Question 1
Which of these is an effector?
- A temperature receptor in the skin
- A muscle in the arm
- The brain
- A hot object
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Answer: B (1)
Question 2
A person touches a hot pan and pulls their hand away. Name the stimulus, a receptor and an effector in this response.
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- stimulus: heat / high temperature / hot pan (1)
- receptor: temperature receptor (in the skin) (1) allow heat receptor
- effector: muscle (in the arm) (1) do not accept brain
Question 3
What is meant by homeostasis? Give two examples of conditions that are controlled by homeostasis.
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- maintenance of a constant internal environment (1) allow keeping conditions inside the body constant
- body water content (1)
- body temperature (1)
Question 4
A seedling is laid on its side in a dark cupboard. After two days its root and shoot have both changed direction. Describe what happens to the root and to the shoot, and name the response in each case.
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- root grows downwards (1) allow towards gravity
- this is positive geotropism / gravitropism (1)
- shoot grows upwards (1) allow away from gravity
- this is negative geotropism / gravitropism (1)
Question 5
A shoot grows towards a window. This response is called
- negative phototropism
- positive phototropism
- positive geotropism
- negative geotropism
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Answer: B (1)
Question 6
A student shines a lamp on one side of a young shoot. After a day the shoot has bent towards the lamp. Explain how auxin causes this response.
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| Level | Marks | What the answer does |
|---|---|---|
| 3 | 5–6 | A clear, ordered explanation that states where auxin is made, how its distribution changes, its effect on cell growth, and the resulting bending towards the light. Scientific terms are used accurately. |
| 2 | 3–4 | Some of the explanation is given, such as auxin moving to the shaded side and the cells growing more, but the sequence is incomplete or a link is missing. |
| 1 | 1–2 | Isolated statements, such as auxin is a hormone or the shoot grows towards light, with little or no explanation. |
Indicative content
- the response is positive phototropism
- auxin is made in the tip of the shoot
- light from one side causes auxin to move to the shaded side
- auxin makes cells elongate
- the cells on the shaded side elongate more / grow faster than on the lit side
- so the shoot bends towards the light
- this gives the leaves more light for photosynthesis