Which scenario best illustrates primary succession?

• A. After a flood that leaves rich soil
• B. After lava flow creates new rock with no soil
• C. After a wildfire that leaves soil intact
• D. In a grassland where seeds are present

Answer: (B)

Primary succession occurs when life starts in a place that has no soil to begin with. In this process, organisms that can live on bare rock, like lichens and mosses, begin to break down the rock and add organic material, slowly building up soil so plants can eventually take hold.

The lava flow scenario fits this best because it creates fresh rock with no soil. There’s nothing yet for plants to grow in, so pioneer organisms begin the soil-building process and set the stage for gradual establishment of a full community.

In contrast, after a flood that leaves rich soil and after a wildfire that leaves soil intact, the area still has soil to support regrowth, so those are secondary succession scenarios. A grassland where seeds are present also doesn’t start from bare rock, so it’s not primary succession.