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The Biological Species Concept quiz #3

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  • What are prezygotic barriers, and what are the five main types that prevent gene flow between species?
    Prezygotic barriers are reproductive barriers that occur before fertilization, preventing mating or fertilization between species. The five main types are habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, and gametic isolation.
  • Why is reproductive isolation essential for speciation according to the biological species concept?
    Reproductive isolation is essential for speciation because it prevents gene flow between populations, allowing them to evolve independently and become distinct species.
  • How does the biological species concept define a species?
    The biological species concept defines a species as a group of organisms that are reproductively isolated from other such groups, meaning they do not exchange genes in nature.
  • What is reproductive isolation and why is it important in the biological species concept?
    Reproductive isolation is the existence of barriers that prevent gene flow between populations, and it is essential because it allows populations to evolve independently and become distinct species.
  • What are the two main categories of reproductive barriers, and how are they distinguished?
    The two main categories are prezygotic barriers, which occur before fertilization, and postzygotic barriers, which occur after fertilization.
  • List and briefly describe the five main types of prezygotic barriers.
    The five main types are habitat isolation (different locations), temporal isolation (different mating times), behavioral isolation (different mating behaviors), mechanical isolation (anatomical incompatibility), and gametic isolation (incompatible sperm and egg).
  • What is an example of mechanical isolation and how does it prevent gene flow?
    An example is different species of damselflies with differently shaped reproductive structures, which prevents them from mating successfully.
  • Describe the three main types of postzygotic barriers.
    The three main types are reduced hybrid viability (hybrids are less likely to survive), hybrid sterility (hybrids are sterile), and hybrid breakdown (later generations of hybrids are weak or infertile).
  • Why can a horse and a donkey produce a mule, but are still considered different species?
    Although a horse and a donkey can mate to produce a mule, the mule is sterile and cannot reproduce, which blocks gene flow and maintains reproductive isolation.
  • What is hybrid breakdown and how does it contribute to reproductive isolation?
    Hybrid breakdown occurs when the first-generation hybrid is healthy and fertile, but subsequent generations are weak or infertile, preventing long-term gene flow between species.