Surface area to volume ratioAQA A-Level Biology: Mind map

Exam questions on Surface area to volume ratio

1. Biology students make cube-shaped models of organisms to investigate how size affects the exchange of substances. They compare a small cube with sides of 3 cm and a larger cube with sides of 6 cm.
   Explain why an organism the size of the 6 cm cube is less able to exchange substances by diffusion across its body surface alone than one the size of the 3 cm cube.2 marks
2. A shrew has a body mass of about 8 g and must feed almost continuously. An elephant has a body mass of about 4000 kg and eats for much of the day, but eats far less food for each kilogram of its body mass. Both are mammals that maintain a constant body temperature.
   Elephants have very large, thin ears with many blood vessels near the surface. Explain how this helps an elephant to lose heat despite its small surface area to volume ratio.2 marks
3. Two cube-shaped model organisms are made. Organism A has sides of 1 cm and organism B has sides of 4 cm. The cells in both models respire at the same rate for each cm³ of volume.
   Calculate the surface area to volume ratio of organism A and of organism B. Show your working.3 marks