Students place quadrats at fixed intervals along a line running away from a tall wall and count the plants of one species in each quadrat. They also measure light intensity at each position. Their results are shown below.
| Distance from wall (m) | Light intensity (lux) | Number of plants |
|---|---|---|
| 0 | 1200 | 3 |
| 2 | 2400 | 7 |
| 4 | 3900 | 12 |
| 6 | 5600 | 17 |
| 8 | 7200 | 21 |
Which conclusion is supported by these results?
Plant numbers rose as light intensity rose, so the extra plants may have caused the higher light readings further from the wall.
Plant numbers rose as light intensity fell, so shade from the wall may have helped this species to grow.
Plant numbers rose by the same amount every 2 m, so distance from the wall may affect them more than light does.
Plant numbers rose as light intensity rose, so light may affect plant numbers, although other conditions may also have changed along the line.
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.