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Questions and Answers
What is an example of geographic isolation?
What is an example of geographic isolation?
Which of the following is NOT a type of reproductive isolation?
Which of the following is NOT a type of reproductive isolation?
What distinguishes convergent evolution from divergent evolution?
What distinguishes convergent evolution from divergent evolution?
Which statement accurately describes homologous structures?
Which statement accurately describes homologous structures?
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How does genetic variation contribute to the survival of a species?
How does genetic variation contribute to the survival of a species?
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What is one of the assumptions required for a population to be in Hardy Weinberg equilibrium?
What is one of the assumptions required for a population to be in Hardy Weinberg equilibrium?
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How does the Hardy Weinberg Principle relate to evolution?
How does the Hardy Weinberg Principle relate to evolution?
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What is the expected frequency of the Ee genotype if the recessive allele frequency is 0.55?
What is the expected frequency of the Ee genotype if the recessive allele frequency is 0.55?
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Which factor can lead to a significant alteration of a gene pool?
Which factor can lead to a significant alteration of a gene pool?
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What does genetic drift primarily involve?
What does genetic drift primarily involve?
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Which scenario best illustrates the founder effect?
Which scenario best illustrates the founder effect?
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What is a defining factor of allopatric speciation?
What is a defining factor of allopatric speciation?
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What typically follows a population bottleneck event?
What typically follows a population bottleneck event?
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Study Notes
Hardy-Weinberg Principle
- Specifies conditions where allele and genotype frequencies in a population remain constant over generations (no evolution)
- Five conditions for no evolution: No mutations, No gene flow, Random mating, No genetic drift, No natural selection
- Allele frequencies can be calculated if the frequencies of genotypes are known.
- The Hardy-Weinberg principle can be used to determine if a population is evolving.
- If allele frequencies change, evolution is occurring.
Hardy-Weinberg Example
- In a population, 6 out of 20 individuals have attached earlobes (ee)
- Frequency of the ee genotype: 6/20 = 0.3
- Frequency of EE genotype: 0.45^2= 0.2025 ~0.2
- Frequency of Ee genotype: 2*(0.45)*(0.55) = 0.495
- Frequency of unattached earlobes: 1 - 0.3=0.7
- Frequency of recessive allele (e): √0.3 = 0.55
- Frequency of dominant allele (E): 1 - 0.55 =0.45
Altering a Gene Pool
- Natural selection
- Genetic drift (Bottleneck effect, Founder effect)
- Gene flow (immigration/emigration)
- Mutations
- Non-random mating
Genetic Drift
- Random fluctuations in allele frequencies, especially pronounced in small populations
- Bottleneck effect: A drastic reduction in population size due to a sudden event (natural disaster, hunting). The surviving population may have a different allele frequency than the original population
- Founder effect: A small group from a larger population colonizes a new area. The new population has a different allele frequency from the original.
Speciation
- Allopatric: Geographic isolation leads to speciation. A population is separated by a geographic barrier (mountain range, river), causing divergence.
- Sympatric: Speciation occurs within a population without geographic isolation through changes in niche, or mating behaviors.
Geographic Isolation
- A physical barrier prevents gene flow between populations, driving divergence.
- Examples: Mountains, canyons, glaciers, rising sea levels.
Reproductive Isolation
- Prevents interbreeding between species, maintaining separate gene pools.
- Four ways reproductive isolation occurs: Geographic isolation, niche differentiation, behavioral isolation, and altered physiology
Punctuated Equilibrium vs. Gradualism
- Punctuated equilibrium: Evolution occurs in bursts of rapid change followed by long periods of little or no change.
- Gradualism: Evolution occurs in slow, steady changes over long periods of time
Genetic Variation
- Essential for the survival of a species and for evolution to occur.
- Genetic variation allows organisms in a population to respond to environmental changes, with variations in traits.
Analogous vs. Homologous
- Analogous structures: Structures in different species that are similar in function but not in evolutionary origin (e.g., wings of birds and insects).
- Homologous structures: Structures that have similar evolutionary origins and structure but may have different functions in different species (e.g., forelimbs of humans, cats, and bats).
Convergent vs. Divergent Evolution
- Convergent: Different species evolve similar traits due to similar environmental pressures (e.g., wings in birds and bats)
- Divergent: Species evolve different traits from a common ancestor due to different environmental conditions (e.g., the forelimbs of mammals).
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Description
Test your knowledge of the Hardy-Weinberg principle and its application in population genetics. This quiz covers conditions for no evolution, allele frequency calculations, and examples related to genotype frequencies. Challenge yourself to understand the mechanisms that influence genetic variation over generations.
