What is ecological succession and how do primary and secondary succession differ?

• A. Secondary succession begins after a disturbance with soil present.
• B. Primary succession begins after disturbance with soil present.
• C. Succession is the gradual change in species composition over time; primary begins on bare rock with slower pioneer species, and secondary follows disturbance with soil present.
• D. Secondary succession occurs only in aquatic environments.

Answer: (C)

Ecological succession is the gradual change in which species occupy a community over time as organisms modify the environment and new species move in. Primary succession starts on bare rock or other surfaces with no soil, so it proceeds slowly because the first colonizers—like lichens and mosses—have to establish soil and nutrients before larger plants can take hold. Secondary succession happens after a disturbance that leaves soil intact—such as a fire, flood, or farming abandonment—so seeds and roots remain in the ground and the ecosystem can rebound more quickly, with grasses and shrubs appearing first and trees following. This description captures both the general idea of succession and the key differences: primary begins on bare rock with slow pioneers, while secondary follows disturbance with soil present and proceeds faster.