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| Question | Answer |
| What are the uses of exchange systems? | Aerobic respiration Metabolic reactions Excretion of wastes |
| How does the surface area: volume ratio of a smaller organism compare to that of a larger organism? | Smaller organisms have bigger surface area:volume ratios than larger organisms |
| What is the equation for the surface area and volume of a sphere? | SURFACE AREA 4πr² VOLUME 4/3 πr³ |
| What is the equation for the surface area and volume of a cylinder? | SURFACE AREA 2πrh+2πr² VOLUME πr² h |
| How does exchange occur in single-celled organisms? | Substances can diffuse directly into/out of the cell across the cell surface membrane. The diffusion rate is quick due to the short distance and high SA:V ratio |
| Why do multicellular organisms need specialised exchange surfaces? | Some cells are too deep within the body Larger animals have a low SA:V ratio Higher metabolic rate; they use up oxygen and glucose faster |
| What are the features of exchange surfacs? | Large surface area Thin (short distance) Good blood supply and/or ventilation |
| Give an example of an exchange surface with large surface area | Root hair cells - a large SA helps increase rate of absorption |
| Give an example of an exchange surface which is thin (short distance) | Alveoli - made of a single layer of thin, flat cells called alveolar epithelium |
| Give an example of an exchange surface which has a good blood supply and/or ventilation | Alveoli are surrounded by a large capillary network, giving each alveolus its own blood supply. Blood constantly takes oxygen away and brings more CO₂ |
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