Autogenic succession is caused by a change in the soil, or plants blocking sunlight; internal ecosystem changes.

• A. External climate change
• B. Changes in soil or shading by plants
• C. Random colonization
• D. Human management

Answer: (B)

Autogenic succession unfolds from changes created by the organisms within the ecosystem itself. As plants grow and die, they build up soil organic matter and alter soil nutrients and structure. The developing vegetation also changes light availability through canopy shading, which redefines which species can establish and persist. These internal modifications to soil and light conditions drive the next stages of succession, without needing external forces to change the environment first.

That’s why changes in soil or shading by plants are the best description. External climate change would be an outside influence, not caused by the ecosystem itself. Random colonization and human management are not internal modifications driving the succession process.