The Effect of Caffeine in Daphnia

Essay by davidraaamosHigh School, 11th gradeD-, November 2014

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David Ramos Rivero Biology AS



The purpose of this experiment is to investigate the effect of caffeine on the heart rate of Daphnia (water fleas). Heart rate is defined as the number of beats per minute. Caffeine (C8H10N4O2) is a stimulant drug that is daily used by millions of people around the world to improve mental alertness and replacing sleep. A Daphnia is a crustacean commonly found in ponds and lakes. These crustaceans have experimented a change of habitat, which has made their anxiety levels rise up, so many Daphnias' will have a greater heart rate due to anxiety and/or many will die.

Structure of Caffeine


My prediction is that the caffeine will increase the Daphnias' heart rate, as caffeine is a stimulant so the amount of neurotransmitters to be released increases so it probably will increase also the heart rate.

Fair Testing

Independent variable: Concentration of caffeine

Control Variables:

Keeping the water and room temperature the same.

Make sure you get Daphnia's of the same age by getting all the Daphnias' with more or less the same size.

Keeping the same species of Daphnia the same.

Dropping the same amount of volume of solution dropped on the Daphnia.

The pH of water by using the same source of water.

Keeping the same amount of time for each Daphnia when they are given the caffeine.

Dependent Variable: The Heart Rate of the Daphnia

Reliability, accuracy and precise

I will observe the heart as the water flea is translucent and the heart can be seen perfectly with a microscope so I can work out the heart rate. At least five trials will be performed for each of the four concentrations and...