The Venus fly trap, Dionaea muscipula, is a plant that can capture insects. Each leaf of a Venus fly trap is modified to form 2 lobes. Fig. 7.1 shows how the leaf of a Venus fly trap appears folded (closed) when an insect has been captured.

1. (a)(i)Suggest a reason why the Venus fly trap needs to capture insects, even though it carries out photosynthesis.[1]
2. (a)(ii)The leaves are specialised to form 2 lobes. The lobes are red on the upper surface. Suggest why the lobes are red.[1]
3. (a)(iii)The lobes have sensory hairs. Touching 1 sensory hair will not cause a response by the leaf. At least 2 sensory hairs need to be touched within 20 seconds to cause a response in the leaves. State the advantage to the plant of producing a response only when 2 sensory hairs are touched within 20 seconds.[1]
4. (a)(iv)When an insect has been trapped, the leaves have to remain closed for a number of days. Suggest why this needs to happen.[1]
5. (b)Action potentials are produced by the Venus fly trap during the closure of a leaf. Each action potential is also associated with a refractory period. This is similar to the action potential and refractory period observed in a mammalian neurone during nerve impulse transmission. Explain the role played by the refractory period in the transmission of an impulse in a mammalian neurone.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.