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How caffeine affects daphnia heartrate

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Aim: How caffeine affects the heart rate of Daphnia (water fleas) During this experiment we were examining the effects of different concentrations of caffeine on a type of water fleas called daphnia; the heart-rate is the dependant variable and the concentration of the caffeine is the independent variable. We tried to keep all of the other variables constant by controlling them. Such as the room temperature; the volume of caffeine; the type of water fleas ect. Our hypothesis is that as the caffeine increases so will the heat rate of the daphnia. This is because caffeine is a stimulant that increases the amount of neurotransmitters being released and therefore the production of the heart. Equipment: * A culture of Daphnia in a beaker of water * A microscope- with two cavity slides * Two dropping pipettes- one with a large mouth and one with a small opening * Cooled Distilled water * Cotton wool * Paper towels * A stop clock Method: 1. We picked out a couple of daphnia from the culture in the beaker with the pipette that has a big mouth. ...read more.


185.67/ 186bpm Our results table for distilled water: No. Of times distilled water was added. No. Heartbeats every minute Average No. Of heart beats per minute (bpm) 1 2 3 4 5 1 169 150 172 174 170 167bpm Graph of results: 186-167 In conclusion: From my results we can tell that the relationship between the caffeine and the heart rate is that as the caffeine increases so does the heart rate. This means, caffeine ?heart-rate. This is as I predicted that this would happen because caffeine is a stimulant drug. This is true as on average the caffeine had 19 more beats per minute than no caffeine. As I mentioned before, this is because the caffeine increase the production of neurotransmitters. Neurotransmitters are the chemicals which allow the transmission of signals from one neuron to another across synapses. They are also found at the endings of motor neurons, where they stimulate the muscle fibres. This means that if the caffeine increases the amount of neurotransmitters that will then consequently increase the stimulation of the muscle fibres and that increases the activity of the heart; causing the heart to beat faster than normal. ...read more.


and therefore its average is not as reliable as we would have liked. To make sure our results we valid we tried to control all the other variables other than the concentration of the caffeine (all which I stated in the introduction). This includes the temperature of the daphnia. It must be understood that the daphnia are living organisms and need to be treated right in the experiment. So, to look after and keep them cool we put the cool water underneath the slide they were on. Another thing we done was when we were not using them we took them out from under the hot light of the microscope so that they would not burn. If I were to do this experiment again I would make sure that I had enough time to repeat both experiments more times to make it more reliable. Also, I would use some kind of data logger to measure the heartbeat of the daphnia; this would eliminate the chance of human error. To make it even more valid I would try to use the same daphnia each time and use a thermometer to see the temperature so it would be easier for be to regulate it. ?? ?? ?? ?? 1 Awo Mahad 12ND How caffeine affect the heart-rate of Daphnia ...read more.

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Here's what a teacher thought of this essay

3 star(s)

This is a well written report.
1. The start of the report is quite brief and is missing several sections, such as a safety section.
2. The tables of data are well presented.
3. The conclusion should use data from the tables to back up the patterns and should also refer to the graph.
4. The evaluation should suggest further research opportunities.

Marked by teacher Luke Smithen 23/07/2013

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