5.2.7Unit 5: Respiration, Internal Environment, Coordination and Gene Technology
Ecological Succession — IAL Edexcel Linear Revision Notes & Topical Questions
5 min read 5 parts Lesson 22 of 36 Unit quiz
Section 1 of 5Primary Succession
Primary succession starts on bare ground with no soil.
1
Wind-blown spores and seeds land on bare rock and pioneer species, such as lichens and mosses, colonise it.
2
Pioneers are tolerant of harsh conditions, and when they die and decompose they form a thin soil.
3
Soil allows small plants such as grasses to grow, adding more organic matter.
4
Shrubs and then trees develop, shading out earlier species, until a stable climax community forms.
5
Each group of species changes the environment in a way that suits the next group more.
Section 2 of 5Secondary Succession
Secondary Succession
Starting point
- Land that has lost its community but still has soil, such as after fire or abandoned farmland.
Speed
- It is faster than primary succession because seeds and nutrients already exist.
Stages
- Annual plants are followed by perennials, shrubs and then woodland.
Climax
- It can reach the same type of climax community as primary succession.
Examples
- A volcanic island is a primary succession, and an abandoned field is secondary succession.
| Feature | Primary | Secondary |
|---|---|---|
| Starting point | Bare rock or sand, no soil | Soil already present |
| Speed | Slow | Faster |
| Examples | Volcanic island, retreating glacier | Fire, felled woodland |
Section 3 of 5Changes During Succession
Soil
- Soil becomes deeper, richer in nutrients and better at retaining water.
Biodiversity
- The number of species increases through the early stages.
Environment
- Conditions become less harsh, so more species can survive.
Biomass
- Total biomass and community stability increase over time.
Section 4 of 5Climax and Management
Climax community
- A stable community with little change, in balance with the climate.
Plagioclimax
- Human activity such as grazing or mowing keeps succession at an earlier stage.
Conservation
- Managers sometimes prevent succession to preserve habitats like heathland or meadow.
Dynamic
- Even a climax community changes slowly when conditions or disturbances change.
Section 5 of 5Exam Checklist & Tips
5.2.7 – Key Points for the Exam
- Succession The gradual change in a community over time.
- Pioneer species The first species to colonise a new area.
- Climax community The stable community at the end of succession.
- Primary succession Succession starting on bare ground with no soil.
- Secondary succession Succession on land where soil remains.
Common Mistakes
- Saying primary succession begins in soil; it starts on bare rock or sand.
- Writing that the climax community never changes.
- Stating that biodiversity is highest in the pioneer stage.
- Forgetting that organisms change their own environment during succession.
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