Why does secondary succession occur faster than primary succession? A. Fewer changes must occur in secondary succession. B. There are more pioneer species in secondary succession. C. The environmental conditions are more extreme in primary succession. D. There are more trophic levels in secondary succession.
The Correct Answer and Explanation is:
Correct Answer: A. Fewer changes must occur in secondary succession.
Explanation:
Secondary succession occurs faster than primary succession primarily because the area affected already has existing soil and, in many cases, some remaining organisms or organic matter. This contrasts with primary succession, where life starts in a barren environment such as bare rock or after a lava flow, and the process must begin from the very beginning with the formation of soil itself.
In primary succession, pioneer species like lichens and mosses are the first to colonize the area. These organisms help break down rock into smaller particles, eventually forming soil. This soil formation process can take hundreds or even thousands of years before plants and other organisms can establish themselves. Therefore, primary succession involves numerous biological and geological steps before it can support complex ecosystems.
On the other hand, secondary succession occurs in areas where a disturbance, such as a wildfire, flood, or human activity like farming, has cleared or disrupted an existing ecosystem but left the soil intact. Because the soil is already present and may contain seeds, nutrients, and microorganisms, plant life can return much more quickly. Grasses and fast-growing plants often reappear first, followed by shrubs and trees. Animals may also return more rapidly due to the available food and shelter.
Fewer changes are necessary during secondary succession because the foundation of the ecosystem, including the soil and sometimes even surviving plants and animals, is still present. This significantly accelerates the recovery process compared to primary succession, which starts entirely from scratch. Therefore, option A correctly identifies that the reduced number of changes needed is the key reason why secondary succession proceeds more quickly than primary succession.
