Daphnia Experiment Research Paper
An Investigation To See The Effect That Alcohol Has Upon The Heart Rate Of Daphnia.
Aim:
In this investigation I am going to see how alcohol affects the heart. Due to the ethical and safety issues involved in using in an investigation such as this I am going to use Daphnia (water flea) to conduct this experiment. Although humans and Daphnia are very different organisms, the affect that alcohol has upon the heart should be similar.
Hypothesis: The hypothesis I am going to test during the investigation is:
‘Increasing the percentage of concentration of alcohol (a depressant) solution, into which a Daphnia is immersed, will significantly cause its heart rate to decrease.’
Background Knowledge: One of the most common crustaceans …show more content…
to be found in lakes, ponds and quiet streams is the 'water flea', Daphnia. These tiny animals are usually less than 3mm in size, so you could put dozens of them on a single fingernail. They're not really fleas – in fact they're not insects at all, but rather crustaceans, more closely related to crabs and shrimp. Water fleas are extremely important in the food chains of ponds and lakes - they harvest the tiny algae cells that convert sun energy into food, and then they pass this energy along to other animals such as fish or other predators. Below is a diagram that shows the anatomy of the daphnia and where everything is in its body:
[1] - Second antenna, used for swimming and sensing the environment.
[2] - Eye controlled by muscles with nerve connections to the brain.
[3] - Legs used for collecting food and stabilizing the animal as it slowly sinks.
[4] - An intestine where ground up food particles are digested.
[5] - A brood pouch for incubating young that hatch from large yolk filled eggs.
[6] - A protective outer shell.
[7] - A heart that pushes clear circulatory fluid around the body.
[8] - Undigested material is eliminated out the anus.
Alcohol is a depressant, which is classed as a drug or chemical, that decreases the activity of any bodily function. The term is most often used to refer to drugs that reduce the activity of the central nervous system. These agents cause sedation or a sleep like state at low doses and reduce general anxiety. Although this information is of particular relevance to humans, it is also true of daphnia. The daphnia, or water flea, is less than 3mm (0.1 in) in length. It is globular in shape and reddish in colour, and is encased in a transparent, bivalve shell, or carapace. The head bears feathery, branched antennae that are used for swimming. They are used, in a dried form, as fish food, and are often seen as a cloud of specks in pond or aquarium. They are very distant relatives of aquatic animals like crabs and shrimps. The transparent carapace makes it possible to watch the internal organs at work, particularly the heart, which is usually red as it is full of oxygen rich blood. There are about twenty-five British species in the family Daphniidae, with the largest being Daphnia Magna.
A daphnia spends much of its time bobbing up and down in the water, with its head uppermost. It tends to sink down a short way before propelling itself back towards the surface of the water with a stroke of its powerful antennae. Like many other creatures living in the upper waters of seas and lakes, the daphnia also migrates up and down every day to different depths. At dusk, the daphnia moves upwards, but during the night the whole population may gradually sink, only to rise again at dawn. As the day persists, the daphnia may gradually sink again.
The daphnia feeds on bacteria and single-celled algae that float on the surface of the water.
It must also filter large amounts of water to strain these particles, and it does this by rhythmically beating its legs, pumping water through the space under its carapace, and using the bristles on its legs as strainers. Because algae are the daphnia’s main food source, it is clearly and advantage for the daphnia to stay where the algae are most densely populated. This is done by sight, but not by spotting the algae at a distance and heading for it. If the daphnia stumbles across a group of algae, the light seen by the daphnia will be slightly red, as most of the blue light in sunlight is removed as it passes through the cloud of algae. The slight redness of the light will cause the daphnia to remain in the location of the algae. The daphnia is in turn eaten by other, larger organisms, making it an important link in the aquatic food …show more content…
chain.
The fact that the daphnia has a transparent body means that it is very easy to study the internal organs under the microscope. This, and the fact that the daphnia reproduces very quickly, means that it is often used to study the effects of drugs on the heart.
