Passage II
Urushiols are the oils in poison ivy that cause allergic reactions in humans. The higher the U: S ratio－the ratio of unsaturated (U) urushiols to saturated (S) urushiols—the more severe the reaction.
From 1999 to 2004, poison ivy plants (PIPs) were grown in 2 identical outdoor plots under identical conditions except for the atmospheric CO2 concentration.
Figure 1 shows, for each plot, the yearly dry biomass per plant. Figure 2 shows the yearly percent of original PIPs surviving in each plot. Figure 3 shows, for each plot in 2004, the percent of U urushiols per plant, the percent of S urushiols per plant, and the U: S ratio per plant.
Figures adapted from "Biomass and Toxicity Responses of Poison Ivy (Toxicodendron radicans) to Elevated Atmospheric CO2." @2006 by the National Academy of Sciences.
11. Based on Figure 2, what percent of PIPs grown in the plot with a CO2 concentration of 370 ppm had died by the year 2003?
Your Answer is
Correct Answer is D
Explanation
Look at the solid line of 370 ppm in figure 2. When the abscissa is 2003, the ordinate percent of original PIPs surviving is about 40%, so the dead PIPs should be 100%-40%=60%