Bird species A and bird species B live in a salt marsh. Bird species A feeds only on shore crabs. Bird species B feeds on shore crabs and marine worms.
The table shows results from two surveys of the same area.
| Organism | Measurement | Survey 1 | Survey 2 |
|---|---|---|---|
| shore crab | estimated population | 124 000 | 31 000 |
| marine worm | estimated population | 187 000 | 185 000 |
| bird species A | breeding pairs counted | 42 | 16 |
| bird species B | breeding pairs counted | 39 | 35 |
Explain how the food relationships could account for the changes in the number of breeding pairs of bird species A and bird species B between survey 1 and survey 2.
After survey 2, the marine worm population falls sharply while the shore crab population remains at its survey 2 estimate.
Predict how the number of breeding pairs of bird species B would change. Explain your answer.
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.