Four out of five animals on Earth are nematodes, making them the most ubiquitous multi-cellular organisms on our planet (Bongers and Ferris 1999). Nematodes significantly affect humans ecologically, biologically, and economically. They can be free-living, animal parasitic, plant parasitic, or insecticidal in nature. Model organisms have long been used in research laboratories and in classrooms to advance our understanding of life and human diseases (WORM 2004). Nematode worms, especially insecticidal nematodes (Figure 1), are excellent model organisms for high school biology inquiry-based laboratory activities.
In a collaborative effort between university researchers and high school science teachers, we designed an inquiry-based laboratory module using two species of insecticidal nematodes to help high school biology students apply scientific inquiry and elements of thoughtful experimental design. Groups of students investigated the insecticidal properties of two nematode species by "asking questions, planning and conducting investigations, using appropriate tools and techniques to gather data, thinking critically and logically about relationships between evidence and explanations, constructing and analyzing alternative explanations, and communicating scientific arguments" (NRC 1996, p. 105).
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Nematodes or roundworms are of inherent biological importance, and although they are popular model organisms in research laboratories and ubiquitous in freshwater, marine, and terrestrial environments, they are often given little significance in most secondary science education curricula. The important ecological niches occupied by these organisms make the study of nematodes in high school classrooms an exciting topic and justify a place in the biology core curriculum (Tylka and Jasalavich 2001).
For instance, free-living nematodes play a major role in carbon cycling and decomposition. One free-living species, Caenorhabditis elegans, was the first animal to have its genome sequenced and is currently used as a model organism in biomedicine, genetics, and developmental biology. (Editor's note: For an activity investigating C. elegans, see "Using Digital Microscopy" in the April/ May 2006 issue of The Science Teacher.) Animal parasitic nematodes cause serious diseases-even death-in humans, pets, and stock animals. Plant parasitic species cause over 100 billion dollars a year in crop damage worldwide. Conversely, insecticidal nematodes-parasitic roundworms that only infect insects-are increasingly being used as an environmental alternative to chemical pesticides to protect our crops from harmful insects (see "Ecology of insecticidal nematodes").
Due to the significance of insecticidal nematodes, and the advantages of using this model organism at the secondary science level, we developed and tested a high school-level nemotology module in the 2005 Gains in the Education of Mathematics and Science (GEMS) program at the Walter Reed Army Institute of Research. In GEMS, students in grades 8-12 spend one to four weeks in an Army lab performing experiments that highlight basic scientific principles (www.usaeop.com/programs/GEMS).
The initial inquiry-based activity involving insecticidal nematodes, introduced to the 2005 GEMS students, was used as an evaluation of the laboratory procedure. The majority of students cited the module as the favorite part of their internship experience. With the preliminary nematology module revealing such broad student interest in insecticidal nematodes, we set to further develop and field-test the activity in high school biology classrooms. The module, which required three class periods to complete, was integrated in several biology classrooms at Lehi High School in Lehi, Utah, with over 300 10th-grade students. The remainder of this article describes the experience and model.
Class period 1: Introduction to scientific inquiry, experimental design, and nematodes
To give students the tools necessary to carry out scientific experiments involving nematodes, the first day of integrating the module into science classrooms was used to introduce scientific inquiry, experimental design, and general nematology. …