A large marine worm takes in dissolved oxygen through a specialised exchange organ. The organ is made of many flattened plates. Water moves continuously over the plates, while blood flows through vessels inside each plate and carries oxygen to the worm's body cells.
State which factor affecting the rate of diffusion is increased by having many plates.
Explain why the continuous movement of water and blood helps oxygen enter the blood quickly.
Two smaller species of marine worm can absorb oxygen across their outer body surfaces.
| Worm | Surface area to volume ratio in mm⁻¹ | Maximum distance from the outer surface to a body cell in mm |
|---|---|---|
| P | 4.0 | 0.5 |
| Q | 1.0 | 2.0 |
Use the data to compare how effectively diffusion across the outer body surface supplies oxygen to the cells of worms P and Q.
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.