Daphnia Investigation

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Katie McCarthy        Biology coursework        Dr Forrest

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. I can get the experiments to be a fair test by trying to keep the Daphnia that we use to be the same one so that it the cardiac output of the Daphnia isn’t different. If I were to use a different daphnia for each experiment then I wouldn’t get the right result as every daphnia has a different cardiac output. I could also use the same way of recording the cardiac output of the daphnia as if you use a different way of recording then that may not be as efficient. Another way of keeping the experiment a fair test is that you can use the same person to record the results as they will do it the same way for each experiment so it wont be different and so that it doesn’t effect the results. The last reason why that we could keep the experiment to a fair test is so that all of the measurements are the same because if there was more of a certain variable then it could change the results. So a quick summary on how I could make this experiment a fair test were:

  • Keeping the same Daphnia for each experiment.
  • Using the same piece of equipment for recording the same for each experiment.
  • Using the same person to do the recording.
  • Use the same measurements then it will be fair.
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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 ...

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