Predictions:
Before starting the experiment I wanted to make some predictions to see that if I thought that what I thought would happen actually did. These were the predictions that I made:
- My first prediction is that I think that the cardiac output would increase if the daphnia were put in caffeine for a minute. I am making this decision because I think that the caffeine will interfere with the reactions of the daphnia's nervous system. The cardiac muscle also maybe affected by this interference of the nerves.
- I think that the cardiac output would decrease if the daphnia were put in ethanol for a minute. I think that the ethanol would do the same thing as the caffeine however the interference my decrease the cardiac muscle to slow down.
- I also predict that the more percentage of the ethanol you use it will get slower and the more of caffeine you use the faster it will beat. The reason why I think this is because the more ethanol and caffeine you use the more affect it may have on the nervous system.
Variables:
There are a number of variables in my experiment that if was changed would vary the results. In order for it to work though I would only have to change one thing at a time. If I were to change more than that it would make my results wrong. These are the variables that are in my experiment:
- The first of the variables is the amount of the drug that we use. I could change the percentage of drug used in each experiment.
- The amount of time we decide to time the heart rate for.
Equipment:
The equipment that I have decided to use is the following:
- Stop Clock
- Microscope
- Glass
- Daphnia's
- Ethanol (0.2%, 0.4%, 0.6% and 0.8%)
- Caffeine (0.2%, 0.4%, 0.6% and 0.8%)
- Pipette
- Pond water
- Glass
This is the equipment that I used and this how I set it out.
I order to have a range of observations results I intend to do the experiment three times so that I can take an average and then I would see if there were any anomalies. I think that three would be a suitable number to choose to make sure that my observations and results are correct.
Safety:
The equipment should be used safely so that we can get the right observations. If something went wrong because the experiment wasn't safe then the observations that we would get would be wrong and also may affect the results. The amount of the ethanol and caffeine that we use should all be to the correct measurement as then the results would be fair. Safety that can be used is that all bags are to be put under the table except the bags would have to be tucked in properly so that no one can trip over the bag. Also this is important as then you won't throw ethanol or caffeine over someone else or kill any daphnia's.
Measurements:
The measurements of the amounts that I am going to use are the following:
- Just a little pond water on the glass
- I am going to use 0.2% of ethanol and caffeine first
- I will also use 0.4% ethanol and caffeine
- 0.6% ethanol and Caffeine
- 0.8% ethanol and caffeine
- Only little amounts of each will be used of the glass of the microscope
- A glass full will be used for the daphnia to be in before experimenting on
Results:
These are the results of my experiment. The first time that I did the experiment I recorded the heart rate of the daphnia while in normal conditions.
Pond water results:
This is a graph to show how many beats a normal daphnia's heart would be while in pond water.
The average of this daphnia's heartbeat was 270.67 heartbeats per 60 seconds. That is a very fast output and that is the normal cardiac output of a daphnia.
The second experiment was to find out what would happen when ethanol was the solution that the daphnia was in. We put the daphnia in the ethanol for 30 seconds before starting out experiment. These are the results that we got from when we used ethanol instead of pond water.
This were the results for ethanol and if you look at the results the more alcohol that was added to the environment that the daphnia the slower that the cardiac output was. This is a graph to show you the variations of the results:
By looking at the graph above you can see that there is quite a variation of the figures that I got
This is for the 0.4% ethanol:
Once again you can see quite a lot of variation between the results. I wanted to see if there was the same kind of variation between the results also in 0.8%. We didn’t manage to do 0.6% but we did do 0.8%. Here are the results:
As you can see here there is quite a variation in these results as well. I have decided so that I can make a best-fit line graph I am going to use the average of each percentage so the results would be:
Now that I have these figures I can do my best-fit graph. Please turn over for best-fit graph.
Observations:
There were not that many observations that were in my investigation. However these were the observations that I saw:
- On 0.2% Ethanol I saw that the heart beat of the Daphnia was not that much as when it was in pond water. However I did see a slight change and this was then proven to me by the result that got.
- On 0.4% Ethanol it was the same kind of observation however it was slower than the 0.2% Ethanol by a bit. However by just looking at it, it was quite hard to tell that it was slower. I did notice that while I was taking the heart beat the pulse of the Daphnia quickened up a little when there was a little dirt by the water flea. The reason for this was because the Daphnia did some physical activity (trying to get the dirt away from itself) and therefore raising it’s heartbeat a little. The way the I observed this was that when I saw a piece of dirt by the Daphnia I realized that the amount of times I was pressing the heart timer was quicker than a second or two before.
- On 0.8% Ethanol it was once again seeing that the cardiac output was slower than the 0.2% and 0.4%. I observed that it was much slower than the 0.2% and it was quite a bit slower than 0.4%. Unfortunately I cant comment on 0.6% because I didn’t get round to doing that percentage.
These were the only observations that I made, I didn’t see much happening during the time that I was taking its heart rate.
Caffeine:
So that I could have a variety of different type of results, I decided also to use caffeine. I decided to do caffeine because I wanted to find out if it did the opposite to Ethanol. These are the results that I got from using caffeine. First experiment that I did was with 0.2% caffeine:
(Before I write the results to 0.2% caffeine I want to remind you of the pond water result: Average was 270.67 beats per minute).
Also before I tell you the results this was done with a different Daphnia because I accidentally killed the one we were using before (when trying to put it in caffeine it got squished up against the glass). SO for the first result you may think that it is wrong because of the figures but that is due to a technical fault.
RESULTS:
0.2% Caffeine:
As you can tell by this result that the heart beat hasn’t increased from when it was in the natural environment of pond water. This may just be because it was a different Daphnia. Despite that there is quite a large variation of results again. This is a graph to show the results:
This graph looks different to all of the graphs you have seen before as the line goes up instead of up down up like it has done on all of the ethanol ones. I don’t know if there is any reason behind this or if it just has occurred like that. Next one that I did was 0.4% caffeine these were the results:
As you can see by looking at the results above these results are not varied that much as they are very close together. This is good and it shows that caffeine does in fact increase the cardiac output because it is faster than 0.2% and also it is faster than the average heart rate in pond water. Below is a graph that shows this result:
Despite what this graph looks like there is not much variation. There are only two beats in it so there isn’t much difference between the results. Next experiment was 0.6% caffeine. During all of these experiments they lied in the chemical for 30 seconds. The reason for this is so the Daphnia could get used to the new environment. This is the result for 0.6% caffeine:
This is a graph to show these results:
By looking at this graph you can see that there is a little variation in the results as there is up to 4 beats difference. This also shows that caffeine speeds up the Daphnia’s cardiac output, as it is faster than 0.4% caffeine. The next was the last experiment that I did and that was 0.8% caffeine. Here are the results:
There is much more variation between these results as it can vary up to about 12 beats. Here is a graph to show these results:
On the next page is a best-fit graph, in order to draw this I need the average heart rate per percentage is are the averages:
Trends and Patterns:
There were a few trends and patterns in my work. Here are the trends and patterns that I found while analysing my results: