BIOLOGY
12th Edition
ISBN: 9781260169614
Author: Raven
Publisher: RENT MCG
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Chapter 21, Problem 4S
Refer to figure 21.5, artificial selection in the laboratory. In this experiment, one population of Drosophila was selected for low numbers of bristles and the other for high numbers. Note that not only did the means of the populations change greatly in 35 generations, but also all individuals in both experimental populations lie outside the range of the initial population. What would happen if the direction of selection were reversed, such that a greater number of bristles was selected for in the low-bristle population, and vice versa? How would the rate of evolutionary change compare with that in the initial part of the experiment before selection was reversed?
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In Drosophila melanogaster, wing shape is an
autosomal trait. Vestigal wing is recessive (v)
to the dominant trait for the normal long
wings (V). In a mainland source population,
the allele frequency of v is 0.02 . A small,
experimental population of 100 flies was
introduced on an island and had 20 flies with
vestigal wings and 40 heterozygotes. What are
the allele frequencies of V and v in this
introduced population? What proportion (%)
of heterozygotes and homozygous recessive
flies would you expect to see after a few
generations of mating on this island? What
phenomenon of population genetics does this
experiment demonstrate?
p+q=1, p^2+ 2pq + q^2 = 1
In the fly speciation experiment described in class, Drosophila from a single culture was split into four isolated cultures, 2 raised on maltose food and two on starch food. After forty generations all possible crosses were done between maltose and starch flies and between the two starch populations. Flies from different food types had very low mating frequencies compared to flies from the same food type but flies from different starch populations only mated at a very slightly lower rate than flies from the same starch population. How would you interpret this finding?
Group of answer choices
A. allopatric speciation is more powerful than sympatric speciation
B. flies are incapable of evolution
C. drift causes divergence more rapidly than selection
D. sympatric speciation is more powerful than allopatric speciation
E. selection causes divergence more rapidly than drift
In the fly speciation experiment described in class, Drosophila from a single culture was split into four isolated cultures, 2 raised on maltose food and two on starch food. After forty generations all possible crosses were done between maltose and starch flies and between the two starch populations. Flies from different food types had very low mating frequencies compared to flies from the same food type but flies from different starch populations only mated at a very slightly lower rate than flies from the same starch population. How would you interpret this finding?
Chapter 21 Solutions
BIOLOGY
Ch. 21.1 - Prob. 1LOCh. 21.1 - Prob. 2LOCh. 21.2 - Prob. 1LOCh. 21.2 - Distinguish between demonstrating that evolution...Ch. 21.3 - Contrast the processes of artificial and natural...Ch. 21.3 - Prob. 2LOCh. 21.4 - Prob. 1LOCh. 21.4 - Prob. 2LOCh. 21.4 - Prob. 3LOCh. 21.5 - Explain the evolutionary significance of...
Ch. 21.5 - Prob. 2LOCh. 21.6 - Prob. 1LOCh. 21.6 - Prob. 2LOCh. 21.7 - Characterize the criticisms of evolutionary theory...Ch. 21.7 - Prob. 2LOCh. 21 - Suppose that a male with a beak depth of 10 mm...Ch. 21 - Prob. 1IQCh. 21 - Prob. 2IQCh. 21 - Prob. 3IQCh. 21 - Why might the evolutionary line leading to...Ch. 21 - Artificial selection is different from natural...Ch. 21 - Gaps in the fossil record a. demonstrate our...Ch. 21 - The evolution of modern horses (Equus) is best...Ch. 21 - Homologous structures a. are structures in two or...Ch. 21 - Convergent evolution a. is an example of...Ch. 21 - Prob. 6UCh. 21 - The possession of fine fur in 5-month human...Ch. 21 - In Darwins finches, a. occurrence of wet and dry...Ch. 21 - Prob. 2ACh. 21 - Convergent evolution is often seen among species...Ch. 21 - What conditions are necessary for evolution by...Ch. 21 - Explain how data shown in figure 21.2a and b...Ch. 21 - Prob. 3SCh. 21 - Refer to figure 21.5, artificial selection in the...Ch. 21 - The ancestor of horses was a small, many-toed...
