SAT Subject Biology Practice Question 419: Answer and Explanation
9. 2-butoxyethanol, a substance found in a general household cleaner, was tested for toxicity to termites. Solutions were made that contained various parts per million (PPM) of 2-butoxyethanol, and 15 mL of each of these diluted solutions was mixed with 150 g of wood chips. Twenty mature termites were added to the wood chips, and the number surviving after 24 hours was determined and recorded. The following graph presents the results.
How is this substance toxic to termites?
A. It paralyzes their jaws so they are unable to eat.
B. It prevents digestion of wood.
C. It kills the microorganisms in the termites' digestive tracks that digest wood.
D. At 40 PPM only 20% of the termites survive.
E. There is no information given that describes the mechanism of toxicity.
Correct Answer: E
E This question is an excellent example of the temptation trap. The experiment description really doesn't tell us anything about how this substance kills the termites, just that it does kill the termites. Choices A, B, and C may be true, but we don't know for sure. The tempting choice is choice D, because that is a true statement. Expecting the graph to continue the pattern it shows, a dose of 40 PPM would leave only 4 termites alive, or 20% of the original population. However, even though it's a true statement, it doesn't answer the question. The best choice is choice E.