Question

case study
the green river valley is home to a diverse ecosystem, including fish, amphibians, birds, small mammals, and a variety of plants. over the past decade, a new factory was built upstream, and chemical runoff has been entering the river.
as a result:

• frogs and other amphibians have become less common.
• fish populations are dying off in the river.
• birds that eat fish or amphibians have begun nesting less.

local citizens noticed the rise and found that the factory’s waste (specific cause) has been altering the natural ecosystem and altering the behavior of the organisms.
the community is now discussing whether to implement stricter regulations to reduce the waste and protect the ecosystem.

5 which of the following best describes what happened to the green river valley?
a) only abiotic components of the ecosystem were affected
b) the ecosystem became more stable due to new species
c) humans negatively influenced the ecosystem, leading to biodiversity loss
d) pollution had no effect on the species living in the river

Explanation:

To solve this multiple - choice question about the Green River Valley case study, we analyze each option:

Option A

If the only cause of ecosystem degradation was overfishing, then improving riparian (streamside) vegetation might not be a relevant solution. Since the case mentions multiple factors like dams, urbanization, and changes in stream flow (implied by the effects on the ecosystem), overfishing being the only cause is not likely. So, option A is incorrect.

Option B

The ecosystem has been degraded (with issues like fewer fish, amphibians, and changes in plant life) over the past decade. A healthy ecosystem is more resilient to new stressors. If the ecosystem is already degraded, it will be less able to handle new stressors. So, this option is correct as it aligns with the concept of ecosystem resilience - a degraded ecosystem has lower resilience.

Option C

The case states that there have been changes in the ecosystem (like fewer fish, amphibians, and changes in plant communities) due to human activities (dams, urbanization, etc.). So, human activity has clearly affected the ecosystem, and this option is incorrect.

Option D

The case shows that human activities (dams, urbanization, changes in stream flow) have had negative effects on the ecosystem (fewer fish, amphibians, and changes in plant life). So, human actions do affect the ecosystem, and this option is incorrect.

• Option A: The case implies multiple degradation causes (dams, urbanization, etc.), not just overfishing.
• Option B: A degraded ecosystem (from past human actions) has less resilience to new stressors, which matches the case context.
• Option C: Human activity (dams, urbanization) clearly impacted the ecosystem.
• Option D: Human actions (e.g., dam building, urbanization) negatively affected the ecosystem.

Answer:

B. The ecosystem became more at risk due to new stressors