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Stack #4713546
| Question | Answer |
|---|---|
| What is evolution? | Descent with modification; change in the genetic composition of a population from generation to generation. |
| What does descent with modification mean? | Species accumulate differences from their ancestors as they adapt to different environments over time. |
| What three mechanisms shown in the slides can cause the evolution of populations? | Natural selection genetic drift and gene flow. |
| What is natural selection? | A process in which individuals with certain inherited traits survive and reproduce at higher rates than others because of those traits. |
| What is genetic drift? | A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. |
| What is gene flow? | The transfer of alleles from one population to another resulting from the movement of fertile individuals or their gametes. |
| What does each mechanism of evolution depend on? | Genotypic variation. |
| How can gene variability be quantified? | As the percentage of loci that are heterozygous. |
| What does heterozygous mean? | Having two different alleles. |
| What is a phenotype? | The observable physical and physiological traits of an organism which are determined by its genetic makeup. |
| What is a genotype? | The genetic makeup or set of alleles of an organism. |
| Can a phenotype be influenced by a single gene? | Yes some phenotypes are influenced by a single gene. |
| Can a phenotype be influenced by multiple genes? | Yes many phenotypes are influenced by multiple genes. |
| Are all phenotypes influenced by genes? | No some phenotypes can be influenced by environmental conditions. |
| What is phenotypic plasticity? | The ability of an individual to produce different phenotypes when exposed to different environmental conditions. |
| What is one major source of genetic variation? | Mutations. |
| What is a mutation? | A change in the nucleotide sequence of an organism's DNA. |
| What can cause mutations? | Errors in DNA replication exposure to UV light other forms of radiation or chemicals. |
| What are the possible outcomes of mutations? | Beneficial neutral or harmful. |
| In what organisms do mutations accumulate more quickly? | Organisms with short generation times such as prokaryotes and viruses. |
| Why can organisms with short generation times accumulate mutations more quickly? | They go through more generations in a given amount of time. |
| How does sexual reproduction introduce genetic variation? | It produces unique combinations of alleles received from parents. |
| What three processes of sexual reproduction introduce genetic variation? | Crossing over independent assortment and fertilization. |
| What is crossing over important for in evolution? | It creates new combinations of alleles and contributes to genetic variation. |
| What is the effect of genetic drift on allele frequencies? | It causes random changes in allele frequencies. |
| Are changes caused by genetic drift related to an allele's effect on reproductive success? | No. |
| In what population size does genetic drift have a greater impact? | Small populations. |
| What can genetic drift do to alleles in a population? | It can increase the chance that certain alleles are lost from the gene pool. |
| What effect does genetic drift have on genetic variation? | It reduces genetic variation. |
| Can genetic drift cause an allele to reach a frequency of 100 percent? | Yes. |
| What does it mean when an allele reaches a frequency of 100 percent? | That allele is fixed in the population. |
| Can genetic drift cause harmful alleles to become fixed? | Yes. |
| What is the founder effect? | Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool is not representative of the original population. |
| Why can the founder population differ genetically from the original population? | The few individuals that form it may carry allele frequencies that do not represent the original population. |
| What happened to Pingelap in Micronesia in 1775? | It was hit by a devastating typhoon. |
| How many individuals survived the storm and famine on Pingelap according to the slides? | Only 20 individuals. |
| What was the rate of achromatism colorblindness on Pingelap about 200 years later? | About 1 in 20. |
| How rare is achromatism normally according to the slides? | About 1 in 30000. |
| What evolutionary mechanism can explain unusually high frequencies of an allele after a population is reduced to very few survivors? | Genetic drift. |
| What is the bottleneck effect? | Genetic drift that occurs when the size of a population is reduced by events such as a natural disaster or human actions. |
| What happens to the genetic composition of a population after a bottleneck? | The surviving population is typically no longer genetically representative of the original population. |
| What is the main difference between the founder effect and bottleneck effect? | The founder effect occurs when a few individuals establish a new population while the bottleneck effect occurs when an existing population is drastically reduced. |
| Why is genetic drift especially significant in small populations? | Chance events have a larger effect on allele frequencies. |
| Can genetic drift lead to loss of genetic variation within a population? | Yes. |
| Does genetic drift change allele frequencies randomly or according to fitness? | Randomly. |
| What happens during gene flow? | Alleles move from one population into another through fertile individuals or their gametes. |
| What is another term associated with movement of individuals that causes gene flow? | Migration. |
| What effect can gene flow have on the population that individuals migrate into? | It can introduce alleles into that population and increase genetic variation. |
