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The Effects of Caffeine on Daphnia
In class we have been studying the heart, and the effects various drugs can have on it.
Caffeine is the drug taken most globally, and can cause problems including raised blood
pressure, insomnia and paranoia.
Since we are looking at the heart, we decided to test the effects exposing daphnia to caffeine
would have on the daphnia's heart.
From research it would appear that in moderation caffeine does not affect the cardiovascular
systems health in a human. However, as more studies on caffeine are conducted it appears
that the affects differ greatly from one person to another, so although it may not affect the
heart rate of one person, it could cause a permanent raise in blood pressure for someone
However multiple studies have concluded that caffeine does stimulate the nervous system,
the respiratory system and the heart.
An exposure to higher concentrations of caffeine will cause a distinct increase in the heart
rate of daphnia.
In our experiment we placed Daphnia under a microscope. They were on a slide with a small
amount of water, on a miniscule amount of cotton wool so we could restrict the movement
while keeping the daphnia alive.
We then located the heart, and counted the heart beats for 30 seconds, doubling it when
We then added a small amount of caffeine to the slide, and counted the heart rate again.
The dependent variable in this experiment was the heart rate of the daphnia before and after
exposure to the caffeine. The independent variable was the concentrations of caffeine we
exposed the daphnia to.
When doing the experiment, we had to consider that the daphnia were living organisms and
could most probably feel pain, and so we had to treat them with respect when we were
following our method.
As you would in any experiment, we wore a lab coat and goggles for our own protection in
case anything was spilt or broken.
Caffeine Conc. Attempt 1. 2. 3. Average
0.0 102 146 146 131.33
0.3 166 154 84 134.67
0.4 180 199 178 185.67
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As you can see from the results, our experiment wasn't very successful as we didn't get to
use all the concentrations all carry out each concentration the recommended five times.
However, you can still see the definite increase in heart rate as we increased the
concentration of caffeine, except from one result, concentration 0.3 attempt three, which was
probably due to human error.…read more
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In order to improve our results, we would have to find more reliable ways to count the heart
rate of the daphnia, or use larger animals so it's easier to find out the heart rate. We would
also have to repeat the experiment more times, as well as carrying out trial runs.
It would also be more accurate if we could find a way to expose the daphnia only to the test
solution, while maybe using more of a range of solutions.…read more