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What did Charles Darwin describe as the 'mystery of mysteries'?
What did Charles Darwin describe as the 'mystery of mysteries'?
What is necessary to study the process of speciation?
What is necessary to study the process of speciation?
What are species described as, according to current understanding?
What are species described as, according to current understanding?
What is indicated by the term 'reproductive isolation' (RI)?
What is indicated by the term 'reproductive isolation' (RI)?
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How does the idea of gaps among species evolve according to Darwin's contributions?
How does the idea of gaps among species evolve according to Darwin's contributions?
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Which of the following factors is crucial in the study of speciation?
Which of the following factors is crucial in the study of speciation?
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What is the relationship between speciation and gene flow?
What is the relationship between speciation and gene flow?
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What type of speciation is primarily examined in the current understanding of evolutionary processes?
What type of speciation is primarily examined in the current understanding of evolutionary processes?
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What does the presence of 'gaps' between diverged taxa signify?
What does the presence of 'gaps' between diverged taxa signify?
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Why is it problematic to draw a hard line when defining species?
Why is it problematic to draw a hard line when defining species?
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What is a key aspect to understand in speciation?
What is a key aspect to understand in speciation?
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What challenges does geographic variation within taxa create?
What challenges does geographic variation within taxa create?
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What role does gene flow play in defining species?
What role does gene flow play in defining species?
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What is the main pursuit in understanding speciation?
What is the main pursuit in understanding speciation?
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What does ongoing polymorphism within populations suggest?
What does ongoing polymorphism within populations suggest?
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How might named species be perceived due to gene flow?
How might named species be perceived due to gene flow?
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What is prezygotic reproductive isolation (RI)?
What is prezygotic reproductive isolation (RI)?
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Which of the following describes noncompetitive gametic isolation?
Which of the following describes noncompetitive gametic isolation?
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How can prezygotic RI affect speciation?
How can prezygotic RI affect speciation?
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What occurs during gametic isolation?
What occurs during gametic isolation?
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What type of postzygotic RI is linked to external factors affecting hybrids?
What type of postzygotic RI is linked to external factors affecting hybrids?
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Which statement is true about intrinsic postzygotic isolation?
Which statement is true about intrinsic postzygotic isolation?
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What role do pollinators play in prezygotic RI?
What role do pollinators play in prezygotic RI?
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What defines postzygotic reproductive isolation?
What defines postzygotic reproductive isolation?
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What is the main factor that led to the formation of the apple host race of the fly?
What is the main factor that led to the formation of the apple host race of the fly?
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Which mode of speciation is characterized by populations evolving in overlapping geographic areas?
Which mode of speciation is characterized by populations evolving in overlapping geographic areas?
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What was proposed by Bush regarding the R.pomonella sibling species group?
What was proposed by Bush regarding the R.pomonella sibling species group?
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What are the potential consequences of traits adapting individuals to one habitat when they migrate to another?
What are the potential consequences of traits adapting individuals to one habitat when they migrate to another?
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How may the geographic distribution of populations change during speciation?
How may the geographic distribution of populations change during speciation?
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What is the term used for speciation that is influenced by hybrid ancestry and reduced fitness?
What is the term used for speciation that is influenced by hybrid ancestry and reduced fitness?
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What is the significance of opsin genes in the context of parapatric divergence?
What is the significance of opsin genes in the context of parapatric divergence?
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Why is it difficult for intrinsic reproductive isolation (RI) to evolve in sympatric populations?
Why is it difficult for intrinsic reproductive isolation (RI) to evolve in sympatric populations?
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What does RI stand for in the context of speciation?
What does RI stand for in the context of speciation?
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What does the strict categorization of speciation modes not always reflect?
What does the strict categorization of speciation modes not always reflect?
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Where is the evolution of D-M incompatibilities more likely to occur?
Where is the evolution of D-M incompatibilities more likely to occur?
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What type of external factors can contribute to divergent ecological selection pressures?
What type of external factors can contribute to divergent ecological selection pressures?
