A-Level Biology

Investigating Plant Succession in Mini-Ecosystems

Plant succession is one of those A-Level Biology topics that really comes alive when students can see it happening rather than just memorising definitions. While textbooks focus on dunes, quarries and post-glacial landscapes, the same principles can be explored very effectively using mini-ecosystems in the classroom or lab.

These small-scale systems allow students to observe how plant communities change over time, how abiotic factors influence growth, and how competition gradually shapes an ecosystem.

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What Is Plant Succession?

Plant succession is the gradual change in species composition of a community over time.

Students need to understand two key types:

• Primary succession – begins on bare substrate with no soil (e.g. rock, sand)

• Secondary succession – occurs where soil already exists after disturbance (e.g. fire, flooding)

In a mini-ecosystem, we usually model secondary succession, as soil and nutrients are already present.

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Creating a Mini-Ecosystem for Succession Studies

A simple bottle, jar or tank can become a powerful teaching tool.

Typical Setup

• Clear container (plastic bottle, aquarium, large jar)

• Soil or compost layer

• Seeds (grasses, fast-growing plants, moss)

• Small stones or sand for drainage

• Controlled water input

• Light source (window or grow light)

Once sealed or semi-sealed, the system becomes largely self-sustaining, allowing long-term observation.

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What Students Can Investigate

Mini-ecosystems allow students to track many aspects of succession:

1. Changes in Species Composition

• Pioneer species establish first

• Slower-growing but competitive species appear later

• Some early species decline due to competition for light and nutrients

2. Abiotic Factors

Students can measure:

• Light intensity

• Soil moisture

• Temperature

• Soil pH (where practical)

These link directly to exam questions on limiting factors.

3. Competition and Adaptation

As biomass increases:

• Competition for light intensifies

• Taller or broader-leaved plants gain advantage

• Root competition becomes more significant

This naturally reinforces ideas about selection pressures and adaptation.

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Linking to the A-Level Specification

This practical work supports several key specification areas:

• Succession and climax communities

• Interactions between biotic and abiotic factors

• Sampling techniques and limitations

• Evaluating experimental design

• Using data to describe ecological change

It also gives excellent material for practical endorsement skills, especially observation, recording, and evaluation.

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Why Mini-Ecosystems Work So Well

From a teaching perspective, they have some big advantages:

• Low cost and reusable

• Safe and manageable in school labs

• Scalable from demonstration to individual projects

• Ideal for long-term data collection

• Excellent for stretch and challenge discussions

Students often become surprisingly invested in “their” ecosystem — which makes the biology stick.

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Exam Tip for Students

When answering succession questions:

• Always link species change to abiotic change

• Use correct terms: pioneer species, competition, biomass, climax community

• Avoid vague phrases like “plants grow better” — explain why

If you’ve built a mini-ecosystem yourself, you’ll have concrete examples ready for extended answers.