Together, the trout population and the plant population in a stream represent which concept?

• A. Community
• B. Population
• C. Species
• D. Ecosystem

Answer: (A)

In ecology, a community is all the populations of different species that live in the same area and interact with one another. The trout and the plants are two distinct species living in the same stream, and they interact in ways that tie their lives together—through food webs, competition for resources, habitat structure, and other relationships. Because multiple species coexist and influence one another in the same habitat, together they form the stream’s biotic community. A single population would mean just one species, while an ecosystem includes both living communities and the physical environment. So, the combination of the trout and plant populations represents a community.