Introduction:

1. Hypothesis: If the worm is from the dish of water that contains depressant, then its pulsation rate, in pulses per minute, will be lower than the pulsation rate of the worm from the dish of pure water. Variables: Independent-depressant added to pure water Dependent-worm pulsation rate (pulse/minute) Constants- water temperature, amount of water, pulse counter, nutrients fed, and type of worm Control Group- pure water worms The Effect of a Depressant on LumbriculusvariegatusBy: Samantha Gramlich and Alison O’HearnAlbion High School Conclusion: Our data results are inconclusive. Contrary to our hypothesis, the average pulse rate of the worms from the dish of depressant water, 36.6 pulses per minute, was faster than the average pulse rate of the worms from the dish of pure water, 21.4 pulses per minute. The results of our experiment may have been affected by the trauma the worms experienced while being transferred from dish to dish. Perhaps waiting for the worms’ pulse rates to regulate before measurement would have improved out results. In addition, our tests spanned over a period of two days, which may have increased error. It is also possible that the refrigerator used to store the worms was kept too cold overnight, thus having an extreme effect on the pulse rate. Ideally, all worms should be tested on the same day, eliminating temperature issues. Materials: California blackworms, pipette, calculator, pure water, microscope, stopwatch, 4 uncontaminated dishes, cover slip, viewing slide (with well), permanent marker.. Procedure: Place five worms in a dish of pure water and five worms in a dish of water with depressant. Using a pipette, place a worm from the dish of pure water on a slide with a well, with a minimum amount of water. On 100x, focus on a single vessel, and count the worm’s pulsation for one minute. Remove worm from slide, using pipette, and place in a separate dish for worms after use. Always keep pure water and depressant water worms separate. Repeat with four worms from pure water, and repeat with all five worms from depressant water. Record and analyze data. Introduction: The Lumbriculusvariegatus is the scientific name for a California blackworm. It lives in shallow water which makes it easy to find in ponds. In this lab we are observing the effect of a depressant on the pulse rate of theLumbriculusvariegatus. We think that a depressant will slow down the pulse rate. The California blackworm is ideal for this experiment because it is easy to observe the pulse rate in the dorsal blood vessel due to its transparency and its closed circulatory system. • Results: • The average pulse rate of the worm from the depressant water dish was 36.6 while the average pulse rate of the worm from the pure water dish was 21.4. The outliers in both groups effected the mean pulse rate. Reference: www.eeob.iastate.edu/faculty/Drewesc.htdoc