Required Practical 10 Flashcards
Required practical 10: Investigation into the effect of an environmental variable on the movement of an animal using either a choice chamber or a maze.
This experiment is based on woodlice. What do woodlice do that make them suitable organisms for this experiement?
When woodlice reach an unfavourable environment, they increase the frequency at which they change direction and move faster.
Increasing their chances of finding a favourable environment and increasing chances of survival.
This is kinesis and when a choice chamber is set up with different environments, woodlice seek to move to a favourable environment
What is the equipment list?
A choice chamber
Woodlice
Water
A drying agent (anhydrous calcium chloride)
Dark paper/Cardboard
Paper towels
Spoon
What is the method for this required practical? (6 steps)
1) Set up a choice chamber with four different quadrants: light and damp, light and dry, dark and damp, dark and dry
2) Using dark paper/cardboard block out the light on one half
Use the wet paper towels to make damp areas
Use a drying agent to make dry areas
3) Place 10 woodlice in the centre of the choice chamber using a spoon
4) Leave for 10 minutes
5) Record how many woodlice are in each quadrant
6) Repeat by moving woodlice back to centre of choice chamber, repeat steps 3-4
Why is a spoon used instead of forceps to place the woodlices?
A spoon is used instead of forceps to avoid causing harm to the woodlice
What statistical test can be used to determine whether the observed results differ from the expected results?
A chi squared test can be use to determine whether the observed results differ from the expected results
How will you know by using the calculated value that you can reject the null hypothesis?
If the calculated value exceeds the critical value at the 0.05 level of significance, you can reject the null hypothesis.
Why do you reject the null hypothesis if the calculated value exceeds the critical value?
You can reject the null hypothesis because there is less than a 5% probability that results are due to chance, so there is a statistically significant difference between the observed and expected values
