BIOLOGY

Section II

8 Questions

Total Time—90 minutes

Reading Period—10 minutes

Writing Period—80 minutes

Directions: Questions 1 and 2 are long free-response questions that require about 22 minutes each to answer and are worth 10 points each. Questions 3–8 are short free-response questions that require about 6 minutes each to answer. Questions 3–5 are worth 4 points each and questions 6–8 are worth 3 points each.

Read each question carefully and completely. You are advised to spend the 10-minute reading period planning your answers. You may begin writing your responses before the reading period is over. Write your response in the space provided for each question. Only material written in the space provided will be scored. Answers must be written out in paragraph form. Outlines, bulleted lists, or diagrams alone are not acceptable.

1. Leucine aminopeptidases（LAPs）are found in all living organisms and have been associated with the response of the marine mussel, Mytilus edulis, to changes in salinity.LAPs are enzymes that remove N-terminal amino acids from proteins and release the free amino acids into the cytosol. To investigate the evolution of LAPs in wild populations of M. edulis, researchers sampled adult mussels from several different locations along a part of the northeast coast of the United States, as shown in Figure 1. The researchers then determined the percent of individuals possessing a particular lap allele,，in mussels from each sample site (table 1).

(a) On the axes provided, construct an appropriately labeled bar graph to illustrate the observed frequencies of theallele in the study populations.

(b) Based on the data, describe the most likely effect of salinity on the frequency of the allele in the marine mussel populations in Long Island Sound. Predict the likely allele frequency at a sampling site between site 1 and site 2 in Long Island Sound.
(c) Describe the most likely effect of activity on the osmolarity of the cytosol. Describe the function ofin maintaining water balance in the mussels living in the Atlantic Ocean.
(d) Marine mussel larvae are evenly dispersed throughout the study area by water movement. As larvae mature,they attach to the rocks in the water. Explain the differences inallele frequency among adult mussel populations at the sample sites despite the dispersal of larvae throughout the entire study area. Predict the likely effect on distribution of mussels in Long Island Sound if theallele was found in all of the mussels in the population. Justify your prediction.

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