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

Does caffeine affect heart rate

Extracts from this document...


Does caffeine affect heart rate? Aim To determine how caffeine effects the heart rate of Daphnia. Prediction I predict that as the concentration of caffeine is increase, the heart rate of the Daphnia will increase. I predict this because of my knowledge of caffeine - it is a type of chemical called a stimulant. When you drink a caffeinated beverage, the caffeine enters into your blood stream dilating the capillaries and causing blood to flow more quickly. If the blood is flowing more quickly, the heart rate needs to increase to pump more blood through the dilated capillaries. In humans, caffeine acts as a stimulant drug, causing increased amounts of stimulatory neurotransmitters to be realeased. At high levels of consumption, caffeine has been linked to high blood pressure and raised heart rate. From this knowledge, I predict that the caffeine will have this effect on the Daphnia too, thus an increase in their heart rate. Risk Assessment If a stroboscope is being used to show the Daphnia's heart rate in this experiment, and you know that you suffer from photosensitive epilepsy, then you need to make sure you make appropriate precautions. Goggles will be worn to prevent any touching of eyes, which could cause irritation. ...read more.


When calculating the heart rate of the Daphnia, we used the method of tapping a pencil on the table and then counting up the marks made. This method of tapping a pencil and someone counting them wasn't very accurate because: When the daphnia's heartbeat got really fast you couldn't keep time with the rapid heartbeat. If you lost count while trying to count the heartbeat and still carried on counting the beats per minute wouldn't be right. There are two main variables for this experiment; the independent variable and the dependant variable. The independent variable is the concentration of the caffeine, which was given to the Daphnia. As you can see in the result table, the concentration was given in 0% (water), 20, 40, 60, 80 and 100% dosages. We could not go any higher because the amount of caffeine would probably cause the daphnia to have a heart attack and die. The dependent is the effect that the independent variable has on the Daphnia's heart rate. When we put the concentration on the daphnia we tried to make it a drop each time, so that each daphnia would be getting the same amount, making the results more accurate. We couldn't get it exact each time but it was very close. ...read more.


As I said in my findings, this is because the Daphnia are very small, and their heart rate is already quite fast, so when the caffeine increased their heart rate, it was hard to keep count of the beats by purely tapping a pencil on the table. I would also do more trials, because as you can see from the results, I did not complete the table of trials for the reliability of the experiment to be sufficient. Therefore, I had to calculate an average with the data I did have, and create a graph using these averages. Not doing 3 trials makes the experiments results less reliable because it could have been chance that these first results show a positive increase as the concentration of caffeine increases. It would have been much more reliable to do 3 trials for each concentration to get an overall average value for each one. As these results are similar to what you would find in humans, if I were to re do this experiment, I may use alcohol to see whether it has the same effect on Daphnia as it does humans. Alcohol is a depressant and therefore slows down the heart rate, so I would test to see whether the same affect happens to the Daphnia in this experiment. Charlotte Johnson Miss Tate ...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)

    If something went wrong because the experiment wasn't safe then the observations that we would get would be wrong and also may affect the results. The amount of the caffeine that we use should all be to the correct measurement as then the results would be fair.

  2. Marked by a teacher

    Does Caffeine affect Heart Rate?

    3 star(s)

    Take a cavity slide and with the use of a dropping pipette places one daphnia and some water on to the side 8. Place cotton wool round the 4 edges of the slide, insuring the daphnia is in the centre of the slide.

  1. Investigation into the factors which affect the heart rate in daphnia.

    of heartbeats will be counted instantly to see how effective the concentration is on the daphnia's heartrate. Then a cavity slide will be placed under the microscope. The test will be done 10 more times, every 30 seconds for caffeine.

  2. Should the cloning of humans be allowed?

    I feel that firstly, only couples who cannot have tried other avenues of having children, for example In vitro fertilisation, and have had these methods fail, could be allowed to have their children cloned from one of the parents. As well as this, if parents decide to create a clone

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

    52 49 46 51 46 46 0.0025 60 58 51 55 59 58 56 56 352 58 62 69 68 55 58 56 0.005 60 56 56 57 55 53 45 48 321 43 61 61 53 51 53 51 0.05 52 51 54 47 49 50 50 52 318

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

    I will use 150ml of water in each new environment so as not to have more or less heat when the Daphnia are adapting. I will also control the possibility of impurities in the water by using tap water for the duration of the experiment.

  1. Effect of Ethanol on the Daphnia heart rate

    Make sure you rinse and dry the slide with the distilled water after each time. You must start from the lowest concentration up to the highest concentration because the Daphnia has to gradually adapt to the changes, you will be reducing the probability of it dying.

  2. Investigating the effects of temperature on the heart rate of Daphnia.

    After recording the result, the test was repeated two more times with the same daphnia. In between the 10 second intervals as we were not actually observing, the light source was turned off in order to keep from heating up the slide and to keep evaporation to minimum.

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