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How caffeine affects Daphnia heartbeat?

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An experiment to determine how caffeine affects the heart rate of Daphnia (water fleas)? Introduction The purpose of this experiment is to determine whether or not caffeine has an affect on the heart rate of Daphnia Hypothesis The Daphnia heart rate will increase with the concentration of caffeine. I based my hypothesis on the fact that humans heart rates increase with caffeine as it acts as a stimulant drug. In the experiment there will be several variables that I need to try and control, the temperature of the water is one of these because if the temperature is higher or lower on the day the results may end up being higher or lower, this would make my results inaccurate. I need to try and limit the human error in the experiment as the daphnia heartbeat is very quick so it will be hard to be completely accurate so we are using the "blind method". We need to use the same microscope throughout testing as others may have different strength lenses. I am also going to keep the species of daphnia the same, as different species may react differently to the caffeine. I will use the same type of caffeine and record the amount of time the daphnia spend in the caffeine before the counting begins, and try to keep this to a similar range. ...read more.


Equipment * Culture of Daphnia * Cavity slides * Dropping pipettes * Distilled water * Caffeine solution of different concentrations * Cotton wool * Stop clock * Microscope * Beakers Method 1. Get all the equipment as shown above 2. Place a few strands of cotton wool on a cavity slide, this restricts the movement of the daphnia 3. Add a couple of drops of distilled water to the slide 4. Use the microscope to look at the daphnia's heart beat 5. Use a stopwatch to record the number of heartbeats per 15 seconds 6. It is easiest to tap a pencil on a piece of paper and count up the pencil marks at the end and times this number by 4 to get results for 1 minute 7. It is best to use a "blind method", where the person who is counting is unaware of which solution has caffeine 8. Repeat the procedure using other daphnia and use several different concentrations of caffeine 9. Repeat each concentration 3 times for accuracy 10. Get the average heartbeat for each concentration Safety * Wear safety goggles * Wear lab coats * Wash hands at end of experiment as we have been dealing with living organisms Fair Test To make it a fair test we will ...read more.


Also this group has not included the results for 0.5 making the data pointless. The group labelled also seems to have 2 inaccurate results at distilled water and 0.5% caffeine so I would also class these as anomalies. Therefore this leaves us with just two sets of results. This means that we need to collect more data for us to be able to get an idea of accurate readings. Evaluation If I were to do the experiment again I would find a more accurate way of counting the heartbeats as they ended up being very fast. One way I could do this would be to use videoing microscope to record the daphnia heartbeat then use a computer program to slow the heartbeat down so I could count it accurately. I could also do more trials to make the readings even more accurate. I would try using Different types of caffeine such as decaf and also try using a different species of daphnia and even see if temperature had an effect. I would also try to do many more different concentrations of caffeine. As I know from my knowledge caffeine is a stimulant so I could experiment using a depressant such as alcohol and see how this affects the daphnia. ?? ?? ?? ?? ...read more.

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A good account of the investigation but a little more attention to detail would have improved it.

Marked by teacher Adam Roberts 26/06/2013

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