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What Is The Effect Of Caffeine Of The Heart Rate Of Daphnia?

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What Is The Effect Of Caffeine Of The Heart Rate Of Daphnia Ross Kalarus Candidate Number: 3052 Daphnia is a small freshwater crustacean; these creatures are known as water fleas they have no physiological way of regulating their body temperature, this means once the temperature of the environment they are in changes their body temperature changes. The carapace of daphnia is translucent which makes them excellent subjects for this experiment as with a microscope you can see the heart. Anatomy of a Daphnia 1. In humans caffeine acts as a stimulant as it increases the amount of stimulatory neurotransmitters which are released. Some neurotransmitters released are norepinephrine and adrenaline which are the neurotransmitters that are involved in ?Fight or Flight? response which is directly involved with increasing heart rate. Caffeine is found in many sources in modern society such as coffee, tea, sports drinks and some chocolates. High levels of caffeine intake have been linked to restlessness, insomnia and anxiety, this can cause to raised stress and blood pressure. This can lead to heart and circulatory problems. A picture of the structure of caffeine can be seen below. The chemical formula of caffeine is (C8H10N4O2). 2. Hypothesis: Caffeine increases the amount of neurotransmitters released which increase heart rate, so as the caffeine solution increases so will the rate of heart beats per minute in the daphnia. ...read more.


Method: 1st step of the experiment is to select the daphnia you want to use in the experiment from the beaker of distilled water they are kept in; selection of daphnia must be that of a relative similar size so the effects of different solutions can be compared accurately. Using the pipette select 3-5 daphnia of the same size and place them in a Petri dish so they are easily accessed later. 2nd step of the experiment is measure out is to measure out volumes of liquids being used, the volume of 1 , volume of 3 and 5 .The volume of distilled water is already measured. 3rd step of the experiment is to rub some wax onto the dip of the cavity slides so when the daphnia is place in it, its movement is restricted, making it easier to observe heart rate. 4th step of the experiment is to place a daphnia that is in distilled water into the cavity in the slide, then place the slide under the microscope and proceed to record the number of beats of the heart for 30 seconds then, double the number for a the amount per minute. Repeat this step 2 more times. ...read more.


The results show that a correlation between heart rate and caffeine concentration, as when the daphnia where in the distilled water or 0 group the average result was 118 beats per minute and when you compare this to the 1 group the average result is 307 beats per minute. Evaluation: My method and therefore my results could be improved by using apparatus that will lead to more accurate results such as a burette instead of a measuring cylinder to make sure my volumes were absolutely accurate as human involvement which included measuring with my eye and not a continuous measuring scale could lead to large amounts of human error. Also as I had difficulty in recording the exact number of beats per minute as I kept finishing with outliers in each test group, I had to use the results provided to me by my teacher to create my table and graphs. Also some ethical issues could be raised with my experiment as I was provided with the daphnia and so do not know what the previous care conditions were for the creatures, also after questioning my teacher I was told that the daphnia will not be returned to their natural habitat after the experiments but will instead be terminated, although this will be as humanly possible. Sources for pictures: 1. http://lanwebs.lander.edu/faculty/rsfox/invertebrates/daphnia.html 2. http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---C/Caffeine-Chemical-Structure.htm ...read more.

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