Unit 6 learning aim D
Effects of caffeine on the heart rate of daphnia
Samuel Gebray
Abstract
This paper contains the report of the experiment done on the effects of caffeine on the heart rate of
daphnia. This experiment was done as a project at Pendelton college. From the literature search
done a hypothesis was made that caffeine does affect the heart rate of daphnia. And so, the
experiment was carried out using a method where three different daphnia were exposed to five
different concentrations of caffeine. Their heartbeat was recorded for a minute and the results
showed that as the concentration of caffeine increases the heart rate of daphnia increases as a
result. Below the results obtained from the experiment can be seen. The results showed that
caffeine does increase daphnia’s heart rate but not by large numbers.
Introduction
Caffeine is known to increase the heart rate and concentration levels in humans, but it is not known
how effective it is on animals or different kinds of organisms. So, to have a fair understanding of
their effects on other organisms, daphnia were the perfect subjects to carry out this kind of
experiment as the effects can be seen immediately because have a transparent body. This is also
efficient at saving time and effort of performing an operation on other animals.
It was ensured that the health and safety concerns were adhered to while carrying out the
experiment, and the risk assessment that was done was followed to the maximum possibility.
Hypothesis: The concentration of caffeine will affect the heart rate of daphnia accordingly which
means if the caffeine concentration increases the heart rate of daphnia will increase same goes for
the opposite. This is because daphnia is a stimulant and it’s known to raise the heart rate of some
species.
Equipment
Microscope
Counter (software that can be installed on the phone)
Dropping pipettes
Tissue
Stopwatch
5 different caffeine concentration solutions
Cavity Slide
Beaker containing Daphnia in pond water
, Participants: myself, teacher, classmate, lab technician.
Method
A Daphnia was taken from the beaker with a pipette and placed in a cavity slide under a
microscope. Using a tissue, dab around the Daphnia to remove the pond water and replace
it with drops of caffeine solution. The daphnia was left for 3 minutes to acclimatise and then
the heart rate was observed & counted (using a counter) under the microscope for 1 minute.
This was done using 5 different concentrations of caffeine (0.0% 0.2%, 0.3%, 0.5% and 0.5%).
When changing or applying higher or new caffeine concentration, water was applied to the
daphnia from the pond water in the beaker to wash off any remaining caffeine solutions and
prevent recording wrong results. Repeats were then carried out with two other Daphnia. So,
5 different caffeine concentrations were applied to three different daphnia.
Ethical considerations
Daphnia are not likely to suffer physical and mental stress. Due to lack of consent from the
daphnia, the amount of suffering on the daphnia could be minimized considering animal
welfare. So, the daphnia were returned to their natural habitat after use. The daphnia was
not put in distilled water, but they were stored in conditions that match their natural
habitat/environment which in this case was pond water. Excessive concentration of caffeine
was not used as it could cause stress or even kill them.
Results & discussion
The results recorded are as follows:
Caffeine Mean heart rate
concentration (bpm)
percentage (%)
0.00 314.3
0.02 323
0.03 340.6
0.05 346
0.06 363
I have identified 340 as an anomaly because unlike the other results/daphnia instead of
going up as the caffeine concentration increases it went down by 1. Because of the time
restrictions, the experiment could not be repeated to fix the anomaly.
Effects of caffeine on the heart rate of daphnia
Samuel Gebray
Abstract
This paper contains the report of the experiment done on the effects of caffeine on the heart rate of
daphnia. This experiment was done as a project at Pendelton college. From the literature search
done a hypothesis was made that caffeine does affect the heart rate of daphnia. And so, the
experiment was carried out using a method where three different daphnia were exposed to five
different concentrations of caffeine. Their heartbeat was recorded for a minute and the results
showed that as the concentration of caffeine increases the heart rate of daphnia increases as a
result. Below the results obtained from the experiment can be seen. The results showed that
caffeine does increase daphnia’s heart rate but not by large numbers.
Introduction
Caffeine is known to increase the heart rate and concentration levels in humans, but it is not known
how effective it is on animals or different kinds of organisms. So, to have a fair understanding of
their effects on other organisms, daphnia were the perfect subjects to carry out this kind of
experiment as the effects can be seen immediately because have a transparent body. This is also
efficient at saving time and effort of performing an operation on other animals.
It was ensured that the health and safety concerns were adhered to while carrying out the
experiment, and the risk assessment that was done was followed to the maximum possibility.
Hypothesis: The concentration of caffeine will affect the heart rate of daphnia accordingly which
means if the caffeine concentration increases the heart rate of daphnia will increase same goes for
the opposite. This is because daphnia is a stimulant and it’s known to raise the heart rate of some
species.
Equipment
Microscope
Counter (software that can be installed on the phone)
Dropping pipettes
Tissue
Stopwatch
5 different caffeine concentration solutions
Cavity Slide
Beaker containing Daphnia in pond water
, Participants: myself, teacher, classmate, lab technician.
Method
A Daphnia was taken from the beaker with a pipette and placed in a cavity slide under a
microscope. Using a tissue, dab around the Daphnia to remove the pond water and replace
it with drops of caffeine solution. The daphnia was left for 3 minutes to acclimatise and then
the heart rate was observed & counted (using a counter) under the microscope for 1 minute.
This was done using 5 different concentrations of caffeine (0.0% 0.2%, 0.3%, 0.5% and 0.5%).
When changing or applying higher or new caffeine concentration, water was applied to the
daphnia from the pond water in the beaker to wash off any remaining caffeine solutions and
prevent recording wrong results. Repeats were then carried out with two other Daphnia. So,
5 different caffeine concentrations were applied to three different daphnia.
Ethical considerations
Daphnia are not likely to suffer physical and mental stress. Due to lack of consent from the
daphnia, the amount of suffering on the daphnia could be minimized considering animal
welfare. So, the daphnia were returned to their natural habitat after use. The daphnia was
not put in distilled water, but they were stored in conditions that match their natural
habitat/environment which in this case was pond water. Excessive concentration of caffeine
was not used as it could cause stress or even kill them.
Results & discussion
The results recorded are as follows:
Caffeine Mean heart rate
concentration (bpm)
percentage (%)
0.00 314.3
0.02 323
0.03 340.6
0.05 346
0.06 363
I have identified 340 as an anomaly because unlike the other results/daphnia instead of
going up as the caffeine concentration increases it went down by 1. Because of the time
restrictions, the experiment could not be repeated to fix the anomaly.
