Effects of Caffeine and Nicotine on Lumbriculus Variegatus

An experiment was conducted to study and explore the circulatory system by exposing Lumbriculus variegatus, black worms, to household drugs. Lumbriculus variegatus was chosen as the experimental organism because of their transparent bodies and their simple physiology. Their transparent bodies help the experimenters to easily see their pulse. Another reason for choosing this specific organism is their body structure—large surface area to size ratio. This feature allows the substances, such as the household drugs, to easily enter their body which then can affect their health.

The household drugs used in this experiment were decaffeinated coffee, tea, instant coffee and tobacco along with caffeine and nicotine. As we increase the concentration of caffeine, there will be an increase in the change in pulsation rates of the L. variegatus. The reason that the pulsation rate increases with the intake of caffeine is because it increases the blood flow velocity in the middle cerebral artery, which in a way increases the pulsation rates.

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Caffeine is known as a stimulant, especially for the central nervous system; because “caffeine increases energy metabolism throughout the brain but decreases at the same time cerebral blood flow. ”(4) Caffeine also acts as an inhibitor for adenosine, which is what allows it to be a stimulant. (2) As we increase the concentration of nicotine, there will also be an increase and right after the maximum change in pulsation rates of the L. variegatus there will be a decrease which will eventually hit 0 beats per minutes.

The reason the pulsation rate increases and then decreases with the intake of nicotine is because it causes an increase in heartbeats and with a large doze it can result to no heartbeat at all.

(3) Since decaffeinated coffee, tea, and instant coffee have caffeine in them there may be increase in the change of the pulsation rate of the L. variegatus. As we add tobacco, there may be an increase in the change in pulsation rates of the L. variegatus.

The reason why we aren’t sure of how much the pulsation rate will go up by is because of the unknown amounts of caffeine in decaffeinated coffee, tea and instant coffee and the unknown amount of nicotine in the tobacco. Looking at the trends of the change in pulsation rates of different concentration of caffeine and the different concentrations of nicotine (taken in the first week), we can determine an estimated concentration of caffeine in decaffeinated coffee, tea and instant coffee and an estimated concentration of nicotine in tobacco (taken in the second week).

Figure 1. This graph shows the effects of different household drugs on pulsation rates. The columns represent the mean change in pulsation rates of different caffeine concentrations and decaffeinated coffee, tea and instant coffee. The error bars of each column represent the standard deviation for that treatment. The control group of the different concentrations of caffeine, taken in the first week, has a mean of -1. 07 beats per minute and a standard deviation of 1. 48. On the other hand, the control group of the different household drug treatments, taken in the second week, has a mean of 0. 19 beats per minute and a standard deviation of 1. 90.

Figure 2. This graph shows the effects of different household drugs on pulsation rates. The columns represent the average change in pulsation rates of different concentrations of nicotine and the unknown concentration of tobacco. The error bars of each column represent the standard deviation for that treatment. The control group of the different concentrations of nicotine, taken in the first week, has a mean of -1. 07 beats per minute and a standard deviation of 1. 48. On the other hand, the control group of the household drug tobacco, taken in the second week, has a mean of 0. 19 beats per minute and a standard deviation of 1. 90.

The independent variable of this experiment is the different types of treatments we used, the caffeine, nicotine, decaffeinated coffee, tea, instant coffee, and tobacco. The dependent variable is pulsation rates of L. variegatus before and after they were in the treatments. The standardized variable of this experiment would be the temperature of the surroundings of the L. variegatus, the three pulsation rates taken for each worm before and after the treatments, and also the amount of time each worm was kept in their respective treatments.

The level of treatment for this experiment would be ten because of the six different concentration treatments of caffeine and nicotine along with the four household drugs. The sample size of the experiment differed from some treatments to other. For the three different concentrations of caffeine and nicotine, the sample size was 18 black worms each. The sample size of the control treatment of week 1 was 6 black worms. 12 black worms were used for the control of week 2, decaffeinated coffee and instant coffee. 11 black worms were used for the tea treatment and 15 were used for the tobacco treatment.

There were three replications of the pulsation rate readings per worm before and after the treatment. With all this information we were able to get the results we got. According to the results, the columns of caffeine in figure 1, of this experiment the hypothesis for caffeine is partially accepted. There is an increasing trend in the change of pulsation rates with increasing concentrations of caffeine, which is why we the hypothesis is accepted. However when the concentration of caffeine reaches 10. 0mM, the change in pulsation rate is lower than the change in pulsation rate; which is why we partially accept the hypothesis.

Studies have shown harmful effects during the usage of large concentrations of caffeine; and its result could have been this dramatic change in the change of pulsation rates. (6) After the treatment of the different concentrations of caffeine, the black worms started moving around much more than before the treatments. According to the results, the columns of nicotine in figure 2, of this experiment the hypothesis for nicotine is accepted. There is an increasing trend in the change of pulsation rates with increasing concentrations of nicotine until 0. 25mM, and there is also the decreasing trend in the change of pulsation rates with the concentration of nicotine reaching 1. 0mM.

We had expected to see an increase in the change of pulsation rates for the decaffeinated coffee, tea and instant coffee, which was the trend that the graph followed. Their change in pulsation rates were all above the 0 beats per minute because they all had some caffeine in them. Looking at the trends of the change in pulsation rates of different concentration of caffeine, we can determine an estimated concentration of caffeine in decaffeinated coffee, tea and instant coffee.

The concentration of caffeine in decaffeinated coffee and tea would be less than 1mM or between 3mM and 10mM; in instant coffee it would be between 1mM and 3mM or 3mM and 10mM. The graph didn’t follow the trend we had expected to see for tobacco. The mean of the change in pulsation rate was below 0 beats per minute, which means that the pulsation rate of the L. variegatus after the tobacco treatment was less than the pulsation rate before the treatment.

Looking at the trends of the change in pulsation rates of different concentration of nicotine, we can determine an estimated concentration of nicotine in tobacco; which would be more than 1. 0mM. The reason why we didn’t see the expected results was because with a large enough dose the pulsation rates will start to go down and eventually stop. (3) After the treatment of tobacco, the black worms were slow in their movements. One reason why the exact amount of caffeine and nicotine concentration can’t be determined in all the household drugs used in this experiment is because the data is not very reliable.

Figure 1 and 2 shows this by having a big standard deviation for all the treatments and their concentrations. Big standard deviations mean that the data is very diverse and therefore less reliable. This wide spread of data could have been caused by errors in the experiment. There are many causes of error that have and could have happened during this experiment and that might affect the results. One thing that definitely brings a difference between the results of each treatment would be caused by the fact that not every treatment had an equal number of sample size.

The results could also have been affected by the differences in the worm. The age, genetic makeup, general health, and the size of the worm can really affect the pulsation rates as well. Errors like looking at different segments of the body during the reading of pulsation rates can also occur. Some errors can be avoided to improve the experiment while others can’t be. Errors such as looking at different body segments and the sample size could be fixed by making sure you are looking at the same body segment even if L. variegatus is moving, and the sample size for each treatment could be set to the same number.

The differences in worms can’t really be avoided because each worm is different from the other in some way or the other. To conclude, the results of this experiment cannot be applied to other systems. The results cannot be applied to organisms that have completely different physiology than the L. variegatus. Despite the fact that the results can be applied to organisms that share the same physiology as the L. variegatus, it can’t really tell us much about the other organisms because the data isn’t reliable.