Daphnia experiment

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The effect of caffeine on the
heart rate of daphnia
Hypothesis
The daphnias' heart rate will be higher in the caffeine solution
Variables
The independent variable is the caffeine solution you put the daphnia in and
the dependent variable is the heart rate of the daphnia. There are other
variables that can also affect the heart rate, such as the heat of the lamp in
the microscope. Therefore, you must make sure you turn the lamp off as soon
as you finish using it. Also the daphnia might try to escape from the cotton
wool, which would increase the heart rate. However, you can't control this.
There will be a control, which is pond water without any caffeine. A control is
necessary because this will provide a baseline measurement to compare the
other measurements to. You will be able to see if the heart rate has increased
or decreased compared to the baseline measurement.
Ethics
There are some ethical issues to take into account with this experiment
because we are using live creatures. If the temperature is too high or if there
is too high a concentration of caffeine, the daphnia will die. Therefore, we need
to make sure to control the concentration and temperature as much as we can.
Because they are invertebrates, daphnia can be used in research, but aren't
protected under British law. Because they are so small, daphnia can be killed
or injured unintentionally. Some might argue, that because daphnia have
simple nervous systems, they can't feel pain like we can, so it is acceptable for
them to be experimented on.
Risk Assessment
Hazard Risk Precaution
Standard Can be dropped and Be careful when carrying
Glassware seriously injure someone if the glassware. Seek
they touch the broken immediate medical
glassware attention if someone gets
injured
Electrical Someone could touch Dry hands carefully after
equipment electrical equipment with washing them. Seek
immediate medical

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Daphnia They might die during the Make sure the daphnia
experiment for several have enough water, don't
reasons: they might dry up, have too high a
too much caffeine, the heat concentration of caffeine,
is too high turn the lamp off between
tests
Procedure
1. Transfer the daphnia to a cavity slide with a few drops of distilled water.
2. Add some cotton wool to the cavity slide to make sure the daphnia can't
move.
3.…read more

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Analysis
The daphnia I tested in distilled water had a higher heart rate than those in the
caffeine solution. There is a 7.1% increase from the mean heart rate in the
caffeine solution to the mean in the distilled water.…read more

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