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Investigating The Effect Of Drugs On the Heart Rate of a Daphnia.

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Investigating The Effect Of Drugs On the Heart Rate of a Daphnia Plan In this investigation I will be finding out the effects of alcohol on a daphnia's heart rate. To do this investigation I will first need a beaker of fresh water, which has daphnia living in it. The water needs to be fresh and has to be their normal environment so that their heart rates are normal. I then take out 3 beakers and fill each of them half way. One beaker will be filled with distilled water (0.0% alcohol), one with 1% concentrated alcohol and the other is used for mixing the solution. I then make a table to record my results in, I will use the headings; concentration of 1 ml alcohol and Heart Rate for 1 minute which will be measured in beats per minute. I then take out my microscope and a lamp, which I will use to magnify the daphnia. With a pipette I will take a sample of the fresh water and add it to a fourth beaker, which now has living daphnia in there. With the one millilitre syringe I will take a small amount of distilled water from the beaker so that it is ready for my first experiment. Then I will take a small volume of fresh water, trying to get just one daphnia in the large pipette to put onto a slide, which has a slight dip in. The dip is there so that the daphnia and the water does not float off the slide. Then I will use tissue paper to absorb as much of the fresh water as I can off the slide without drying out the daphnia and killing it. As soon as I have done that I will add a small amount of the distilled water from the syringe onto the slide so that the distilled water surrounds the daphnia. ...read more.


Once the transmitter has delivered the impulse it breaks down. When a person takes a stimulant it also affects other parts of the body and your organs. It results in quickened reactions and makes a person more alert. Also, because they are more alert and ready for action, they need to produce more energy to supply the body cells. This mans that glucose is released from the liver and more oxygen is taken into the lungs because there has been an increase in your the heart rate. For depressants this process is the opposite. They stop the release of neurotransmitters and stop the neurotransmitters acting on the second neurone. When an electrical impulse is taken to the ending of the first neurone, the impulse has to wait to be taken across to the second neurone by the neurotransmitters. This means that they have to wait so our body's action are slowed down. Because they have slowed down reactions, less energy is needed because we are doing less activity. Less glucose and less oxygen are required so the heart rate decreases. We look at daphnia's heart rate because it is very easy to find and we can count the number of beats per minute. I think that adding more alcohol to the daphnia's environment, it will decrease their heart rate. I think that this will happen because of the research I did in my background information. Because the number of neurotransmitters being released decreases, this will result in slower reactions, less energy will be needed to supply the cells which results in a slower breathing rate. Because there is slower breathing, oxygen isn't taken into the lings as quick so the heart doesn't have to pump the blood as fast to supply the cells with oxygen. This results in a lowered heart rate. Because it may be hard to take an accurate reading for the daphnia's heart rate I will do the experiment twice, this way I can check to see if the information I have gathered is correct. ...read more.


I did the experiment twice because I knew that there would be a good chance of the daphnia dying when I was reading its heart rate and this may of gave me unaccurate results. Also if I had two sets of results I would be able to compare them and look for patterns between the two. On the graph I did a line of best fit for the two experiments so that you can see the general trend of the experiment. As the alcohol concentration increased, the daphnia's heart rate decreased. When I measured the heart rate it wasn't as accurate as it should have been because it beating many times in 30 seconds. Also I had to change the daphnia in experiment one because it died, so this daphnia had a higher heart beat compared to the original one. I think if I was to do the experiment again I would count the number of time the heart beat for 15 seconds then multiplied the answer by four. This way I would not of miscounted and I would get much more accurate results. If I was to repeat the experiment again I would first have a better lamp or put the microscope in the window so that I could see the daphnia more clearly. When I first looked at the daphnia I couldn't find its heart rate but I think this was because I couldn't see the slide very well. Another thing I would do is when I put the daphnia into it's new environment I would leave it to rest for five minutes, this way the affects of the alcohol on the daphnia would have time to work and I would get a better reading of how the alcohol decreases its heart rate. Another way I could improve my experiment was when I was timing how many time the daphnia's heart beated I could use another two people and we could count for ten seconds each then add our scores together and multiply by two. This would make it more accurate aswell. ...read more.

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