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Questions and Answers
Which of the following is NOT a primary mechanism that directly alters allele frequencies in a population?
Which of the following is NOT a primary mechanism that directly alters allele frequencies in a population?
What is the evolutionary consequence of natural selection?
What is the evolutionary consequence of natural selection?
In a population of birds, large beaks are favored because they can crack open tough seeds. What type of selection is this?
In a population of birds, large beaks are favored because they can crack open tough seeds. What type of selection is this?
A population of fish lives in a lake that has both dark and light-colored rocks. Fish with medium coloration are more visible to predators. Consequently, very light and very dark colored fish are more common. What type of selection is operating in this scenario?
A population of fish lives in a lake that has both dark and light-colored rocks. Fish with medium coloration are more visible to predators. Consequently, very light and very dark colored fish are more common. What type of selection is operating in this scenario?
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In a hypothetical bird population, birds with average-sized wings are better able to fly long distances and avoid predators. Birds with very small or very large wings struggle to survive. What type of selection is most likely at play?
In a hypothetical bird population, birds with average-sized wings are better able to fly long distances and avoid predators. Birds with very small or very large wings struggle to survive. What type of selection is most likely at play?
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What is genetic drift?
What is genetic drift?
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Which of the following is a potential consequence of genetic drift?
Which of the following is a potential consequence of genetic drift?
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A small group of birds colonizes a previously uninhabited island. The allele frequencies in this small group do not perfectly represent the allele frequencies of the mainland population from which they came. What is this an example of?
A small group of birds colonizes a previously uninhabited island. The allele frequencies in this small group do not perfectly represent the allele frequencies of the mainland population from which they came. What is this an example of?
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A massive flood drastically reduces the size of a rabbit population. By chance, the surviving rabbits have a higher proportion of brown fur alleles than the original population. This is an example of:
A massive flood drastically reduces the size of a rabbit population. By chance, the surviving rabbits have a higher proportion of brown fur alleles than the original population. This is an example of:
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What was the result of the bottleneck effect on the greater prairie chicken population in Illinois?
What was the result of the bottleneck effect on the greater prairie chicken population in Illinois?
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Which of the following is a direct consequence of genetic drift?
Which of the following is a direct consequence of genetic drift?
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What is the primary effect of gene flow on the genetic variation between populations?
What is the primary effect of gene flow on the genetic variation between populations?
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In the Lake Erie water snake example, why does the mainland population maintain a strong banding pattern despite unbanded snakes having better camouflage on islands?
In the Lake Erie water snake example, why does the mainland population maintain a strong banding pattern despite unbanded snakes having better camouflage on islands?
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Which of the following is a direct source of new alleles in a population?
Which of the following is a direct source of new alleles in a population?
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How can gene flow increase a population's fitness, as illustrated by the example of insecticide resistance in mosquitoes?
How can gene flow increase a population's fitness, as illustrated by the example of insecticide resistance in mosquitoes?
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While both genetic drift and gene flow can alter allele frequencies, what distinguishes natural selection from these mechanisms?
While both genetic drift and gene flow can alter allele frequencies, what distinguishes natural selection from these mechanisms?
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Why are harmful recessive alleles often maintained in a population?
Why are harmful recessive alleles often maintained in a population?
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Which of the following is a reason why natural selection cannot produce 'perfect' organisms?
Which of the following is a reason why natural selection cannot produce 'perfect' organisms?
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What is the role of crossing over in sexual reproduction?
What is the role of crossing over in sexual reproduction?
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What is a 'fixed' locus in the context of population genetics?
What is a 'fixed' locus in the context of population genetics?
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Why are adaptations often described as 'compromises' in the context of natural selection?
Why are adaptations often described as 'compromises' in the context of natural selection?
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What is the primary use of the Hardy-Weinberg equation?
What is the primary use of the Hardy-Weinberg equation?
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In what way do chance events, alongside natural selection, influence the evolutionary trajectory of organisms?
In what way do chance events, alongside natural selection, influence the evolutionary trajectory of organisms?
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If a population is in Hardy-Weinberg equilibrium, what does this imply about the allele and genotype frequencies?
If a population is in Hardy-Weinberg equilibrium, what does this imply about the allele and genotype frequencies?
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How do new combinations of existing alleles arise in sexually reproducing organisms?
How do new combinations of existing alleles arise in sexually reproducing organisms?
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Genetic variation is a prerequisite for evolution. What is the BEST definition of genetic variation?
Genetic variation is a prerequisite for evolution. What is the BEST definition of genetic variation?
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A population of butterflies displays a wide range of wing colors, determined by several different genes. What type of variation does this BEST describe?
A population of butterflies displays a wide range of wing colors, determined by several different genes. What type of variation does this BEST describe?
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Why might geographically isolated populations be more prone to genetic differences compared to populations that interbreed frequently?
Why might geographically isolated populations be more prone to genetic differences compared to populations that interbreed frequently?
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Flashcards
Genetic Variation
Genetic Variation
Differences in genes or DNA sequences among individuals.
Hardy-Weinberg Principle
Hardy-Weinberg Principle
A law used to determine if a population is evolving based on allele frequencies.
Natural Selection
Natural Selection
The mechanism that consistently causes adaptive evolution by favoring certain traits.
