Learning and habituationEdexcel A-Level Biology A: Subtopic test

1. 1
   A student moves into a flat beside a railway line. During the first week she is woken several times each night by passing trains. By the fourth week the trains no longer wake her, although she can still hear her alarm clock and wakes at once when her phone rings.

   (a)

   Which statement best describes the learning shown by the student?

   [1 mark]

   • AA response that becomes stronger each time a stimulus is repeated
   • BA reduced response to a repeated stimulus that is not harmful or rewarding
   • CA new response formed by associating two different stimuli
   • DA reduced response caused by tiredness of the muscles

   (b)

   What is the main advantage to the student of habituation to the train noise?

   [1 mark]

   • AShe will detect trains more quickly in future
   • BHer sensory receptors become more sensitive to sound
   • CHer sleep is longer because the noise is louder
   • DHer nervous system does not waste energy responding to a stimulus that is not a threat, so sleep is not interrupted

   (c)

   Suggest how the fact that she still wakes to her alarm clock shows that the loss of response to the trains is habituation and not damage to her hearing.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Researchers repeatedly touched the siphon of a sea slug (Aplysia) with a soft brush at one-minute intervals. At first the slug withdrew its gill sharply each time. After 30 touches the withdrawal was very weak. Recordings showed that the sensory neurone still produced action potentials of the same size and frequency, but the depolarisation produced in the motor neurone had become smaller. After a ten-minute rest, a touch again produced a strong withdrawal.

   (a)

   Which conclusion is best supported by the recordings from the slug?

   [1 mark]

   • AThe change that reduces the response occurs at the synapse between the sensory neurone and the motor neurone
   • BThe sensory neurone has become unable to generate action potentials
   • CThe motor neurone has lost its ability to conduct action potentials
   • DThe gill muscle has been permanently damaged by the touches

   (b)

   The strong withdrawal returned after a ten-minute rest. What does this show about the reduced response?

   [1 mark]

   • AThe synapse between the neurones has been permanently damaged
   • BThe sensory neurone has been replaced by new neurones
   • CThe change is reversible, so the reduced response was not due to permanent damage or loss of the effector
   • DThe slug has formed an association between the touch and food

   (c)

   Explain how the change at the synapse leads to the weaker withdrawal of the gill.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigated habituation in garden snails. She touched one tentacle of each snail gently with a clean cotton bud every 30 seconds and counted the touches until the snail failed to withdraw its tentacle on three consecutive touches. She tested ten snails. She then touched the other tentacle of each snail, and after five minutes of rest touched the first tentacle again. All ten snails withdrew the other tentacle at once. Eight of the ten snails withdrew the first tentacle again after the rest.

   (a)

   Describe three variables that the student should keep constant to make the results valid.

   [3 marks]

   (b)

   Evaluate how far the student's observations show that the snails had habituated rather than tired.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A farmer uses gas-powered bangers that explode at regular two-hour intervals to scare crows from a field of ripening cereal. For the first two days the crows fly away at each bang. After a week they continue to feed while the bangers sound. The farmer wants to find a way to keep the crows away.

   (a)

   Explain, in terms of synaptic transmission, why the crows eventually ignore the bangers.

   [6 marks]

   (b)

   Evaluate ways in which the farmer could reduce habituation in the crows.

   [6 marks]

   Total for question 4: 12 marks

End of questions