Worksheets and lesson ideas to challenge students aged 11 to 16 to think hard about surface area to volume ratio (GCSE and Key Stage 3)
Overview: surface area to volume ratio is an important biological concept for students to master – relevant to gas exchange, heat loss and cell structure. To calculate this ratio involves some simple maths, but it’s worth practicing this with students and clarifying units for area and volume. Some data to use for adults and infants can be found here.
Key concept: when the surface area to volume ratio is small, organisms require specialised structures to enable gas exchange to take place.
Where to start?
Surface area can be a quite a challenging concept for students to understand. A simple way to introduce this concept is to ask students whether they would use more wrapping paper to wrap a DVD boxset, or to wrap each DVD individually. You can also think about the volume of icing required to ice one cake, or each slice individually.
Surface area to volume ratio: why don’t bacteria have lungs?
- Why don’t bacteria have lungs?
- Why do babies get cold quickly?
- Why do babies dehydrate faster than adults in warm weather?
- Why are mitochondrial membranes folded?
These are great questions to use to explore the concept of surface area to volume ratio in your classroom. Multicellular organisms require a gas exchange system as diffusion would occur too slowly. Babies get cold quickly because they have a large surface area to volume ratio and so transfer heat quickly to their surroundings. The inner membrane of mitochondria is folded to increase the surface area available for respiration to take place.