Question

Describe three types of prezygotic isolating mechanisms and show how each might contribute to speciation.

Answer 1

Pre Zygotic Isolating Mechanisms

Pre Zygotic isolating Mechanisms are those which prevent mating and fertilization between different species. It is of different types,

* Mechanical Isolation

* Habitat Isolation

* Temporal Isolation

* Mechanical Isolation

In Mechanical Isolation the genital parts are incompatible which prevents successful mating and fertilization. There will be difference in structure, position and other characters of genital parts of different species. This prevents mating between different species.

Example - Bush babies have distinctly shaped genitalia that will only fit other members of the same species.

In the case of plants it is related to pollinators. Each species of plant have a specific pollinator. Flowers which  structured for bee polination will not be compatible with flowers which use humming birds as pollinators.

This isolation mechanism prevents interbreeding of different species and leads to speciation.

* Habitat Isolation

Habitat Isolation prevents the interbreeding of two species by placing them in different habitats. Both species encounter each other rarely since they live in diffeent habittats.

Example- Two species of Garter snakes , once lives in land and other in water.

It also prevents interbreeding between different species and cause speciation.

* Temporal Isolation

Temporal Isolation occurs due to different mating seasons. Even closely related species couldnot interbreed due to different mating times.

example- rana aurora , breds during january- march

Rana boylii, breeds during march to may

This also leads to speciation by preventing mating between different species.