Why do most real ecosystems resemble open systems?

• A. Most real ecosystems are open because they exchange energy and matter with the environment.
• B. Real ecosystems are closed and do not exchange energy.
• C. Open and closed terms are interchangeable.
• D. Ecosystems exchange energy but not matter.

Answer: (A)

Ecosystems are open systems because they constantly exchange both energy and matter with their surroundings. Sunlight provides energy that flows through the living and nonliving parts of the system, driving processes like photosynthesis and warming the environment, while much of that energy ultimately escapes as heat. Matter, such as nutrients and organic material, moves across boundaries too—input comes from soil, water, and air, and outputs occur through processes like leaching, respiration, decomposition, or export to other systems. This ongoing exchange keeps ecosystems connected to the larger environment and supports continual cycling and energy flow.

The best choice reflects this reality by stating that ecosystems exchange both energy and matter with the environment. The other ideas either imply no exchange, treat open and closed as interchangeable, or suggest energy moves but matter does not, which doesn’t align with how real ecosystems function.