This is a picture of a Daphnia Magna. From the picture you can clearly see the heart:
Variables:
In order to test out my hypothesis, I am going to look at how different concentrations of alcohol affect the heart rate of a single daphnia. In this experiment, the variable that changes is the concentration of the alcohol. All of the other variables- for example temperature, length of time in the concentration of alcohol and recovery time- remain the same. Also, I will try to use the same daphnia for all of the experiments, because different daphnia will have different natural heart rates, in the same way that humans do. However, it may not be possible to use the same daphnia all the time, because daphnia have a tendency to die when used in experiments. If the daphnia does die, it will be replaced by one of similar size and development.
Apparatus:
Below is a list of the apparatus I used during the experiment and reasons as to why I used them:
1. Pipette – This was used because it is the easiest things to use too transport the Daphnia from the water bath to the test tube, and from the test tube to the cavity slide.
2. 100 ml measuring cylinder – Used to make up the different concentrations in (see method for the different concentrations). This was the only measuring cylinder big enough.
3. 10 ml measuring cylinder – Used to measure out 10 ml of the alcohol concentration to put the Daphnia in to.
4.
25 ml flask – Used to put the 10 ml of the concentration into as well as the Daphnia so it could be observed and exposed to the concentration.
5. Ethanol – I used this to make up my alcohol concentrations, as it was the easiest and most common chemical used.
6. Distilled Water – used as the main thing in the concentrations and also used to put the Daphnia in after they were subjected to the alcohol concentration to try and bring their heart rate back to normal. It is used as the control as it is pure and free from chemicals that could affect the Daphnia’s heart rate, thus making the test fairer.
7. Microscope – Used to observe the heart rate of the Daphnia, under a low power.
8. Cavity Slide – Used to put the Daphnia onto so it could be observed. Due to the cavity on it, it meant it was easier to use than a normal slide as some of the concentration was put onto it also.
9. Cavity Tile – Used to put the Daphnia into after it had been in the concentration of alcohol. The cavities were full of distilled water.
10. Safety Mat – This was used to protect the bench from any spillages of ethanol as other people have to use the bench and ethanol is a dangerous chemical.
11. Safety Goggles – These were used to protect my eyes from the vapour from the ethanol as it can lead to
irritation.
12. Stopwatch – I used a stopwatch to time 15 seconds while the daphnia was under the microscope being observed and also the time 5 minutes while the Daphnia was in the concentration.
13. Calculator – I used this to help me count the heart rate of the Daphnia, as it was a lot easier to do than use my head to count. The way in which I used the calculator is described in the method.
Below is a diagram of the apparatus used during the experiment:
Safety:
During the experiment there are some cautions I will have to take in order to make it completely safe for others and me around me. The main safety precaution is ensuring that I conduct the experiment in an appropriate manner and do not take any risks when doing things. Other things such as wearing safety goggles are important because the vapour from the ethanol could cause some irritation in my eyes. Another thing is to have a safety mat down on the bench to stop any spillages from going onto the bench and causing a risk to others that may use it after me. Also a very important safety point is to ensure that I handle the glass wear with care and make try not to break anything like it.
Method:
Below is a step-by-step description of how I conducted my experiment and used the equipment listed previous:
1. Firstly I made up the correct concentrations of the alcohol solutions, using ethanol and distilled water. The measurements are listed below in the table:
Concentration
Required (%) Amount of
Ethanol (ml) Amount of
Distilled Water (ml) Total Volume
(ml)
Control group - 0 0 100 100
0.2 0.2 99.8 100
0.4 0.4 99.6 100
0.6 0.6 99.4 100
0.8 0.8 99.2 100
1.0 1.0 99 100
2. I got the Daphnia from the water bath and put it into a 25ml flask of distilled water for 5 minutes. This was the control group to find the normal heart rate of the Daphnia.
3. After 5 minutes was up I removed the Daphnia from the distilled water, with a pipette, placed it onto a cavity slide, and put it under the microscope that was on a low power.
