Learning and habituationEdexcel A-Level Biology A: Flashcards

Exam questions on Learning and habituation

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.
   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
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.
   Explain how the change at the synapse leads to the weaker withdrawal of the gill.2 marks
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.
   Describe three variables that the student should keep constant to make the results valid.3 marks