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What are different types of genetic variations?
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What is an example of natural selection?
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Chapter 23
Chapter 23: The Evolution of Populations
| Question | Answer |
|---|---|
| What are different types of genetic variations? | Natural selection, Genetic drift, gene flow |
| What is an example of natural selection? | The more visible darker beetles have been preyed on at a higher rate, causing lighter beetles (and the alleles they carry) to become more common over time. |
| What is an example of genetic drift? | By chance alone, alleles encoding darker color have become more common over several generations. chance events that alter allele frequencies |
| What is an example of genetic drift? | The arrival of beetles with a spotted color pattern have brought new alleles into the population. (the transfer of alleles between populations |
| Consider the following mutations to the nucleotide sequence of a gene. Which of these would be a frameshift mutation? | a single nucleotide-pair insertion A frameshift mutation occurs whenever the number of nucleotide pairs that is inserted or deleted is not a multiple of three. |
| Many nucleotide variations occur within _______, noncoding segments of DNA lying between ______, the regions retained in mRNA after RNA processing . | introns, exons |
| True or False? Without genetic variation, evolution cannot occur. | True |
| Genetic variation originates when ____________, ________________, and ______________. | mutation, gene duplication, or other processes produce new alleles and new genes such as sexual reproduction |
| How do new alleles arise? What does it mean? | mutation, a change in the nucleotide sequence of an organism’s DNA. |
| What causes mutations? | Mutations can be caused by factors such as errors in DNA replication, exposure to UV light and other high-energy forms of radiation, and exposure to certain chemicals. |
| What is "point mutation"? | A change of as little as one base in a gene |
| What is neutral variation? | differences in DNA sequence that do not confer a selective advantage or disadvantage |
| True or False? In multicellular organisms, only mutations in cell lines that produce gametes can be passed to offspring. | True |
| Sexual reproduction then shuffles existing alleles and deals them at random to produce individual genotypes. What are the three mechanisms contribute to this shuffling? | crossing over, independent assortment of chromosomes, and fertilization |
| In sexually reproducing organisms what 3 processes lead to genetic variation? | Independent assortment, crossing over and random fertilization |
| The Hardy-Weinberg approach describes a population that is not evolving. What are the 5 conditions that need to be met for this to be true? | no mutations, random mating, no natural selection, extremely large population size and no gene flow |
| What are the 4 causes for evolutionary change? | genetic drift, gene flow, mutation and natural selection |
| What are the three mechanisms that alter allele frequencies directly and cause most evolutionary change? | natural selection, genetic drift, and gene flow (violations of conditions 3–5). |
| By consistently favoring some alleles over others, __________ _________ can cause adaptive evolution, in which traits that enhance survival or reproduction tend to increase in frequency over time. | natural selection |
| What is the founder effect? | When a few individuals become isolated from a larger population, this smaller group may establish a new population whose gene pool differs from the source population |
| A severe drop in population size can cause the ___________ ________, so named because the population has passed through a “bottleneck” that greatly reduces its size | bottleneck effect |
| What is gene flow? | The transfer of alleles into or out of a population due to the movement of fertile individuals or their gametes. |
| Homologous pairs of chromosomes are lined up independently of other such pairs during ___________. | metaphase I |
| Crossing over, resulting in an increase in genetic variation, occurs between _____________. | nonsister chromatids of homologous chromosomes |
| In human gamete production there is an average of _____ crossover events per chromosome pair. | 2-3 |
| Consider a population of wildflowers in which the frequency of the red allele CR is p = 0.7. What is the frequency of the white allele (CW ) in this population? | 0.3 |
| This Punnett square shows allele combinations for all genetic crosses in the wildflower population in Part A. C^R-->p=0.7 C^W--> q=0.3 C^R-->p=0.7 C^W--> q=0.3 What are the genotype frequencies in | 0.49 CRCR (red flowers), 0.42 CRCW (pink flowers), 0.09 CWCW (white flowers) |
| Consider a wildflower population with the following allele and genotype frequencies. Frequency of the CR allele: p = 0.6 Frequency of the CW allele: q = 0.4 Frequency of CRCR : 50% Frequency of CRCW : 20% Frequency of CWCW : 30% Is this population i | No, the frequency of genotype CRCW is too low. |
| Sugar glider is a marsupial (mammal with a pouch, such as kangaroos) that has skin between its legs that allows it to glide down. Similarly, the flying squirrel has skin between its legs. However, the flying squirrel is not a marsupial. Based on this info | analogy |
| Of the following anatomical structures, which is most homologous to the bones in the wings of a bird? | bones in the flippers of a whale |
