Primary succession occurs when pioneering organisms start to colonize a new habitat, like on a new volcanic island that has never experienced plant growth.

• A. After a wildfire
• B. On bare rock with no prior plant growth
• C. In a mature forest
• D. In a desert with established plants

Answer: (B)

Primary succession happens in places where there is no soil or organic matter to begin with. In such lifeless environments, pioneering organisms like lichens and mosses are the first to colonize. They can tolerate harsh, bare-rock conditions, and as they grow, they slowly break down rock and add organic material when they die. This process starts to build a thin layer of soil, which allows more complex plants to establish over time and sets the stage for gradual changes in the community.

The volcanic island example is a classic case: the island has never had plant growth, so there is no soil to support established vegetation. The first colonizers are those hardy pioneers, and soil develops from their activity, marking primary succession.

Why the other scenarios aren’t primary succession: after a wildfire, there is still soil and often remaining seeds or root systems, so new growth proceeds on that existing substrate—secondary succession. In a mature forest, the ecosystem has already progressed beyond the initial colonization and settled into a stable community, not primary succession. A desert with established plants already has both soil and a community of organisms, which also reflects secondary development relative to bare rock.