Q.93 The term “ecological succession” refers to:
(A) A process wherein newer species populate a region that was devoid of flora and fauna
(B) A transition phase wherein one particular set of species is replaced by another set of species
(C) Changes in the community due to a disturbance in the habitat
(D) All the above
Ecological succession definition describes the predictable, directional change in community structure over time as one set of species replaces another. This GATE Life Sciences question tests core ecology knowledge from standard textbooks like Odum.
Option Analysis
(A) A process wherein newer species populate a region that was devoid of flora and fauna
This matches primary succession, starting on bare areas like new volcanic rock with pioneer species (e.g., lichens) building soil for later communities.
(B) A transition phase wherein one particular set of species is replaced by another set of species
Correct core definition: succession involves seral stages where early species (pioneers) modify the environment, outcompeted by successors until climax community.
(C) Changes in the community due to a disturbance in the habitat
This describes secondary succession or disturbance response (e.g., forest regrowth post-fire), a subset but not the full ecological succession definition.
(D) All the above
Best answer, as it encompasses primary (A), general replacement (B), and secondary/disturbance-driven (C) processes in a complete ecological succession framework.
Succession Stages and Types
| Type | Starting Point | Key Process | Example |
|---|---|---|---|
| Primary | Bare, lifeless area (no soil) | Pioneer colonization to climax | Lava flow → lichens → forest |
| Secondary | Disturbed habitat (soil present) | Faster regrowth post-disturbance | Fire-cleared field → shrubs → trees |
Succession progresses via nudation (bare area), invasion (pioneers arrive), competition/coaction, reaction (environment changes), and stabilization (climax). Primary is slower; secondary quicker due to existing soil.
GATE Exam Insights
For competitive exams, recall Clements’ holistic view: communities as superorganisms evolving predictably to climax. Disturbances reset to early seral stages, emphasizing (D) as comprehensive. Practice PYQs linking to biodiversity, ecosystem stability.
