Grade 9 Ecology Practice Exam 2026 - Free Ecology Practice Questions and Study Guide

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Invasive species are problematic for native ecosystems because they outcompete natives for resources, disrupt food webs, and reduce biodiversity; zebra mussel in North American freshwater systems is a common example.

They always increase biodiversity.

They outcompete natives for resources, disrupt food webs, and reduce biodiversity; zebra mussel in North American freshwater systems is a common example.

They are easy to manage and rarely cause problems.

They sometimes benefit ecosystems.

The main idea here is that invasive species generally pose problems for native ecosystems because they can outcompete natives, alter food webs, and lower biodiversity, with zebra mussels in North American freshwater systems serving as a classic example.

The best choice among these options recognizes the ecological reality that, while invasives are typically harmful, there can be context-specific, sometimes positive, effects as well. Saying they sometimes benefit ecosystems captures that nuance and avoids implying an absolute outcome. The other statements lean into extremes or restate the problem without acknowledging any potential exceptions, which makes them less accurate overall.