Chapter 23 Practice test.docx - Summary of Results 23 The...

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Summary of Results Site Title: Campbell Biology, 8/e 23: The Evolution of Populations > Practice Test 1. In the context of populations, how do we define evolution ? Your Answer: Evolution is a change in a population's allelic frequencies over generations Correct. This is the definition of microevolution, which focuses on evolutionary change in populations. -------------------------------------------------------------------------------- 2. Which of the following mechanisms can alter allele frequencies? Your Answer: all of the above ( genetic drift, natural selection,gene flow ) Correct. Natural selection, gene flow, and genetic drift can all cause microevolution -------------------------------------------------------------------------------- 3. Which example below correctly describes average heterozygosity? Your Answer: Average heterozygosity refers to the average percentage of loci that are heterozygous in a population. Correct. Researchers use average heterozygosity to measure the number of polymorphisms in a population. -------------------------------------------------------------------------------- 4. The human genome consists of approximately 3 billion base pairs. If humans typically differ from one another by about 3 million base pairs, what is the nucleotide variability of Homo sapiens? ( Concept 23.1) Your Answer: 1% Correct Answer: 0.1% No. Check your math. -------------------------------------------------------------------------------- 5. Which example below would most likely be a cline? Your Answer: Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions. Correct. A cline is a graded change in a trait along a geographic axis. -------------------------------------------------------------------------------- 6. New alleles originate from _____. Your Answer: mutation Correct. Although mutations most often do not result in favorable adaptations, they are the primary way that new alleles come about. -------------------------------------------------------------------------------- 7. Sexual recombination includes the shuffling of chromosomes in _____ and fertilization. Your Answer: meiosis Correct. Sexual recombination occurs with the crossing over and independent assortment of chromosomes. -------------------------------------------------------------------------------- 8. Which type of mutation plays the most important role in increasing the number of genes in the gene pool? Your Answer: rearrangement of gene loci Correct Answer: duplication No. Such a mutation would most likely be harmful, and it does not generate new genetic material. --------------------------------------------------------------------------------
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9. In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individuals showing the dominant trait. When the gene frequency is reexamined at the end of the year, _____. Your Answer: the frequency of the individuals who express the dominant phenotype will go down and the frequency of homozygous recessive individuals will go up Correct. The frequency of individuals who express the dominant phenotype should decline, and the proportion of individuals who express the recessive phenotype (homozygous recessives) should increase.
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