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Tropic responses: exam questions

5 questions, 14 marks. Write your answers on paper, then open each mark scheme.

Spec 14.5Questions and mark scheme (PDF)3 pages

Question 1

A seedling is placed on its side in the dark. After some days the root grows downwards. Which statement describes this response?

  1. Growth away from gravity
  2. Growth towards light
  3. Growth towards gravity
  4. Growth away from light
[1 mark]
Show mark scheme for question 1

Answer: C (1)

Question 2

Define the term phototropism.

[2 marks]
Show mark scheme for question 2
  • a response in which parts of a plant grow (1)
  • towards or away from the direction of the light source (1)

Question 3

Supplement (what this means)Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean

Light shines on a shoot from one side only. Explain why the shoot grows towards the light.

[4 marks]
Show mark scheme for question 3
  • auxin is made in the shoot tip (1)
  • auxin diffuses down the shoot (1)
  • auxin is unequally distributed: more auxin on the shaded side (1)
  • auxin stimulates cell elongation (1)
  • cells on the shaded side elongate more so the shoot bends towards the light (1)
  • Max 4

Question 4

A student investigates phototropism in cress seedlings. Describe how the student could carry out the investigation and state two variables that should be kept the same.

[4 marks]
Show mark scheme for question 4
  • grow seedlings in a box / container with a hole or slit so light comes from one side only (1)
  • have a control set with light from all sides, or in the dark (1)
  • leave for several days and observe / measure the direction of growth (1)
  • same species / age / height of seedlings (1)
  • same temperature / volume of water / light intensity (1)
  • Max 4

Question 5

Supplement (what this means)Supplement: only for the Extended papers (2 and 4). Core students can skip it. What the labels mean

A potted plant is laid on its side in the dark. After two days the shoot has bent upwards. Explain this response.

[3 marks]
Show mark scheme for question 5
  • auxin is unequally distributed: more on the lower side of the shoot (1)
  • auxin stimulates cell elongation, so cells on the lower side elongate more (1)
  • shoot bends upwards / away from gravity (1)
Stuck on one?Read the notesFlashcards