Tormentil is a low-growing plant found on heathland.
Students placed quadrats along one belt transect from open heath into an area of dense gorse. Their pilot results are shown in the table.
| Distance along transect in m | Percentage cover of tormentil | Light intensity in lux |
|---|---|---|
| 0 | 72 | 58 000 |
| 2 | 63 | 49 000 |
| 4 | 52 | 39 000 |
| 6 | 37 | 27 000 |
| 8 | 21 | 15 000 |
| 10 | 8 | 6 000 |
The students claim that light intensity is the only factor affecting the distribution of tormentil.
Describe how the students should extend their investigation to obtain reliable evidence about the relationship between light intensity and tormentil abundance, and how they should use the evidence to decide whether their claim is justified.
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.