CAIE A Level Biology 9700 · Homeostasis
A student investigates the response of stomata in leaves of a tomato plant. Under normal daylight conditions, the stomata are open. When the plant is subjected to drought stress, the stomata close. Explain the cellular mechanisms that lead to stomatal opening in response to light and closure in response to water stress.
6 marks, so the mark scheme is looking for about 6 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.