Students want to estimate the number of daisies in a field using quadrats.
Which method best reduces selection bias?
placing quadrats where daisies are clearly visible
throwing quadrats from one corner of the field
placing quadrats beside the path across the field
using random coordinates to position each quadrat
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.