4. I focused in on the Daphnia and identified its heart with help from the diagram on page 1.
5. Using the calculator I counted the heart rate of the Daphnia. To do this I pressed the [1] and [+] buttons. I then pressed the equals [=] button, which displayed the number [2]. The calculator acted as a counter and every time I pressed the equals button the numbers increased by 1. I pressed the button every time I saw the Daphnia’s heart beat. I counted the heart rate for 15 seconds and then I multiplied it by 4 to make it into the heart rate over a minute.
6. The results were then recorded in a table, shown in the results.
7. After I used distilled water, I moved onto the concentrations of alcohol starting with 0.2%.
8. I took the 100ml-measuring cylinder full of 0,2% concentrate, measured out 25ml of it using a pipette, and put it into a 25ml flask.
9. Then I took the Daphnia from the water bath using a pipette and put it into the concentrate for 5 minutes.
10. During this time I rote down some observations of what I could see from the behaviour of the Daphnia.
11. After the 5 minutes was up the Daphnia was removed and put onto the cavity slide, under the microscope.
12. The heart rate was taken, as in Step 5 and recorded.
13. Steps 7 – 12 were then repeated using the different concentrations.
14. All the concentrations were tested 3 times and then an average was found.
Results:
Below are the results that were obtained during the experiment:
Concentration of Alcohol (%) Result 1
(BPM) Result 2
(BPM) Result 3
(BPM) Average Result
(BPM)
Control – 0 160 172 180 171
0.2 136 131 146 138
0.4 120 131 124 125
0.6 124 114 121 119
0.8 96 100 104 100
1.0 106 103 90 100 Observations:
Whilst the experiments were being carried out I noted down a few observations about the Daphnia’s behaviour in the different concentrations.
When the Daphnia was put into the Distilled water it swam around very quickly and changed direction quickly and at right angles.
As the concentrations increased the speed of its movements began to slow down considerably, to the extent where it just sank to the bottom of the flask in the 1.0% concentration. Its movements turned from right angles to having to go round in an arched shape, showing that the alcohol had affected more than just its heart rate.
Analysis:
As the concentration of alcohol was increased the heart rate of the Daphnia decreased. This is what I can tell from the results that I obtained.
The change in heart rate from the control group to the 0.2% concentration was 33 BPM. This is almost double the most significant difference in BPM between the groups, of 19 BPM from 0.6% to 0.8%. Just from looking at that it is clear to see that alcohol does affect the heart rate of Daphnia, as the heart rate dramatically reduces from normal when put into the weakest solution.
Although research has been done on the subject, no one is sure how or why alcohol affects the heart. Normally, alcohol acts on body systems under the control of the CNS. It is thought that alcohol works by inhibiting the action of the neurotransmitters that transmit nerve impulses across a synapse. However the heart of a human is outside the control of the CNS, while Daphnia have no CNS present. In both organisms the rate of the heart beat is controlled by the autonomic nervous system, being accelerated by the sympathetic system and depressed by the parasympathetic system. The heart rate is also influenced by the hormone adrenaline, which has a similar effect as the sympathetic nervous system in that it causes the heart to beat faster. This is the so-called ‘fight or flight’ reflex. It is possible that alcohol works in a similar way to adrenaline. They are both chemicals transported in the blood, so it is possible that their action on the heart is similar.
Although the overall results were expected, for the first three sets of concentrations the Daphnia’s movements were practically unchanged, but for the other two the behaviour changed drastically. This abnormality could be caused by the fact that when humans consume a small amount of alcohol, up to about 40mg of alcohol per 100ml of blood, they become more active than usual, even though the heart rate may drop.
There is one anomaly that I have circled on my graph and that comes at the 0.8% concentration. At first I thought it was the 1.0% concentrate result that was the anomaly, but from looking at the graph I could tell that it was actually the 0.8% concentrate. This is because it does not fit in with the pattern of the graph and makes the line too steep from the 0.6% to 0.8% concentrations. I would have expected this to come out at around the 110 BPM mark as this would fit into the graph and give me a good correlation.