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In what type of divergence do populations remain in contact but adapt to different ecological niches?
In what type of divergence do populations remain in contact but adapt to different ecological niches?
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What complicates the identification of candidate loci in speciation studies?
What complicates the identification of candidate loci in speciation studies?
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Which statement best describes an effect of divergent ecological selection on hybrid populations?
Which statement best describes an effect of divergent ecological selection on hybrid populations?
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What must be established to discern the evolutionary chronology of reproductive isolation?
What must be established to discern the evolutionary chronology of reproductive isolation?
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What characterizes parapatric speciation?
What characterizes parapatric speciation?
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How does the rate of gene flow in parapatric speciation compare to other modes of speciation?
How does the rate of gene flow in parapatric speciation compare to other modes of speciation?
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What presents a challenge in verifying parapatric speciation?
What presents a challenge in verifying parapatric speciation?
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What is indicated by the term 'transporter' speciation?
What is indicated by the term 'transporter' speciation?
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Which of the following best describes the process involved in the divergence of taxa in parapatric speciation?
Which of the following best describes the process involved in the divergence of taxa in parapatric speciation?
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What is a key aspect of reproductive isolation (RI) models relevant to parapatric speciation?
What is a key aspect of reproductive isolation (RI) models relevant to parapatric speciation?
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How do historical patterns of species ranges inform our understanding of speciation?
How do historical patterns of species ranges inform our understanding of speciation?
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Which organism examples are related to the concept of transporter speciation?
Which organism examples are related to the concept of transporter speciation?
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Study Notes
Modes and Mechanisms of Speciation
- Speciation is the evolutionary process where a group of inbreeding populations diverges into two or more reproductively isolated groups
- There are about 8.7 million eukaryotic species on Earth
- Species are fundamental units of biodiversity
- Darwin described the formation of new species as the "mystery of mysteries"
- Reproductive isolation is the barrier of reproduction and gene exchange between different incipient species; occurring before or after zygote formation
- Prezygotic isolation occurs before zygote formation (before fertilization)
- Postzygotic isolation occurs after zygote formation (after fertilization)
Classifying Barriers to Gene Flow
-
Prezygotic isolation: Barriers to gene flow that occur before the formation of a zygote
- Temporal isolation: Differences in timing of breeding seasons or times of activity
- Mating isolation: Differences in mating signals (e.g., calls, dances, pheromones) or mating behaviors that prevent interbreeding
- Habitat isolation: Differences in the habitats where species live (e.g., different ecological niches)
- Behavioral isolation: Differences in courtship rituals or other behaviors that prevent interbreeding
- Pollination in plants: Differences in flower structure, pollination mechanisms or timing
- Mechanical isolation: Differences in reproductive structures prevent successful mating
- Gametic isolation: Differences in gamete structures or chemical signals that prevent successful fertilization
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Postzygotic isolation: Barriers to gene flow that occur after the formation of a zygote
- Intrinsic postzygotic isolation occurs internally and is independent of the environment
- Genomic incompatibilities between species result in hybrid inviability (unsuccessful development) or sterility (unsuccessful reproduction)
- Extrinsic postzygotic isolation are influenced by the environment; meaning hybrids have lower fitness in the wild
- Intrinsic postzygotic isolation occurs internally and is independent of the environment
Modes of Speciation
- Allopatric speciation: Populations are geographically separated, preventing gene flow
- Peripatric speciation: Occurs when a small population breaks off from the main population and forms new specie in a new habitat.
- Sympatric speciation: Populations live in the same geographic area, but still diverge
- Parapatric speciation: Populations diverge while in contact along a geographic boundary.
Evolutionary Mechanisms Causing Population Divergence
- Natural selection: Selection pressures in different environments cause populations to evolve different traits.
- Sexual selection: Individuals with traits that are attractive to the opposite sex are more likely to reproduce, leading to divergence in mating preferences.
- Hybrid, Polyploid, and Homoploid Speciation: Processes that involve hybridization between species
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BIOL 424 Test #3