CAIE A Level Biology 9700 · Gas exchange
A student examines transverse sections of a trachea and a bronchiole under a light microscope. The trachea wall contains distinct C-shaped rings of cartilage, while the bronchiole wall contains no cartilage but has a relatively thicker layer of smooth muscle. Explain the functional significance of these differences in the distribution of cartilage and smooth muscle between the trachea and bronchioles.
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.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.