Ecological Succession and Balance
NCERT Class 12 • Biology • Chapter "Ecosystem" | NCERT Class 10 • Science • Chapter "Our Environment"
Ecological Succession and Balance
An ecosystem is not fixed. Over time the community of organisms living in an area changes in an orderly and predictable sequence until it reaches a relatively stable state. This process is ecological succession, and its end point is the climax community.
Types of Succession
- Primary succession begins on a surface where no life existed before, such as bare rock, a new volcanic island or a newly formed sand dune.
- It starts with pioneer species such as lichens and mosses, which can survive on bare rock and slowly create soil.
- As soil builds up, grasses, herbs, shrubs and finally trees can establish themselves.
- Primary succession is very slow because soil has to be created from nothing.
- Secondary succession begins where an existing community was destroyed but the soil remains, as after a fire, flood or abandonment of a field.
- It is much faster because soil, seeds and nutrients are already present.
- The climax community is the stable final stage in balance with the local climate and soil.
Ecological Balance and Its Disturbance
- Ecological balance is the state in which the populations of species in an ecosystem remain relatively stable over time.
- It rests on the interdependence of producers, consumers and decomposers and on the cycling of nutrients.
- Deforestation, overgrazing, pollution, overfishing and introduction of alien species all disturb this balance.
- An alien or invasive species can multiply unchecked because its natural predators are absent in the new place.
- Removing a single species can have effects far beyond it, since the food web links everything to everything else.
- Keystone species have an effect out of proportion to their numbers, so their loss changes the whole ecosystem.
- Restoring balance requires afforestation, pollution control, protection of habitat and regulated use of resources.
| Type | Starts On | Speed |
|---|---|---|
| Primary succession | Bare rock or new surface | Very slow |
| Secondary succession | Soil after disturbance | Much faster |
| Climax community | Stable final stage | Persists till disturbed |
Climax community — the stable final community that develops at the end of ecological succession, in balance with the local climate.
Exam me kaise aata hai
- Succession that begins on bare rock is — primary succession
- The first organisms to colonise bare rock are — pioneer species
- The stable final stage of succession is the — climax community
- A species multiplying unchecked in a new place is — an invasive species
UPSC/State PSC ke liye
- Secondary succession is faster precisely because soil already exists, which shows that soil formation is the slow step in primary succession.
- Invasive species succeed because they arrive without the predators, parasites and competitors that limited them in their original home.
Yahan confuse hote hain
✗ Primary and secondary succession take the same time | Primary is far slower because soil must form first | ✓
✗ An ecosystem never changes once formed | It changes through succession until it reaches a climax | ✓
✗ Removing one species affects only that species | The food web transmits the effect widely | ✓
Ek nazar me
- Succession is the orderly change of a community until it becomes stable.
- Primary succession starts on bare rock with pioneer species and is very slow.
- Secondary succession starts with soil already present and is faster.
- Ecological balance rests on interdependence and is disturbed by human activity and invasive species.
Ab practice karein
Ecosystem aur ecology se har exam me concept based questions aate hain. ExamAtlas ke mock test se abhi practice karein.