Which term describes gradual long-term changes in an ecosystem?

• A. Independent variable
• B. Prediction
• C. Succession
• D. Dependent variable

Answer: (C)

Gradual long-term changes in an ecosystem are described by ecological succession. Over time, communities change as pioneer species colonize an area, alter the environment, and allow other species to move in, leading to a different, often more complex community. This process can occur after a disturbance that resets the environment (secondary succession) or in places where life starts from bare rock with soil development (primary succession). Succession captures the idea of long-term, directional changes in which the species present and the structure of the ecosystem evolve step by step. The other terms are about experiments: an independent variable is what you deliberately change, a dependent variable is what you measure, and a prediction is a statement about what you expect to happen. They don’t describe the gradual, time-based changes in ecosystems.