Thursday, September 23, 2010

The Feminization of Frogs Due to Atrazine

This blog post will be comparing a primary source and a secondary source, more specifically a newspaper article and a peer-reviewed study on the subject of the chemical atrazine feminizing male frogs. The primary source was a study approved on January 15, 2010 entitled, “Atrazine induces complete feminization and castration in male African clawed frogs (Xenopus laevis)”. It was released online in the Proceedings of the National Academy of Sciences, and was based on a study led by researchers at the University of California Berkeley. The secondary source that was based on this was a newspaper article that was published on March 1st, 2010 in the Globe and Mail and was titled, “Weed killer can turn male frogs into females, study finds”. These two sources can be compared in two areas: the presentation of the information and the presentation of the limitations.

The first thing that should be addressed is that the newspaper article was clearly not as detailed as the primary source. This is to be expected because newspapers are meant to be read by the general public and therefore must be worded and presented in such a way so that everyone can understand. This secondary source must therefore broaden some of the information in the original article. For example, when the primary source lists the effects of the atrazine on the frogs, it only lists three of the many listed in the primary source- “decreased testosterone levels, feminized larynxes, and decreased sperm production” (Mittelstaedt par. 19) while there are more listed in the primary source, such as the changes in behaviour in the frogs when they competed for mating purposes. Because the primary source's main audience is the world of academia, the words used in the presentation of the article are more scientifically-minded and complicated. This sometimes makes it more difficult for the secondary source to present the information without changing the original meaning of the article.

The primary source presents its information and garners strength for its claims by consistently referring to previous studies and the other side of the argument that claims that atrazine does not cause feminization in frogs. The article then proceeds to explain how their findings and their process of carrying out the experiment is better. This can be seen as a rather effective approach. For example, towards the beginning of the article, it says, “Although a few studies suggest that atrazine has no effect on amphibians under certain laboratory conditions ...” (Hayes 4612) and it then proceeds to provide two sources to show that studies proclaim this, and proceeds to explain why these other studies are wrong. The article also uses studies that prove their claims are correct and these are used as references, such as mentioning that studies with certain fish and leopard frogs found similar feminization as a result of atrazine. In heavily referencing many of their claims, one can look up their evidence, which makes for a stronger study. It was also noticed that the study makes it very clear that the exposure level used on the frogs is a level that the amphibians would experience year round. This struck me as a good thing because in increasing the external validity of the experiment, the conclusions they reach from their research appear stronger and more convincing to the reader. With this primary source, it seems that one is presented with a wealth of information and nothing is changed or worded differently, so one can be fairly sure that one is receiving the most reliable information.

The way that the secondary source is presented is fairly different. Firstly, it should be stated that the newspaper article was published two months after the primary source was originally released. This allowed time for the original research to be reviewed and for controversy over the findings to form and therefore be able to be presented in the newspaper article. The secondary source is also extremely short in comparison to the study. Unlike the primary source, the newspaper article is not as heavily referenced and, perhaps most obviously, is not as biased as the primary source. This means that the secondary source addresses both sides of the controversy involved in the research and does not attempt to rectify that the research done on the frogs is correct in all its claims. For example, the article says that Health Canada conducted a review of atrazine in 2007 that said the chemical “does not entail an unacceptable risk to the environment” (Mittelstaedt par. 13) but is looking into new research. Also, the secondary source has experts in the field talk about their opinions, for example, it has the spokesperson for the company that produces atrazine say, “We stand behind the safety of our product” (Mittelstaedt par. 9). However, the secondary source does not put forth the different opinions with as much evidence and background as the primary source does, and it uses vague terms such as “some researchers” (Mittelstaedt par. 16). But the article does contain seemingly reputable sources and refers to well-established institutions such as the U.S. Environmental Protection Agency. All this serves to show the reader that the research is complicated and controversial, while someone reading the primary source might be led to believe that it is not because of the bias involved in the original article.

Both the primary source and secondary source have different limitations and the sources also discuss their limitations differently. Firstly, the primary source does not discuss the limitations of the experiment in a major way. The study referred to a data problem that occurred once when only four of the five behavioural trials could be replicated because of a lighting problem (Hayes 4616). The primary source is more concerned not with presenting their limitations, but by presenting how their research went beyond the limitations of other studies. For example, it refers to a study that looked at the long-term reproductive effects of atrazine on amphibians, but says that the study did not look at morphology like theirs did. However, both the primary and secondary source mention how it is speculated that “atrazine causes frogs to increase the amount of a key enzyme known as aromatase, that converts testosterone to estrogen” (Mittelstaedt par. 16). Both sources mention this, and, interestingly, both sources present that in a way that rebukes the statement. The primary source follows the normal pattern of presenting an argument and disproving it, while the secondary source uses an expert opinion, an environmental biologist from the University of Guelph, to say that “that theory doesn't stand up to closer examination” (Mittelstaedt par. 17).

Finally, the last limitation, though not presented on purpose, comes towards the end of the secondary source. Though a primary source may sometimes be limited by its bias, the last paragraph of the secondary source illustrates the problems that occur when one uses a secondary source. The last paragraph is worded in such a way so that it provides the opposite impression that the primary source was trying to illicit. It gives the impression that the doses given to the frogs are above those normally found in groundwater (it says that the concentrations of atrazine found in groundwater were 1.2 parts per million, while the frogs were given doses of about 2.5 parts per million) (Mittelstaedt par. 20), while the primary source explained that the exposure levels of the frogs to the chemical was a normal year-round exposure level for the frog. This is a confusing concluding sentence because it puts the external validity, which is very important, in question. It is a consequence of the audience change. Because secondary sources must be made simpler, it increases their limitations. In conclusion, sometimes there are sacrifices that must be made when a secondary source is written.

An African clawed frog.

Works Cited

Hayes, Tyrone B. ““Atrazine induces complete feminization and castration in male African clawed frogs (Xenopus laevis).” Proceedings of the National Academy of Sciences (2010): p. 4612-4617. Web. 23 Sept. 2010.

Mittelstaedt, Martin. “Weed killer can turn male frogs into females, study finds.” The Globe and Mail (2010): n. pag. Web. 23 Sept. 2010.

Links to the articles:

- Alison Conrad, Student #0704294

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