A scientist compares two multicellular organisms. Each organism is modelled as a solid cuboid.
The organisms contain the same number of respiring cells per cubic centimetre. Oxygen can enter only across the outer surface.
| Organism | Total surface area (cm²) | Volume (cm³) | Maximum distance of a cell from the outer surface (cm) |
|---|---|---|---|
| M | 54 | 27 | 1.5 |
| N | 78 | 27 | 0.5 |
Calculate the surface area to volume ratio of each organism.
Give each ratio in the form n:1n:1n:1.
Explain which organism is more likely to need a specialised exchange surface and a transport system.
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.