A student records plant abundance along one transect. Abundance decreases as light intensity decreases. Soil moisture also increases along the transect.
Why can the student not conclude that light alone caused the change?
Soil moisture also varies and could affect plant abundance.
Light intensity is biotic and cannot affect plant abundance.
A transect measures distance and cannot record plant abundance.
Plant abundance must remain constant when soil moisture changes.
39 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.