Determine the most likely reason why natural selection may cause prezygotic reproductive isolating mechanisms to evolve if postzygotic reproductive isolating mechanisms are already present

Determine the most likely reason why natural selection may cause prezygotic reproductive isolating mechanisms to evolve if postzygotic reproductive isolating mechanisms are already present, but natural selection can never cause the evolution of postzygotic reproductive isolating mechanisms.

Natural selection may lead to the evolution of prezygotic reproductive isolation in organisms that already have postzygotic isolation to prevent wasted reproductive effort.
Prezygotic isolation can evolve if postzygotic isolation has generated genetic variation during earlier periods of anagenesis.
If postzygotic isolation is present, then natural selection is already acting on the same suite of traits that may lead to evolution of prezygotic isolation.
Prezygotic reproductive isolating mechanisms are the necessary physiological and behavioral precursors for the evolution of postzygotic isolation via natural selection.

Expert Solution

Reproductive isolation and geographical isolation are two major mechanisms that lead to evolution of new species. Reproductive isolation can further be divided into two parts on the basis of whether the barrier is acting before or after the formation of zygote. If barriers are present before zygote formation, it is called pre zygotic isolation, whereas if barriers act after the formation of zygote, it is called post zygotic isolating mechanism.

Pre zygotic isolation mechanisms include mechanisms which prohibit mating or don't allow formation of a zygote . It includes gamete incompatibility, different mating signals, different maturation timing , etc. On the other hand, post zygotic barriers include hybrid sterility , zygote mortality, etc. Post zygotic isolation leads to wastage of energy and resources, whereas pre zygotic barriers prevent wastage of reproductive effort.

Thus, most likely reason for evolution of pre-zygotic isolation mechanisms is :

Natural selection may lead to the evolution of prezygotic reproductive isolation in organisms that already have postzygotic isolation to prevent wasted reproductive effort.

gladiator answered 2 years ago

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