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Daphnia Investigation

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Plan: The plan of this project was to find out what would happen to the daphnia if the conditions of its habitat were changed. I plan to change the water that the Daphnia is used to living in to either ethanol or caffeine. I wanted to see if anything happened to the Daphnia's cardiac output or if something else happens. Background Information: Daphnia's is the name of a group of small, aquatic crustaceans commonly called "Water Flea" Because their exoskeletons are clear; it is possible to watch Daphnia hearts without cutting the open. This allows the changes in Daphnia heart rate to be studied easily. The normal habitat of a Daphnia is lakes, rivers and ponds they are also used as fast food for fish. They are used as a fast food for fish because they swim fast and they make the fish fight for their food and not to just to rely on the food just coming to them. A usual life span of a Daphnia is two or three days. Daphnia's are usually females and only a few males are produced the reason for this is they are not needed as much as females are. Fair test: It is important that this experiment is kept to a fair test because if it isn't then the results will not be accurate, as I need them to get accurate results. ...read more.


* 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: Many Heart beats 1st Time 258 2nd Time 274 3rd Time 280 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. About of heart beats per min 1st Time 2nd Time 3rd Time 0.2% 246 238 256 0.4% 238 234 254 0.6% ----- ----- ---- 0.8% 190 182 212 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. ...read more.


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: * * * * * Katie McCarthy Biology coursework Dr Forrest 1 1 ...read more.

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