Evidences of Evolution from the Biogeographical distribution

 

In the world , there are no any uniform distribution of species of any organism. Each one has different geographical distribution from the others species. Some others species are restricted or confind to one or more limited area.

Remember 👌👌The study of geographical distriburion  of organism called Biography.

On the basis of flora and fauna, Alfred Russel wallace divided the complete geographical land of world in six major biographical regions, these regions are called realms. These realms are separated by various barrier. Palearctic realm is separated  from Nearctic by the Pacific and Atlantic ocean. Similary Palearctic realms  are separated from Ethiopian and Oriental realm by Sahara desert and  Himalaya respectively. and   These realms are as follows .

Nearctic  realm - North American from Mexico to Arctic and greenlands.

Palearctic realm - Europe ,North Asia upto Himalaya and North Africa uptown Sahara desert.

Neotropical realm  - Central and South America ,Mexican lowland  and West indies.

Oriental realm - Asia including India, Srilanka,Malaya, Sumatra, Borneo, java and Philippines.

Ethiopian realm - South Africa from Sahara desert  and Madagascar.

Australian realm- Australia, Tasmania, Newzealand 

The flora and fauna of each realm signifies the past history of realm. In past history, we can explore about the changes  of earth and evolution of animal and plant species.

According to concept of evolution, A new species is orignated in nature only one time and no any  species is present permanently in its area where it has been orignated. When the population of such new species is increased  than its member start to migrate in all direction and may cross the geographical barrier. These member get changes in their features according to climatic condition of new geographical area and origin of new specieses takes  place.

Primtive Mammals like Prototherian and metatherian  were orignated and spreaded through out the world in the Mesozoic era. At that tome, Australia was the part of Asian continent but later on from Asian continent. During this time carnivore eutherian mammals were evolved and they finished the primtive mammals. Whereas the  Eutherian mammals did not evolved in Australia hence Australia is only continent that have primtive mammals.

Charles Darwin observed the climatic condition of Galapagous island during his sea voyage. This island was located of south America. Due to variable climatic condition, Darwin used the term  for this island.

Darwin marked great variation in shape and size of birds and also in Beak and plumage in color. These birds are now called Darwin finches. Related species of birds was observed by Darwin in south America also.

 

Darwin concluded that  South America was the original habitat of these Birds. Later on these birds were  migrated  in Galapagous island and adapted themselves to survive in variable environmental condition .

If two regions are separated by the by the geographical barriers and climatic condition are same in  these both region but tthey have different fauna and flora due to evolution. For example - South American and Africa are two such continent.