This anomaly could have down to a number of reasons such as; an error in the measurements of the chemicals, the concentration not being mixed up properly, the Daphnia not completely recovering from the previous concentration or an error in the counting. Personally I think that it was the fact that the Daphnia had not completely recovered from the previous experiment. This is because whilst observing the behaviour of the Daphnia when it was in the distilled water, recovering from the previous experiment, it did not ever get back to full speed and was acting slightly docile when moving around, as apposed to whizzing around the flask like usual.
Evaluation:
The results that I obtained from doing the experiment show clearly that alcohol does effect the heart rate of a Daphnia and therefore, the heart rate of a human should also act in this way. The results look to be reliable, from the graph as the line does show a good correlation between the concentrations. The only exception to this is the anomaly at 0.8%, but this is not a big change in the result as it was only roughly 10 BPM out from what I would have expected it to be. I took three results from each concentration and found an average of this as this makes the results more reliable. This is because, just taking one result would leave it open for a lot of anomalies as the Daphnia could act very differently from the first result to the third result from each concentration. For example, in my results, if I had only taken one result, the first one then it would have meant that I would have had two clear anomalies. These would occur between 0.4% & 0.6%, and 0.8% & 1.0%. At 0.4% the first result was 120 BPM and at 0.6% it was 124 BPM. A difference of 4 BPM, where the higher concentrate produced a higher heart rate. Also, at 0.8% it was 96 BPM and at 1.0% it was 106 BPM, a difference of 10 BPM in favour of the higher concentration. So, therefore, it proves that multiple readings should be taken to make results more reliable.
There were a few limitations of my experiment. These are listed below:
• Although it is accepted that alcohol affects humans and Daphnia in similar ways, they are still very different organisms, so will be affected in different ways. Although the general effects will be the same i.e. decreasing of the heart rate, the amount of variation will be different. Due humans being much larger than Daphnia, a much larger quantity would be required and also a longer amount of time for it to affect the human. To achieve the results of this on humans, a large medical study would need to be undertaken.
• The temperature of the solution in which the Daphnia is immersed will affect the heart rate; if it is warmer it will increase the heart rate. Also, when the Daphnia is put onto the microscope it is exposed to a concentrated light, which will of course give off heat and therefore increase the heart rate of the Daphnia as, the experiment goes on. This would lead to a higher BPM of the Daphnia and the only way I can think of to over come this is to always switch the microscope off after every time of using it so it does not get too hot.
• Living creatures tend to behave in an unpredictable way. Although the same Daphnia was used in all the experiments, the problem of unpredictability is still significant. For example the experiments were carried out over a couple of days, so the Daphnia’s behaviour may vary from day to day. Also the conditions of the laboratory may have changed, e.g. the temperature of the room could bring about slight changes in the behaviour of the Daphnia. The only way to change this would be to conduct the experiment in one day and also conduct the experiment on more than one Daphnia. But due to the time allocation I was unable to do this.
• Finally, it was not always easy to count the Daphnia’s heartbeat, even using a calculator as the counter. This was because it sometimes moved around under the microscope so I could not see the heart properly and also because it beat so fast it was not easy to keep up with it. This would have had a slight effect on the results as it would have meant that thee odd BPM would have been missed, thus changing the averages by one or two.
Further Work:
Below are a few suggestions of what further investigations I could conduct to help me research more into the topic:
1. I could change the type of alcohol used to a proper drinking spirit or beer to see if this effects the Daphnia, as this would be more ecologically valid towards the statement of … ‘Alcohol has the same effect upon Daphnia as humans’, this is because humans do not drink ethanol as it is a very dangerous chemical. This would also lead into another investigation.
2. I could do the experiment above, but use humans. This would then allow me to be sure of the similarities of the effect of alcohol upon both humans and Daphnia.
3. I could also do an observational experiment on humans that are under the influence of alcohol as to whether they, like Daphnia, become more docile and slow down.
Finally, from the results obtained I can confirm that my hypothesis is correct and accept that alcohol does have a significant effect on the heart rate of Daphnia, and therefore, humans.
