A large aquatic animal takes in oxygen from water across respiratory surfaces inside its body. A disease can damage these surfaces.
A scientist measured the same-sized region of respiratory surface in a healthy animal and in an animal with damaged surfaces. The temperature and oxygen concentration of the water were the same for both animals.
| Respiratory surface | Total surface area in the region in cm² | Mean barrier thickness in mm | Blood flow in cm³ per minute | Rate of oxygen transfer in mg per minute |
|---|---|---|---|---|
| Healthy | 180 | 0.004 | 20 | 0.64 |
| Damaged | 105 | 0.010 | 8 | 0.16 |
Calculate the percentage decrease in the rate of oxygen transfer from the healthy surface to the damaged surface.
Use the data to explain why the rate of oxygen transfer is lower across the damaged respiratory surface.
140 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.