A conservation group sampled woodlice in a woodland plot where rotting logs lie scattered across the ground. The group placed ten quadrats at randomly selected positions and counted the woodlice in each quadrat. Quadrats 3 and 8 happened to land on rotting logs.
| Quadrat | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|
| Number of woodlice | 2 | 0 | 21 | 1 | 3 | 0 | 2 | 18 | 1 | 2 |
One member of the group says that the count from quadrat 3 alone would have given a good estimate of the woodlice in the plot.
Explain why the mean of all ten quadrats gives a better estimate than quadrat 3 alone. Use the results in your answer.
82 exam-style questions on Edexcel GCSE Biology 9.1 Ecosystems and interdependence, covering 9.1.1 Levels of organisation in ecosystems, 9.1.2 Abiotic and biotic factors, 9.1.3 Importance of interdependence, 9.1.4 Parasitism and mutualism, and 9.1.5 Determining number of organisms in an area. Each one has a worked solution and a mark scheme showing where the marks go.