A massive farm near our school has recently had a
decrease in crop production (e.g., not as many plants are
successfully growing). A soil ecologist was notified. She
immediately noticed that there were no worms, bacteria, or
other microorganisms in the soil, even though she knew that
many organisms were present in the soil five years ago. Based
on this information, she would probably say that the population
density of microorganisms had
a. Increased
b. Decreased
c. Immigrated
d. None of the above