Daphnia Lab

The following experiment determines the effects of 50 ml tobacco extract on the heart rate of a crustaceans Daphnia Magna. Daphnia represents a small group of aquatic crustaceans, also known as “water fleas”, with clear exoskeletons, which makes studying their heart rate effortlessly. The heart rate can be observed using a microscope and counted under varying conditions. (Pritchard, J. B.) In this case, changing the type and concentration of natural plant substances reveals the effects of the plant defense mechanisms on the specimen of Daphnia Magna. Tobacco (Nicotiana tabacum) was the plant chosen for the experiment. Since, nicotine in tobacco is a stimulant, it is predicted that if Daphnia exposed to this substance would have an increased

Upon completion of the experiments, Daphnia specimen exhibited extremely low heart rate while in its natural environment, which highlighted the negative effects of plant defense mechanisms on other

As a result, plants have adapted ways to protect themselves against their natural predators by implementing “defense mechanisms”. Such adaptations may be structural or chemical, where structural mechanisms are simply parts of plant structural arrangement, such as thorns. Chemical defense mechanisms are more complex, and involve production of retarding chemical compounds and toxins. These volatile compounds are often released when the plant is damaged, and have physical effects on the predator. (Steppuhn, A., Gase, K., Krock, B., Halitschke, R., & Baldwin, I. T.) This experiment examines the natural defense mechanism of a tobacco plant, and its effects. Approximately 5% of a tobacco plant constitutes a naturally occurring alkaloid, nicotine, which functions as a resistant factor against herbivore pests. (Bennett, R. N., & Wallsgrove, R. M.) Nicotine is toxic to most herbivores through its interaction with the nervous system. Nicotine acts as a blocking agent to certain neurotransmitters, which are responsible for regulation of physical processes. Generally, it considered to a stimulant, thus nicotine has an effect on heart rate regulation. More complex organisms, such as mammals, are able to the effects of nicotine and rid of it from the system fairly quickly, since the half-life of nicotine is about an hour. Yet, smaller species, are not able to combat the effects of