FACULTY NOTES

Divide students into equally sized groups to form 3 total groups. Assign one group to Figure 3.1, one group to Figure 3.2, and one group to Figure 3.3. In a larger class, you can divide students into 6 groups (two groups to each figure). There are three different portions of the story or rather three "pieces" of information represented by the three figures, respectively. Students are then to interpret the data given in their figure and ensure that each member of their group thoroughly understands the information, as they will be required to explain it to someone who has not seen the figure yet. Give students sufficient amount of time to accomplish this. Then assign students to new groups, so that each member of each new group has information from a different figure. Therefore the new groups should each contain 3 members, one student having information about Figure 3.1, one from Figure 3.2, and one from Figure 3.3. These students are now to teach each other their "pieces" of information to "piece together the puzzle" with the goal of understanding the indirect effects of the introduced biocontrol agents. (Make sure that students read the figure legends. In particular, make sure students understand that 'seropositive' means that the mice are carriers of hantavirus. If this is not understood, it can create problems.) You may need to inform students that transmission rates will increase with increases in the density of the carriers. Instructors could reinforce this concept by asking students to consider the conditions under which diseases spread more rapidly (among crowded residential college students, etc). For information about use of Jigsaws in teaching see http://tiee.ecoed.net/teach/teach_glossary.html.

As a breakdown of the figures, students should be able to conclude that (1) gall fly larvae are present in large densities in areas that contain knapweed, (2) deer mice are present in large densities in areas that contain knapweed, (3) deer mice diets primarily consist of gall fly larvae and their diets fluctuate with the life cycle of the gall fly, and (4) both the density and proportion of deer mice that carry hantavirus are higher in areas that contain knapweed. Therefore the continued presence of knapweed allows for the persistence of gall flies, which provide additional food for deer mice, carriers of hantavirus, a virus that is transmitted to humans and can be fatal. Further, instructors may wish to discuss with the students the issue of correlation and causation. Although the separate pieces of the puzzle suggest that more knapweed allows more biocontrol agents to flourish, which allows more mice to live in knapweed areas, which in turns causes more and a greater proportion of seropositive mice, instructors could explain that these were correlations, and causation has not been supported by manipulative experiments.

Building on the discussion of correlation vs. causation, instructors could discuss with students how an experiment could be designed in this system. Alternatively, if manipulative experiments are not possible in science, instructors may wish to discuss how researchers/scientists deal with this situation.

Student Assessment

Essay Quiz

If a seed chewing biological control agent is found in Asia, discuss the costs and benefits of introducing this agent to the United States to control Lespedeza cuneata.

Concept Map

Have students create a concept map to depict the relationships between knapweed, gall flies, deer mice, hantavirus, and human health. Ask them to consider other components of the system, such as native plants, native insects, small mammals, gallfly parasitoids, and predators (see box 1 from Pearson, D.E. and Callaway, R.M. 2003. Indirect effects of host-specific biological control agents. Trends in Ecology and Evolution 18 (9): 456-461.) Concept maps are useful tools. They help students organize ideas about interconnected phenomena and faculty to literally "see" what students are thinking about a particular topic. If your students have not worked with concept maps before, briefly describe what they are, perhaps with an example. For more information go to http://www.flaguide.org/cat/conmap/conmap1.php