Daphnia experimentation

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Abdullah Jafar Chowdhury                Biology (Unit 1)

27/10/2007                CHO07066533

The effect of Caffeine on the heart rate

Aim:

To investigate the effect of caffeine on the heart rate of Daphnia (water fleas).

Background Knowledge:

Daphnia are tiny water fleas with an average size of less than 3mm. Daphnia are translucent invertebrates (have no backbone) and their outer body is made up of a hard shell which protects the whole body except for the head. Daphnia’s are found in ponds, lakes, and calm streams where the temperature is between 21-24°C (68-71°F). Daphnia reproduce rapidly. Up to 13 billion related offspring can occur within 60 days for one Daphnia. In winter the eggs are thick-shelled and thin shelled in the summer. In warmer temperatures the eggs will hatch female, and in colder temperatures the eggs will be male.

Daphnia’s will be used to experiment the on as although they are tiny in size their heart beat can be examined through a microscope because of their transparency.

Caffeine is produced by plants as an insecticide. Cocoa in South America, coffee in Africa and tea in Asia has all been used for hundreds of years to produce “pick me up” drinks containing caffeine. These days, caffeine is used as a flavour enhancer in a wide range of cola and other soft drinks. In addition, it has medicinal uses in aspirin preparation, and is found in weight-loss drugs and as a stimulant in students’ exam-time favourites like Pro-plus and Red Bull.

In humans, caffeine acts as a stimulant drug, causing increased amounts of stimulatory neurotransmitters to be released. At high levels of consumption caffeine has been linked to restlessness, insomnia and anxiety, causing raised stress and blood pressure. This can lead to heart and circulation problems.

Hypothesis

I hypothesise that the heart rate of the water fleas will increase if the concentration of caffeine is increased. I also predict that the aforementioned increase in heart rate will result in the flea dying.

I believe that this will occur because the heart muscle will not be able to cope with the increase in beats. The resulting stress on the heart causes it to stop and the flea will die.

Apparatus

  • Culture of Daphnia: to conduct the experiment on.
  • Cavity Slides: to place the flea and a few drops of water in.
  • Dropping pipettes: 2 needed for dropping the solution and fleas
  • Distilled water: needed to note down the original heart rate of the Daphnia.
  • Caffeine tablets: needed to dissolve into water to make caffeine solution of varying concentrations.
  • Cotton wool: to restrict the movements of the water flea.
  • Measuring syringes: 2 needed to measure out solution.
  • Test tubes: 5 needed to place solution in.
  • Stopwatch: to ensure that inspection times are uniform.
  • Paper towels or filter paper: to remove excess solution from around the flea.
  • Microscope: to examine the flea accurately.
  • Test tube rack: to place tubes containing the different solutions in.

Risk Assessment

In this experiment there are many risk factors posed to the student. The use of microscopes with a lighted base and glassware sometimes can cause injury to the student if they are not careful while handling such fragile equipment.

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With the microscope, such heavy equipment must be carefully handled especially in a lab, where puddles may be found on the floor. Slips and trips can occur while holding heavy equipment. Also, microscopes that do not use a mirror but electrical lighting, need to be checked that the voltage of the light is at a comfortable level, and cannot blind someone. Low-level lighting will also help by not evaporating the solution on the cavity slides.

The glassware, such as beakers, test tubes, can easily shatter, so you have to be careful whilst handling such fragile equipment. Keep the ...

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