Sampling and Fieldwork Techniques

To study the distribution and abundance of organisms in the real world, ecologists use sampling techniques. You cannot count every single organism in an ecosystem, so you take a sample and use it to estimate the total population. This lesson covers the key sampling methods you need for AQA GCSE Biology, including the Required Practical on using quadrats and transects.

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Why Do We Sample?

It is usually impossible to count every organism in a habitat because:

• The habitat may be too large
• Organisms may move around (animals)
• Counting every individual would take too long and be too expensive
• The process of counting might disturb the habitat

Instead, ecologists take representative samples and use them to make estimates about the whole population. For results to be reliable, samples must be: