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Daphnia are the organisms that are involved in this experiment to find out what effect alcohol has on their heartbeat.

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INTRODUCTION Daphnia are the organisms that are involved in this experiment to find out what effect alcohol has on their heartbeat. It is easy to study the effects of alcohol on the heart of Daphnia as the organ can be easily seen through the transparent body of Daphnia. The number of heartbeats may be counted before submersion in alcohol and after submersion in alcohol to investigate the effect of alcohol. Daphnia belong to the Phylum Arthropoda and are Branchiopoda which belong to the class, Crustacea. Daphnia are invertebrates and also have an exoskeleton, jointed appendages, a dorsal heart and open blood system. The effect of alcohol on humans is that it slows down the heartbeat, so it may be that alcohol will have the same effect on Daphnia. WHY??? However, it is possible that the heartbeat of Daphnia may not decrease if submerged in alcohol. This is because Daphnia differ to humans in many ways firstly Daphnia are invertebrates whereas humans are vertebrates. Also, like most crustaceans Daphnia live in an aquatic environment and so it could be possible that the heart of Daphnia may be adapted differently to respond to ethanol. Alcohol effects the transmission of the nerve pulses along neurones to produce the affect that it does so on the heartbeat of Daphnia. Alcohol interferes with the nervous system by slowing down the nerve impulses that are sent down neurones from the brain. Alcohol does this by binding with the receptor sites where normally certain neurotransmitters may only bind with the receptor sites in the membrane. This means that the nerve impulses consequently will slow down and so also slowing down the heartbeat of the Daphnia. ...read more.


This time interval was timed accurately by using a tape that a 'click' noise every 10 seconds. Then this procedure had to be carried out for each of the 24 remaining Daphnia. The number of dots in each of the boxes had to be counted to give the number of heartbeats for 10 seconds. The heartbeat in the 10 second intervals had to be counted for each of the 25 Daphnia. Then the final step was to transfer the number of heartbeats that were counted into a raw results table accurately and into the appropriate box. CONCLUSIONS & DISCUSSIONS From the graphs that I have drawn I have noticed a clear trend, which is as the concentration of alcohol that the Daphnia is submerged in increases the greater the decrease of their heart rate. The general trend of the graphs A-E is that after the Daphnia have been submerged in alcohol their heart rate falls, but after returning to water the heart beat gradually rises. This trend is for the graphs drawn of the average number of heartbeats every 10 seconds, of the 5 Daphnia tested for each of the 5 concentrations. Alcohol has this effect on the heartbeat of Daphnia because alcohol is a depressant and therefore it affects the nervous system of the Daphnia. It is the nerve impulses that regulate the heartbeat in crustaceans, like Daphnia, as is the case with most other animals. The nerve impulses are generated by neurones that are found in nerve cells. These impulses are transported by motor neurones to the cardiac muscle causing the heart to beat. Ethanol interferes with the nerves by binding with the receptor proteins that are located in the cell membranes of the postsynaptic node. ...read more.


I would also ensure that the Daphnia were tested for a longer period after being returned to water from their environment. This is because after 3 minutes of recording the heartbeat some of the Daphnia had not returned to their resting heart rate. It would be interesting to find out how long it takes for the Daphnia's heartbeat to return to the resting heart rate after submersion in different concentrations of alcohol solution. I would use more than five concentrations of ethanol solution to test the Daphnia with, in a future experiment. Possible concentrations of ethanol that could be used are 5x10-1gcm-3, 5x10-2gcm-3, 5x10-3gcm-3, 5x10-4gcm-3 and 5x10-5gcm-3. Another limitation to the experiment that I carried out was that not all of the Daphnia were tested on one day. Therefore, by the following day the age of the Daphnia was different to the Daphnia involved in the experiment on the previous day. As the Daphnia age it is possible that changes take place in the way that the heart functions. If I were to carry out a further investigation into the effect of alcohol on the heartbeat of Daphnia I would want to determine where exactly in the body of the Daphnia the alcohol affects. To find out if the alcohol has a direct effect on the heart or if it affects the nervous system I would dissect the heart from several Daphnia and submerge only the heart in alcohol. In future experiments it would also be interesting to find out the effect of caffeine on the heart rate of the Daphnia and whether it produces similar results to the experiment using alcohol or not. It would also be interesting REFERNCES BOOKS INTERET- WEBSITE ADDRESS CONTENTS PAGE Content Page Abstract Introduction Method Results Conclusion & Discussions Evaluation- Variability Analysis - Limitations & Errors Sima Narendraji BIOLOGY COURSEWORK ...read more.

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