Investigation into the factors which affect the heart rate in daphnia.

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Mandeep Kamboo

Investigation into the factors which

 affect the heart rate in daphnia

Introduction

I am going to investigate how various chemicals such as alcohol, aspirin and caffeine have an effect on the rate of heartbeat in daphnia. Daphnia are aquatic crustaceans, who live in the water. They have a simple heart which is visible under the microscope.  

Prediction

I predict that caffeine will increase the number of heartbeats per minute because caffeine increases the blood pressure in humans, which stimulates the central nervous system and stimulates the action of the heart and lungs. Therefore, I would expect caffeine to also stimulate the heart and nervous system in daphnia. Caffeine 0.75% will have the highest amount of heartbeats per minute. Aspirin slows down the number of heartbeats, per minute therefore for aspirin 0.1% the heartbeats will be slower compared to caffeine 0.75% as caffeine has greater effect on heartbeat then aspirin. The higher the concentration of caffeine, the higher amount of heartbeats per minute.

Apparatus

  • Cavity slide
  • Microscope
  • Daphnia
  • Stopwatch
  • Counter
  • Beaker
  • Pipette
  • Caffeine (0.01%, 0.1%, 0.05%, 0.75%)
  • Aspirin (0.05%, 0.75%, 0.1%.)

Plan

A daphnia will be placed on the cavity slide using a pipette, which is filled with a small amount of water. The cavity slide will then be placed under a microscope, and to count the number of heartbeats a countertimer will be used. The number of heart beats for one minute will be counted, however this will be done by counting the number of heartbeats in 15 seconds and then multiplying the number of heartbeats by four.

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Each experiment will be repeated ten times every ½ minute (30 seconds), this is because the more times each experiment is done the better and more reliable the results will be, as the results in each experiment will be averaged. If each experiment is repeated ten times, it also shows how the heartrate varies with time. I will use the same daphnia when doing the experiment as daphnia’s heartrate varies between individuals, this will also make it a fair test. If the daphnia dies, the experiment will have to be redone, as it would not be a fair test ...

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