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- For the trichome selection experiment, the null hypothesis is that there will be no difference between the mean number of trichomes in the second generation compared to the parent generation. The following bar graph shows the data from the experiment, including error bars showing ± 2 standard deviations (a measure of variation for a group of data as a whole). Based on the data provided, do you reject or fail to reject the null hypothesis? Select the answer that most strongly supports your choice and correctly justifies the response. Based on the data provided, do you reject or fail to reject the null hypothesis? Select the answer that most strongly supports your choice and correctly justifies the response. A. Reject the null hypothesis, as variation, shown by the error bars, is greater after selection. B. Reject the null hypothesis, as there is no overlap between the means as shown by the error bars. C. Reject the null hypothesis, as the error bars for the two groups show…arrow_forwardIn class we investigated the reason cystic fibrosis is maintained in the human population in higher frequency than we expected given the deleterious effects of being homozygous at the CFTR gene. We calculated the actual mutation rate of the CFTR gene to be 6.7 x 10-7. The mutation rate expected under mutation-selection balance was 4 x 10-4. What is the most plausible explanation as to why cystic fibrosis is maintained in the human population at a higher frequency than we expect? a. Negative selection against the CFTR deleterious alleles is too weak to eliminate the alleles from the human population. b. Positive selection for the CFTR deleterious alleles is likely occurring in response to some other selective pressure in the human population, possibly resistance to typhoid fever. c. The CFTR gene has an exceedingly low mutation rate causing humans to have no genetic variation at that gene. d. The CFTR gene has an exceedingly high mutation rate and that is…arrow_forwardStudents in a genetics laboratory began an experiment in an attempt to increase heat tolerance in two strains of Drosophila melanogaster. One strain was trapped from the wild six weeks before the experiment was to begin; the other was obtained from a Drosophila repository at a university laboratory. In which strain would you expect to see the most rapid and extensive response to heat-tolerance selection, and why?arrow_forward
- A dominant mutation in Drosophila called Delta causes changes in wing morphology in Delta/Delta+ heterozygotes. Homozygosity for mutant alleles (Delta/Delta) is lethal prior to the adult stage. In a population of 150 adult flies, it was determined that 60 had normal wings and 90 had abnormal wings. What is the frequency of the mutant Delta allele in this population?arrow_forwardPINE TREE NEEDLES Variation among members of a population can lead to natural selection, but only if two conditions are met: First, the trait must be relevant to an individual's survival and/or reproductive rate. Second, variation in this trait must be heritable, that is, at least partly controlled by genes. a. How might you design an experiment to determine the importance of needle length in determining survival and reproduction? b. How might you test the extent to which needle length is heritable?arrow_forwardA dominant mutation in Drosophila called Deltacauses changes in wing morphology in Delta/+ heterozygotes. Homozygosity for this mutation (Delta /Delta) is lethal prior to the adult stage. In a population of 150 flies, it was determined that 60 hadnormal wings and 90 had abnormal wings.a. What are the allele frequencies in this population?b. Using the allele frequencies calculated in part (a),how many total zygotes must be produced by thispopulation in order for you to count 160 viableadults in the next generation?c. Given that there is random mating, no migration,and no mutation, and ignoring the effects ofgenetic drift, what are the expected numbers ofthe different genotypes in the next generation if160 viable offspring of the population in part(a) are counted?d. Is this next generation at Hardy-Weinberg equilibrium? Why or why not?740 Chapter 21 Variation and Selection in Populationsarrow_forward
- Which of the following is the LEAST CONVINCING argument against micromutationism? Advantageous mutations of large effect are more resistant to loss by drift than advantageous mutations of small effect. Mutations of small effect are more likely to be advantageous than mutations of large effect. Empirical studies suggest that some adaptive traits are governed at least in part by loci of large phenotypic effect.arrow_forwardWhat are two reasons why a selection limit is reached in which artificial selection no longer has an effect?arrow_forwardEugene Eisen selected for increased 12-day litter weight (total weight of a litter of offspring 12 days after birth) in a population of mice (E. J. Eisen. 1972. Genetics 72:129–142). The 12-day litter weight of the population steadily increased, but then leveled off after about 17 generations. At generation 17, Eisen took one family of mice from the selected population and reversed the selection procedure: in this group, he selected for decreased 12-day litter weight. This group immediately responded to the reversed selection: the 12-day litter weight dropped 4.8 g within 1 generation and dropped 7.3 g after 5 generations. On the basis of the results of the reverse selection, what is the most likely explanation for the leveling off of 12-day litter weight in the original population?arrow_forward
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