Massachusetts MCAS Biology Practice Test – Prep, Questions & Study Guide

Primary succession and secondary succession are both processes that describe how ecosystems develop over time, but they occur under different conditions. The defining characteristic of primary succession is that it takes place in environments that are completely barren and devoid of soil and life, such as after a volcanic eruption or on a newly formed sand dune. In these situations, the initial colonizers are typically pioneer species like lichens and mosses that can survive in extreme conditions and begin the soil formation process.

On the other hand, secondary succession occurs in areas where an existing ecosystem has been disturbed or damaged but where soil and some life forms still remain, such as after a forest fire, hurricane, or human activities like farming. This means that the recovery process can proceed more rapidly than in primary succession, as the soil already contains seeds, nutrients, and organisms that are advantageous for regrowth.

This contrast is fundamental to understanding ecological restoration and the resilience of different ecosystems, making the specified difference between primary and secondary succession clear and distinct.