BIO GEOGRAPHICAL EVIDENCE-

• The patterns of distribution of animals and plants in different parts of the globe are termed as biogeography.
• It is believed that around carboniferous period or slightly earlier all the present day continents formed a single large, irregular land mass called Pangaea.
• Pangaea splited up and the smaller masses (continents) lighter than the underlying earth crust material gradually floated over it to their present position.
• As the continents drifted away, the sea separated them, forming barriers to free intercontinental movements of organisms. Due to different environmental continents, organisms evolved independently in them.
• Earlier whole land mass of Globe was one piece called Panagea. 200 - 300 million years ago it got divided as follows -

• Sclater (1858) first divided globe in six zoogeographical regions on the basis of avian fauna.
• A.R.Wallace (1876) divided more scientifically on the basis of entire flora and fauna as:

• Wallace's Line divides Oriental and Australian region.
• Darwin (1831) during his expedition on H.M.S. Beagle visited Galapagos Islands (900 Km off West coast of South America) and found many endemic (restricted) species.
• He studied 13 different subspecies of finches (Darwin's finches by David Lack 1947) with different eating habits (originally seed-eating).
• He reasoned it as suitable adaptation brought by environmental conditions and called the islands as " living laboratory of evolution "
• Discontinuous (Allopatric) distribution: When closely related genera are found in different regions.
• This indicated that after arising from common stock they were geographically separated and evolved differently.
• Due to the geographical barrier they remained isolated and evolved as genera, examples - 
• Continuous (Sympatric) distribution: When closely related genera are found in the same or connected region. e.g. Prototheria and Metatheria are found only in Australian region.
• Sometimes referred as restricted distribution. endemic fauna.