Core Practical: Investigating Population Size Using Quadrats and Transects

This lesson covers the core practical on investigating population size using quadrats and transects as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand how to use random sampling and systematic sampling to estimate population size, calculate population estimates and evaluate the reliability of your results.

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Why Sample?

It is usually impossible to count every organism in a habitat. Instead, scientists take samples — small representative portions of the habitat — and use the data to estimate the total population.

For sampling to be valid:

• It must be representative of the whole area
• It must avoid bias (personal choice about where to sample)
• Multiple samples must be taken to ensure reliability

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Equipment