Grey squirrels were brought to the UK from North America in the 1870s. Red squirrels are native to the UK. Both species eat nuts and seeds. Grey squirrels can also digest acorns, which red squirrels cannot digest. Grey squirrels carry a virus that kills red squirrels but does not harm grey squirrels.
Table: The estimated number of red squirrels and grey squirrels in the UK in 1950 and in 2020
| Species Estimated number in 1950 Estimated number in 2020 |
|---|
| :---: :---: :---: |
| Red squirrel 1 200 000 160 000 |
| Grey squirrel 800 000 2 700 000 |
Calculate the percentage decrease in the number of red squirrels between 1950 and 2020.
Give two biotic factors described in the information that have caused the number of red squirrels to decrease.
Suggest why grey squirrels compete more successfully than red squirrels for food.
63 exam-style questions on AQA GCSE Biology 7.1 Adaptations, interdependence and competition, covering 7.1.1 Communities, 7.1.2 Abiotic factors, 7.1.3 Biotic factors, and 7.1.4 Adaptations. Each one has a worked solution and a mark scheme showing where the marks go.