Fig. 1 is a photograph-style line drawing of a Venus flytrap plant in a botanic garden. An insect has touched trigger hairs inside one leaf. The open leaf i...
Question 1 Report
Fig. 1 is a photograph-style line drawing of a Venus flytrap plant in a botanic garden. An insect has touched trigger hairs inside one leaf. The open leaf is shown on the left and the same leaf after closing is shown on the right. Although plants do not move from place to place like most animals, their cells can respond to changes in their surroundings. The plant grows in soil with very little available nitrate.
(a) Describe the response of the leaf when the insect touches the trigger hairs. [3]
(b) Explain how catching an insect helps this plant to grow in nitrate-poor soil. [4]
(c) State the main source of energy used by the plant to make food. [1]
(d) Explain why the closing of the leaf is not locomotion. [3]
(e) Design an investigation to test whether repeated touching of a trigger hair causes the leaf to close. [3]
Answer Details
(a) The trigger hairs detect touch and are stimulated. The two leaf lobes move together, closing around and trapping the insect. This is a plant response to a stimulus. [3]
(b) An insect contains protein and other nitrogen-containing compounds. The plant digests the insect, then absorbs nitrogen-containing substances or nitrates. Nitrogen is needed to make amino acids and proteins, which are used to make new cells and support growth. [4]
(c) The main energy source is light from the Sun. [1]
(d) Closing happens in only part of the plant, the leaf. The whole plant does not change position because it remains rooted in the same place. It is movement, but not locomotion. [3]
(e) Use similar-sized open leaves. Touch each leaf's trigger hairs a stated number of times and record whether it closes and/or the time taken to close. Include comparable leaves that are not touched as a control, while keeping light intensity, temperature and watering the same. [3]
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