Aim:
In this investigation I am going to see how alcohol affects the heart. Due to the ethical and safety issues involved in using in an investigation such as this I am going to use Daphnia (water flea) to conduct this experiment. Although humans and Daphnia are very different organisms, the affect that alcohol has upon the heart should be similar.
Hypothesis: The hypothesis I am going to test during the investigation is:
‘Increasing the percentage of concentration of alcohol (a depressant) solution, into which a Daphnia is immersed, will significantly cause its heart rate to decrease.’
Background Knowledge: One of the most common crustaceans …show more content…
to be found in lakes, ponds and quiet streams is the 'water flea', Daphnia. These tiny animals are usually less than 3mm in size, so you could put dozens of them on a single fingernail. They're not really fleas – in fact they're not insects at all, but rather crustaceans, more closely related to crabs and shrimp. Water fleas are extremely important in the food chains of ponds and lakes - they harvest the tiny algae cells that convert sun energy into food, and then they pass this energy along to other animals such as fish or other predators. Below is a diagram that shows the anatomy of the daphnia and where everything is in its body:
[1] - Second antenna, used for swimming and sensing the environment.
[2] - Eye controlled by muscles with nerve connections to the brain.
[3] - Legs used for collecting food and stabilizing the animal as it slowly sinks.
[4] - An intestine where ground up food particles are digested.
[5] - A brood pouch for incubating young that hatch from large yolk filled eggs.
[6] - A protective outer shell.
[7] - A heart that pushes clear circulatory fluid around the body.
[8] - Undigested material is eliminated out the anus.
Alcohol is a depressant, which is classed as a drug or chemical, that decreases the activity of any bodily function. The term is most often used to refer to drugs that reduce the activity of the central nervous system. These agents cause sedation or a sleep like state at low doses and reduce general anxiety. Although this information is of particular relevance to humans, it is also true of daphnia. The daphnia, or water flea, is less than 3mm (0.1 in) in length. It is globular in shape and reddish in colour, and is encased in a transparent, bivalve shell, or carapace. The head bears feathery, branched antennae that are used for swimming. They are used, in a dried form, as fish food, and are often seen as a cloud of specks in pond or aquarium. They are very distant relatives of aquatic animals like crabs and shrimps. The transparent carapace makes it possible to watch the internal organs at work, particularly the heart, which is usually red as it is full of oxygen rich blood. There are about twenty-five British species in the family Daphniidae, with the largest being Daphnia Magna.
A daphnia spends much of its time bobbing up and down in the water, with its head uppermost. It tends to sink down a short way before propelling itself back towards the surface of the water with a stroke of its powerful antennae. Like many other creatures living in the upper waters of seas and lakes, the daphnia also migrates up and down every day to different depths. At dusk, the daphnia moves upwards, but during the night the whole population may gradually sink, only to rise again at dawn. As the day persists, the daphnia may gradually sink again.
The daphnia feeds on bacteria and single-celled algae that float on the surface of the water.
It must also filter large amounts of water to strain these particles, and it does this by rhythmically beating its legs, pumping water through the space under its carapace, and using the bristles on its legs as strainers. Because algae are the daphnia’s main food source, it is clearly and advantage for the daphnia to stay where the algae are most densely populated. This is done by sight, but not by spotting the algae at a distance and heading for it. If the daphnia stumbles across a group of algae, the light seen by the daphnia will be slightly red, as most of the blue light in sunlight is removed as it passes through the cloud of algae. The slight redness of the light will cause the daphnia to remain in the location of the algae. The daphnia is in turn eaten by other, larger organisms, making it an important link in the aquatic food …show more content…
chain.
The fact that the daphnia has a transparent body means that it is very easy to study the internal organs under the microscope. This, and the fact that the daphnia reproduces very quickly, means that it is often used to study the effects of drugs on the heart.
