Effect of Stimulant on Pulse Rate of Lumbriculus Variegates

1. By Julia Lawrence and Kirsten Liddle Conclusion Our hypothesis that stimulant would increase the pulse rate of the Blackworms was not proved by our data. In the data we collected, the average pulse rate was four pulses higher in the plain water worms than in the stimulant worms. Our data may be inaccurate, however, due to the fact that we tested the worms over a two day period and thereby increased the number of variables. Some of the worms were kept in a refrigerator over the weekend and then were tested. This change in temperature may have impacted the worms. Another source of error may have occurred during the actual counting process because we varied the location where we counted the pulses on the worms due to movement. If we repeated this experiment, we would test all the worms on the same day and try to be more consistent with where we count the pulses. • Methodology Cont. • Return the worm to a separate container so that they are not tested again. Repeat this process with all five worms. Then repeat the entire process using five worms from the stimulant container. • Materials • Ten Blackworms, microscope, well-slide, stimulant, stop watch, pipette, four holding cups, slip cover, distilled water. Introduction For this experiment, we tested a stimulant on Lumbriculus Variegates to observe the effect on its pulse rate. Lumbriculus Variegates, also known as the California Blackworm, was chosen because of its transparent cell wall which makes it easy to observe its pulse rate. A stimulant typically increases heart rate, therefore, we hypothesized that if a stimulant was given to a blackworm then its average pulse rate would increase. Ind. Variable: Stimulant Dep. Variable: Number of Pulses/Min Control Group: Worms in Plain Water Constants: Water temp., food fed, where pulse rate is counted, time spent under microscope. Effect of Stimulant on Pulse Rate of Lumbriculus Variegates Methodology Procedure: Select five worms from the plain water container and using the pipette, place one worm on the well-slide. Cover the worm with a coverslip and then place the slide on the microscope stage. After focusing the microscope, find the worm’s pulse rate and have your partner begin the timing. Time the pulse rate for thirty seconds and then double it to get the number of pulses per minute. Results The averagepulse rate of the stimulant worm was 20 while the average pulse rate of the plain water worm was 24. There were outliers in both groups, which may have effected the overall results of this experiment. References http://www.eeob.iastate.edu/faculty/DrewesC/htdocs