The term ecosystem refers to what?

• A. A network of water bodies
• B. A single species in isolation
• C. A collection of rocks and minerals
• D. A community of living organisms interacting with their physical environment

Answer: (D)

An ecosystem is a system where living things interact with their physical surroundings, with energy flowing through the community and matter cycling within it. It includes all the organisms—plants, animals, microbes—as well as the air, water, soil, climate, and sunlight in a given place. These interactions shape how communities form, grow, and respond to changes, because energy moves through food webs and nutrients are recycled via processes like decomposition and respiration.

That makes the description of a community of living organisms interacting with their physical environment the best fit. It goes beyond just water bodies, it isn’t about a single species in isolation, and it isn’t merely rocks and minerals, since all those interactions between living and nonliving components are essential to what an ecosystem is.