The following list represents two types of reproductive isolation (Column P) that can lead to speciation. Column Q represents the processes by which these isolations can occur.

​Select the option that represents the correct match between the prezygotic and postzygotic isolation types listed in Column P and the processes described in Column Q?​

Correct option is C

Reproductive isolation is classified into prezygotic and postzygotic mechanisms:

• Prezygotic isolation occurs before fertilization, preventing different species from mating or forming a zygote.
• Postzygotic isolation occurs after fertilization, leading to reduced survival or fertility of the offspring.

Matching Column P (Isolation Type) with Column Q (Processes):

1. Prezygotic Isolation (A):

   • i. Seasonal isolation: Prevents interbreeding due to differences in mating seasons (also called temporal isolation). (Correct for prezygotic)
   • iv. Stigmatic SI response: Refers to self-incompatibility (SI) mechanisms in plants, preventing pollen from fertilizing eggs of different species. (Correct for prezygotic)

2. Postzygotic Isolation (B):

   • ii. Hybrid inviability: Occurs when the zygote forms but fails to develop properly, leading to early death. (Correct for postzygotic)
   • iii. F₂ breakdown: Refers to hybrid offspring (F₂ generation) being weak, sterile, or inviable, preventing further hybridization. (Correct for postzygotic)

Thus, the correct matching is A → i and iv, B → ii and iii, which corresponds to option (c).

Information Booster:

1. Prezygotic barriers prevent fertilization, ensuring species remain distinct.
2. Temporal (seasonal) isolation occurs when species reproduce at different times, preventing interbreeding.
3. Mechanical and gametic isolation are other forms of prezygotic isolation seen in plants and animals.
4. Postzygotic isolation reduces hybrid survival or fertility, preventing genetic mixing between species.
5. Hybrid inviability leads to early embryo death due to genetic incompatibility.
6. Hybrid sterility (e.g., mules) prevents further gene flow between species.
7. F₂ hybrid breakdown ensures that even if F₁ hybrids survive, their descendants suffer reduced fitness.