In this lab, students measure the diversity of soil invertebrates that are collected from areas with different vegetation composition or cover, depending on the questions and hypothesis that the students generate. Student-generated questions include:
- How does different vegetation affect soil invertebrate diversity?
- How much does soil invertebrate diversity vary across a plant community?
- How does sampling intensity affect soil invertebrate diversity measurements?
- How do soil factors, such as chemistry, water status, etc. affect invertebrate diversity?
Students spend two four-hour lab sessions on this project. A field trip is made to the study site. Students, working in small groups, decide what question they are going to answer, develop a hypothesis, and design an experiment to test that hypothesis. After collecting soil and litter, they return to the lab where invertebrates are extracted from their samples using a set of Berlese-Tullgren funnels. Invertebrates are identified to Class, Order, and Family, when possible using keys provided in lab, or ecotype (morphologically based classification).
Data are entered in spreadsheets, diversity indices are calculated, and statistical tests are performed. Students then work alone and write a research-style paper with references made available to them by the instructor, in addition to others they locate on their own.
At the conclusion of the lab, students will:
- Learn about the incredibly diverse invertebrate community found in soil (literally under their feet).
- Learn how to quantify diversity of different soil invertebrate communities and generate hypotheses about underlying ecological processes that consider the factors that affect soil invertebrate diversity in different environments.
- Understand some of the basics of asking and attempting to answer ecological questions (beginning with observations in the field, focusing broad questions towards narrower answerable ones, developing hypotheses, designing and conducting a field-based research project to answer these questions, using skills in experimental design and data analysis, e.g., use of spreadsheets, simple statistics, data reduction, developing clear figures and tables that address specific questions, and generating a formatted paper or presentation based on their research findings).
- Advance their scientific critical thinking skills by revising their initial questions and hypotheses due to their findings as well as findings by others in published literature.
- Learn how to read scientific literature and place their work within its scientific context.
- Advance their skills in scientific collaboration within their peer community.
- Advance their skills in communicating scientific findings to peers (written and/or oral) presentation of research results).
- Field clothing
- Shovels & trowels, tapes or rulers
- Ziplock bags for transporting soil and litter samples
- Berlese-Tullgren funnels, with lights and alcohol or other preservative to catch invertebrates (Funnels can be purchased from Carolina Biological Supply, http://www.carolina.com. However, you can also construct your own. See the list of web sites below for instructions on how to make your own inexpensive, but highly effective, Berlese-Tullgren funnels.)
- Dissection microscopes
- Clear nail polish—Wet & Wild is the recommended brand
- Invertebrate guides (Soil Invertebrate Key) and data sheets (Data Tallysheet)
- Transportation to field site(s)
- Use of computers for a 2-3 hour block for data analysis
Summary of What is Due
From this lab, students individually submit an original research paper, based on the data their group collected and the literature that they consulted.
- Principal Ecological Question Addressed: What are the environmental correlates of variation in soil invertebrate community diversity?
- Ecological Topic Keywords: community ecology, biodiversity, Shannon index, species diversity, dominance, richness, soil invertebrates, edaphic conditions
- Science Methodological Skills Developed: field work, hypothesis generation and testing, invertebrate taxonomy, systematics, microscopy, statistics, graphics, data analysis, scientific writing
- Pedagogical Methods Used: