Flatworms are multicellular animals with a very thin, flat body.
Flatworms do not have a blood circulatory system.
Which statement explains how flatworms can survive without a circulatory system?
Their flat shape gives a large surface area : volume ratio and short diffusion distances.
Their flat shape gives a small surface area : volume ratio, so they need less oxygen.
Their cells respire anaerobically, so no oxygen needs to be transported to the cells.
Their large volume lets oxygen be stored in the body, so it does not need transporting.
114 exam-style questions on OCR GCSE Biology 2.2 The challenges of size, covering 2.2.1 Exchange surfaces and surface area : volume ratio, 2.2.2 Substances transported in organisms, 2.2.3 The human circulatory system, 2.2.4 The heart and blood vessels, 2.2.5 Red blood cells and plasma, 2.2.6 Uptake of water and mineral ions by plants, 2.2.7 Transpiration and translocation, 2.2.8 Xylem and phloem, 2.2.9 Environmental factors and water uptake, and 2.2.10 Using a potometer. Each one has a worked solution and a mark scheme showing where the marks go.