This is a picture of a Daphnia Magna. From the picture you can clearly see the heart:
Variables:
In order to test out my hypothesis, I am going to look at how different concentrations of alcohol affect the heart rate of a single daphnia. In this experiment, the variable that changes is the concentration of the alcohol. All of the other variables- for example temperature, length of time in the concentration of alcohol and recovery time- remain the same. Also, I will try to use the same daphnia for all of the experiments, because different daphnia will have different natural heart rates, in the same way that humans do. However, it may not be possible to use the same daphnia all the time, because daphnia have a tendency to die when used in experiments. If the daphnia does die, it will be replaced by one of similar size and development.
Apparatus:
Below is a list of the apparatus I used during the experiment and reasons as to why I used them:
1. Pipette – This was used because it is the easiest things to use too transport the Daphnia from the water bath to the test tube, and from the test tube to the cavity slide.
2. 100 ml measuring cylinder – Used to make up the different concentrations in (see method for the different concentrations). This was the only measuring cylinder big enough.
3. 10 ml measuring cylinder – Used to measure out 10 ml of the alcohol concentration to put the Daphnia in to.
4.
25 ml flask – Used to put the 10 ml of the concentration into as well as the Daphnia so it could be observed and exposed to the concentration.
5. Ethanol – I used this to make up my alcohol concentrations, as it was the easiest and most common chemical used.
6. Distilled Water – used as the main thing in the concentrations and also used to put the Daphnia in after they were subjected to the alcohol concentration to try and bring their heart rate back to normal. It is used as the control as it is pure and free from chemicals that could affect the Daphnia’s heart rate, thus making the test fairer.
7. Microscope – Used to observe the heart rate of the Daphnia, under a low power.
8. Cavity Slide – Used to put the Daphnia onto so it could be observed. Due to the cavity on it, it meant it was easier to use than a normal slide as some of the concentration was put onto it also.
9. Cavity Tile – Used to put the Daphnia into after it had been in the concentration of alcohol. The cavities were full of distilled water.
10. Safety Mat – This was used to protect the bench from any spillages of ethanol as other people have to use the bench and ethanol is a dangerous chemical.
11. Safety Goggles – These were used to protect my eyes from the vapour from the ethanol as it can lead to
irritation.
12. Stopwatch – I used a stopwatch to time 15 seconds while the daphnia was under the microscope being observed and also the time 5 minutes while the Daphnia was in the concentration.
13. Calculator – I used this to help me count the heart rate of the Daphnia, as it was a lot easier to do than use my head to count. The way in which I used the calculator is described in the method.
Below is a diagram of the apparatus used during the experiment:
Safety:
During the experiment there are some cautions I will have to take in order to make it completely safe for others and me around me. The main safety precaution is ensuring that I conduct the experiment in an appropriate manner and do not take any risks when doing things. Other things such as wearing safety goggles are important because the vapour from the ethanol could cause some irritation in my eyes. Another thing is to have a safety mat down on the bench to stop any spillages from going onto the bench and causing a risk to others that may use it after me. Also a very important safety point is to ensure that I handle the glass wear with care and make try not to break anything like it.
Method:
Below is a step-by-step description of how I conducted my experiment and used the equipment listed previous:
1. Firstly I made up the correct concentrations of the alcohol solutions, using ethanol and distilled water. The measurements are listed below in the table:
Concentration
Required (%) Amount of
Ethanol (ml) Amount of
Distilled Water (ml) Total Volume
(ml)
Control group - 0 0 100 100
0.2 0.2 99.8 100
0.4 0.4 99.6 100
0.6 0.6 99.4 100
0.8 0.8 99.2 100
1.0 1.0 99 100
2. I got the Daphnia from the water bath and put it into a 25ml flask of distilled water for 5 minutes. This was the control group to find the normal heart rate of the Daphnia.
3. After 5 minutes was up I removed the Daphnia from the distilled water, with a pipette, placed it onto a cavity slide, and put it under the microscope that was on a low power.
