TR.EVOLUTION.2B
BIOLOGY CURRICULUM 2006
the farmer and the fly: PART I
Scenario part I.
A farmer was working with chickens at an agricultural research station. The population of flies in the chicken house was so large that the health of the chickens was affected. So the farmer decided to spray the chicken house and the chickens with a solution of insecticide, Formula A. The insecticide worked well and killed nearly all of the flies.
Sometime later, however, the number of flies was again large. The farmer sprayed the chicken house and the chickens with insecticide, Formula A again. Many of the flies were killed, but not all.
Unfortunately, after a short time, the flies repopulated the chicken house. The farmer sprayed the chicken house and the chickens with insecticide, Formula A again. The farmer continued to do this each time the flies repopulated the chicken house. After each spraying, the farmer noticed that the insecticide was becoming less and less effective at killing the flies.
Scenario part II.
A researcher at the station noted that one large batch of Formula A had been mixed at the beginning of the spring. The farmer had used the same solution for each spraying. Based on this, the researcher suggested the insecticide could have decomposed over time and therefore become less effective with each spraying.
Scenario part III.
The researcher at from the agricultural facility then mixed a new batch of the Formula A, insecticide. This batch was used to spray the flies in the chicken house. When this was done, most of the flies had survived.
The researcher then went to a different chicken house and sprayed the flies with the new batch of the Formula A, insecticide. When this was done, most of the flies had been killed. The fresh batch of Formula A, insecticide had produced two very different results.
Scenario IV.
The farmer is very concerned about his chickens. So far, a clear explanation for why the insecticide is not working in the first chicken house, has not been determined.
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