Postzygotic Isolation

Postzygotic isolation takes effect after hybrid zygotes form. Zygotes may die early, be weak, or be sterile. Postzygotic isolation mechanisms take effect after fertilization, while the embryo is developing. Postzygotic mechanisms include zygotic mortality, hybrid inviability, and hybrid sterility.

Sometimes fertilization does occur between different species, but the hybrid embryo is weak and dies.

In some instances the hybrids are vigorous but sterile. An example would be a mule that is produced by a male donkey and a female horse.

This animation (Audio - Important) reviews prezygotic and postzygotic ixolation mechanisms.

REVIEW: The primary reason for hybrid sterility is

REVIEW: Isolating mechanisms that take effect before or during fertilization are termed

REVIEW: Hybrid inviability is an example of what kind of isolation?

REVIEW: Reproductive isolating mechanisms _____ .
a. prevent interbreeding
b. prevent gene flow
c. reinforce genetic divergence
d. all of the above

REVIEW: When potential mates occupy overlapping ranges but reproduce at different times, this is a case of _____ isolation.

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