CAIE A Level Biology 9700 · Control and coordination
Venus fly trap plants (Dionaea muscipula) capture insects by rapid closure of their modified leaves. The leaves have sensory hairs on the inner surface. When an insect touches a hair, an action potential is generated. However, the trap often does not close after a single touch; it requires two touches within about 20 seconds. Explain how repeated stimulation leads to trap closure.
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.
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