SAT Subject Biology Practice Question 418: Answer and Explanation
8. 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.
At which dose does 50% of the termite population survive?
A. 15 PPM
B. 20 PPM
C. 25 PPM
D. 30 PPM
E. 35 PPM
Correct Answer: C
C The experiment started with groups of 20 termites each, and 50% of that is 10 termites. The dose that allows 10 termites (or 50% of the termite population) to survive is 25 PPM 2-butoxyethanol.