1.
A large amount of gene flow is now occurring among human populations due to intermarriage among people from different ethnic groups and regions of the world. Is this phenomenon increasing or decreasing racial differences in our species? Explain.
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2.
Speciation resulting from polyploidy appears to be much more common in plants (especially ferns) than animals. According to one hypothesis, mutations leading to polyploidy are more common in plants because the germ line and soma are not separated, as they are in animals. As a result, polyploidy can arise from an error during mitosis as well as an error in meiosis. Specifically, if nondisjunction occurs at anaphase during mitosis, it can result in a polyploid cell line. If these cells later differentiate into germ-line cells and undergo meiosis, and if the diploid gametes self-fertilize, viable polyploid offspring result. Does this scenario make sense? Comment.
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3.
Ellen Censky and co-workers recently documented a colonization event. After two hurricanes passed through the Caribbean Sea in the fall of 1995, a large raft made up of fallen trees and other debris drifted to the shore of an island called Anguilla. At least 15 individuals of the green iguana left the raft and went onto the island. Iguanas were not found on Anguilla prior to this event. Based on the wind patterns during the storms, the researchers propose that the 15 iguanas originally lived on the island of Guadalupe.
Outline a short-term study designed to test the hypothesis that genetic drift produced allele frequency differences in the two populations.
Outline a long-term study designed to test the hypothesis that natural selection will produce changes in the characteristics of the two populations over time.
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4.
All over the world, natural habitats are being fragmented into tiny islands as suburbs, ranches, and farms expand. In effect, vicariance is occurring at a scale never before seen in the history of life. Based on the data presented in this chapter, do you predict that speciation will take place in the newly isolated populations? Or do you predict that they will be wiped out before speciation can occur?
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