) is more relevant to early succession stages. Calculating net primary productivity of a specific indicator species (Option D) and recording the number and type of producers (Option C) do not directly address the overall community stability (a key aspect of approaching a climax community) as effectively as determining if the ecosystem has a relatively stable species composition (which can be inferred from the species number graph, and Option A, determining if keystone species are present two years after, is too short - term and not comprehensive for climax community assessment).

Answer:

A. Determine if the keystone species in the ecosystem is present two years after the volcanic eruption
B. Measure the biomass of the pioneer species present before and after the volcanic eruption
C. Record the number and type of producers present every year after the eruption
D. Calculate the net primary productivity of a specific indicator species every year after the eruption

The answer is none of the options are correct. A better approach would be to observe the long - term stability of the species composition (not just two years for keystone species as in A). But among the given options, if we assume that after a certain period (implied in the graph's later stability), if we consider the general idea of community stability (even if the options are not perfect), Option A is the closest in terms of looking at species (though the time frame is an issue). But strictly speaking, these options are not ideal for determining climax community approach. However, if forced to choose from the given:
The answer is A. Determine if the keystone species in the ecosystem is present two years after the volcanic eruption (with the caveat that the time frame is too short in a real - world ecological context for climax community determination).