What is the difference between primary and secondary succession?

The distinction between primary and secondary succession centers on the conditions in which each process occurs. Primary succession happens in lifeless areas, such as those formed by volcanic eruptions, glacial retreats, or areas where no soil exists initially. In these situations, the ecosystem must start from scratch, typically beginning with pioneer species like lichens or mosses that can colonize bare rock or substrates lacking soil.

In contrast, secondary succession follows a disturbance in an existing ecosystem, such as a forest fire, flood, or human activity like farming that disrupts the current community but leaves the soil intact. Because soil and some remnants of life are present after the disturbance, this type of succession generally happens more quickly than primary succession, as the necessary nutrients and conditions for plant growth are already available.

Therefore, the statement clearly describing that primary succession occurs in lifeless areas while secondary succession occurs where a disturbance has taken place captures the fundamental difference between these two ecological processes.