CAIE A Level Biology 9700 · Gas exchange

Gas exchange: describe question

Describe4 marksStandard

A student identifies the following tissues in the wall of a bronchus from a photomicrograph: ciliated epithelium, goblet cells, smooth muscle, and elastic fibres.

Describe the function of each of these tissues in the gas exchange system.

How this question is marked

4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.

Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.

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