Question

acid precipitation that results from the burning of fossil fuels disrupts the nutrient cycles in an environment. some of these disruptions greatly affect the organisms that live in an ecosystem. for example, bacteria that play important roles in the nitrogen cycle cannot tolerate a decrease in the ph of soil due to acid precipitation. which statement explains how an ecosystem is likely to be affected by this disruption of the nitrogen cycle? a animal populations in the ecosystem will find other sources of nitrogen and change very little. b the sizes of plant populations in the ecosystem will decline due to lack of soil nitrogen. c there will be little effect because there is plenty of free nitrogen in the atmosphere. d new kinds of plants will begin to grow in the ecosystem and restart the nitrogen cycle.

Explanation:

• Option A: Animals rely on plants (which need soil nitrogen) for nutrients, so they can't easily find other nitrogen sources and will be affected, so A is wrong.
• Option B: Bacteria in the nitrogen cycle help convert nitrogen into a form plants can use. If these bacteria are affected by acid precipitation (lowering soil pH), soil nitrogen availability for plants decreases. Less nitrogen means plants struggle to grow, so plant populations decline. This makes B correct.
• Option C: Atmospheric nitrogen is not directly usable by most plants; they need nitrogen - fixing bacteria to convert it. So the large amount of atmospheric nitrogen doesn't prevent the effect of disrupted nitrogen cycle, C is wrong.
• Option D: New plants won't suddenly grow to restart the nitrogen cycle, especially since the environmental issue (acid precipitation affecting bacteria) still exists. Also, most plants need the nitrogen cycle to function properly, so D is wrong.

Answer:

B. The sizes of plant populations in the ecosystem will decline due to lack of soil nitrogen.