• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The effect of caffeine concentration on the heart rate of Daphnia.

Extracts from this document...


The effect of caffeine concentration on the heart rate of Daphnia Aim To conduct an experiment into the relationship between the heart rate of a Daphnia and its exposure to various concentrations of caffeine. Method For this experiment we had: Culture of Daphnia in various concentrations (%) of caffeine (0.0, 0.0025, 0.005, 0.025, 0.05, 0.25, 0.5) Two cavity slides A pipette Stop watch Microscope Ice water Firstly, a job was designated to each member of the group and each had a counter, a recorder and a controller. The controller always set up each slide to ensure that the other members of the group were unaware of the concentration of caffeine that the Daphnia were exposed to, thereby eradicating bias, and also controlled the time. The counter would count the number of heart beats in ten second intervals by stabbing at a piece of paper with a pen, in an 'S' shape. This allowed for easy counting and a control on human error. The recorder counted the dots on the paper to ensure that an extra heart beat was not added here and there in order to make the results match their prediction. A microscope was then set up and the x10 lens was used to ensure that the Daphnia's heart could be seen clearly. The slide was then set up. Some ice water was then placed on one cavity and the second cavity slide placed on top of the first. ...read more.


Discussion The chemical formula for caffeine is C8H10N4O2 and is known medically as trimethylxanthine. Caffeine also belongs to a class of compounds called methylxanthines. When in its pure form, caffeine is a white crystalline powder with a very bitter taste. Medically, caffeine is useful as a cardiac stimulant and also as a mild diuretic. Recreationally, it is used to provide a "boost of energy" or a feeling of heightened alertness. Among its many actions, caffeine operates using the same mechanisms that amphetamines, cocaine and heroin use to stimulate the brain. On a spectrum, caffeine's effects are more mild than amphetamines, cocaine and heroin, but it is manipulating the same channels. Adenosine is one of these chemicals. Adenosine is a relatively simple, nitrogen-containing compound used widely by the body. It forms the core of adenosine triphosphate, or ATP, the energy-storage molecule that powers most of the biochemical reactions inside cells. In the brain, adenosine secretion by cells such as neurons often reflects how busy the cells are. Areas that are active generate adenosine; areas that aren't active tend not to. As adenosine is created in the brain, it binds to adenosine receptors. The binding of adenosine causes drowsiness by slowing down nerve cell activity. In the brain, adenosine binding also causes blood vessels to dilate to allow more oxygen perfusion to the body during sleep. ...read more.


Apart from sources of error, other considerations must be taken when conducting an experiment. Firstly safety. There were not many safety issues which arose from this experiment. The experimenters were aware of what to do in the instance of a slide breaking exposing them to sharp glass. They were to dispose of it cleanly and safely in a designated bin. If the liquid being used had been hazardous they would, of course, have taken the necessary procedure to protect themselves; for instance wearing protective clothing. One safety issue that may arise if a stroboscope were to be used would be the effect on people who may suffer from epilepsy. The second consideration is that of ethics. Living organisms were used in this experiment, and inevitably some suffered as a direct cause of the experiment. Many exposed to the higher concentrations died. This meant there was a need to weigh up the costs and benefits of using these organisms for this particular experiment. The cost of the experiment was the poisoning of the Daphnia and as a result their death. On the other side of the argument, the next generation of doctors and scientists may be being trained through this experiment. As a result of this weighing up, it was decided that it was ethically justified to use these Daphnia in this experiment, especially as they were bred as fish food and would have died anyway; and they were a valid method of measuring heart rate. Anjali Lockett 1 05/05/2007 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Humans as Organisms section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Humans as Organisms essays

  1. Marked by a teacher

    Does Caffeine Affect Heart Rate?

    4 star(s)

    Start Finish 38 55 152 220 173 227 Caffeine 44 65 176 224 48 59 192 236 CONCLUSION: The results obtained clearly show that the higher the concentration of the caffeine, higher the heart rate. This proves the original prediction.

  2. Peer reviewed

    the effect of caffeine on heart rate

    3 star(s)

    Evaluation: I have kept all the control factors the same in order on having a fair test. If I was going to do this experiment again I would ask 2 more females to drink fizzy water and 1 more male to do not drink at all.

  1. Stem Cell Research

    because the embryonic stem cells are able to form any type of tissue, even those that would not usually be able to be cultured (such as muscle cells or nerve cells). These cell lines are important for the testing of drugs because they give the opportunity to safely test the

  2. Should the cloning of humans be allowed?

    Cells could be taken from a person suffering from a disease and used to help cure the disease. For example a person could be suffering from macular degeneration, which is a disease which destroys vision. To help improve the person's eyesight, cells would be taken from the person and cloned

  1. The heart rate of a Daphnia (water flea)

    around the body; therefore a faster heart rate is needed to pump these nutrient around. This is what my prediction explained earlier, so I was right in saying that enzymes play a great role in the heart rate and that is related to metabolic rate. The results support the prediction.

  2. Does caffeine affect heart rate

    We controlled this by setting the room thermostat at one constant temperature throughout the experiment. The amount of water is very important, because we tried to suck all the water out of the cotton wool on which the daphnia were placed before adding the caffeine to the daphnia.

  1. Effect of Caffeine on Heart Rate in Daphnia

    Thus, when they are inhibited by caffeine, the stimulatory signal remains active for a longer period of time resulting in a greater sense of alertness (a CNS effect) but also a higher heart rate, blood pressure and respiratory rate. This can clearly be seen in the results, that the daphnia's

  2. Effect of Ethanol on the Daphnia heart rate

    Another reason for this is that if you start at the highest concentration, the impact on the Daphnia will be too dramatic and you will not see any trends once you try a lower concentration, it will have an effect of "intoxication".

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work