International A Level Biology / Membranes and transport
Gas exchange surfaces and Fick's law revision notes
Edexcel International A Level Biology (YBI11), chapter 4: Membranes and transport, specification point 2.1. Part of the full course.
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Surface area to volume ratio helps explain why large organisms need specialised gas exchange surfaces. Fick’s law shows how surface area, concentration difference and diffusion distance affect the rate of diffusion.