Question

Explain in detail how does allopatric speciation occur?

Answer 1

Speciation can be defined as a gradual process by which populations evolve into different species. A species can be defined as a group of populations that can interbreed. During speciation, two or more distinct populations are formed by the members of a population that can no longer breed with each other.

Complete answer:
Allopatric speciation is the most common form of speciation. Allopatric speciation is speciation that happens when due to geographic changes two populations of the same species become isolated from each other. Gene flow between the population ceases when the populations become geographically isolated from each other.

Steps of Allopatric Speciation:
Members of a population of the same species are separated into more than one group by a geographic change. Geographical changes include the formation of a new mountain range or waterway or development of canyons etc. Also, increased human activities like agriculture, pollution, construction of buildings can cause some members of a population to migrate.
Over the time different gene mutations build up in these separated populations. The genetic mutations lead to variations in the genes which further develops different characteristics between the separated populations.
Due to genetic variations these populations become so different that the members of these populations can no longer breed with each other, if members of these populations were to be in the same habitat at the same time. This is known as allopatric speciation.

Examples of Allopatric Speciation: Darwin’s Finches
Galapagos finches studied by Charles Darwin are one of the best examples of allopatric speciation. The Galapagos island possesses around 15 species of finches which possess specialized beaks for eating different types of foods like insects, seed and flower. All of these finches might have evolved from a common ancestor and might have emigrated to different islands. As these populations occupied their respective islands, they became isolated from each other. Over the time new mutations arose and these mutations caused the birds to be most adaptable to their respective environments. After a few generations these mutations became more prominent and this led to the formation of many different species over time.

Note: Formation of new species over the time due to geographical barrier reflects allopatric speciation. Darwin finches are one of the best examples of allopatric speciation. Allopatric speciation is one of the most common forms of speciation.