1 Sometimes one encounters a species with a highly variable phenotype for a particular characteristic Darwin s theory seems to tell us that natural selection should favor one phenotype over others Which evolutionary mechanism could maintain such variation within a population for long periods of time a frequency dependent selection 2 Studies of a bird population reveal variation in the number of eggs per nest Birds laying small numbers of eggs obviously have less reproductive success than other birds However birds laying large numbers of eggs are also less successful in reproduction each of their many chicks receives less food and consequently many of them do not survive In terms of reproduction the most successful birds are those that lay an average number of eggs The selection mode operating on the number of eggs per nest is a stabilizing selection 3 Natural selection has the effect of reducing a population s genetic variation by removing disadvantageous genotypes Which of the following explains how diploidy contributes to maintaining or preserving genetic variation in spite of natural selection a selection cannot act on recessive alleles in heterozygous individuals 4 The Pingelapese people of the East Caroline Islands are descended from 20 survivors of a typhoon and subsequent famine in1775 Among the survivors was an individual heterozygous for a recessive mutation that causes achromatopsia a condition that causes color blindness extreme sensitivity to light and poor visual acuity Although this condition is usually very rare affecting about 1 person in 20 000 about 20 of today s 3000 Pingelapese are achromats The most likely explanation for the plight of the Pingelapese is a Bottleneck effect 5 In a certain plant a blue flower color is dominant over white flower color In an isolated location 1000 plants are growing 360 have blue flowers and 640 have white flowers Assuming Hardy Weinberg conditions what is the frequency of the dominant allele a 20 6 In an evolutionary context fitness is best defined as a the ability to survive and leave fertile offspring 7 Microevolution can occur when immigrants from another population mate with members of the receiving population This process is called a Gene flow 8 Which of the following is NOT TRUE of genetic drift a its effects are enhanced by gene flow 9 The source of new genetic variation in sexually reproducing species is a mutation 10 In a very large population of butterflies the dominant allele for red spots is R The recessive genotype rr has no red spots Red spots on the wings briefly frighten bird predators often allowing the butterfly with red spots to escape The frequency for R in this population is 0 5 If these conditions continue which of the following should we expect in 15 years a the frequency of r will be less than 0 5 11 The loss of genetic variation present in a large population when a new population is formed by a small number of individuals from the original population is called a Founder effect 12 Hypothetical scenario the greater prairie chicken populations in Kansas are reduced from the current 750 000 to 200 in two decades as natural prairie is converted into suburban zones Which of the following is the best prediction about the remaining population 100 years later a It will have much less genetic diversity 13 Which of the following statements about natural selection is INCORRECT a it causes adaptive change in populations by directly acting upon maladaptive genotypes of individuals 14 In a population of 500 snarks 300 individuals are homozygous dominant at the purple spotted locus SS 150 are heterozygous Ss and 50 have no spots ss Determine the allelic frequencies a p 0 75 q 0 25 15 A certain butterfly species has two color forms that are produced by a simple autosomal gene with complete dominance A biologist surveys a population of these butterflies five times over two decades and each time the proportions are 75 dominant phenotype 25 recessive phenotype Which of the following is a reasonable inference conclusion based on evidence based on this information a Population is in H W equilibrium
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