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# IMG_0003 - Midterm Exam BioSci 110 Spring 09 RUBRIC 4(3 pts...

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Unformatted text preview: Midterm Exam, BioSci 110, Spring 09 RUBRIC 4. (3 pts] In 1978, 72% of the mosquito population was resistant to DDT and 13% were carriers of the resistance allele. What were the frequencies of genotypes and of the r and R alleles in the 1978 population? Show your work! [1 pt] Genotype frequencies: 72% (or 0.72) rr 13% (or 0.13) Rr 15% (or 0.15) RR [1 pt] Frequency of r = (72+72+13)/200 = 0.785 [1 pt] Frequency of R = (13+15+15)/200 = 0.215 5. [6 pts] Construct a scientific argument. In science, CLAIMS are based on EVIDENCE (data) and are supported by WARRANTS (our knowledge of biology). This question was graded based on both the content of your answer, and the structure of the argument (were evidence and warrants interconnected, and did they support your claim?) a. [2 pts] Did the mosquito population evolve over the 20 years of DDT spraying? Clearly state your CLAIM in one sentence. [2 pts] Yes, the mosquito population evolved. b. [2 pts] On what EVIDENCE do you base your claim? [2 pts] The frequency of r and R alleles in the population changed between 1958 and 1978. Frequency of r was 0.115 in ’58 and 0.785 in ’78; Frequency of R was 0.885 in ’58 and 0.215 in ’78. Alternatively, using the allele frequencies of r and R in 1978, you can predict genotypic frequencies and compare them to the observed genotype frequencies in 1978. The predicted frequencies in 1978 (rr= 0.616; rR = 0.337; RR = 0.05) are different than the observed (rr= 0.72; rR = 0.13; RR = 0.15). c. (2pts] What WARRANT(S) support your argument? (Hint: how do we define evolution?) [2 pts] We define evolution as the change in allele frequency that occurs in a population over time. The data (evidence) above indicate that the mosquito population underwent such a change for the alleles that control DDT resistance. Alternatively in 1978 the population was not in HW equilibrium, based on the observed genotype frequencies being different than the predicted ones. This means the population was evolving. DDT spraying was a selective agent; the mosquito population was under natural selection, meaning that at least one of the HW assumptions was violated between 1958 and 1978. ...
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