AS Biology daphina experiment

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AS Biology daphina experiment
2016-01-16 19:21:29
AS Biology experiments
AS Biology
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  1. What is the independent variable?
    Caffine concentration
  2. What is the dependent variable?
    The heart rate of the Daphina
  3. What variable need to be controlled? ( 5 marks)
    • Temperature
    • Volume of solutions
    • Stress of Daphnia
    • Size of Daphnia
    • Time of¬†acclimatisation
  4. Describe an the Daphina experiment? ( 8 marks)
    • Prepare different ranges of concentration of caffeine solution of equal volume
    • Using a pipette, remove one Daphina from pond water and place it on a cavity slide with cotton wool on it to stop it moving off the slide.
    • Leave the Daphina on the slide for 5 minutes to allow it to acclimatise.
    • Using another pippette extract a a certain amount of your solution into it and then place a small drop of the caffeine solution on the Daphina¬†
    • Then place the cavity slide under the light microscope and focus it on the beating heart of the Daphina
    • Start the stopwatch and then count the number of heartbeats for 30 seconds by drawing dots on a piece of paper when a heartbeat is seen or video recording the event then multiply this value by two to find the heart beat per minute.
    • Repeat the experiment again with the same concentration 2 more time using a different Daphina each time.
    • Then repeat the experiment using different concentrations of caffeine solution repeating the experiment at each concentration 3 times.
  5. What factors can affect the result of the Daphina investigation?( 3 marks)
    • Ensuring Daphnia were same size
    • Ensuring enough data is collected
    • Counting of heart beat can be inaccurate due to human error
    • If left too long under microscope, tempincreases (due to lamp) = increased heart rate
  6. What ethical factors are there in the Daphina investigation? (2 marks)
    • Too high concentration of caffeine kills
    • Daphnia
    • Daphina cant give consent to partake in the test and may feel pain
  7. Why is a Daphina used ( 4marks)
    • They are invertebrates
    • So are simpler organism
    • they have a less sophisticated nervous system so may feel less or no pain.
    • Invertebrates are more distantly related to human than other vertebrates