Practise Questions Jan. 2012 Key

Explain what they mean using the formal terms you

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Unformatted text preview: 7. Some biologists encapsulate evolution by natural selection with the phrase “mutation proposes, selection disposes”. Explain what they mean, using the formal terms you have learned to describe evolutionary processes. 18. Of all the mutations that occur in a population, why do only a small fraction become widespread among the population’s members? 19. In 1986 a nuclear power accident in Chernobyl, USSR (now Ukraine) led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident? a. Mutation by itself led to major changes in rodent physiology over time. b. Mutation led to increased genetic variation and a higher rate of evolutionary change. c. Mutation caused genetic drift and decreased fitness. d. Mutation caused the fixation of new alleles. 20. Why are mutations important in evolution, when most mutations are harmful? Mutation is the only way new alleles are created within a population. Although most are harmful, a very small number of mutations are beneficial. Through time, these beneficial mutations can become more numerous within a population as the population adapts to the environment. 21. Natural selection can only act on traits: a. that reduce mortality b. that confer a reproductive advantage. c. that are acquired in an individual's lifetime. d. that are heritable. e. that are adaptive. 22. The intermediate form of a trait is favored when __________ selection occurs a. stabilizing b. directional c. disruptive d. frequent e. none of these 23. When a population’s allele frequencies are shifting in a consistent direction, ______ selectio...
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