HABITUTION CPAC OLIVIA BENNY
Aim: To investigate habituation to a stimulus in snails
Scientific introduction:
In this experiment we are investigating the response of snails to a stimulus and the change in speed over time
(habituation). It is first important to define what habituation is: a decrease in the strength or occurrence of a behaviour
after repeated exposure to the stimulus that produces the behaviour, this allows animals to avoid wasting energy by
responding to a repetitive harmless stimulus. Habituation doesn’t occur in snails but in every organism and even in
humans. An example of animals is when a shadow is casted over a young bird which may frighten the young bird but with
repeated exposure there will no longer fear it therefore no response. Kandel conducted experiments on habituation
specifically studying the molecular biology of Aplysia californica who used jet pressure water on the gills of a giant sea slug
to see the response of the slug from repeated stimulation. In this experiment I will be using a giant African land snail.
The giant African land snails are also known as achatina fulica and have a light to dark brown shells with vertical stripes of a
darker shade of brown on them. They have an average life span of 5-7 years; however, some have lived up to 10 years [1].
My hypothesis is that with more repeats the time taken for the eye stalks to come out will decrease as the snails would
have adapted to the stimulus and withdraw its responses more, this is because of the science theory behind it. With
repeated stimulation, the calcium ion channels in the presynaptic membrane is less responsive which means less calcium
ions cross the membrane into the presynaptic sensory neurone and therefore fewer neurotransmitters are released into
the synaptic clef which means the action potential across the post synaptic membrane is less likely. Fewer action potentials
are produced in the post synaptic motor neurone so less of a response is observed [5]
Variables:
Control variables The control variable is the variable that should be kept the
same to allow reliable and accurate results, with minimal
error
Age & Size = snails should look roughly the same
in repeats
Point where the bud touches = should be poked
between the snails’ eyes in a gentle manner
Same cotton wool bud used each time
Conducted in the same environment, same
temperature and same light intensity
When to stop the stopwatch = when the eye
stalks both are fully extended
Carried out on the same surface
Independent variables
Dependant variables The dependant variable is the variable measured which is
the time taken for the eye stalks to remerge from the
shell, the variable is measured in seconds using a
stopwatch
Equipment:
Giant African land snail The snail is used as this is the organism which habituation
will be investigated on, by providing a stimulus in snails
the responses will be shown
Dampened cotton wool bud Used to provide a stimulus to the snail in order to observe
a response from the stimulus, it is damp so no harm is
done to the organism and does not disturb the snails
Clean firm surface To allow the snail to travel on, so it’s clean and no cross
contamination, no harmful chemicals/ substances that
may cause specific harm to the snail
Stopwatch To measure the response to the stimulus and the time it
takes for it to go back to normal
Aim: To investigate habituation to a stimulus in snails
Scientific introduction:
In this experiment we are investigating the response of snails to a stimulus and the change in speed over time
(habituation). It is first important to define what habituation is: a decrease in the strength or occurrence of a behaviour
after repeated exposure to the stimulus that produces the behaviour, this allows animals to avoid wasting energy by
responding to a repetitive harmless stimulus. Habituation doesn’t occur in snails but in every organism and even in
humans. An example of animals is when a shadow is casted over a young bird which may frighten the young bird but with
repeated exposure there will no longer fear it therefore no response. Kandel conducted experiments on habituation
specifically studying the molecular biology of Aplysia californica who used jet pressure water on the gills of a giant sea slug
to see the response of the slug from repeated stimulation. In this experiment I will be using a giant African land snail.
The giant African land snails are also known as achatina fulica and have a light to dark brown shells with vertical stripes of a
darker shade of brown on them. They have an average life span of 5-7 years; however, some have lived up to 10 years [1].
My hypothesis is that with more repeats the time taken for the eye stalks to come out will decrease as the snails would
have adapted to the stimulus and withdraw its responses more, this is because of the science theory behind it. With
repeated stimulation, the calcium ion channels in the presynaptic membrane is less responsive which means less calcium
ions cross the membrane into the presynaptic sensory neurone and therefore fewer neurotransmitters are released into
the synaptic clef which means the action potential across the post synaptic membrane is less likely. Fewer action potentials
are produced in the post synaptic motor neurone so less of a response is observed [5]
Variables:
Control variables The control variable is the variable that should be kept the
same to allow reliable and accurate results, with minimal
error
Age & Size = snails should look roughly the same
in repeats
Point where the bud touches = should be poked
between the snails’ eyes in a gentle manner
Same cotton wool bud used each time
Conducted in the same environment, same
temperature and same light intensity
When to stop the stopwatch = when the eye
stalks both are fully extended
Carried out on the same surface
Independent variables
Dependant variables The dependant variable is the variable measured which is
the time taken for the eye stalks to remerge from the
shell, the variable is measured in seconds using a
stopwatch
Equipment:
Giant African land snail The snail is used as this is the organism which habituation
will be investigated on, by providing a stimulus in snails
the responses will be shown
Dampened cotton wool bud Used to provide a stimulus to the snail in order to observe
a response from the stimulus, it is damp so no harm is
done to the organism and does not disturb the snails
Clean firm surface To allow the snail to travel on, so it’s clean and no cross
contamination, no harmful chemicals/ substances that
may cause specific harm to the snail
Stopwatch To measure the response to the stimulus and the time it
takes for it to go back to normal
