In the late 1940's, scientists released a group of chemicals, pyrethroids, to help kill insects in auricular crops. By the year 2000, over 100 insect species were resistant to pyrethroids and scientists had to develop a new plan to kill them.
Explain what happened genetically in the insect population over time as the insects were exposed to pyrethroids.
Responses
A The toxicity of pyrethroids weakened over time.The toxicity of pyrethroids weakened over time.
B The allele for pyrethroid resistance increased throughout the population.The allele for pyrethroid resistance increased throughout the population.
C Pyrethroid resistance became the dominant allele in the insect populations.Pyrethroid resistance became the dominant allele in the insect populations.
D Most insects had the allele for pyrethroid resistance, but it remained masked.
B The allele for pyrethroid resistance increased throughout the population.
B The allele for pyrethroid resistance increased throughout the population.
Over time, as the insects were exposed to pyrethroids, natural selection favored individuals that possessed the allele for pyrethroid resistance. These individuals were able to survive the effects of the chemicals and reproduce, passing on their resistant alleles to their offspring. As a result, the frequency of the pyrethroid resistance allele increased in the insect population.
The correct answer is C - Pyrethroid resistance became the dominant allele in the insect populations.
When the insects were exposed to pyrethroids, some individuals within the population may have had a genetic variation that allowed them to survive the exposure. These individuals with the genetic variation for resistance were more likely to survive and reproduce compared to those without the variation, who were more susceptible to the chemicals.
Over time, through natural selection, the resistant individuals have a higher chance of passing on their genes for resistance to their offspring. As a result, the frequency of the allele for pyrethroid resistance increases within the insect population.
As more generations of insects are exposed to pyrethroids and survive due to their resistance, the overall genetic makeup of the population shifts towards individuals carrying the resistance allele. Eventually, pyrethroid resistance becomes the dominant allele, meaning that the majority of the insects in the population possess the genetic variation for resistance.
This phenomenon is an example of natural selection and evolution, where the genetic composition of a population changes over time in response to selective pressures like exposure to a specific chemical.