Two species of barnacle, species R and species S, live attached to the rocks on a rocky shore. Barnacles cannot move once they have attached to a rock. Species R grows faster than species S and pushes species S off the rock wherever the two species meet. Species R cannot survive being uncovered by the tide for long periods, but species S can. Where both species are present, species S is found only on the upper part of the shore, which is uncovered by the tide for several hours each day. Scientists removed all of species R from one area of the shore. Species S then spread downwards into the lower part of that area.
Explain why species S is normally found only on the upper part of the shore.
Suggest why species S spread downwards after species R had been removed.
Species R and species S both feed by filtering small organisms out of the sea water. Explain why the two species also compete with each other on the lower part of the shore.
40 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.