Red squirrels and grey squirrels live in the same forest. Both species eat nuts and seeds.
The Table shows the number of each species in the forest between 2000 and 2020.
Table
| Year | Number of red squirrels | Number of grey squirrels |
|---|---|---|
| 2000 | 400 | 0 |
| 2005 | 300 | 120 |
| 2010 | 180 | 260 |
| 2015 | 90 | 380 |
| 2020 | 40 | 450 |
Calculate the percentage decrease in the number of red squirrels between 2000 and 2020.
Explain why the number of red squirrels decreased.
Grey squirrels carry a virus that kills red squirrels but does not harm grey squirrels.
State whether the virus is a biotic factor or an abiotic factor. Give a reason for your answer.
Suggest one resource, apart from food, that red squirrels and grey squirrels could compete for.
Explain why the number of red squirrels could increase if grey squirrels were removed from the forest.
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.