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INTRODUCTION
I. The foraging behavior of fruit flies is important to observe for a number of reasons. One of the reasons foraging behavior of the fruit fly (Drosophila melanogaster) is studied is to determine whether fruit flies are capable of learning, as well as the behavioral significance of a behavior, in terms of adaptation (Prokopy & Roitber 1984). Moreover, the foraging behavior of fruit flies reveals the behavior of so-called Rover flies versus Sitter flies. A rover fly expends more energy seeking food, whereas sitters expend less energy, but is more efficient, given low population densities (Fitzpatrick et al. 2007) -- a phenomenon called negative frequency-dependent selection. Thus, both strains of flies exhibit different behaviors, evolutionary foraging strategies that are encoded by a single gene, for -- with its alleles depicted as either forR or forS (Sokolowski 1980). Moreover, it has been experimentally-demonstrated that allelic variation plays a key role in actual attraction to a food source (Shaver 1998). In addition, by mutating genes, Sokolowski (2001) has shown that different genotypes cause the phenotypic expression of different foraging behaviors. Thus, foraging in fruit flies is significant to study for a number of reasons -- and there are limitless conditions and variations of foraging that can be also observed, such as the behavior of the for gene. Even behaviors caused by the addition of sound, lighting, temperature, and odors as well as the additive influence of other chemicals such as quinine, can yield important findings (Bell 1991). In addition, Periera & Sokolowki (1991) found that Rovers achieved copulation faster, and for a longer time period than Sitters. This evolutionary strategy suggests that Rovers, having taken the risk of finding food at longer distances, exhibit a more successful reproductive behavior. Finally, the study of fruit flies (as opposed to other insects) is convenient due to the fruit fly's simple genome, its easily-observable behavior, and its short lifespan.
II. A. In this lab, the foraging behavior of Drosophila melanogaster was studied. A hungry population of wingless female and male strains were observed exhibiting one of four behaviors in an environment called an arena. The four behaviors including feeding on banana-flavored sucrose, unflavored sucrose, both banana-flavored sucrose, and not feeding at all. Based on theory advanced by Aracena (2011), fruit flies prefer food sources that are in the process of rotting, i.e. they prefer the bacteria and fungi growing on the food source rather than the food source itself. Aracena's (2011) theory suggests that, in this experiment, fruit flies would prefer banana-flavored sucrose. While the banana itself is not rotting (the sucrose is merely flavored by the banana), it stands to reason that fruit flies may have certain chemoreceptors that respond to the odor of banana flavor, due to the fact that bananas rot, thereby providing an ample food source of fungi and bacteria for the foraging fruit fly.
B. In this experiment, sucrose was used because Aracena (1996) found that fruit flies prefer sucrose over fructose and glucose in "semi-natural conditions (Aracena 1996). In this experiment, the null hypothesis states that there will be no difference between observed and expected behaviors of the fruit flies. Thus, the fruit flies will behave in a statistically-proportionate manner, with each group consisting of 25% of the fruit fly population. However, based on Aracena's (2011) theories, it is hypothesized that the results of the experiment will show that the majority of the fruit fly population will mainly prefer the banana-flavored sucrose, while the solution that contained sucrose and banana-flavored sucrose will be second, and the solution that contained only sucrose will be favored last by the foraging fruit flies. The flies who do not eat, according to this hypothesis, will be last, as they are fruit flies that are hungry. A hungry fruit fly is more likely to feed from any of the available food sources.
RESULTS
The results of this experiment reflected the hypothesis. After 30 minutes, there was a far greater number of non-feeding fruit flies (n = 105) than the other two groups of feeding fruit flies. However, after 60 minutes, the numbers were vastly different. However, the non-feeders (n = 34) outnumbered the feeders who fed on both the banana-flavored sucrose and plain sucrose (n = 22).
Chi-Square Test (AFTER 30 minutes)
Chi-Square Test (AFTER 60 minutes)
Using p > .05, and df = 3, X² was determined to be 318.08 after 30 minutes, while X² was
calculated as 67.6, after 60 minutes. After reviewing the Chi-Square Table, both of these
numbers were found to be significantly greater than the odds of probability being the sole factor
for the resultant tables above.
DISCUSSION
I. The results of this experiment clearly confirmed that the null hypothesis can be rejected, or nullified. Thus, the alternative hypothesis holds up, showing that factors other than chance alone are responsible for the deviation between the observed and the expected behavior of the fruit flies. However, the numbers were extremely high, indicating that probability played an almost nil role in the observed differences in fruit fly behaviors. This was an unexpected aberration, and after multiple re-calculations, the chi-square test probabilities (p) were reproducible. Thus, it cannot be stated with full confidence that these numbers accurately reflect the low probability of chance being a factor, with such small deviations. Frankly, I was surprised that so many fruit flies fed from the sucrose-only cells, after 30 minutes (n = 45). However, it is reasonable to presume that, after 60 minutes (when the fruit flies became hungrier), that number tapered off, and the number of fruit flies feeding from the banana-flavored sucrose cells increased from n = 49 to n = 65.
II. Despite the apparent ease of this experiment, the protocol was in dire need of one very significant improvement. After 30 minutes and 60 minutes in the arena, it was unclear which food (sucrose-only or banana-flavored sucrose) was supposed to be red or blue. That is, although it was later deduced that the fruit flies with red abdomens fed from sucrose-only cells, and the fruit flies with blue abdomens fed from banana-flavored sucrose cells, there was much initial confusion as to which color properly labeled which fruit fly food cell. This could have been an error with significant ramifications, an error that could account for the large numbers that completely defied the odds of a null hypothesis. One of many vital lessons learned from this experiment was the importance of proper lab protocol, which includes a maximum effort on the part of researchers to utilize Quality Assurance, or QA (Baker 2016). Moreover, according to Baker (2016), inadequate data logging can be solved by recording data in digital or bound logbooks, as opposed to loose leaf paper (Baker 2016). Thus, protocol could have stood some improvement, and such improvement could have bettered efforts at data collection, as well as the subsequent calculation of results. Ultimately, it is worth speculation that an error in QA led to the wrong conclusion.
Works Cited
Baker, Monya. "Quality Time." Nature 529 (2016): 456-458. Web.
Fisher, R.A. & Yates, F. Statistical Tables for Biological Agricultural and Medical Research, 6th Ed., Table IV, Oliver & Boyd, Ltd., Edinburgh.
Prokopy, Ronald J., and Bernard D. Roitberg. “Foraging Behavior of True Fruit Flies: Concepts of Foraging Can Be Used to Determine How Tephritids Search for Food, Mates, and Egg-laying Sites and to Help Control These Pests”. American Scientist 72.1 (1984): 41–49. Web.
Prokopy, Ronald J., and Bernard D. Roitberg. “Foraging Behavior of True Fruit Flies: Concepts of Foraging Can Be Used to Determine How Tephritids Search for Food, Mates, and Egg-laying Sites and to Help Control These Pests”. American Scientist 72.1 (1984): 41–49. Web
APA
Prokopy, Ronald J., and Bernard D. Roitberg. “Foraging Behavior of True Fruit Flies: Concepts of Foraging Can Be Used to Determine How Tephritids Search for Food, Mates, and Egg-laying Sites and to Help Control These Pests”. American Scientist 72.1 (1984): 41–49. Web
APA
Prokopy, Ronald J., and Bernard D. Roitberg. “Foraging Behavior of True Fruit Flies: Concepts of Foraging Can Be Used to Determine How Tephritids Search for Food, Mates, and Egg-laying Sites and to Help Control These Pests”. American Scientist 72.1 (1984): 41–49. Web
