Daphnia Investigation

Authors Avatar

Frank Longford        Page         

Investigation: Does Caffeine Affect Heart Rate?

Aim

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

Background Information

Caffeine is a stimulant that targets the central nervous system and metabolic processes of organisms. Some plants produce caffeine naturally as an insecticide.

Caffeine is used worldwide, both as a recreational and medical drug.

Commercially, caffeine is used as a flavour enhancer and mild stimulant in a wide range of soft drinks, including Coke, Red Bull and Pro-plus.

Daphnia are members of the invertabrate family. They are small crustaceans, between 0.2 and 5 mm in length and are commonly known as “water fleas”. In many species, the Daphnia’a body is transluscant and can be observed clearly under a mircoscope.

The heart of a Daphnia is located at the top of the back, just behind the head. Their average heart rate is approximately 180bpm under normal conditions.

Ethical Issues

There are many arguments against the use of animals in scientific experiments. The most controversial issues tend to be related to the unatural conditions in which they are kept and the somewhat risky tests that they are exposed to.

Water fleas, such as Daphnia are classed as “unconcious” invertebrates and are therefore unlikey to experience emotions such as fear or anxiety that mammals do. Their transparent bodies also allow a heart beat to be recorded under a micorscope without the use of any invasive techniques, minimising the stress that could be placed on the invertebrate

When using animals in experiments, it is important to survey what is needed to be done to ensure that they remain in a almost stress-free environment. For this experiment, it is particulally important to succed this, as stress causes an increase in heart rate and could therefore produce inaccurate results.

Join now!

Preparing Concentrations

For this experiment, a large volume of 0.5mol caffeine solution shall be provided. This shall be refered to as a “100%” concentration. Different concentrations of caffeine can be made by diluting the solution with distilled water using the following methods:

Pure distilled water can be referred to as a “0%” caffeine solution.

Variables

Method

  1. Set up apparatus. (see “Setting up a Microscope”)
  2. Select and extract a Daphnia organism using a dropping pipette. For each experiment, take care to ensure that no Daphnia organisms are used ...

This is a preview of the whole essay