| What is adaptive evolution? | A process in which traits that enhance survival or reproduction tend to increase in frequency over time. |
| What is relative fitness? | The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. |
| What does natural selection alter within a population? | The frequency of heritable traits. |
| What are the three types of natural selection shown in the slides? | Directional selection disruptive selection and stabilizing selection. |
| What is directional selection? | Natural selection in which individuals at one end of the phenotypic range survive or reproduce more successfully than other individuals. |
| What happens to the phenotype distribution during directional selection? | The population shifts toward one extreme of the phenotypic range. |
| If individuals with very dark fur reproduce more successfully than medium and light individuals what type of selection is occurring? | Directional selection. |
| If individuals with very light fur reproduce more successfully than medium and dark individuals what type of selection is occurring? | Directional selection. |
| What is disruptive selection? | Natural selection in which individuals on both extremes of a phenotypic range survive and reproduce more successfully than intermediate individuals. |
| What happens to intermediate phenotypes during disruptive selection? | They have lower survival or reproductive success than individuals at both extremes. |
| If both very light and very dark individuals are favored over medium-colored individuals what type of selection is occurring? | Disruptive selection. |
| What is stabilizing selection? | Natural selection in which intermediate phenotypes survive or reproduce more successfully than extreme phenotypes. |
| What happens to extreme phenotypes during stabilizing selection? | They are selected against. |
| If medium-colored individuals have greater reproductive success than both light and dark individuals what type of selection is occurring? | Stabilizing selection. |
| Which type of selection favors one extreme phenotype? | Directional selection. |
| Which type of selection favors both extreme phenotypes? | Disruptive selection. |
| Which type of selection favors intermediate phenotypes? | Stabilizing selection. |
| What is balancing selection? | Natural selection that maintains two or more phenotypic forms in a population. |
| What is heterozygote advantage? | When individuals that are heterozygous for a trait have greater fitness. |
| What can heterozygote advantage produce if the heterozygote has an intermediate phenotype? | A form of stabilizing selection. |
| Why can natural selection not create perfect organisms? | Natural selection is limited by existing variation historical constraints trade-offs and interactions among chance the environment and selection. |
| Can natural selection act on traits that do not already exist as variation in the population? | No selection can act only on existing variation. |
| How do historical constraints limit evolution? | Adaptation has to occur using existing structures or traits because selection does not invent entirely new structures from nothing. |
| What does descent with modification imply about adaptations? | Adaptations must develop through modifications of existing structures or traits. |
| Why are adaptations often compromises? | Trade-offs among traits mean that improving one function may reduce the ability to perform another. |
| What is an evolutionary trade-off? | A situation in which the ability to perform one function may reduce the ability to perform another. |
| What factors interact during evolution according to the slides? | Chance natural selection and the environment. |
| How can chance influence evolution? | Chance events can establish less fit organisms in populations such as island populations. |
| How can environmental change affect natural selection? | Changing environmental conditions and habitats alter the conditions under which natural selection acts. |
| What model is used to determine whether evolution is occurring in a population? | The Hardy-Weinberg model. |
| What is the Hardy-Weinberg model? | A null model used to test whether evolution is occurring in a population. |
| What relationship does the Hardy-Weinberg model explain? | The relationship between allele frequencies in a gene pool and the genotypes produced by that gene pool. |
| What is Hardy-Weinberg equilibrium? | The state of a population in which no evolution is occurring and allele frequencies are not changing over time. |
| What does it mean if a population deviates from Hardy-Weinberg equilibrium? | Evolution is occurring. |
| How can Hardy-Weinberg deviations help identify the cause of evolution? | You can determine which Hardy-Weinberg condition is not being met. |
| What are the five assumptions of the Hardy-Weinberg model? | No mutations random mating no selective advantage infinite population size and no gene flow. |
| Does Hardy-Weinberg equilibrium allow mutations? | No. |
| Does Hardy-Weinberg equilibrium require random mating? | Yes. |
| Can there be a selective advantage under Hardy-Weinberg equilibrium? | No. |
| What population size is assumed by the Hardy-Weinberg model? | An infinite population size. |
| Does Hardy-Weinberg equilibrium allow gene flow into the gene pool? | No. |
| What does p represent in the Hardy-Weinberg equations? | The frequency of allele 1. |
| What does q represent in the Hardy-Weinberg equations? | The frequency of allele 2. |
| What does p² represent? | The frequency of one homozygous genotype. |
| What does 2pq represent? | The frequency of the heterozygous genotype. |
| What does q² represent? | The frequency of the other homozygous genotype. |
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808kadynt