Biology Lab Essay

Introduction This week in Biology Lab we learned the effects of caffeine and nicotine on heart rate. Based on previous knowledge of caffeine and nicotine, I came up with the following hypothesis; The presence of nicotine will slow the heart rate of the worm and the presence of caffeine will speed the rate up. My hypothesis was based on what I seen in everyday life. A person who smokes a lot of cigarettes usually have a slower heart rate, whereas a person whom drinks a lot of caffeine sodas are hyper and have a faster heart beat. I think the effect of caffeine and nicotine will have the same effect on the species we are using in class, a freshwater blackworm. Materials & Methods To begin this lab we first had to build a viewing chamber to view our worms under the microscope. To make the viewing chamber we had to use about 12 wax like parafilm sheets on a slide. We made sure each of the sheets fit on the slide, and stacked them up to make sure that the worm could not get out. We used a heating plate to melt the parafilm sheets but we had to be careful not to let the slide get to hot because it would burn. Using a razor we had to cut out a trough. This is where the worm would sit in so we could view it under the microscope. Our teacher has prepared us with 3 different molarities of caffeine and 3 different molarities of nicotine. Using a dropper we had to put about 3 drops of caffeine or nicotine on the worm. A new worm is used for each different trial/molarity. At the end of each trial we had to record what happened to the worm and what we saw under the microscope. The old worm was to be disposed in a bowl with everyone else’s used worm. Results & Data The first picture above shows how the worm looked under the microscope with just water. Notice that the vessels are spaced apart allowing the blood to flow with ease. With the presence of caffeine the blood vessels of the worm relaxed or separated more allowing blood to flow causing the heart to beat faster. The final picture shows what was saw under the microscope when the worm had nicotine in it. The vessels are more closer together making it harder for the blood to flow. Decreased blood flow equals decreased heart rate. On a few attempts the worms died because at first I did not know that the worms lived on water, or because I would put to much of a solution into the viewing chamber than the worm could take. The higher the concentration the more drastic the results. The pictures shown are only for the lowest molarity of caffeine and nicotine used in this lab. Conclusion My hypothesis for this lab was correct. The effect of nicotine made the worm heart rate lower and the effect of caffeine made the heart rate speed up. Caffeine and nicotine effect worms and humans in the same way.