CAIE A Level Biology 9700 · Control and coordination
The Venus fly trap (Dionaea muscipula) captures insects by rapidly closing its modified leaf lobes. Each lobe has sensitive hairs. If a single hair is touched once, the trap does not close. However, if the same hair is touched twice within about 20 seconds, the trap snaps shut. Explain why the trap only closes in response to repeated stimulation.
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.
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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