Question

Distinguish between postzygotic and prezygotic isolating mechanisms. Which might evolve first if speciation were sympatric? Which might evolve first if speciation were allopatric?

Answer 1

Reproductive isolation is a mechanism that keeps species from mating with others. Prezygotic barriers prevent members of different species from mating to produce a zygote, a single-celled embryo. such as temporal isolation, habitat isolation, behavioral isolation and gametic isolation. Postzygotic barriers keep hybrid zygotes—one-celled embryos with parents of two different species—from developing into healthy, fertile adults. Postzygotic barriers are often related to the hybrid embryo's mixed set of chromosomes, which may not match up correctly or carry a complete set of information.

Allopatric speciation is speciation that results when a population is separated by a physical barrier. It is also referred to as geographic speciation. Sympatric speciation is speciation that occurs without physical separation of members of the population. role in evolution Sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region.Allopatric speciation is the evolution of species caused by the geographic isolation of two or more populations of a species.

So If sympatric speciation is there than prezygotic will be having higher chances of evolution as they are going to mate with only simillar species and hence leads to variation.

where as in case of allopatric speciation postzygotic will evolve better because they are ready to mate with different species because of physical barrier leads to formation of new species.