Q.Distinguish between primary and secondary succession.
🔒You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.
🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Ecological Succession
Plant succession is the gradual, orderly replacement of one plant community by another on the same site, seen whenever a barren or disturbed area is re-colonised over time. The first colonisers are pioneers; the intermediate communities that replace one another in sequence are seral communities; and the final, stable community is the climax community (the end-state itself called the climax). Succession is driven by three classes of cause acting in sequence — initiating causes (abiotic/biotic factors that create bare or disturbed ground, determining whether primary or secondary succession follows), continuing causes (migration, aggregation, competition, reaction — the ongoing processes reshaping the community), and stabilizing causes (chiefly climatic, and what eventually locks the community in place). It shares recognisable characteristics wherever it occurs: it is systematic, driven by changing abiotic/biotic factors, converts an unstable community into a stable one, and steadily increases species diversity, biomass, niche specialisation and soil humus while food relationships grow from a simple chain into a complex web. It is classified along several axes: primary (starting on genuinely barren ground, no prior community, slow) versus secondary (starting on a disturbed site with soil already present, faster); autogenic (driven by the vegetation's own biotic effects on itself) versus allogenic (driven by external abiotic factors); and autotrophic (green plants dominate early on, energy content rises) versus heterotrophic (bacteria/fungi/animals dominate early on, energy content falls). The process itself runs through seven fixed stages — nudation (bare ground appears), invasion/migration (propagules arrive), ecesis (the species establishes and can reproduce), aggregation (population grows), competition (for water, nutrients, light, space), reaction (the community modifies its own habitat and gets di …
The two kinds of succession are distinguished by what the land looks like when succession begins, and that starting condition in turn decides how fast the process runs. Comparing the substratum is therefore the key to telling them apart. …
The two types of ecological succession differ mainly in the starting substratum and, consequently, in speed.
| Basis | Primary succession | Secondary succession |
|---|---|---|
| Starting point | Begins in areas that never had any living organisms before — a bare, lifeless substratum, e.g. newly cooled lava, bare rock, newly formed sand dunes | Begins in areas where a pre-existing community was destroyed or removed, e.g. abandoned farmland, burnt or flooded areas |
| Substratum/soil | No soil is initially present; soil has to be formed from scratch by weathering and pioneer organisms | Some soil or sediment already exists from the earlier community |
- CBSE 2025Set F1 markMCQQ.In which of the following does secondary succession take place?(a) On sand(b) In degraded forests(c) On bare rocks(d) Newly formed ponds
›Reveal solutionSolution
Secondary succession starts on land that already had life and still has soil (e.g. degraded forests); bare rock, sand and new ponds are primary succession sites.
Succession is of two kinds:
- Primary succession starts on lifeless, soil-free surfaces — bare rocks, newly cooled lava, sand dunes, or newly formed ponds — and is very slow because soil must first form. …
- CBSE 2024Set ANNUAL1 markMCQQ.Which one of the following does not evolve further?(a) Climax community(b) Primary Succession(c) Pioneer Species(d) Seral Community
›Reveal solutionSolution
A climax community is the stable, self-perpetuating end-stage of ecological succession and does not evolve further under existing conditions.
Ecological succession proceeds through a pioneer community, a series of changing seral (transitional) communities, and finally reaches a climax community that is in equilibrium with the prevailing climate and environment. Because the climax community is stable and self-maintaining, it does not undergo further directional change unless the environment itself is …
- CBSE 2022Set ANNUAL1 markQ.What do you mean by Pioneer species?
›Reveal solutionSolution
Pioneer species are the hardy first colonisers of an empty habitat, initiating the process of ecological succession.
When ecological succession begins on an entirely new or disturbed substrate (such as bare rock in xerarch succession, or a newly formed pond in hydrarch succession), the very first organisms to establish themselves there are called pioneer species. They are typically hardy, fast-dispersing, stress-tolerant organisms (e.g. lichens and mosses on bare rock, or phytoplankton in a new pond) capable of surviving harsh initial conditions with little soil or nutrients. Through their growth and death, pioneer species gradually modify the environment (e.g. by adding organic …
- CBSE 2018Set ANNUAL1 markMCQQ.Lichens and Mosses are the stages of which type of succession?(a) Hydrarch(b) Marsh(c) Psammarch(d) Xerarch
›Reveal solutionSolution
Xerarch succession begins on dry, bare substrates like rock, starting with crustose lichens and progressing through mosses before herbs, shrubs, and trees establish.
Ecological succession that begins in a dry area (e.g., bare rock) is called xerarch succession, and it proceeds through a well-defined sequence of seres:
- Crustose lichens (pioneer community) colonise bare rock, secreting acids that weather the rock surface and begin soil formation.
- Mosses replace lichens once a thin layer of soil has formed, further building organic matter. …
- CBSE 2017Set ANNUAL1 markQ.What is meant by ecological succession?
›Reveal solutionSolution
Succession is the sequential, directional replacement of communities in an area, culminating in a stable climax community.
Ecological succession is the natural process by which the community structure of an area changes progressively over time. It starts with pioneer species that are able to colonise a bare (primary succession) or disturbed but previously vegetated (secondary succession) area. These pioneers gradually alter the local environment (e.g. by contributing to soil formation), making conditions suitable for other, often more complex, species to establish. This replacement continues through a series of intermediate seral stages until a relatively stable, self-sustaining climax community is reached, w …
- CBSE 2016Set ANNUAL1 markQ.What is ecological succession?
›Reveal solutionSolution
Succession is the sequential, directional change of communities in an area, ending in a stable climax community.
Ecological succession refers to the natural, sequential process by which the species composition of a community in a particular area changes over time. It begins when pioneer species colonise a bare or disturbed area (primary succession, e.g. bare rock) or a previously vegetated but disturbed area (secondary succession, e.g. after a fire or flood). These pioneers gradually modify the environment (soil formation, microclimate), making it suitable for other species to invade and eventually replace them. This sequence of communities (the sere) continues through several intermediate stages until a relatively stable, self-perpetuatin …
🎓Unlock everything free for 14 days
- ✓Full step-by-step solutions
- ✓Concept-first explanations
- ✓Methods, shortcuts & mistakes
- ✓PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.