Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
For decades, humans have used insecticides like DDT, pyrethroids, and organophosphates to control mosquito populations. These chemicals kill mosquitoes by damaging their nervous systems or interfering with reproduction. However, when the same chemical is used year after year, a few mosquitoes survive because of genetic mutations that make them less sensitive to the toxin.
Those survivors reproduce, passing on their resistance genes to the next generation. Over time, the proportion of resistant mosquitoes increases. This is a clear, measurable case of natural selection - the environment (in this case, repeated insecticide exposure) favors individuals with traits that improve survival.
One well-studied mutation, known as the kdr (knockdown resistance) gene, alters a sodium channel in mosquito nerve cells, preventing insecticides from binding effectively. Mosquitoes with one or two copies of this mutation can survive doses that would kill nonresistant mosquitoes.
Scientists use mathematical models to represent how quickly resistance spreads. They track allele frequencies - the percentage of resistant (R) versus nonresistant (r) genes - and survival rates before and after insecticide application. For example, when spraying begins, perhaps 10% of mosquitoes carry the R allele. After ten years of repeated insecticide exposure, that number might climb to 80% or higher.
These data help public health programs adjust strategies. Some rotate insecticides to slow resistance or use biological control methods like releasing sterile males. The evolution of insecticide resistance shows how natural selection can cause a quantitative shift in population genetics within just a few generations.
Natural selection is not always slow - when selective pressure is strong and variation exists in a population, measurable genetic change can occur in years, not millennia. Mosquitoes offer a powerful reminder of how quickly evolution can shape the world around us.
Graph of Information - Figure 1.
Graph of Information - Figure 2.
Figure 3.
Figure 4.
Using Table 1, describe how the percentage of resistant mosquitoes changed from 2005 to 2024. What does this trend suggest about natural selection?
Explain why repeated use of the same insecticide increases the percentage of mosquitoes carrying the kdr resistance mutation.
According to Table 1, in which year did resistant mosquitoes first reach 70% or more of the population?
According to the reading, what functional advantage does the kdr mutation provide?
Using Table 2 and Figure 2, describe how the frequency of the R allele changes across the nine modeled generations. What mathematical pattern does this represent?
Does the data support the claim that strong environmental pressures - like repeated insecticide use - can cause rapid evolutionary change in mosquito populations?
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Evidence:
Reasoning: