Define primary succession.

The colonisation and development of a community in a previously uninhabited area with no soil, such as bare rock or volcanic lava.

What are pioneer species?

The first organisms to colonise a bare habitat, typically lichens and mosses that can survive harsh conditions and begin soil formation.

Explain how pioneer species modify the environment during succession.

They weather rock, add organic matter when they die, and improve soil quality, enabling other species to colonise.

Define climax community.

The final, stable stage of succession where the community is in equilibrium with the environment and species composition remains relatively constant.

What is deflected succession?

Succession that is prevented from reaching the climax community by human activity or natural events, maintaining the ecosystem at an earlier seral stage.

Define distribution in an ecological context.

Where organisms are found within an ecosystem.

OCR A-Level Biology H420

Cell Structure

Topic overview Microscopy, slide preparation and staining Biological drawings, magnification and resolution Eukaryotic cell ultrastructure The secretory pathway and the cytoskeleton Prokaryotic and eukaryotic cells compared

Biological Molecules

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Cell Division, Cell Diversity and Cellular Organisation

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Classification and Evolution

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Excretion as an Example of Homeostatic Control

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Patterns of Inheritance

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Ecosystems

Succession, distribution and abundance

3 things to know
Components 02 and 03

Overview

Pioneer species, climax communities and deflected succession, and estimating abundance with quadrats, transects, percentage cover and mark-release-recapture.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

Explain primary succession.

Process

How is population size estimated for mobile animals?

Key term

Describe how random sampling is carried out using quadrats.

Questions from this subtopic

Each one with the model answer underneath.

1
Define primary succession.
Model answer
The colonisation and development of a community in a previously uninhabited area with no soil, such as bare rock or volcanic lava.
2
What are pioneer species?
Model answer
The first organisms to colonise a bare habitat, typically lichens and mosses that can survive harsh conditions and begin soil formation.
3
Explain how pioneer species modify the environment during succession.
Model answer
They weather rock, add organic matter when they die, and improve soil quality, enabling other species to colonise.
4
Define climax community.
Model answer
The final, stable stage of succession where the community is in equilibrium with the environment and species composition remains relatively constant.
5
What is deflected succession?
Model answer
Succession that is prevented from reaching the climax community by human activity or natural events, maintaining the ecosystem at an earlier seral stage.
6
Define distribution in an ecological context.
Model answer
Where organisms are found within an ecosystem.

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