Question

Describe two different examples of prezygotic reproductive barrier and two different examples of postzygotic reproductive barrier.

Repeat wit similar types do not receive full credits.

Answer 1

Prezygotic reproductive barrier and postzygotic reproductive barrier are terms usually used in the context of Reproductive isolation Which collectively comprises of mechanisms that hinder the formation of a hybrid, That is Two different species producing an offspring. The development of an organism starts with the process of Fertilization where the Egg and the sperm fuse to form a zygote that is diploid (This zygote then divides to form the whole organism).

Prezygotic reproductive barrier: Prevents the formation of the zygote (The process of Fertilization)

Example 1: Habitat Isolation, If the Ecological habitat of 2 species is different. Then they do not mate. The best example is of Lions and Tigers. Lions are mostly found in open woodlands whereas Tigers and found in Rain forests. They are known to be found together in the Gir forest but are not social at all. Tigons and Ligers are examples of hybrid offsprings formed but this is due to an artificial change in the environment (Zoo).

Example 2: Mating season, If the mating season of species A is summer and species B is winter. They do not form offsprings.

Postzygotic reproductive barrier: Zygote is formed but does not develop into a fertile offspring.

Example 1: Hybrid sterility, Even if the offspring is formed, The offspring is not fertile. The best example of that is of a mule that is not fertile and is a hybrid formed from a donkey and a horse.

Example 2: Hybrid Inviability: Here the offspring is formed but is weak to develop. It is also possible that the offspring develops but as generations pass by due to the incompatibility of Genes the generation degenerates.

Good luck.