A seaweed builds up iodide ions until the concentration inside its cells is 1000 times the concentration in the seawater around it. Which observation would give the strongest evidence that this uptake is by active transport?
Uptake slows when the seaweed is put in seawater at a lower temperature
Uptake slows when the seaweed is put in seawater of a higher salinity
Uptake stops when the seaweed is put in seawater containing no oxygen
Uptake stops when the seaweed is put in seawater containing no iodide
58 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.