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Which of the following best describes the genetic variation of a population?
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Genetic variation in a population results from evolutionary forces that cause changes in ____.
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BIOL Chapter 20
Genes Within Populations
| Question | Answer |
|---|---|
| Which of the following best describes the genetic variation of a population? | Genetic variation refers to the fact that different individuals of a population have different alleles of genes. |
| Genetic variation in a population results from evolutionary forces that cause changes in ____. | allele frequencies |
| The process, in which advantageous traits that are heritable become more common in successive generations, is called ____. | natural selection |
| Evolution can result from any process that changes the ____ composition of a population. | genetic |
| The amount of genetic variation present in naturally occurring populations is _____. | significant |
| Different alleles of genes are found within different individuals of a population. This is known as ____. | genetic variation |
| For a population to be in Hardy-Weinberg equilibrium, _____. | there must be no migration into or out of the population |
| Which of the following is true of evolutionary forces in natural populations? | Evolutionary forces can alter allele frequencies in natural populations. |
| The number of copies of an allele in a population divided by the total number of all alleles for that gene in a population is the _____. | allele frequency |
| Darwin proposed that the mechanism of evolution is ____. | natural selection |
| Which is a correct version of the Hardy-Weinberg equation for genotype frequencies in a population in equilibrium? | p2 + 2pq + q2 = 1 |
| Changes in allele frequencies within a population may result from _____, which are changes in the nucleotide sequences of an organism's DNA. | mutations |
| Natural populations exhibit significant phenotypic and ____ variation. | genotypic |
| Regarding a particular trait in a population of painted turtles (Chrysemys picta), 14% of the turtles have the homozygous dominant genotype, 70% are heterozygous, and 16% are homozygous recessive. What is the value of q2? | 0.16 |
| Hardy-Weinberg equilibrium requires that the population size is _____ and that mating is _____. | large and random |
| You are studying a gene which has two alleles, A and a. You determine that in a population of snails, 34% of all alleles of this gene are a. This number (34%, or 0.34) represents the | allele frequency of a |
| If the frequency of allele b in a population is equal to 0.7 then the frequency with which a gamete will carry allele b, is equal to ____ if the population is in Hardy-Weinberg equilibrium. | 70% |
| For a gene with two alleles whose frequencies are p and q, the Hardy-Weinberg equation states that the genotypes that are possible for the population are p2 + 2pq + q2, which is equal to | (p + q)2 |
| Consider a gene with two alleles, one dominant, and the other recessive. If this population is in Hardy-Weinberg equilibrium with respect to this gene, what would happen to the dominant allele from generation to generation? | Its frequency will remain unchanged |
| For a gene with two alleles, A and a, with allele frequencies given by p and q respectively, identify the chance that an offspring will inherit the following combinations of alleles in a population that is in Hardy-Weinberg equilibrium. | AA=p2 Aa=2pq aa=q2 |
| What is the ultimate source of all new alleles? | mutation |
| Select the conditions that must be met for a population to be in Hardy-Weinberg equilibrium. | no new mutations occur, the population is very large, no migrations, no natural selection, and mating is random |
| The frequency of a gamete carrying a particular allele in a population is equal to which of the following? | The frequency of the allele in the population |
| Which of the following agents of evolutionary change occurs when alleles move from one population to another? | gene flow |
| Which is a correct version of the Hardy-Weinberg equation for genotype frequencies in a population in equilibrium? | p2 + 2pq + q2 = 1 |
| Self-fertilization in plants is an example of what evolutionary process? | Nonrandom mating |
| If the frequency of heterozygotes in a population of mice is 0.48 for a particular gene, what would be the frequency of heterozygotes in future generations if the population is in Hardy-Weinberg equilibrium? | 0.48 |
| When individuals in a population tend to mate with other individuals that are phenotypically similar, we are observing | assortative mating |
| New mutations are not a major factor affecting the allele frequencies in a population because | the rate at which new mutations occur is low |
| What evolutionary mechanism results in random changes in allele frequencies from one generation to the next? | genetic drift |
| What is gene flow? | The movement of alleles into or out of a population. |
| The change in allele frequencies that occur due to the colonization of a new location by a small group of individuals is called | the founder effect |
| Select all of the following that are examples of nonrandom mating. | selection of mates with similar phenotypes selection of mates with dissimilar phenotypes |
| The type of nonrandom mating in which phenotypically similar individuals mate is called | assortative |
| ______ is the ultimate source of genetic variation. | mutation |
| Select all of the following that can result from a population bottleneck. | The surviving members of the population may have different allele frequencies than the original population. The genetic diversity of the surviving population is usually lower than the genetic diversity of the original population. |
| What is genetic drift? | Random changes in the allele frequencies of a population over time |
| What is the founder effect? | Changes in allele frequencies that result from the colonization of a new location by a small group of individuals from a larger population |
| _____ selection is a type of natural selection in which competition for mates drives the evolution of certain traits. | intrasexual |
| _______ selection is a form of sexual selection based on same-sex competition usually involving males, in which the winner "gains" a mating partner. | intrasexual |
| A dramatic reduction in population size due to a natural disaster or destruction of habitat and the resulting change in the allele frequencies of the new population is called | the bottleneck effect |
| Which type of selection acts to eliminate individuals which are intermediate on a phenotypic range? | Disruptive selection |
| Sexual selection is a type of natural selection in which the evolution of certain traits is driven by which of the following types of competition? | competition for mates |
| _______ selection favors individuals at one extreme of a phenotypic range. Those individuals usually have greater reproductive success in a particular environment. | Directional |
| A sudden and permanent change in the environment can lead to a type of natural selection called ______ selection. | directional |
| Which of the following is a driving force of intersexual selection? | Female choice of males based on certain characteristics |
| Which type of selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes? | Stabilizing selection |
| The bottleneck effect occurs when allele frequencies change due to _____. | an event that drastically reduces population size |
| Birds that lay intermediate numbers of eggs have greater fitness than birds that lay either too many or too few eggs. This is an example of which type of selection? | Stabilizing |
| Beaks in African black-bellied seedcracker finches are small or large, but not intermediate in size. This is an example of _____ selection. | disruptive |
| A population of finches migrates to a small island where most of the seeds are large. On the island, birds with large beaks are more likely to survive, and over time, the mean beak size of the population increases. This is a natural selection known as | directional |
| Which of the following conditions is most likely to lead to directional selection? | A sudden, relatively permanent change in the environment |
| _____ selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes. | stabilizing |
| Which of the following is an example of stabilizing selection? | Newborn babies of intermediate weight are most likely to survive; both high and low birthweights are associated with increased infant mortality. |
| Selection against intermediate-sized beaks in African black-bellied seedcracker finches is an example of which of the following? | disruptive selection |
| Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment? | directional |
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