Searching for Variation between Populations of Bean Beetles (Callosobruchus maculatus)

Project Background:

At Renton Technical College, we have been interested in redesigning our introductory biology labs for non-majors to better align with the core competencies recommended by Vision and Change, especially on familiarizing students with the process of science, data analysis, and scientific communication. We knew that we wanted our students to be able to design experiments, collect their own data, and make mistakes that could later be corrected. Since we are a small school without any laboratory assistance, we needed a study organism that could be easily maintained and that had been studied by others. We came across the website beanbeetles.org, which contains detailed information about raising these beetles, identifying males and females, and laboratory experiments that have been tested by other instructors. Because maintaining a beetle population requires only a container and a supply of dried beans, they make an ideal study organism for labs with limited resources.

Bean beetles (Callosobruchus maculatus) are cosmopolitan pests that infest multiple species of dried beans. They originated in Africa and have spread throughout areas with warm climates in Africa, Asia, and other continents. In the United States, they are sold by pet supply companies as feeder insects for reptiles and amphibians.

C. maculatus adults live for about 2 weeks, during which time they mate and lay eggs on dried beans. The eggs hatch and larvae burrow into the beans, where they develop for approximately 4-7 weeks depending on ambient temperature, after which adult beetles emerge from the beans. Emergence holes cause significant weight loss in these beans, and the presence of beetles is unsightly and reduces their economic value. Insect damage is the most significant cause of crop loss to cowpeas (black eyed peas), which are easily infested by C. maculatus, and this has led to interest in controlling these insects, especially in Africa and Asia.

Our project focuses on searching for differences between populations of bean beetles that might be relevant to their ability to infest different types of beans. We are using populations of beetles that have been raised on 3 different bean types, plus one population that was obtained from a feeder insect supply store. The theme of searching for between-population variation is woven into multiple lab experiments throughout the quarter. Students learn to use microscopes by looking for visual differences between beetle populations. They make hypotheses and design experiments to test for differences in oviposition preference between populations. Finally, they extract beetle DNA and use PCR to amplify STR regions of the beetle genome and look for genetic differences between these populations. Finally, they present their work at a mini-poster symposium and reflect on whether they have detected any differences that might be relevant to the beetles’ ability to spread or move to novel host beans. Students are expected to keep a detailed lab notebook with background, procedures, results and conclusions for each experiment. Writing their own background and procedures prior to lab gives them practice researching reliable sources and a deeper understanding of each experiment.

General Course Description:

BIOL&160, General Biology, 5credits, no prerequisites

This is a general biology class intended for allied health students, though non-majors at RTC may take it as well. This class is a prerequisite for Microbiology and Anatomy & Physiology. It focuses on biology at the cellular level and includes topics such as basic chemistry, macromolecules, cell structure and function, cellular respiration and photosynthesis, cell division, DNA replication, and protein synthesis. These are challenging topics, and since there are no required prerequisites, students often come in with very little science background. Most sections meet for 2 hours, 3 times per week, and one weekly session is devoted to lab.

Major challenges with this course include the lack of student prior knowledge and the heavy content load. Prior to implementing the research component, each lab day focused on one of the topics from the lecture. Students were given a worksheet at the beginning of the lab that required them to either do a pre-planned experiment related to the topic or model a process they’d learned about in class. While this helped students to learn some of the core concepts in biology, it was not very effective at teaching laboratory competencies or experimental design and analysis. One challenge that the new labs have created is that now we have even less time for students to practice and learn the concepts. Some instructors in the department have started asking students to take exams on their own time using a webcam and a monitoring program in an attempt to increase class time. There is no question that this class requires a heavy time investment from students.

Despite the downsides where time is concerned, there is no question that the new labs have forced students to develop important skills such as:

• Researching and writing background information and procedures with limited guidance
• Breaking a project into chunks and delegating tasks to group members
• Designing experiments and collecting data
• Data analysis and graphing with the help of computer tools (Microsoft Excel)
• Finding and reading peer-reviewed articles
• Reflecting on possible errors and redoing experiments
• Communicating the results of their own research project

The official course description and outcomes as listed in the course catalog and syllabi are:

COURSE DESCRIPTION: This course is designed for students who are not biology majors, but may go into a science or Allied Health field. Students explore the basic biological principles that describe and explain the nature of life. Topics include cell biology, molecular biology (including basic biochemistry and DNA structure and function), metabolism, and genetics. Students practice skills in both the classroom and laboratory through formats such as group exercises, laboratory activities, quizzes and exams.

COURSE OUTCOMES  – After successfully completing this class you should be able to:

1. Use (follow, understand and apply) the scientific method,
   1. by performing experiments to test formulated hypotheses and understanding the basic components of the design of those experiments
   2. by solving problems with the correct use of appropriate scientific notation and equipment
   3. by quantifying (observing, describing and measuring) various empirical phenomena
   4. by logically reaching valid conclusions based on these data through critical analysis and interpretation
2. Describe each step of the scientific method. Practice the method by making observations and developing experiments.
3. List the four kinds of organic molecules and explain the general structure and function of each.
4. Explain the major parts of a cell and what their functions are.
5. Explain how materials move into and out of cells, across membranes.
6. Explain the first and second laws of thermodynamics and apply them to examples in the body.
7. Describe the structure of an enzyme, the importance of enzymes and explain how an enzymes functions.
8. Describe what cellular respiration is and why it is important.
9. Describe each of the three steps of cellular respiration in detail including the reactants, products and pathways.
10. Describe what photosynthesis is and why it is important.
11. Describe each step of photosynthesis. What are the reactants, products and pathways?
12. Compare and contrast cellular respiration and photosynthesis.
13. Describe how cell division occurs. Explain why it is important.
14. Describe the way that gametes are made, meiosis.
15. Analyze mono and di-hybrid genetic crosses, sex-linked crosses, and crosses where complete dominance, incomplete dominance and co-dominance are involved.
16. Describe how DNA copies itself (DNA replication).
17. Describe how a protein is made (transcription and translation).