Question

a the competition between the native species made the ecosystem unstable, and addition of the non-native species increased how unstable it was. b the ecosystem was unstable with the two native species but was stabilized with the introduced non-native species. c the competition between the native species made the system stable, and competition with the non-native species made it more stable. d the ecosystem was stable with two native competitors but became unstable through competition with a non-native species.

Explanation:

To solve this, we analyze each option based on ecological principles (competition and ecosystem stability).

• Option A: Says native competition made ecosystem unstable and non - native increased instability. But usually, competition can lead to stable coexistence or other outcomes, not just increasing instability.
• Option B: Claims native species made ecosystem unstable and non - native stabilized it. There's no strong ecological basis for non - native species always stabilizing an unstable native - species ecosystem.
• Option C: States native competition made system stable and non - native competition made it more stable. This goes against typical ecological understanding as adding a non - native competitor often disrupts the existing stable relationships.
• Option D: The ecosystem was stable with two native competitors (which is possible as they can reach a competitive balance) and became unstable with a non - native species (as non - native species can disrupt the existing ecological balance, leading to instability). This aligns with ecological concepts of competition and ecosystem stability.

Answer:

D. The ecosystem was stable with two native competitors but became unstable through competition with a non - native species.