Slime mould sensitivity to light prac
Introduction:
Slime mould (Physarum polycephalum) is a eukaryote and a heterotroph. As a eukaryote it has different organelles (structures) within each cell. A heterotroph means that it has to consume other organisms to obtain its food.
These organisms have an interesting taxonomy and cannot be easily be classified as either a plant or an animal.
Slime moulds are an easy organism to work with in the lab, they can inform us on basic responses of cells to stimuli such as light and gravity.
In this experiment we will be investigating the response of individual slime moulds to light by giving them two options, one of darkness and one of light. The responses of the slime mould will be monitored and recorded.
Hypothesis:
Slime mould are sensitive to light and will move away from light to a place of darkness.
Materials and method:
Petri dish with plain agar
An oat flakewith a started slime mould
Cardboard to create a dark / light environment
Cut and fold the card as indicated to create a dark / light cover for the petri dish.
Place the petri dish with the slime mould in the card cover so that the oat flake is half in dark and half in light.
The response of the slime mould will be monitored and recorded over one week, both the direction and the extent (length) will be recorded.
Record new position of slime mould as D2, D1, L1 or L2
D2 D1 L1 L2
Dark Light
Side Side
Results:
D2 – 4, 12, 4 = 20
D1 – 4, 7, 6 = 17
L1 – 4, 11, 8 = 23
L2 – 7, 8, 4 = 19
Our research does not show a specific response to light by the slime mould.
Discussion:
The results do not show that the slime mould has a preference for either light or dark. It is reasonable to assume that they do have a preference.
There are several sources of error that may have affected our results. These are that the dark / light cover did not create a totally dark option for the slime moulds.
There was no light supplied that kept the light side illuminated during the night. Also when we recorded our results the slime mould had travelled all over the petri dish and there was no way to determine which direction the slime mould initially went.
To overcome these limitations we should create an environment where the light / dark options are clearer. Also we should record our results more quickly so we can record the initial direction of the slime mould.
This experiment informed us of how slime moulds grow and behave, and although did not address our hypothesis it has given us the knowledge to conduct better experiments in the future.