CAIE A Level Biology 9700 · Gas exchange
The human gas exchange system includes airways of varying diameters, from the trachea to the bronchioles. Compare the structure of the trachea with that of a bronchiole and explain how the distribution of cartilage and smooth muscle in each is related to its function.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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