A full write-up of core practical 18 for Biology A (SNAB). It includes a improved method, a results table, colour-coded bar graphs, analysis and interpretation of the data with Spearman's tests and conclusions about significance, background research and link to results and respective bibliography w...
Aim:
To investigate habituation to a stimulus in snails.
Independent Variable:
The number of pokes with a cotton wool bud
Dependent Variable:
Time taken for the eye stalks to re emerge from the shell (measured in seconds using a
stopwatch)
Control Variables:
● Age and size – snails that look roughly the same should be used for repeats
● Handling history – all snails should have developed in the same habitat
● Point where bud touches – the cotton wool bud should be poked in between the
snail’s eye stalks very gently
● Repeats carried out on the same surface
● When to stop the stopwatch – should be when both eye stalks are fully extended
Method:
1. Collect one giant African land snail, and place it on a clean, firm surface. Allow the
snail to get used to its new surroundings for a few minutes until it has fully emerged
from its shell.
2. Place snails on damp paper to allow them to acclimate for longer - lack of moisture
encourages them to stay in their shell.
3. Dampen a cotton wool bud with water. Firmly touch the snail between the eye stalks
with the dampened cotton wool bud and immediately start the stopwatch.
4. Measure the length of time between the touch and the snail being fully emerged from
its shell once again, with its eye stalks fully extended.
5. Measure the length of the eye stalks each time to ensure that this variable is
controlled.
6. Repeat the procedure in step 3 for a total of 15 touches, timing how long the snail
takes to re-emerge each time.
7. Record your results in a suitable table.
, Results:
Number of times prodded: Time taken for snail 1 to re- Time taken for snail 2 to re-
emerge (s) emerge (s)
1 20 52
2 6 106
3 9 25
4 11 24
5 5 20
6 7 17
Snail 1:
Snail 2:
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