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 began entering the river.
as a result:

• some fish populations declined sharply.
• frogs and other amphibians became less common.
• certain plants near the riverbank died off.
• birds and mammals that relied on fish or plants as food began moving away.

local scientists studied the area and found that the decline in one species caused a chain reaction affecting multiple organisms and altering the structure of the ecosystem.
the community is now debating whether to implement stricter regulations to reduce pollution and restore the river ecosystem.
question 7/16
7 which of the following is an example of a chain reaction caused by the disruption?
a more fish being born because predators are gone
b the factory increasing its production without consequences
c the river water becoming warmer due to sunlight
d frogs declining, causing birds and mammals that eat them to move away

Explanation:

A chain reaction in an ecosystem occurs when a change in one species affects others in a sequential way. In option D, the decline of frogs (a result of the initial disruption from the factory's chemicals) leads to birds and mammals that rely on frogs for food moving away. This shows a sequential impact (frogs decline → predators of frogs are affected). Option A is the opposite of a chain reaction from disruption (it's a positive change without a preceding negative disruption - related chain). Option B has no indication of a chain of species impacts. Option C is a direct environmental change (sunlight - not a disruption - related chain of species interactions).

Answer:

D. Frogs declining, causing birds and mammals that eat them to move away