Which statement best defines ecological succession?

• A. A rapid change in population size caused by predation.
• B. A single generation replacement.
• C. The progressive change in species composition of an ecosystem over time after a disturbance.
• D. The mutual benefit of species in a community.

Answer: (C)

Ecological succession is the gradual, directional change in which the species makeup of an ecosystem shifts over time, usually after a disturbance or major environmental change. It begins with pioneer species that first colonize barren ground, and as these organisms grow and die, they alter soil, light, moisture, and nutrient conditions. Those changes make the habitat suitable for other species, leading to a new community composition, and the process continues until a relatively stable, mature community develops (though the end point can vary by system). This idea—a progressive change in which the species present in an ecosystem evolve over time after a disturbance—best captures what ecological succession is. The other statements describe different concepts: rapid population changes driven by predation are about population dynamics, a single generation replacement doesn’t reflect the successive, multi-generational shifts in community composition, and mutualism refers to beneficial interactions, not the long-term change in which species are present.