Podcast
Questions and Answers
What is meant by genetic drift in the context of demes?
What is meant by genetic drift in the context of demes?
- It refers to the intentional selection of specific alleles by humans.
- It is the exchange of genetic material between different species.
- It is the random change in allele frequency due to sampling error. (correct)
- It describes the uniform distribution of alleles in a population.
How did the Cit+ strain evolve to utilize citrate in aerobic conditions?
How did the Cit+ strain evolve to utilize citrate in aerobic conditions?
- By duplicating the gene encoding citrate transporter expression. (correct)
- By randomly integrating citrate genes from the environment.
- By acquiring a new gene from a different species.
- Through a mutation that permanently activated aeration genes.
What is gene flow?
What is gene flow?
- The genetic variation caused by mutations in a population.
- The evolution of traits due to environmental changes.
- The natural selection acting on a population.
- The movement of alleles between previously separate populations. (correct)
What occurred in the Long Term Evolution Experiment (LTEE) studied by Richard Lenski?
What occurred in the Long Term Evolution Experiment (LTEE) studied by Richard Lenski?
What advantage did the Cit+ strains have in the LTEE?
What advantage did the Cit+ strains have in the LTEE?
What was a significant finding about DNA repair rates in the LTEE?
What was a significant finding about DNA repair rates in the LTEE?
Why does selective and reproductive isolation affect genetic variation?
Why does selective and reproductive isolation affect genetic variation?
What happens to alleles during the sampling process described in genetic studies?
What happens to alleles during the sampling process described in genetic studies?
What was the main effect of the drought on the Geospiza Fortis population?
What was the main effect of the drought on the Geospiza Fortis population?
Which of the following best describes genetic drift?
Which of the following best describes genetic drift?
What is meant by the phrase 'survival of the fittest' in the context of natural selection?
What is meant by the phrase 'survival of the fittest' in the context of natural selection?
Which postulate indicates that certain traits are passed from one generation to the next?
Which postulate indicates that certain traits are passed from one generation to the next?
Which statement about mutations is accurate?
Which statement about mutations is accurate?
Which of the following mechanisms is NOT a main mechanism of evolution?
Which of the following mechanisms is NOT a main mechanism of evolution?
In the study of the medium ground finch, what was observed about the relationship between midbeak depth and offspring?
In the study of the medium ground finch, what was observed about the relationship between midbeak depth and offspring?
How do mutations function in the context of evolution?
How do mutations function in the context of evolution?
What was the primary observation made by Rosemary and Grant (1976-1978) on Geospiza fortis finches?
What was the primary observation made by Rosemary and Grant (1976-1978) on Geospiza fortis finches?
What is a key concept of Darwin’s first postulate?
What is a key concept of Darwin’s first postulate?
What happens when a mutation has no selective value?
What happens when a mutation has no selective value?
What is the outcome of gene flow between populations?
What is the outcome of gene flow between populations?
What is an example of instant speciation in tree frogs?
What is an example of instant speciation in tree frogs?
How does genetic drift affect allele frequencies?
How does genetic drift affect allele frequencies?
What defines a eukaryotic species?
What defines a eukaryotic species?
What happens to recessive advantageous alleles in a population?
What happens to recessive advantageous alleles in a population?
What is the primary driver of speciation?
What is the primary driver of speciation?
How can gene flow reduce genetic variation between populations?
How can gene flow reduce genetic variation between populations?
What characteristic allowed Cit+ strains of E. coli in Lenski’s experiment to use citrate in aerobic conditions?
What characteristic allowed Cit+ strains of E. coli in Lenski’s experiment to use citrate in aerobic conditions?
What is the outcome of selective and reproductive isolation between populations?
What is the outcome of selective and reproductive isolation between populations?
Which factor is a direct result of chromosomal duplication in tree frogs?
Which factor is a direct result of chromosomal duplication in tree frogs?
What best describes natural selection?
What best describes natural selection?
