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The Effect of Caffeine on Heart Rate

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The Effect of Caffeine on Heart Rate

In this experiment we are trying to find out how the concentration of
caffeine can affect the heart rate of a brine shrimp.

Caffeine is a stimulant and mainly affects the central nervous system,
and will increase your heart rate.

Caffeine affects daphnia in the same way as it affects a human; the
experiment was done the same as ours except we used a brine shrimp.

Caffeine is popular in our society, but yet it is not part of a
healthy diet. Large amounts of caffeine can cause serious health
related problems. It is possible to use daphnia to test different
amounts of caffeine to see how much challenges human health.


Caffeine is a type of stimulant that speeds your body up and can
affect the nervous system, and other parts of the body. This stimulant
belongs to the xanthenes group. Caffeine dissolves in water and
alcohol. It can cause serious health related problems like heart
problems, digestive problems, various different kinds of cancer, and
birth defects.
The average adult should have no more than 300 mg per day.
Caffeine can be found naturally in some plants, but it can also be
made by humans in a laboratory, or factory. Caffeine can be found in
many popular foods like coffee, tea, cocoa, soda, and chocolate.
Caffeine can become addictive if taken in large amounts. Caffeine
tastes bitter, and has no smell. It only occurs naturally in small
Caffeine has tiny crystals on it that look like needles. Caffeine was
produced from plants in the pure form in 1820.
Caffeine is used in prescriptions for some disorders to increase
circulation. When taken in large amounts it can cause loss of sleep
and headache.


This graph shows the over all average results from both trials one and
two. It shows how the three levels of caffeine tested, affected the
overall heart rate of the daphnia tested in this experiment.


This graph compares the averages for both trials one and two. This
graph shows how the heart rate of the daphnia changed either by
increasing or decreasing throughout this experiment. It shows the
specific affect of the various caffeine levels on the daphnia in trial
one and two and compares the results.

Caffeine molecule




My Plan

In my investigation I am trying to find out how varying the
concentration of caffeine can affect the heart rate of a brine shrimp.

To make sure that the practical is a fair test only the concentration
of the caffeine will be changed, the caffeine is the independent
variable, the same shrimp will be used, the shrimp is the dependent
variable, and the concentration of the salt water will stay the same.

I am going to test each particular concentration of caffeine three
times to make sure that my results are accurate and reliable.

If the results seem out of pattern or trend then I will repeat these
concentrations of caffeine again so that it is a fair test.

I will be using one brine shrimp throughout the experiment, the
highest concentration used will be 5mg/ml and the lowest is 1mg/ml.

Preliminary Work

To find my range of results I will find the highest concentration of
caffeine and the lowest concentration of caffeine.

The lowest concentration was 1mg/ml and the highest concentration was

The highest concentration took an average of 193.3secs.

The lowest concentration took an average of 128.6secs.

The rest of our results will have an average in between these to

If we use a higher concentration which is higher than 5mg/ml then our
eyes may not be able to recognise approximately the total number of
beats, and if we use a concentration which is too low then we will run
out of time.

Concentration of caffeine (mg/ml)

Average time (secs)






· Concentrations of caffeine

· Room temperature

· Gender of shrimp

· Age of shrimp


The dependant variable (the heart rate of brine shrimp) will increase
as the independent variable (caffeine) increases, because caffeine is
a stimulant which causes the heart rate to increase.

Caffeine is a mild stimulant to the nervous system, the age and size
of the shrimp can make a difference in the effect.

So if I use a large shrimp then the heart rate will be less than what
a smaller shrimp’s heart rate is, this is the same for age.



1. Once you have set up the microscope and gathered all the equipment,
then collect your shrimp.

2. Place the shrimp in the glass well along with a few drops of salt

3. Place the shrimp onto the glass slide along with three drops of sea
salt, place the glass slip on top of the shrimp and place under the

4. Count the pulse of the shrimp over 30 seconds, do this three times.

5. First you need to put the shrimp into the lowest concentration of
caffeine which is 1mg/ml and give the shrimp time to adjust

6. Then place the shrimp on the glass slide along with 3 drops of the
solution using the pipette, and place under the microscope and measure
the pulse over 30 seconds.

7. Repeat this three times.

8. Next use another concentration of caffeine and repeat procedures

Equipment used

· Microscope (40 magnification)

· Pipette

· Shrimp

· Glass Well

· Glass slide

· Cover slip

· Concentrations of acid 1mg/ml-5mg/ml.


Concentration of caffeine mg/ml

Heart rate of Brine Shrimp (beats per minute)


1st Test

2nd Test

3rd Test
































As can be seen from both the graph of my results and the statistical
analysis of my results, alcohol effects. The overall effect of alcohol
was, as expected, to decrease or increase respectively, the heart rate
of the Artemia.

The graphs show positive correlation and my results prove my
hypothesis to be right as when you increase the concentration of
caffeine then also the heartrate goes up.

The results show that the hypothesis should be accepted because the
more caffeine placed into the water the higher the heart rate.

If I were to conduct this experiment again I would have a more
accurate way of measuring the heartbeats, I would like to use more
trials to make my results more accurate and reliable, I would also use
a wider range of caffeine levels.

Percentage differences

The largest percentage increase was from 2-3mg/ml of caffeine.

0-1mg/ml 7.2%

1-2mg/ml 16.8%

2-3mg/ml 18%

3-4mh/ml 1.8%

4-5mg/ml 0.6%


I feel that the experiment went as planned as the results matched my
hypothesis; my results were as exact as I could get them.

The results however are not completely accurate as I may have missed a
beat while counting the heart rate there may have been an equipment
error, may not have used the digital clock correctly, and the shrimp
did not have a constant heart rate.

To make my results more accurate and reliable I tested each
concentration on caffeine three times.

How to Cite this Page

MLA Citation:
"The Effect of Caffeine on Heart Rate." 18 Apr 2014

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