What characterizes a nonindigenous species?

A nonindigenous species is characterized as one that is not native to a specific region or ecosystem. This distinction is crucial for understanding ecological balance and the impact of species on local environments. Nonindigenous species are often introduced through human activity—whether intentionally for agriculture or decoration, or unintentionally through shipping and trade. These species can disrupt local ecosystems by outcompeting native species for resources, introducing diseases, or changing habitat conditions.

The first option refers to native species, which are those that naturally occur in a particular ecosystem and have evolved adaptations to thrive in that environment. The second option suggests genetically modified organisms, which may or may not be indigenous to a region but are altered through biotechnology rather than being defined by their native status. The fourth option discusses species found exclusively in freshwater, which does not directly relate to the concept of being nonindigenous, as nonindigenous species can inhabit a variety of environments, including marine and terrestrial systems. Thus, option C correctly identifies a nonindigenous species by highlighting its lack of native status to a specific area.