Goldenrod Gall Flies: Writing a Lab Report in the Form of a Scientific Paper
In this biology lab, students investigate whether goldenrod gall fly larvae collected from restored prairie area are different from larvae collected from a small native prairie 10 km away. They look for biochemical differences in proteins using cellulose acetate electrophoresis. Students determine the genotype of each gall fly; students compare the combined class' genotypes for the two groups of gall flies statistically using chi-square analysis. Students read a related scientific paper and discuss it in a subsequent lab session. Students write a full lab report describing their results using standard scientific paper formatting. A detailed description of this format and the writing process is provided.
- Students learn to use the technique of cellulose acetate electrophoresis to separate proteins.
- Students work with real data and analyze the data using statistics. They gain an understanding of how p-values are used in scientific writing.
- Students understand the concepts of gene flow and genetic drift.
- Students learn to read scientific papers and write in this format; this helps them understand how science is communicated.
Context for Use
This laboratory activity is used in labs for an introductory college biology course at a small, liberal arts college. The lab allows students to address a legitimate scientific question by collecting local organisms in the field, looking at biochemical differences, analyzing numerical data with statistics, and synthesizing their results within the context of previously published papers. Lab size is limited by equipment; in our labs, 24 students, working in groups of 3, successfully share 4 gel-loading systems. Data collection can be accomplished in a 3 hour lab period, not including time for collecting material in the field.
The technique of cellulose acetate electrophoresis is extremely flexible, and can be used on any local organism. For more information on this technique, see the Association for Biology Laboratory Education Lab: "Measuring Genetic Variability in Natural Populations by Allozyme Electrophoresis" by James M. Bader.
The associated guide for writing lab reports is a general resource which could be useful in many contexts.
Description and Teaching Materials
Flow of the Lab Project:
- Students collect goldenrod galls one week in lab, which takes approximately 45 minutes (including a 15-minute walk each way to the collection site). They read the file Goldenrod Gall Collection (Microsoft Word 21kB Mar15 06) before the lab.
- The students perform cellulose acetate gel electrophoresis the subsequent week in lab, which takes approximately 2-3 hours. Students read the Lab Manual Chapter (Acrobat (PDF) 6.1MB Mar15 06) before the lab.
- As part of the process of learning to read and write scientific papers, students complete a Library Assignment (Microsoft Word 26kB Mar15 06) requiring them to find a scientific paper and do some cursory analysis of its structure. This assignment is discussed in lab the week following the data collection, so students can see how similar the format is across their lab section. A key for this assignment is available on request from the author.
- The file Sample Results (Excel 38kB Mar15 06) contains example data collected during one term.
- The Data Analysis Worksheet (Acrobat (PDF) 92kB Mar15 06) is given to students along with the compiled data from their lab; students use this to calculate a chi-square statistic.
- Students all read the same scientific paper and discuss it during a lab session. These Discussion Questions (Microsoft Word 40kB Mar15 06) are handed out in lab to guide discussion. A key to these questions is available on request from the author.
- Once data are compiled, students write a draft of the Materials and Methods and Results sections of their lab report, which is turned in for a grade (due one week after data collection). After they receive feedback on these sections, students meet individually with an undergraduate teaching assistant to discuss a draft of their Introduction and Discussion sections (usually 1-2 weeks later). They are given time to revise these drafts, and turn in a full lab report (this is due approximately 5 weeks after data collection). Throughout this process, they use the Lab Report Guide (Acrobat (PDF) 348kB Mar15 06) to help them write a lab report in the format of a scientific paper.
Teaching Notes and Tips
We chose to study goldenrod gall fly larvae because the live organisms can be collected in the field in the fall and winter in Minnesota. The technique is extremely flexible and can be used to compare populations of many organisms. Part of the beauty of the technique is the ability to take students into the field for organism collection, do biochemical analysis of the organisms, and answer evolutionary questions about them.
Cellulose acetate electrophoresis is simple, but the equipment and gels are expensive. One source is Helena Laboratories in Beaumont, Texas; they also have an excellent reference book on cellulose acetate electrophoresis.
One challenge is to convince students to make use of the Lab Report Guide as a resource. The Guide's format is designed to be student-friendly, with short summaries of what belongs in each section followed by lengthier FAQ-style information. Students often realize the benefits of using the Lab Report Guide after they receive grades on their drafts of Materials and Methods and Results sections.
References and Resources
- ABLE lab on Allozyme Electrophoresis
- Genetic Variability and Gene Flow in Metepira Ventura (Araneae, Araneidae). Ramirez and Fandino, Journal of Arachnology 24:1-8, 1996.