BIOLOGY
12th Edition
ISBN: 9781260169614
Author: Raven
Publisher: RENT MCG
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Chapter 20, Problem 3S
Based on a consideration of how strong artificial selection has helped eliminate
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In Africa we find albinism in around 1 in every 5,000 individuals. This is puzzling, because albinism may reduce survival, for instance due to increased risk of skin cancer. What evolutionary mechanism (natural selection, mutation, genetic drift, or gene flow) is a viable explanation for the consistent observation of a few children born with albinism each generation and why?
Selection confers a reproductive advantage to individuals based on their adaptations, and therefore causes the alleles carried by those individuals to increase in the population. Selection can be simulated by having your partner remove any three individuals of a particular suit as you deal the cards into a pile. The fitness of that variant is therefore 0.77 (10/13 survive), while the fitness of the other three variants remains at 1.0 (13/13 survive). Recalculate allelic (suit) frequencies after selection.
1. What is the effect of selection on reproduction, allelic diversity, and frequency?
2. What would happen if similar selection continued over several generations?
Cite references.
Some genetic disorders are caused by autosomal recessive alleles. Many such alleles are recessive lethals, causing lethality very early in life (say, before the age of 20 yrs). Intuitively one might suggest that selection working on human population should completely remove such alleles from the population. Yet, there are many examples of such lethal genetic disorders occurring in low frequency in several human populations. Why is it almost impossible to completely remove these seemingly fitness-detrimental alleles from the population? Under what condition, extinction of such an allele from a population can be achieved?
Chapter 20 Solutions
BIOLOGY
Ch. 20.1 - Define evolution and population genetics.Ch. 20.1 - Prob. 2LOCh. 20.2 - Explain the HardyWeinberg principle.Ch. 20.2 - Describe the characteristics of a population that...Ch. 20.2 - Prob. 3LOCh. 20.3 - Define the five processes that can cause...Ch. 20.3 - Prob. 2LOCh. 20.4 - Prob. 1LOCh. 20.4 - Prob. 2LOCh. 20.4 - Demonstrate how the success of different...
Ch. 20.5 - Prob. 1LOCh. 20.5 - Prob. 2LOCh. 20.5 - Prob. 3LOCh. 20.6 - Define frequency-dependent selection, oscillating...Ch. 20.6 - Prob. 2LOCh. 20.7 - Define and contrast disruptive, directional, and...Ch. 20.7 - Prob. 2LOCh. 20.8 - Explain how experiments can be used to test...Ch. 20.9 - Prob. 1LOCh. 20.9 - Prob. 2LOCh. 20.10 - Prob. 2LOCh. 20 - If all white cats died, what proportion of the...Ch. 20 - Assuming that the values on the x-axis represent...Ch. 20 - Prob. 3DACh. 20 - Prob. 4DACh. 20 - Examine the index of copper tolerance on nonmine...Ch. 20 - Prob. 6DACh. 20 - Why are rare alleles particularly likely to be...Ch. 20 - Prob. 2IQCh. 20 - Prob. 3IQCh. 20 - Prob. 4IQCh. 20 - Prob. 5IQCh. 20 - Prob. 6IQCh. 20 - Prob. 7IQCh. 20 - Prob. 8IQCh. 20 - Prob. 9IQCh. 20 - Assortative mating a. affects genotype frequencies...Ch. 20 - When the environment changes from year to year and...Ch. 20 - Many factors can limit the ability of natural...Ch. 20 - Stabilizing selection differs from directional...Ch. 20 - Founder effects and bottlenecks are a. expected...Ch. 20 - Relative fitness a. refers to the survival rate of...Ch. 20 - For natural selection to result in evolutionary...Ch. 20 - Prob. 8UCh. 20 - In a population of red (dominant allele) or white...Ch. 20 - Genetic drift and natural selection can both lead...Ch. 20 - Prob. 3ACh. 20 - Prob. 4ACh. 20 - In Trinidadian guppies a combination of elegant...Ch. 20 - On large, black lava flows in the deserts of the...Ch. 20 - Based on a consideration of how strong artificial...
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- Is it likely that the selection coefficient (s) is similar in value for the three populations shown? Is it important to know if the amount of genetic variation for the trait under selection is approximately equal in all three populations in the graph? Why or why not?arrow_forwardFor 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_forwardFitness is, most correctly, a technical term. What does it mean? What two things do you suppose govern the rate of evolution by natural selection? Explain how Darwinian evolution can decrease and increase the frequency of an allele (or a more complex heritable trait, for that matter)arrow_forward
- PINE 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_forwardArtificial selection is when people selectively choose individuals with a certain desired trait to use as parents of the next generation. It is done to domesticated (or semi-domesticated) organisms. It has produced such monstrosities as bubble-eyed goldfish, revealing the potential for selection acting on heritable variation to produce varieties appearing very different than their ancestors. How is that different from natural selection? (Select all that apply) A- In artificial selection, humans directly cause new mutations to occur, whereas natural selection relies on mutations that occur randomly over time. B- Artificial selection can lead to organisms that would be unfit to survive in the wild, whereas natural selection usually makes the population better adapted. C- Artificial selection is directed ahead of time towards an intentional goal; not so with natural selection. D- Really, they are exactly the same process. Both cause what seems to be design without a designer. E-…arrow_forwardStorage of excess carbohydrates in the diet in the form of fat would have helped human populations survive famine. However, this process is also a risk factor for obesity and type 2 diabetes in modern populations. Modern populations vary greatly in the prevalence of type 2 diabetes, but there is no evidence that alleles increasing type 2 diabetes susceptibility have been under positive selection in human populations. Which of the following is the best inference we can draw from these findings. Selected answer will be automatically saved. For keyboard navigation, press up/down arrow keys to select an answer. b C d Past selection for alleles increasing fat storage probably does not explain differences in type 2 diabetes prevalence in modern populations. Storage of excess carbohydrates probably does not contribute to type 2 diabetes. There is no genetic basis for differences between populations in type 2 diabetes. Fat storage has always been a deleterious trait for humans.arrow_forward
- what is the meaning of fitness ?what two things do you suppose govern the rate of evolution by natural selection?arrow_forwardGreen dragons are known by Knights of the Realm to be cleverer and thus more dangerous than both red and brown dragons. Molecular evolutionary alchemists working for the king have determined that a gene called FIZBAN has an average dN/dS (nonsynonymous rate/synonymous rate) ratio of 1.06 in green dragons, compared to 0.66 and 0.44 in red and brown dragons, respectively. What type of selection is this gene under in each dragon species? What type of trait might this gene contribute to? Give an evolutionary history of this gene in green dragons, including principles of population genetics in your answer.arrow_forwardIf both mutation and drift are acting simultaneously, predict how this will influence variation in that population. Will variation increase, decrease, or be maintained at some equilibrium, etc.? (note: consider how mutation and drift each affect variation within a population).arrow_forward
- Apply the VIDA table to the evolution of sickle cell disease to justify whether it is an instance of evolution by natural selection. Answer the following questions. Is there variation in this trait in the population? How exactly does it vary? Is the trait at least partly inherited? Is there selection for this trait in a particular environment? (What is the selective pressure? And how does a trait give an advantage or disadvantage in that environment?) What is the evidence that this trait makes organisms better adapted to their environment?arrow_forwardWhy might some light-skinned populations, such as the Japanese, be missing the F374 allele for lighter skin pigmentation? (Hint: Consider the various forces of evolution that may be at play.)arrow_forwardWhat are considered significant factors in maintaining the surprisinglyhigh levels of genetic variation in natural populations ?arrow_forward
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