Investigating Ecosystems

This lesson covers the practical methods used to investigate ecosystems, including quadrats, transects, kick sampling, mark-release-recapture, and statistical analysis, as required by the Edexcel A-Level Biology specification (9BI0), Topic 10 -- Ecosystems.

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Why Sample?

It is usually impossible to count every organism in an ecosystem. Instead, ecologists take samples and use the data to estimate population size, distribution, and abundance. Good sampling must be:

• Representative -- the sample should reflect the whole area
• Random -- to avoid bias (using random number generators for coordinates)
• Sufficient in size -- more samples = more reliable data

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Quadrats

A quadrat is a square frame (commonly 0.5 m x 0.5 m or 1 m x 1 m) placed on the ground to define a sample area. Organisms within the quadrat are counted or their cover is estimated.

Types of Data Collected