Leeches attach to the skin of fish and feed on their blood. The leeches later detach and the fish remain alive.
Scientists kept two groups of similar young fish in identical tanks for eight weeks. Leeches were added to one tank only. The table shows the results.
| Tank | Mean mass gain of fish in g |
|---|---|
| Without leeches | 60 |
| With leeches | 35 |
Name the ecological relationship represented by this feeding behaviour.
State which organism is the host in this relationship.
Use the results to give one effect of the leeches on the fish.
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.