CAIE A Level Biology 9700 · Homeostasis
A gardener notices that during a period of drought, the leaves of a tomato plant wilt and the stomata close. Outline the mechanism by which guard cells control stomatal aperture, including the role of abscisic acid (ABA) during water stress.
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.
Outline means: Give the main points briefly. Less detail than describe, but every key step has to be there. One short line per step, in order. The marks are for coverage, not depth.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.