Concept:Ecological succession is the gradual and predictable change in the structure and species composition of a community over time.
Explanation:Succession occurs in two main forms.
Primary succession starts on surfaces with no previous community, such as bare rock or after a volcanic eruption.
Secondary succession begins in areas where an existing community has been disturbed but the soil remains, such as after a forest fire.
During succession, species composition, population sizes, and interactions change step by step.
These changes are orderly and lead toward a more stable, mature ecosystem called the climax community.
Therefore, succession is not random movement or competition alone; it is a predictable ecological process.
Answer:D. The gradual and predictable change in a community over time.