A predator population increases one year and then decreases the next year, and A. A beaver dam temporarily reroutes a river. Hence the correct option is b.
Two environmental changes that would likely make an ecosystem less stable are represented by options A and B. Option A involves the temporary rerouting of a river due to a beaver dam. While this alteration can have localized effects on water flow and habitat, it may not necessarily lead to a widespread destabilization of the entire ecosystem.
On the other hand, involves fluctuations in a predator population, with an increase in one year followed by a decrease in the next. Such variations in predator numbers can have cascading effects on the abundance and distribution of prey species, disrupting the balance within the ecosystem. This kind of instability, characterized by unpredictable changes in predator-prey dynamics, can reverberate through various trophic levels, impacting the overall ecological equilibrium.
These two scenarios highlight how both physical alterations (option A) and fluctuations in population dynamics (option B) can contribute to decreased stability in an ecosystem, emphasizing the interconnected nature of ecological processes. Hence the correct option is b.