Question

1) Use real-world examples to outline the steps of the speciation process (both dispersal and vicariance) and to differentiate between allopatric and sympatric speciation.

2) Describe the various ways reproductive isolation could occur and lead to speciation (both prezygotic and postzygotic mechanisms).

Answer 1

1. Speciation process involves following three stages:

(i) Separation: Separation occurs when a part of population gets separated from the rest of the population. When a group of individuals of a species are separated by a natural barrier for example newly formed canyon, mountain range, or from a lake. This helps population to grow and adapt in a new environment and get separated from rest of the species. In sharks separation occurs when they get separated from tidal waves, tsunamis, and underground sea canyons.

(ii) Adaptation: Adaptation happens when a group of individual of a species are exposed to new environment. As result of environmental change they acquire differnt traits to adapt in that environment. Example of adaptation is the color of the great white sharks, because its color is very difficult to see in the dark and at the rocky bottom where it usually swims.

(iii) Reproductive isolation: Reproductive isolation means when groups of same species cannot interbreed anymore due to adaptation to different environment to make them more fit for the new environment. Different types of sharks cannot interbreed, for examples hammerhead, bull, and great white sharks.

Difference between allopatric and sympatric speciation:

Allopatric	Sympatric
Species are living in different environment and niche	Species are living in the same environment and niche.
Because of differnt environment they develope differet traits	They differ because of other reproductive reasons, for example different mating time

2. Prezygotic isolation is prevention of formation of zygote. It usually happens because two species cannot mate and eggs cannot be fertilized.

Postzygotic isolation is inability of produce offsprings and resulting into end of the lineage progression, it includes hybrid inviability, hybrid sterility and hybrid "breakdown."