1. 1
   A runner training barefoot on a grassy track steps on a sharp, hidden pebble. Before she consciously feels any pain, her foot has already lifted away from the pebble.

   (a)

   What type of structure detects the sharp stimulus of the pebble under the runner's bare foot?

   [1 mark]

   • AAn effector
   • BA receptor
   • CA relay neurone
   • DA motor neurone

   (b)

   Which part of the nervous system coordinates this rapid withdrawal response without first involving the brain?

   [1 mark]

   • AThe spinal cord
   • BThe retina
   • CThe cerebellum
   • DThe pituitary gland

   (c)

   Describe the sequence of events, in order, from the stimulus being detected to the foot being withdrawn.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student is reading a book indoors in dim light. She then walks outside into bright sunlight and, a little later, looks up to focus on a distant bird flying overhead.

   (a)

   What happens to the circular muscles of the iris as the student walks outside into bright sunlight?

   [1 mark]

   • AThey relax, making the pupil larger
   • BThey relax, making the pupil smaller
   • CThey contract, making the pupil larger
   • DThey contract, making the pupil smaller

   (b)

   Which structure in the eye changes shape to allow the student to focus on the distant bird after reading her book close up?

   [1 mark]

   • AThe cornea
   • BThe retina
   • CThe lens
   • DThe iris

   (c)

   Explain how the eye changes to bring the distant bird into focus after the student has been reading a book close up.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A gardener places a potted seedling on its side in a dark cupboard for several days. When it is removed, the root of the seedling is found to have grown downwards, curving away from its original horizontal position, while the shoot has curved upwards.

   (a)

   A gardener places a potted seedling on a windowsill so that light only reaches it from one side. After several days the shoot has bent noticeably towards the light. Explain how the plant hormone auxin causes this bending.

   [3 marks]

   (b)

   Explain, in terms of auxin distribution and cell growth, why the root has grown downwards even though it was kept in the dark.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An athlete is running a long-distance race on a hot afternoon. As his muscles work harder, his core body temperature starts to rise. At the same time, before the race began, the excitement of the starting gun caused his heart rate to increase sharply and his liver to release extra glucose into his blood.

   (a)

   Explain how the skin helps to prevent the athlete's body temperature rising too far above normal while he continues to run in the heat.

   [6 marks]

   (b)

   Explain the role of adrenaline in preparing the athlete's body for the physical demands of the race at the start, before he begins running.

   [6 marks]

   Total for question 4: 12 marks

End of questions