Campbell Biology: Concepts & Connections (8th Edition)
8th Edition
ISBN: 9780321885326
Author: Jane B. Reece, Martha R. Taylor, Eric J. Simon, Jean L. Dickey, Kelly A. Hogan
Publisher: PEARSON
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Chapter 13, Problem 13TYK
It seems logical that natural selection would work toward genetic uniformity; the genotypes that are most fit produce the most offspring, increasing the frequency of adaptive alleles and eliminating less adaptive alleles. Yet there remains a great deal of
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Recall that the Hardy-Weinberg model makes the following assumptions:
No mutations
Extremely large population
No gene flow
No selection
You score flower colour in a very large natural population where flower colour is a co-dominant trait where white and red are homozygotes (CWCW and CRCR) and pink are heterozygotes (CWCR). Taking your observed phenotypes and genotypes, you apply the Hardy-Weinberg principle and find an excess of homozygous individuals (that is, individuals with either white or red flowers).
Give two plausible explanations for this excess of homozygotes in the natural population.
The Hardy–Weinberg principle states that allele and genotype frequencies remain constant from one generation to the next, as long as specific conditions are met.Choose Yes or No for the conditions that must be met from the provided statements below.
Mutations are exponentially occurring.
All members of the population breed.
Everyone produces the same number of offspring.
The population is infinitely large.
There is no migration in or out of the population.
No net mutations are occurring.
Natural selection of beneficial traits is occurring.
Natural selection is not occurring.
All mating is completely random.
Offspring are able to migrate out of the population.
When selection favors homozygotes over heterozygotes it is likely that...
Incorrect answer -
both alleles will be maintained in the population at frequencies different from those predicted by Hardy-Weinberg principles.
Correct Answer -
genetic diversity will decrease as one of the alleles will become fixed within the population.
Question:
In detail, please explain why the correct answer is correct and also please explain in detail, why the incorrect answer is not correct.
Chapter 13 Solutions
Campbell Biology: Concepts & Connections (8th Edition)
Ch. 13 - Summarize the key points of Darwins theory of...Ch. 13 - Complete this concept map describing potential...Ch. 13 - Which of the following did not influence Darwin as...Ch. 13 - Natural selection is sometimes described as...Ch. 13 - In an area of erratic rainfall, a biologist found...Ch. 13 - If an allele is recessive and lethal in...Ch. 13 - In a population with two alleles, B and b, the...Ch. 13 - Within a few weeks of treatment with the drug 3TC,...Ch. 13 - Prob. 9TYKCh. 13 - Write a paragraph briefly describing the kinds of...
Ch. 13 - In the early 1800s, French naturalist Jean...Ch. 13 - Sickle-cell disease is caused by a recessive...Ch. 13 - It seems logical that natural selection would work...Ch. 13 - SCIENTIFIC THINKING Cetaceans are fully aquatic...Ch. 13 - A population of snails is preyed on by birds that...Ch. 13 - Advocates of scientific creationism and...
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- An allele A is present in a population at a frequency of 0.29, and there is only one other allele at the same locus. Fitness is associated with variation at the locus carrying the A allele such that there is a selection coefficient s equal to 0.03. What would you expect the frequency of the A allele to be after one generation of natural selection. Compute your result up to four decimal places.arrow_forwardWhich of the following comparisons between natural and sexual selection between is FALSE? O Variation underlying traits must have a genetic basis and be heritable under both natural and sexual selection. Under sexual selection, fitness is defined in terms of offspring number, whereas under natural selection offspring number and survuval influence fitness. Both natural and sexual selection require variation in traits that affect fitness. Under natural selection, fitness is compared across all individuals within a population, whereas for sexual selection comparisons of fitness are only relevant among individuals within a given sex (i.e., males only or females only).arrow_forwardIf gene A/a is not in Hardy-Weinberg equilibrium due to natural selection such that individuals with the genotype AA have a fitness value of 1.0, heterozygotes have only slightly reduced fitness at 0.9, and individuals with the genotype aa have a fitness value of 0.6, what kind of change in allele frequency would you expect to see over time assuming you start with equal frequencies of the 2 alleles?arrow_forward
- Which of the following is likely to be observed if there has been a strong positive selection on a particular genetic locus within a population? Group of answer choices There will be a lot of variation in DNA surrounding the genetic locus in question within the population. There will very little variation in DNA surrounding the genetic locus in question within the population. You will see very low frequencies of the genetic locus in questionarrow_forwardA population of birds has two alleles encoding for three different phenotypes: long wings, wingsss, and mid-length wings. . The initial frequency of the Sallele was 0.63 and the sallele was 0.37. However 97% of the long-winged birds survived to reproductive age56% of mid-length birds survived to reproductive age, and only 10% of short-winged birds survived to reproductive age. You are going to determine if natural selection has an effect on the allele frequency What is the expected frequency of the Sallele in the next generation when you incorporate the survival rate? Please use as many decimals points as possible when doing your calculations. Please answer using four decimal points. (Your population can be 100 or 1000 individuals or any numberreally up to you.I work with 1000but that won't change the results because we are talking about frequency.)arrow_forwardWhat are the similarities and differences between natural selection and selective breeding?arrow_forward
- Much attention is given to the existence of genetic variation in populations.Why do evolutionary biologists give so much attention to this? Explain mechanisms thatgenerate genetic variation in populations. Explain mechanisms that maintain geneticvariation in populations. Provide examples and dataarrow_forwardThree genotypes occur in a population of birds: DD, Dd, and dd. D is the dominant allele, and encodes the dark - coloured birds; light - coloured mice have the genotype dd. There are initially 60 DD, 60 Dd, and 60 dd birds in a population, and the selection coefficient against light - coloured birds is 0.4. If 80% of each dark - coloured genotype survives (48 DD and 48 Dd), how many light-coloured birds would you expect to see in the next generation?arrow_forwardWhich of the following statements about genetic fitness and/or selection is false? Group of answer choices Individuals with low fitness have greater selection coefficients Fitness involves both relative viability and reproductive success Individuals with high fitness have greater selection coefficients Selection against recessive alleles tends to be slower overall than dominant alleles because of the survival in heterozygotesarrow_forward
- if gametes from a gene pool combine randomly to make only a small number of zygotes, the allele frequencies among the zygotes may be quite different than they are in the gene pool, why? (choose one from below) 1. the effects of natural selection are more pronounced in small populations 2.changed in allele frequencies over many generations are inevitable with sexual reproduction 3. alleles combine more randomly with a small number of zygotes 4. the effects of sampling error are more pronounced with smaller samplesarrow_forwardWhich of these scenarios is an example of disruptive selection? Darker colored morphs in a butterfly population are more adaptive than lighter colored morphs, and lighter colored morphs are eliminated from the population. Intermediate gray morphs of a butterfly population are maintained, and the extreme dark and light color morphs have been eliminated. The dark and light color morphs of a butterfly population are maintained, and the intermediate gray morph has been eliminated from the population. A new, unique color form arises from a mutation in a population of butterflies.arrow_forwardAt least one of the discoverers of this genetic equilibrium (Hardy) developed this HW equation to show that the dominant allele will not always take over the population just because that allele has a dominant effect on the phenotype. What additional factor would have to be present to cause a dominant allele to increase to a frequency of 100%? Why is this factor essential for the dominant allele to "take over" the gene pool?arrow_forward
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