Two multicellular aquatic animals, J and K, take in oxygen from the water. Their body surfaces are permeable to oxygen. Animal K also has a folded exchange organ connected to vessels containing circulating fluid.
| Measurement | Animal J | Animal K |
|---|---|---|
| body surface area in mm2\mathrm{mm^2}mm2 | 24 | 48 000 |
| body volume in mm3\mathrm{mm^3}mm3 | 4 | 480 000 |
| greatest distance from the body surface to a cell in mm | 0.15 | 25 |
| activity level | low | high |
Explain which animal is more likely to obtain enough oxygen by diffusion across its body surface, why the other animal requires the folded exchange organ and circulating fluid, and how a large decrease in circulation rate would affect its oxygen uptake.
102 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.