### GCSE Biology Required Practical - Quadrat Sampling

Investigate the relationship between organisms and their environment using field-work techniques, including quadrats and belt transects.

• This investigation involves the use of a belt transect along a gradient (e.g. shaded area to an area with no shade).
• It involves students thinking about how to sample their chosen area, including the identification and observation of plants/organisms.

How to estimate population size using random sampling with a quadrat?
Observe changes in population along a transect.

00:00 Estimating population - random sampling
01:10 Counting organisms
02:07 Calculating population
02:40 Using a transect
03:50 Analysis - biotic & abiotic factors

Required Practical: Sampling Organisms

1. Sampling organisms by using random sampling.

Check out the sample question and solution on Sample Assessment Material (page 48), paper 1BI0/1BH and 1BIO/1BF.

A scientist wanted to estimate the number of earthworms in a field using a quadrat.
The scientist places the quadrats at random on the surface of the area being sampled and then watered the area with a very dilute solution of mustard.
This causes the earthworms to come to the surface to be counted.
Give a reason why the quadrats were placed at random.

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