A multicellular aquatic animal has no blood circulatory system when it is newly hatched. Oxygen enters across its whole outer surface.
The animal keeps the same body shape as it grows.
| Stage of growth | Total surface area / mm2\text{mm}^2mm2 | Volume / mm3\text{mm}^3mm3 | Greatest diffusion distance / mm\text{mm}mm |
|---|---|---|---|
| Newly hatched | 22 | 4.0 | 0.25 |
| Older | 88 | 32 | 0.50 |
Calculate the surface area to volume ratio of the animal at each stage of growth.
Give each answer in the form n:1n:1n:1.
Explain why the older animal is more likely than the newly hatched animal to need a blood circulatory 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.