Allele Frequencies
Allele Frequencies
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Mutation
Mutation
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Phenotype vs. Genotype
Phenotype vs. Genotype
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Crossing Over
Crossing Over
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Gene Pool
Gene Pool
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Heterozygote Protection
Heterozygote Protection
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Hardy-Weinberg Equilibrium
Hardy-Weinberg Equilibrium
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Genetic Drift
Genetic Drift
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Loss of Genetic Variation
Loss of Genetic Variation
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Fixed Harmful Alleles
Fixed Harmful Alleles
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Gene Flow
Gene Flow
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Effect of Gene Flow on Variation
Effect of Gene Flow on Variation
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Adaptation to Local Environments
Adaptation to Local Environments
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Limitations of Natural Selection
Limitations of Natural Selection
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Adaptive Evolution
Adaptive Evolution
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Directional Selection
Directional Selection
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Disruptive Selection
Disruptive Selection
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Stabilizing Selection
Stabilizing Selection
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Founder Effect
Founder Effect
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Bottleneck Effect
Bottleneck Effect
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Greater Prairie Chicken Case Study
Greater Prairie Chicken Case Study
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Study Notes
Evolution of Populations
- Evolution occurs when allele frequencies in a population change over time.
- Genetic variation is necessary for evolution by natural selection; variation in genes or other DNA sequences among individuals.
- Gregor Mendel's work on pea plants demonstrated discrete heritable units (genes).
- Phenotype is the product of inherited genotype and environmental influences.
- Natural selection only acts on variation with a genetic component.
- Phenotypic differences determined by a single gene are often classified as either/or (e.g., purple or white pea flowers).
- Phenotypic differences determined by multiple genes show gradations (e.g., coat color in horses or height in humans).
- Genetic variation arises from mutations, gene duplication, or other processes.
- Organisms with short generation times, like bacteria, develop genetic variation rapidly.
- Sexual reproduction recombines existing alleles to create genetic variation.
- Mutations are changes in the nucleotide sequence of DNA.
- Mutations can be caused by replication errors or exposure to radiation or chemicals.
- Mutations can be harmful, silent, or beneficial.
- Harmful recessive mutations can be hidden from selection in heterozygous individuals.
- "Heterozygote protection" maintains a pool of alleles that might be beneficial if the environment changes.
- New combinations of existing alleles occur through crossing over, independent assortment, and fertilization.
The Hardy-Weinberg Principle
- The Hardy-Weinberg principle describes the expected genetic makeup of a non-evolving population at a particular locus.
- Genetic variation is necessary for evolution, but doesn't guarantee it will occur.
- For a population to evolve, one or more factors that cause evolution must be present.
Gene Pools and Allele Frequencies
- A population is a group of individuals of the same species living in the same area and interbreeding.
- Geographically isolated populations seldom exchange genetic material.
- The gene pool includes all copies of every allele at every locus in all population members.
- A locus is fixed when all individuals are homozygous for the same allele.
- Phenotypes have allele frequencies that can be calculated.
Hardy-Weinberg Equilibrium
- A non-evolving population has constant genotype and allele frequencies between generations.
- Mendelian segregation and recombination of alleles are necessary for constant frequencies.
- A population obeying Hardy-Weinberg equilibrium shows no evolutionary change.
Natural Selection, Genetic Drift, and Gene Flow
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Natural selection, genetic drift, and gene flow are three major evolutionary mechanisms that alter allele frequencies.
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Natural selection is driven by differential reproductive success. Organisms with traits better suited for their environment are more likely to reproduce, passing their beneficial traits to offspring. This causes adaptive evolution.
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Directional selection favors individuals at one extreme of a phenotypic range.
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Disruptive selection favors individuals at both extremes of a phenotypic range.
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Stabilizing selection favors intermediate variants and acts against extreme phenotypes.
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Genetic drift is a random process; chance events lead to unpredictable allele frequency changes between generations.
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The smaller the population sample, the greater the chance of random deviation from the expected result.
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Genetic drift tends to reduce genetic variation by randomly losing alleles.
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The founder effect occurs when a few individuals become isolated from a larger population, establishing a new population with different allele frequencies than the original.
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The bottleneck effect involves a drastic reduction in population size due to environmental change. This results in a gene pool that might not reflect the original population.
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Gene flow is the movement of alleles among populations through the movement of fertile individuals or gametes (e.g., pollen).
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Gene flow tends to reduce variation among populations (not within them).
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Gene flow can influence adaptation to local environments and may increase a population's fitness in specific conditions, such as insecticide resistance.
Natural Selection and Adaptive Evolution
- Only natural selection consistently increases allele frequencies that provide a reproductive advantage.
- Genetic drift and gene flow may increase or decrease the frequency of beneficial alleles in a population.
Why Natural Selection Cannot Fashion Perfect Organisms
- Natural selection acts on existing variations, not new ones.
- Evolution is inherently constrained by historical factors.
- Adaptations are often compromises.
- Variations in the environment and chance play a role.
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Description
Explore the key concepts of evolutionary biology with this quiz on the evolution of populations. Test your understanding of genetic variation, natural selection, and the contributions of Gregor Mendel. This quiz covers fundamental principles that shape biological evolution and the differences in phenotypes.
