STUDENT INSTRUCTIONS

Work together in groups of four. Pair with one other person in the group. In each pair, one person should work on the problem while the other coaches. Choose who will have each role for the first two figures then switch roles for the two figures.


First, examine Figure 2A. In this experiment, stems of milkweed leaves were put into tubes containing water. Five three-day-old monarch larvae (instar is a stage of development) were placed on each leaf. The bar indicates variation between the five replicates.

• In Figure 2A, compare larval survival after feeding on leaves with Bt pollen with those leaves dusted with untransformed pollen or the control leaves with no pollen.


• Do you think the evidence indicates that differences in monarch larvae survival on leaves dusted with Bt pollen is due to the effects of Bt pollen?

Describe and interpret Figure 2B. Here the researchers sought to determine if there were significant differences in the numbers of larvae surviving in Bt corn fields and non-Bt corn fields in two different states, in order to analyze the toxicity of transgenic pollen on monarch larvae.

• Does this new study discredit the original study? Explain why or why not.

Figure 2C and 2D are from an experiment conducted a couple years after the first study. The vertical bars in both indicate variation between replicate larvae. Figure 2C is based on data from laboratory bioassays which investigated effects of Bt toxin on the weights of monarch butterflies. Bioassays are experiments that use living things to test the toxicity of chemicals. Figure 2D shows results of a contamination study. In this case researchers studied whether monarch larvae were affected by contaminants in the samples by comparing the varying levels of sifting of the pollen. Examine both figures.

• In Figure 2C, what were the effects of the various hybrids’ pollen on the weights of monarch first instars?


• Did this vary between pollen levels tested?


• In Figure 2D, how do larvae whose diet contained beginning pollen or siftings of the contaminated pollen compare with larvae that consumed finely sifted pollen (most contaminants were removed)?


• What conclusion about the cause of the monarch larvae’s reactions to the samples can you draw from this figure?


• Does this new study discredit the original study? Explain why.


• Is the overall implication of this study similar to that of Figure 2B’s study?


• What investigation(s) would you propose next?

Check your answers with the other pair in your group.