• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Daphnia experiment - Does caffeine affect heart rate?

Extracts from this document...

Introduction

DOES CAFFEINE AFFECT HEART RATE? PLAN The aim of the following experiment is to determine whether the amount of caffeine concentration affects heart rate in Daphnia. Hypothesis When caffeine is added to water containing Daphnia, its heart will be observed to be beating faster. SCIENTIFIC BACKGROUND Daphnia Daphnia, popularly known as water fleas, are small crustaceans that live in fresh water such as ponds, lakes, and streams. They serve as an important source of food for fish and other aquatic organisms. Daphnia are excellent organisms to use in bioassays because they are sensitive to changes in water chemistry and are simple and inexpensive to rise in an aquarium. Daphnia hearts a fairly easily seen but counting the number of beats can be difficult. Counting is easier if each heart beat is recorded by tapping a pencil on a piece of paper and counting up the pencil marks after the specified time. In addition, cooling the daphnia before the experiment may help slow their heart rate: heart rate is highly temperature dependant. An I Cam above the eye-piece of the microscope to project an image of the slide onto a large screen may also help with counting. ...read more.

Middle

A cover slip helps stop the water evaporating. 2. Place a few strands of cotton wool on a cavity slide; this will help restrict the movement of the water flea. 3. Uusing a pipette, transfer one large water flea to a cavity slide. Remove the water from around the water flea using filter paper, then add one or two drops of distilled water. 4. Use as much water as you can and do not use a cover slip. 5. Together these precautions will help maintain sufficient oxygen supply to the flea. A cavity slide filled with iced water and placed under the slide will act as a heat sink. 6. View the water flea under low power. Focus on its heart which can be seen through it translucent body. 7. Use a stop watch to record the number of heart beats per minute. 8. Tap a pencil on a piece of paper and count up the pencil marks at the end of the time period. 9. Record the heart rate at intervals of two minutes over a 10 minute period. It is a good idea to do a 'blind' study to avoid bias in the results. ...read more.

Conclusion

This may not be the case when we get errors from places and so to get an even better result we should look at the results and take out some of the anomalous results. An example of an anomalous result is that I had got a lower heart beat rate when using a 0.00001% concentration of caffeine and if my prediction is to be right this cannot be. I then have to blame this on systematic errors. As I have mentioned before we may have to see different daphnia for different concentration this by itself will produce a very high % error as we can only assume that the heart beat for every daphnia will be the same but in reality it is not. This can also be put down to just clumsy result taking. As we had left this one till last it is clear that we could not really be bothered to be as accurate as we had been with the other ones. Another example is that the room may have been at different temperatures at different times and therefore this is an error as we know that the temperature will also make a difference to the heart beat. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Exchange, Transport & Reproduction section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Here's what a teacher thought of this essay

3 star(s)

This write up has some good background information but marks would be lost due to a lack of precise scientific language and the method described might well produce unreliable results.

Marked by teacher Adam Roberts 11/04/2013

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Exchange, Transport & Reproduction essays

  1. Marked by a teacher

    Affect Of Varying Salt Concentration on Red Blood Cell Haemolysis

    4 star(s)

    test tubes at room temperature and will also be stirred regularly Picture shows two test tubes, test tube1 shows no signs of haemolysis as this blood sample has introduced to an isotonic solution where the water potential in the saline solution sample is equal to that with in the erythrocytes.

  2. Marked by a teacher

    An Investigation into the Water Potential Of Root Vegetables.

    4 star(s)

    generally there was very little error arising from any measurements of solutions made. Cutting the vegetables would have been the major source of error in the procedure. The sizes of the vegetable pieces varied by 2mm either side of the 2cm length they were supposed to have.

  1. Marked by a teacher

    The effect of caffeine on heart rate

    3 star(s)

    After that, I moved one of the water flea to the cavity slide. This was done using a pipette. Also, water from the cavity slide was removed- this was done using filter paper. Few drops of distilled water or pond water were added.

  2. The Effect of Different Substrates on the Rate of Respiration on Yeast (Saccharomyces cerevisiae).

    Thus when it comes to the experiment, this area needs to be controlled and only one pathway be allowed in order to make it a reliable investigation. For practical reasons it would be easier for the yeast to respire anaerobically.

  1. beetroot experiment

    rates depending upon their ability to enter the hydrophobic interior of the membrane bilayer. Diffusion refers to process by which molecules intermingle as a result of kinetic energy of random motion. It is the movement of particles from higher concentration or chemical potential to lower chemical potential.

  2. Effect of Caffeine on the Heart Rate of Daphnia

    In humans, caffeine is a central nervous system (CNS) stimulant, which temporarily reduces drowsiness and restores alertness. The precise amount of caffeine necessary to produce effects varies from person to person depending on body size and degree of tolerance to caffeine.

  1. Investigate one factor that affects the rate of respiration of yeast

    I will place a thermometer in the beaker and keep a close eye on the temperature. If it falls, I will add more hot water to the water bath until it reaches 40oC, I will add cold water if it exceeds. pH: (a factor I am going to keep constant)

  2. Investigating Water Potential Of Potatoes.

    High osmotic pressure NET MOVEMENT OF WATER MOLECULES After looking at diagram 1 and the previous information given, you will appreciate that there will be net movement of water molecules from the left of the selectively permeable membrane to the right.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work