Identification: Classify each of the following situations as either a pre- or po

Question

Identification: Classify each of the following situations as either a pre- or postzygotic isolating mechanism (first space) and then specifically which type of pre-or postzygotic isolating mechanism (second space): In flowering plants, the pollen is often transferred from the pistil of one plant to the stigma of another by some type of animal (eg., bee, hummingbird). As a result, there are times when the pollen of one species ends up on the stigma of another. But for fertilization to occur, a pollen tube must from that allows the pollen to reach and fertilize the ovum. In most cases, this will not occur when the wrong pollen reaches stigma due to differences in the structure of the pollen. A short hike through the Sandia Mountains from early spring to late summer will often reveal several different species of penstemon. The Rocky Mountain penstemon blooms in the spring while the very similar inflated penstemon blooms in late summer. As a result, hybrids are rarely encountered. Ligers are the results of a cross between a make lion and a female tiger. All known male offspring of these crosses have been infertile. Norway rats and black rats are very similar. Attempts cross the two species have led to pups being born, but they die within hours. When male fruit flies of one species (Drosophila melanogaster) attempt to mate with females of another (D. pseudoobscura), the courtship generally goes unnoticed by the females.

Explanation / Answer

9a.pre zygotic

9b.The prezygotic reproductive isolation mechanism is-Gameti

11a.post zygotic

11b.Hybrid Sterility: Even if the hybrid offspring is otherwise perfectly healthy, either one or both sexes is sterile.

This means it doesn't have functional gametes.

We have hybrid sterility to blame for one of the biggest bummers in biology: ligers.

Unfortunately, a liger cannot mate with another liger to make a baby liger, because ligers are sterile hybrids between tigers and lions. We'll just have to face our disappointment head on with this one.

12a.post zygotic.

12b.Hybrid inviability: The hybrid offspring is either weaker than the parent species, or totally inviable (meaning it cannot stay alive).

This could be caused by minor or major genetic defects, and even slightly reduced viability can cause big decreases in reproduction.

10a.pre zygotic

10b.Temporal Isolation: Fertilization is prevented if plants flower during slightly different times

13a.pre zygotic

13b.

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