Reproductive isolating mechanisms fall into two main categories:
isolating mechanisms and
isolating mechanisms.

Question

Reproductive isolating mechanisms fall into two main categories: 
 isolating mechanisms and 
 isolating mechanisms.

BlackTom AI · Accepted Answer

The question presents a statement about reproductive isolating mechanisms and asks you to fill in two blanks with the appropriate categories.

For the first blank (空白1): The correct term is prezygotic. Prezygotic isolating mechanisms prevent mating or fertilization from occurring before a zygote is formed. They include barriers such as temporal isolation (different breeding times), habitat isolation (different habitats), behavioral isolation (different mating rituals), mechanical isolation (incompatibilities in reproductive structures), and gametic isolation (sperm and egg incompatibility). These barriers stop gene flow at or before the formation of a zygote, hence they are categorized as prezygotic.

For the second blank (空白2): The correct term is postzygotic. Postzygotic isolating mechanisms act after fertilization has occurred, reducing the viability or reproductive success of hybrids. Examples include reduced hybrid viability (hybrids fail to develop or survive), reduced hybrid fertility (hybrids are sterile, such as mules), and hybrid breakdown (first-generation hybrids are viable and fertile, but subsequent generations are sterile or inviable). These mechanisms prevent gene flow after a zygote has been formed, which is why they are classified as postzygotic.

In summary, the two blanks should be filled with prezygotic for the first and postzygotic for the second, aligning with the classic two-category framework of reproductive isolation that distinguishes barriers before versus after fertilization and zygote formation.

Reproductive isolating mechanisms fall into two main categories: isolating mechanisms and isolating mechanisms.

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Crosses between female horses and male donkeys produce mules. Gene flow between the gene pools of horses and donkeys is prevented by I. hybrid sterility. II. a pre-zygotic isolating mechanism. III. a post-zygotic isolating mechanism.

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Two species of a plant cannot interbreed, because their flowers differ in size and shape and require pollination by different species of bee. This is a/an ___ isolating mechanism.

Two species of a plant cannot interbreed, because their flowers differ in size and shape and require pollination by different species of bee. This is a/an ___ reproductive barrier.

Prezygotic isolating mechanisms are typically more common than postzygotic mechanisms. One explanation is that prezygotic mechanisms are less costly in terms of and , and so natural selection has favored them.

Although they both prevent successful interbreeding among members of different species, isolating mechanisms prevent the formation of a zygote, whereas isolating mechanisms prevent successful reproduction of a hybrid after successful fertilization has occurred.

In some cases, species are defined by the ability of members to interbreed or the extent of isolation.

Mechanisms that prevent genetic exchange between members of different species and often play a role in plant and animal speciation are termed reproductive mechanisms.

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