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The Heart Rate of Daphnia Under Different Conditions

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Introduction

THE HEART RATE OF DAPHNIA UNDER DIFFERENT CONDITIONS. Aim: To investigate the heart rate of daphnia under different conditions, such as drugs. Theory: There are different types of drugs. Some are depressants and some are stimulants. By depressants we mean that they slow down the rate of metabolism. Stimulants increase the body's metabolism. Heart rate is one indicator of increased or decreased metabolism. Drugs affect the heart rate of daphnia the same way as humans. Caffeine and nicotine are stimulants they will increase the heart rate of daphnia as well as humans. Ethanol, alcohol and aspirin are depressants and they will slow down the heart rate of daphnia. Because of different concentrations of alcohol we have to do a serial dilution. Example: If we have 10% of alcohol to start with and the final is 2%, then volume of water is 0.8 and alcohol is 0.2. So the dilution factor is 5 (1 part original, 4 parts of water). ...read more.

Middle

25x 60s/10s 150 144 180 162 294 132 change in heart rate -6 30 12 144 -18 % difference in heart rate 96 120 108 196 88 Discussion and Evaluation. From the results we can see that, daphnia heart rate is affected by drugs. We could tell which drugs were stimulants and which were depressants. The pond water acted as a control and from the control we were able to judge which drugs did what. According to our results 10% ethanol was a depressant since the averaged heart beat was lower than the control. This is mainly because in daphnia's, the heart rate is nerve pulse regulated. Meaning that impulses are sent to the neurons, which then carry the signal to the cardiac muscle causing the heart to slow down. If we add the 10% ethanol it interferes with the nerves, causing the heart rate to decrease. Our results for 10%ethanol are proven to be correct. ...read more.

Conclusion

Another possibility for this would be mainly because of its small surface area and body mass. In the experiment some of the errors that occurred were, the heartbeat was irregular due to the fact that we could not measure the amount of drug to pour on the daphnia at each moment, so we could have put more nicotine than caffeine making our results seem to be that some drugs are more stimulant or depressants. An improvement could be tried to put the same amount at each time to be able to do a more appropriate comparison. The other was we could have not given the daphnia time to adjust before we put the next drug in order to get more accurate results. An improvement would be to give more time for adjustment. Another error was that we used one daphnia and so maybe if we put the drugs maybe they were absorbed and thus no accurate results. An improvement would be to have a daphnia for every drug. The other was there was no enough time to do the experiment. An improvement could be more time. ...read more.

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