A student investigates the distribution of a plant species called glasswort at two sites in a salt-marsh community. The student records the following data.
| Measurement | Site R | Site S |
|---|---|---|
| Concentration of dissolved salts in soil water (soil salinity) / g L−1^{-1}−1 | 18 | 32 |
| Number of snails feeding on glasswort per m2^22 | 3 | 3 |
| Percentage cover of glasswort / % | 42 | 15 |
The student concludes that soil salinity may affect the distribution of glasswort.
State which measurement in the table is an abiotic factor.
Explain why the data support the student's conclusion but do not prove that soil salinity is the only cause of the difference in glasswort cover.
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.