4. I focused in on the Daphnia and identified its heart with help from the diagram on page 1.
5. Using the calculator I counted the heart rate of the Daphnia. To do this I pressed the [1] and [+] buttons. I then pressed the equals [=] button, which displayed the number [2]. The calculator acted as a counter and every time I pressed the equals button the numbers increased by 1. I pressed the button every time I saw the Daphnia’s heart beat. I counted the heart rate for 15 seconds and then I multiplied it by 4 to make it into the heart rate over a minute.
6. The results were then recorded in a table, shown in the results.
7. After I used distilled water, I moved onto the concentrations of alcohol starting with 0.2%.
8. I took the 100ml-measuring cylinder full of 0,2% concentrate, measured out 25ml of it using a pipette, and put it into a 25ml flask.
9. Then I took the Daphnia from the water bath using a pipette and put it into the concentrate for 5 minutes.
10. During this time I rote down some observations of what I could see from the behaviour of the Daphnia.
11. After the 5 minutes was up the Daphnia was removed and put onto the cavity slide, under the microscope.
12. The heart rate was taken, as in Step 5 and recorded.
13. Steps 7 – 12 were then repeated using the different concentrations.
14. All the concentrations were tested 3 times and then an average was found.
Results:
Below are the results that were obtained during the experiment:
Concentration of Alcohol (%) Result 1
(BPM) Result 2
(BPM) Result 3
(BPM) Average Result
(BPM)
Control – 0 160 172 180 171
0.2 136 131 146 138
0.4 120 131 124 125
0.6 124 114 121 119
0.8 96 100 104 100
1.0 106 103 90 100 Observations:
Whilst the experiments were being carried out I noted down a few observations about the Daphnia’s behaviour in the different concentrations.
When the Daphnia was put into the Distilled water it swam around very quickly and changed direction quickly and at right angles.
As the concentrations increased the speed of its movements began to slow down considerably, to the extent where it just sank to the bottom of the flask in the 1.0% concentration. Its movements turned from right angles to having to go round in an arched shape, showing that the alcohol had affected more than just its heart rate.
Analysis:
As the concentration of alcohol was increased the heart rate of the Daphnia decreased. This is what I can tell from the results that I obtained.
The change in heart rate from the control group to the 0.2% concentration was 33 BPM. This is almost double the most significant difference in BPM between the groups, of 19 BPM from 0.6% to 0.8%. Just from looking at that it is clear to see that alcohol does affect the heart rate of Daphnia, as the heart rate dramatically reduces from normal when put into the weakest solution.
Although research has been done on the subject, no one is sure how or why alcohol affects the heart. Normally, alcohol acts on body systems under the control of the CNS. It is thought that alcohol works by inhibiting the action of the neurotransmitters that transmit nerve impulses across a synapse. However the heart of a human is outside the control of the CNS, while Daphnia have no CNS present. In both organisms the rate of the heart beat is controlled by the autonomic nervous system, being accelerated by the sympathetic system and depressed by the parasympathetic system. The heart rate is also influenced by the hormone adrenaline, which has a similar effect as the sympathetic nervous system in that it causes the heart to beat faster. This is the so-called ‘fight or flight’ reflex. It is possible that alcohol works in a similar way to adrenaline. They are both chemicals transported in the blood, so it is possible that their action on the heart is similar.
Although the overall results were expected, for the first three sets of concentrations the Daphnia’s movements were practically unchanged, but for the other two the behaviour changed drastically. This abnormality could be caused by the fact that when humans consume a small amount of alcohol, up to about 40mg of alcohol per 100ml of blood, they become more active than usual, even though the heart rate may drop.
There is one anomaly that I have circled on my graph and that comes at the 0.8% concentration. At first I thought it was the 1.0% concentrate result that was the anomaly, but from looking at the graph I could tell that it was actually the 0.8% concentrate. This is because it does not fit in with the pattern of the graph and makes the line too steep from the 0.6% to 0.8% concentrations. I would have expected this to come out at around the 110 BPM mark as this would fit into the graph and give me a good correlation.
