The increase in number of animals by reproduction makes them distribute in all directions. Dispersal continues until barrier is reached. The reason for such discontinuous distribution of related groups is due to the development of the barriers or due to the extinction of forms In the intermediate area.
The idea of Zoogeography was originally contributed by P.L Sciater. He studied the geographical distribution of birds in his paper
‘Schema distributions avium geographicae’. He divided the continents into six Geographical regions.
Huxley grouped four regions that cover Africa, Eurasia, and North America are called the unit as ‘Arctogaea’. He included South America and Australia under Notogaea’.
Blanford divided the land masses into three main divisions
1,Arctogaea; Eurasia; North America and Africa.
2) South American region
3) Australian region. S
According to Darlington the continents of the whole world can be divided into.
1. Nearctic region
2. Palaearctic region
3. Neotropical region
4. Ethiopian region
6. Australian regions.
The accepted system of continental faunal regions.
1 . Realm Megagaea : This includes four zoogeographical regions.
Region - 1 . Nearctic region : This includes North America and Mexico abov tropics.
Region - 2. Palaearctic region : This region comprises Eurasia abo tropics and Northern corner of Africa.
Region - 3. Oriental region : This includes tropical Asia and associated Islands.
Region -4. Ethiopian region : This includes Africa and Southern region of Arabia.
II. Realm Neogaea : Region - 5 . Neotropical region. This includes South America, Central America and Southern part of Mexico.
III. Realm Notogaea: Region -6. Australian region: This region includes Australia, New Guinea, Tasmania, Newzealand and some neighboring islands.