| In a hypothetical environment, fishes called pike-cichlids locate their prey by sight and eat small, immature algae-eating fish. Thus, the population of algae-eaters experiences predatory pressure from pike-cichlids. Which of the following possible change | decreased day-time activity by algae-eaters |
| Continental drift (plate tectonics) has moved continents around the globe. Which of the following predictions would be most likely? | The most recently separated continents will have the most closely related species. |
| A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; however, after several years, the farmer sees more and more pigweed growing once again in the fields. Which | Triazine-resistant weeds were more likely to survive and reproduce than were non-resistant individuals. |
| Starting from the wild mustard Brassica oleracea, plant breeders have created the strains known as Brussels sprouts, broccoli, kale, and cabbage. Which of the following statements is correct with regard to the wild mustard? | There is enough heritable variation in the wild mustard to permit these different varieties. |
| DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Instead, DDT is now largely ineffective against many insects. Which of the following possible actions would have had the best chance of preventing this evolution of D | The use of DDT should have been interspersed with the use of other pesticides that have a different mode of action. |
| Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. One allele (T1) codes for an enzyme that makes the toxin, and another allele (T2) code | 0.48 |
| Which one of the following conditions would most likely cause allele frequencies to change by chance? | mutation |
| Which of the following statements about evolutionary forces is accurate? | Unlike the other evolutionary forces, natural selection is the only force that improves the match between the organism and its environment. |
| A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (A2A2), the same percent as at the beginning of the breeding program. The rest | 0.50 |
| A population of dark-eyed junco birds became established near the California coastline, many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display dur | mutations in the coastal population |
| Natural selection changes allele frequencies because some ________ survive and reproduce better than others. | individuals |
| In a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of the allele A2 is 0.3. What is the frequency of individuals that are homozygous for this allele? | 0.09 |
| In peas, a gene controls flower color such that R1 = purple and R2 = white. The purple allele is dominant to the white allele. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibriu | 0.80 |
| Point mutations in noncoding regions of DNA results in ___________. | neutral variation |
| Which of the following statements correctly describes a population in Hardy-Weinberg equilibrium? | Allele and genotype frequencies in the population will remain constant from generation to generation. |
| Natural selection leads to adaptation, but there are many organisms on earth that exhibit characteristics that are less than ideal for the environment. Which of the following statements correctly explain(s) this? | -selection can act only on existing variations. -evolution is limited by historical constraints. -adaptations are often compromises. -chance, natural selection, and the environment interact. |
| Antibiotic resistance in bacteria is an example of which of the following? | Directional selection |
| In the Hardy-Weinberg, q^2 represents ______________________. | the expected frequency of the homozygous recessive genotype |
| In the context of populations, how do we define evolution? | Evolution is a change in a population's allele frequencies over generations. |
| Which of the following would seem to be an example of neutral variation? | Human fingerprints |
| Which of the following set of conditions is required for Hardy-Weinberg eqilibrium? | Random mating, no natural selection, and a large population |
| In a population that is in Hardy-Weinberg, 64% of the individuals express the recessive phenotype for a particular gene locus. What is the expected frequency of the dominant allele in this population? | 0.2 |
| In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individuals showing the dominant trait. When the gene freq | the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up |
| A population of squirrels is preyed on by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is r | Disruptive selection |
| At what level does gene variability quantify genetic variation? | Whole-gene |
| Which statement below is true about sexual selection? | Sexual selection can result in sexual dimorphism- marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction. |
| Which of the following id the best example of gene flow? | Wind blows pollen from one population of plants to another and cross-fertilization occurs. |
| In a population that is in Hardy-Weinberg equilibrium, 64% if the individuals express the recessive phenotype for a particular gene locus. What is the expected frequency of the recessive allele in this population? | 0.8 |
| Sexual recombination includes the shuffling of chromosomes in __________________ and fertilization. | Meiosis |
| Which of the following can form entirely new alleles? | Mutation |
| If this group is in Hardy-Weinberg equilibrium, what percentage of the group is heterozygous for the sickle hemoglobin allele? | 32% |
| No to people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is _______________. | the reshuffling of alleles in sexual reproduction |
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