This anomaly could have down to a number of reasons such as; an error in the measurements of the chemicals, the concentration not being mixed up properly, the Daphnia not completely recovering from the previous concentration or an error in the counting. Personally I think that it was the fact that the Daphnia had not completely recovered from the previous experiment. This is because whilst observing the behaviour of the Daphnia when it was in the distilled water, recovering from the previous experiment, it did not ever get back to full speed and was acting slightly docile when moving around, as apposed to whizzing around the flask like usual.
Evaluation:
The results that I obtained from doing the experiment show clearly that alcohol does effect the heart rate of a Daphnia and therefore, the heart rate of a human should also act in this way. The results look to be reliable, from the graph as the line does show a good correlation between the concentrations. The only exception to this is the anomaly at 0.8%, but this is not a big change in the result as it was only roughly 10 BPM out from what I would have expected it to be. I took three results from each concentration and found an average of this as this makes the results more reliable. This is because, just taking one result would leave it open for a lot of anomalies as the Daphnia could act very differently from the first result to the third result from each concentration. For example, in my results, if I had only taken one result, the first one then it would have meant that I would have had two clear anomalies. These would occur between 0.4% & 0.6%, and 0.8% & 1.0%. At 0.4% the first result was 120 BPM and at 0.6% it was 124 BPM. A difference of 4 BPM, where the higher concentrate produced a higher heart rate. Also, at 0.8% it was 96 BPM and at 1.0% it was 106 BPM, a difference of 10 BPM in favour of the higher concentration. So, therefore, it proves that multiple readings should be taken to make results more reliable.
There were a few limitations of my experiment. These are listed below:
• Although it is accepted that alcohol affects humans and Daphnia in similar ways, they are still very different organisms, so will be affected in different ways. Although the general effects will be the same i.e. decreasing of the heart rate, the amount of variation will be different. Due humans being much larger than Daphnia, a much larger quantity would be required and also a longer amount of time for it to affect the human. To achieve the results of this on humans, a large medical study would need to be undertaken.
• The temperature of the solution in which the Daphnia is immersed will affect the heart rate; if it is warmer it will increase the heart rate. Also, when the Daphnia is put onto the microscope it is exposed to a concentrated light, which will of course give off heat and therefore increase the heart rate of the Daphnia as, the experiment goes on. This would lead to a higher BPM of the Daphnia and the only way I can think of to over come this is to always switch the microscope off after every time of using it so it does not get too hot.
• Living creatures tend to behave in an unpredictable way. Although the same Daphnia was used in all the experiments, the problem of unpredictability is still significant. For example the experiments were carried out over a couple of days, so the Daphnia’s behaviour may vary from day to day. Also the conditions of the laboratory may have changed, e.g. the temperature of the room could bring about slight changes in the behaviour of the Daphnia. The only way to change this would be to conduct the experiment in one day and also conduct the experiment on more than one Daphnia. But due to the time allocation I was unable to do this.
• Finally, it was not always easy to count the Daphnia’s heartbeat, even using a calculator as the counter. This was because it sometimes moved around under the microscope so I could not see the heart properly and also because it beat so fast it was not easy to keep up with it. This would have had a slight effect on the results as it would have meant that thee odd BPM would have been missed, thus changing the averages by one or two.
Further Work:
Below are a few suggestions of what further investigations I could conduct to help me research more into the topic:
1. I could change the type of alcohol used to a proper drinking spirit or beer to see if this effects the Daphnia, as this would be more ecologically valid towards the statement of … ‘Alcohol has the same effect upon Daphnia as humans’, this is because humans do not drink ethanol as it is a very dangerous chemical. This would also lead into another investigation.
2. I could do the experiment above, but use humans. This would then allow me to be sure of the similarities of the effect of alcohol upon both humans and Daphnia.
3. I could also do an observational experiment on humans that are under the influence of alcohol as to whether they, like Daphnia, become more docile and slow down.
Finally, from the results obtained I can confirm that my hypothesis is correct and accept that alcohol does have a significant effect on the heart rate of Daphnia, and therefore, humans.