Question

Reproductive isolating mechanisms are divided into categories based on when they act. _____ isolating factors prevent fertilization from taking place; _____ isolating factors result in failure of the fertilized egg to develop into a fertile individual.
A. Pre-zygotic; pre-zygoticB. Pre-zygotic; post-zygoticC. Post-zygotic; post-zygoticD. Post-zygotic; pre-zygotic

Answer 1

Answer: (B) Pre-zygotic; post-zygotic.

Explanation:

Prezygotic isolation occurs before fertilization of eggs. It occurs between the two sex gametes and deter sexual reproduction between different species.

However, individuals are considered to be diverge on the phylogeny tree and different species, when they cannot reproduce.

Mechanisms of prezygotic isolation include habitat isolation, gamete isolation, mechanical isolation, behavioral isolation, and mating seasons.

Whereas, postzygotic isolation prevents the formation of fertile offspring. This phenomenon leads to production of an hybrid offspring from different species and this is a form of speciation in nature.

Mechanisms of postzygotic isolation include hybrid inviability, hybrid breakdown, and hybrid sterility.