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.

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Here is the question and the answer choices to consider: 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.

Option a: prezygotic. This option fits because the barrier prevents fertilization from occurring in the first place, due to mechanical differences in flowers and reliance on different pollinators. Since mating/fertilization does not occur, it is a prezygotic isolating mechanism.

Option b: genetic. Genetic isolation typically refers to differences in genes that prevent successful reproduction after mating, such as chromosomal incompatibilities or hybrid sterility. Here, the barrier acts before any mating or fertilization, so this label is inappropriate.

Option c: physiological. Physiological isolation would involve incompatibilities at the physiological level after mating (for example, gamete incompatibility inside the reproductive tract). In this plant scenario, there is no post-mertilization physiological barrier described; the problem is functional before fertilization.

Option d: biological. This term is too broad and vague for a specific isolating mechanism. While it could loosely refer to reproductive barriers, it does not name the precise prezygotic mechanism at work.

Option e: postzygotic. Postzygotic isolation occurs after fertilization, such as reduced hybrid viability or sterility. Since the species cannot interbreed due to pollination incompatibility, this option does not apply.

In summary, the scenario describes a barrier that prevents fertilization from occurring due to mechanical and pollinator differences, which is characteristic of prezygotic isolation. The other options describe barriers that act after mating or are too vague to capture the situation.

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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.

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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 ___ 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.

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

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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