How do advantageous recessive alleles spread in a population?
How do advantageous recessive alleles spread in a population?
What does "fitness" mean in evolutionary terms?
What does "fitness" mean in evolutionary terms?
What does reproductive isolation achieve in eukaryotic species?
What does reproductive isolation achieve in eukaryotic species?
Which mechanism does NOT directly lead to speciation?
Which mechanism does NOT directly lead to speciation?
Why are mutations described as the "raw materials" of evolution?
Why are mutations described as the "raw materials" of evolution?
Flashcards
Genetic Drift
Genetic Drift
A change in allele frequency in a population due to chance events.
Population
Population
A group of organisms of the same species that live in a defined area and interbreed.
Gene Flow
Gene Flow
The movement of alleles (genes) between populations.
Natural Selection
Natural Selection
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Speciation
Speciation
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Biogeography
Biogeography
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Evolution
Evolution
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Adaptation
Adaptation
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Variation within a species
Variation within a species
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Heritability of traits
Heritability of traits
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Survival of the fittest
Survival of the fittest
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Mutations
Mutations
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Study Notes
Evolution and Speciation
- Three main mechanisms drive evolution: natural selection, genetic drift, and gene flow.
Darwin's Postulates
- Rosemary and Grant (1976-78) studied the medium ground finch (Geospiza Fortis) observing beak shape variation.
- Their data shows a correlation between midparent beak depth and offspring beak depth.
- In 1978, despite a significant population decrease due to drought, the relationship between parent and offspring beak depth remained consistent.
1976 Drought Impact
- A 1976 drought reduced seed availability, favoring larger, harder seeds.
- This led to a decrease in the finch population and an increase in average beak depth.
1978 Finch Population Recovery
- In 1978, only 90 finches survived the drought.
- The population mean beak depth increased, indicating selection for birds with larger, stronger beaks.
- This natural selection was driven by the change in available food sources and the relationship between birds and their beaks.
Darwin's Postulates, Explained
- Postulate 1: Individuals within a species are variable. Traits, such as beak shapes—hard, shallow, or small—vary.
- Postulate 2: Some of this variation is heritable; offspring inherit traits from their parents.
- Postulate 3: Reproduction is not random. Certain traits allow survival and reproduction better under specific environmental conditions.
Genetic Drift
- Genetic drift occurs, even without natural selection, because not all sperm and eggs contribute to the next generation. This creates a sampling error.
- A sample of sperm or eggs may over-represent one allele (fixed) or under-represent another in the next generation.
Natural Selection and Allele Fixation
- Dominant advantageous alleles are quickly noticeable in both heterozygotes and homozygotes, rapidly increasing in frequency.
- Recessive advantageous alleles take longer to become noticeable because they only appear in homozygotes and take time to reach the appropriate frequencies.
Long-Term Evolution Experiment (LTEE)
- Richard Lenski's experiment with E. coli illustrated evolution and adaptation.
- Starting with 12 identical E. coli populations, researchers observed increased growth rates and DNA repair mechanisms.
- In some populations, the E.coli developed the capacity to utilize citrate under aerobic conditions, a phenotypic shift not previously possible.
Gene Flow
- Gene flow is the movement of alleles between populations.
- This can occur via migration of adults or gametes.
- Factors like genetic drift, gene flow, and selective isolation influence biodiversity and speciation.
Speciation
- A species is a group of organisms capable of interbreeding and producing fertile offspring.
- Eukaryotic species are reproductively isolated, preventing offspring with other species.
- Factors like genetic drift, gene flow, and selective isolation can lead to diversification and speciation.
- In the specific case of tree frogs, chromosomal duplication during meiosis can trigger instant speciation.
Citrate Metabolism
- E. coli in aerobic conditions do not typically utilize citrate as a carbon source.
- Certain populations developed a duplicate citrate transporter gene, allowing them to utilize citrate and leading to higher fitness rates in these populations.
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