A flatworm is a multicellular animal that lives in ponds. A flatworm is 20 mm long and 15 mm wide, but only 0.50 mm thick. It has no lungs, no gills and no blood system. All of the oxygen a flatworm needs diffuses in across its body surface.
Suggest two features of the body of a flatworm that allow diffusion alone to supply all of its cells with oxygen.
A different pond animal has the same volume as a flatworm, but its body is shaped like a sphere. Explain why this animal needs a transport system, but a flatworm does not.
A flatworm becomes more active. Explain why the rate at which oxygen diffuses into the flatworm increases.
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.