Along the length of a river there exists a species of green sunfish. In order to provide electricity to area homes, a hydroelectric dam is built that separates the lower river area from a newly formed lake above. After many, many years, the green sunfish in the river and lake are sampled and found to be phenotypically very different. Which of the scenarios listed below is the best hypothesis to explain the microevolutionary changes observed?

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    The presence of the dam increased the amount of random mating that occurred between the river and lake fish, and natural selection selected for the best-fit organisms.
    The dam caused different environmental conditions to be formed in the lake versus the river, and natural selection selected for the best-fit organisms in both environments.
    The dam forced an increase in the amount of gene flow between the populations, and natural selection selected for the best-fit organisms in each group.
    The electricity produced in the dam caused mutations in the river sunfish, and natural selection selected for the best-fit organisms.
asked May 19, 2013 in Biology by anonymous
    

1 Answer

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The dam caused different environmental conditions to be formed in the lake versus the river, and natural selection selected for the best-fit organisms in both environments.
answered May 20, 2013 by Bioshare ~Top Expert~ (34,070 points)

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