measure 2ml of fertiliser and add it to the test tube to create the solution. To add the algae to the
solution I will use a pepet to transfer the algae to the measuring tube. Once i have measured 2ml
of algae i will pour it into the solution.I will then label the test tube so I don't get my results
mixed up. The solution will then be left for one week before I gather my results.
To gather my results I am going to use a counting cell. This will show me how much algae has
grown during the week. The counting cell is a plastic slide with small walls around the outside. it
is made up of squares, for every two squares that are covered, there is an algal count of one. To
use the counting cell, you pour the solution into the counting cell until it fills up to the rim, then
you place the cell under a microscope. For my results, I have to multiply the initial recordings by
ten. To get the average, I will use the mean result for each measurement.
Safety
To ensure a safe and enjoyable experiment I will follow these rules:
Wear safety goggles at all times
Remain standing throughout
Report any spills imediatley
Abide the basic lab safety rules
Be sensible with all the equipment
Fair Test
To make sure that this experiment is a fair test, I am going to make all of the measurements as
accurate as possible, all of the volumes must be the same. To do this, I will have to use the most
accurate measuring tube available. The solutions will have to be left in a safe place where they
can't be altered, but also where there is the same ammount of light and temperature. Also, I
must ensure that the algae I use is of the same species, otherwise the reproduction rate would
be different. If any of those variables were changed then the experiment would be made void.
Equipment List
During this experiment I will be using:
Measuring tube
18 test tubes
3 test tube racks to hold 6 test tubes
Bottle of fertiliser
Bottle of algae
Pepet
Safety glasses
Counting cell
Microscope
Results
Analysis
The graph I have produced shows that my prediction was very accurate up until there is 10ml
of fertiliser. This confirms that as there is more fertilsier added the more algae will be produced.
When it gets to 10ml though, the algal count drops to around the same as with 6ml of fertiliser.
This cannot be an anomalous result, because all three experiments showed the same trend. I
believe this was because of the lack of osmosis taking place. However, my results table show
an anomalous result in the second set of results when there is 0ml of fertiliser.
Evaluation
I think that my experiment went very well having only one anomlous result. I believe that this
was due to a counting error on my part. The reason for the algal count dropping when the
solution was solely fertiliser was because osmosis could not take place. Osmosis is when water
moves through the cell membrane and goes into the cell vacuole, pushing against the cell wall,
the cell wall stops the cell from bursting. The water moves to areas of lower water concentration
helping the cells grow. Since there is no water, this process cannot happen resulting in less algae
being produced.
This evidence is very reliable because all three results show the same steady trend of a very
similar gradient. To extend the experiment I could take different samples at different stages of
the experiment. This would perhaps give me a wider range of results, making my experiment
more accurate. Also, in future experiments I could change the variable to temperature, light or
species. Temperature would change the speed the cells work at. Light would increase
photosynthesis, meaning more cells being produced. Different species of algae have different
reproduction rates so this would create an interesting range of results.
This experiment had no real problems, but using the counting cell was quite hard (this would
explain the anomalous result) so my results were not as accurate as they should have been, so
an alternative would have been extremley helpful.
