4. Repeat the procedure in step 3 for a total of ten touches, timing how long the snail takes to re-emerge each time.
5. Record your results in a suitable table.
6. Present your results in an appropriate graph.
Safety procedure
Wear goggles and gloves at all times during the experiment.
Make sure hands are washed after the experiment even if gloves have been worn.
Disinfect the work surface after the snails have been put away and either throw all disposable equipment away or disinfect that as well.
Handle the snails carefully DO NOT tap them on the head to harm them this is an experiment to record the time of a stimulus the snail should not be harmed at any point in this investigation.
Variables
The independent variable is touching the snail on the head to time the re-emergence over a period of time.
The dependant variable is the time taken for the snail’s eyes to re-emerge, in theory this should take less time as the experiment continues.
We controlled the pressure exerted upon the snail when touching it; also we kept the area where we touched the snail the same.
Results
Data Analysis
As the results show the snail became used to the stimulus as it took them less time to re-emerges after each time.
As shown from the table and graph at first the snail took a while to re-emerge from being taped on the head but as the experiment continued the snail “adapted” and re-emerged quicker on the whole. The last two tests on the snail failed to produce any response, as it had become accustom to the touch on the head and did not feel it was a threat any longer.
The was an anomaly on test 7 where the time went from 3.97 seconds to 5.13 seconds and then continued to decrease. This may have been due to human error such as the timer not being hit immediately at the point of re-emergence or someone else could have changed the point at which they stopped the timer. Or it could be something else to do with the snail; maybe it was tapped on the head harder than it had before leaving it to think that this time it was a danger.
I believe that the results were correct although there could have been systematic errors from the timer being faulty, which would have not been noticed by us.
Evaluation
My prediction was correct about the snail becoming aware that the tapping on the head was not in fact a threat to it. The gradual reduction of existing responses to repeated presentations of a stimulus is ‘habituation’ this is achieved when stimulated Ca2+ channels become less responsive so less Ca2+ crosses the presynaptic membrane. Less neurotransmitter is released. There is less depolarisation of the postsynaptic membrane so no action potential is triggered in the motor neurone.
Habituation allows the nervous system to optimize sensory-motor processing by eliminating unnecessary responses. It allows us to adapt to the familiar in order to preserve our ability to react rapidly and appropriately to new or dangerous surroundings.
Habituation can be very important to an animal in its natural surroundings.
In the process of this investigation we have had to be careful about the ethics and whether this experiment had a viable reasoning to use the snails in this way. I believe that there were no ethical problems the snails were well treated and not in any danger nor did they have any threat towards them.
If I was to repeat this investigation I would gather more results to make my overall investigation more reliable also by doing this I would be able to pinpoint the outliers and eliminate them so my results would be more reliable. To make my results more accurate I could use a better timer where I would know that there would be no systematic error.
To further develop my investigation I could use other animals to see if habituation is the same with all or if the time taken is different, although we would have to look at the ethical issues we would be faced with if we were to develop our investigation.