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Allopatric and Sympatric Speciation quiz #3

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  • How do dispersal and vicariance contribute to allopatric speciation, and what are the evolutionary implications of each?
    Dispersal involves a subset of a population moving to a new habitat, leading to genetic isolation and often a founder effect due to reduced genetic diversity. Vicariance occurs when a physical barrier splits a population, resulting in two large, isolated groups. Both lead to reproductive isolation and divergence, but dispersal often involves smaller populations and adaptation to new environments, while vicariance typically affects larger populations that remain in their original habitats.
  • What is the main difference between allopatric and sympatric speciation?
    Allopatric speciation occurs when populations are geographically isolated, while sympatric speciation happens within the same geographic area.
  • How does dispersal lead to allopatric speciation?
    Dispersal occurs when a subset of a population moves to a new habitat, resulting in genetic isolation and divergence due to lack of gene flow.
  • What is vicariance, and how does it contribute to allopatric speciation?
    Vicariance is the physical splitting of a habitat by a barrier, which isolates populations and leads to genetic divergence and speciation.
  • Why is the founder effect more likely in dispersal events than in vicariance events?
    Dispersal usually involves a small group colonizing a new area, reducing genetic diversity, while vicariance typically splits larger populations that remain in their original habitats.
  • What are two main mechanisms of sympatric speciation?
    Sympatric speciation can occur through polyploidy or disruptive selection leading to reproductive isolation within the same area.
  • How does polyploidy cause reproductive isolation in sympatric speciation?
    Polyploidy results in organisms with extra sets of chromosomes, making hybrids with different chromosome numbers sterile or nonviable, thus causing reproductive isolation.
  • What is the difference between autopolyploidy and allopolyploidy?
    Autopolyploidy arises from a cell division error within a single species, while allopolyploidy results from hybridization between two species followed by a cell division error.
  • How can disruptive selection lead to sympatric speciation?
    Disruptive selection favors divergent phenotypes, but speciation only occurs if reproductive isolation mechanisms, such as mate choice or niche differentiation, are also present.
  • Why is sympatric speciation considered less common than allopatric speciation?
    Sympatric speciation is less common because it is harder to achieve reproductive isolation when populations are not geographically separated.