You have a population of cockroaches in your kitchen that amounts to 500 adult i

Question

You have a population of cockroaches in your kitchen that amounts to 500 adult individuals. You are tired of living with these scavengers, so you decide to go to the hardware store and buy an insecticide to murder the little devils. You thoroughly spray your kitchen and you are satisfied with the result. Please do some simple calculations below to determine whether your satisfaction is warranted.

1.Remember, you’re starting with 500 individuals. Let’s assume that your kill rate was 98% effective. How many roaches were killed by your treatment?

500 x 0.98 = __490_____ (number killed)

Individuals remaining = _____10_____  

You’re happy for a while. Your kitchen appears to be roach-free. Until one night, a couple of weeks later, you come down to the kitchen at 2:00 AM and its’ roach-o-rama. Yes, they’re back and it’s not pretty.

2.How can you explain this resurgence? Give 2 possibilities.

a.

b.

Undaunted, you pick up your trusty can of Raid and spray again and again just to make sure.    And yet this time, the result is very different. We’re going to assume again that you have a population of 500 roaches in your kitchen. But this time, the kill rate is 10%. OMG!!

3.How did this happen? Write a paragraph explaining how this second result is possible.

a.500 x 0.10 = ________ (number killed) (0.5 point)

b.Individuals remaining = ___________ (0.5 point)

Recall that as diploid organisms, we have two copies of every gene—one from your mother and one from your father. It is also the case that MOST genes for resistance are recessive. This means that the gene for susceptibility is dominant and that a resistant organism would have to have two copies of the gene for resistance to show the trait. With these simple ideas in mind, do some more calculations—

4.In the original population (described in (A) above, before insecticide treatment), calculate the total number of genes for the pesticide trait in the population. I will calculate the first one. You do the rest.

Number of individuals 500 x Number of copies of gene per individual 2 = 1000 genes for trait

Now, remember that some of the individuals in A. are susceptible and some are resistant

a.Multiply the total number of genes for the pesticide trait by the proportion of susceptible individuals to get the total number of susceptible genes in the population   __________ (Hint: you determined this in part A. Second Hint: you can assume that all individuals are homozygous, i.e., that they have only one allele---either the susceptible one or the resistant one).

b.Multiply the total number of genes for the pesticide trait by the proportion of resistant individuals (or determine by subtraction) to get the total number of resistant genes in the population___________

c.What is the percent of both forms of the gene in the initial population? ________

5.Now, do the same calculations for the second population, that was generated after you sprayed for the roaches the first time.

Number of susceptible genes in population___________

Number of resistant genes in population____________  

Percent of resistant genes in population___________  

Please answer these questions about the results of question 5.

6.Does this result meet the definition of evolution? Explain using the numbers you generated in Questions 1 and 2. (2 points)

7.Assuming that the trend established continues with subsequent sprays, what can you expect to happen in your kitchen if you continue the same treatment regime? Explain. (2 points)

8.Should you move? (1 point)

9.Explain why resistance of bacteria to antibiotics is the same phenomenon in a different species. (2 points)

10.What are the lessons we should have learned about using pesticides and antibiotics? Please consult the Rachel Carson material for further clarification if necessary. (2 points)

Explanation / Answer

2)Pest resurgence is observed when pests previously targeted and successfully controlled by pesticide recur, but in higher numbers than they did before. The reason for this can be the removal of predators together with pests. They either die from the pesticide, or move away because their food source has disappeared.The other can be due to multiplication of insects exponentially.With more application of pest the insects slowly increase resistance power towards the pests.

3)kill rate 98% so number survived 500*0.98=490

Individual remaining = 500 -490 =10

4)Total number of susceptible genes=number of genes*susceptible insects=1000*10=10000

Total number of resistant genes=number of genes*resistant insects=(total genes*total insects)-(number of genes*susceptible insects)=(500*1000)-(490*1000)=1000*00=100000

5)kill rate 10% so number survived 500*0.1=50

Individual remaining = 500 -50 =450

Total number of susceptible genes=number of genes*susceptible insects=1000*50=50000

Total number of resistant genes=number of genes*resistant insects=(total genes*total insects)-(number of genes*susceptible insects)=(500*1000)-(50*1000)=1000*450=450000

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