Daphnia Ethanol Experiment

Introduction

Numerous experiments have been conducted to analyze the influence of ethanol on different sections of the human brain and how different concentration levels affect behavior. For example, it has been observed that excessive amounts of ethanol affect the cerebellum. As we know, the cerebellum controls balance and coordination, but when exposed to excessive amounts of ethanol, an individual is more prone to lose balance. Furthermore, the hippocampus, a part of the brain associated with memory, is also impaired by the consumption of ethanol. As the consumption of ethanol increases, long memory retainment decreases. While human beings consume this substance for pleasure despite side effects, there are other species that need

ethanol to successfully reproduce. Drosophila Melanogaster or better known as the fruit fly is known to require specific levels of ethanol in their natural environment to successfully reproduce. Considering that this species has a short lifespan, it is important for this type of fly to have the right environment in order to have the highest reproduction rates. In order to reproduce, the adult fly lays her eggs on fermenting or decaying fruit. After the egg has hatched, larvae feeds from the nesting site to then transform into full adults.

The purpose of this experiment is to determine the ideal concentration of ethanol necessary for the fruit fly to successfully reproduce to become an adult fly, and to analyze how exaggerated amounts of ethanol negatively affect the the life cycle

of the fruit fly.

Methods

Materials & Procedure

For the first experiment, the pulse of Daphnia was presented in a video format.

The videos varied from the concentrations of 0%, 5% and 10% ethanol to calculate the difference in Daphnia’s pulse. Each person then recorded Daphnia’s pulse for ten seconds under 0% ethanol, 5% ethanol, and 10% ethanol.

For the second experiment, the reproduction of fruit fly was manipulated by placing different levels of ethanol into the test tubes in which adult males and females were inserted. First, 2 adult males and 3 adult females were placed inside test tubes for two weeks. These test tubes contained different levels of ethanol in order to determine how many adult flies would hatch depending on the concentration of ethanol in the environment. There were a total of ten groups containing different amounts of ethanol. The five groups of two contained 0%, 1%, 2%, 4%, or 8% ethanol. After the two weeks, hatched adult flies were anesthetized with Fly Nap in order to remove them from the test tube to calculate how many were produced in the different levels of ethanol. They were then counted to determine which level of ethanol concentration best allowed the fruit fly to hatch. After the counting of the flies the adult flies were disposed of into a jar of

oil.

Results

First Experiment: After recording the pulse for Daphnia for ten seconds, we were able to observe a higher pulse rate when Daphnia was exposed to 0% ethanol and a decrease in pulse when it was exposed to 10% ethanol (See Table 1). The average pulse for 0% was 41.645. The average pulse for 5% was 21.322. Lastly, the average pulse for 10% was 0. After running the analysis of variance (ANOVA), it can be stated that there is a statistical significance in the pulse rate of Daphnia when ethanol increases.

Second Experiment: The test that were ran were a between groups and within groups ANOVA. The results indicated that there was a statistically significant difference found in the reproduction of the fruit fly with the within groups as it determined that at a 2% level of ethanol the most larvae successfully hatched into complete adults. The within test conducted in our class also determined that there were low birth rates when there was a lack of ethanol as well as when there was an excess of ethanol.

Dr. Eisen also found that there was a statistically significant difference in the number of adult flies hatching when the between test was ran (See Table 2 and 3). Then, a Tukey multiple comparisons of means test determined that at 2% ethanol, there was a statistically significant difference on how many more larvae hatched in comparison to the other four groups. Through this test, it was also found that there was a statistically significant difference between 1% and 8% ethanol, p < 0.0076; 2% and 8% ethanol, p < 0.0001, 2% and 4% ethanol, p < 0.0227, and 0% and 2% ethanol, p < 0.0014. Therefore, it was determined that although Drosophila requires ethanol for reproduction, having excessive amounts decrease birth rates in the same way that not having enough.

Discussion
The results of first the experiment indicated that the more the more ethanol that Daphnia was exposed to the less likely it would survive. This was demonstrated when the pulse rate was recorded in the different concentrations of 0%, 5%, and 10%. The second experiment indicated that reproduction of Drosophila or the fruit fly varies significantly depending on the environment in which eggs are laid. Although some ethanol must be present, the lack of or excess of can lead to lower rates of successful hatching. The experiment enabled direct observation of different birth rates in varying concentrations of ethanol. The overall results of this experiment suggest that Drosophila best reproduces at a 2% concentration of ethanol whereas reproduction significantly decreases when 0% or 8% of ethanol is present in the environment.