A fish keeps the concentration of salts in its blood at an optimum level. When the salt concentration in the blood rises, cells in the gills pump salts out of the blood. Which part of this control system are the cells in the gills?
The effector, because they bring about the change in the blood
The receptor, because they respond to the salt concentration
The coordination centre, because they process the information
The stimulus, because they alter the concentration of the salts
76 exam-style questions on AQA GCSE Biology 5.1 Homeostasis, covering 5.1 Homeostasis. Each one has a worked solution and a mark scheme showing where the marks go.