Continental Drift, Plate Tectonics and Biogeographical Scenario

The continents are engaged in a continuous hori zo ntal moveme nt sc ientifically designated as continental drift. This endl ess motion res ults from th e so-called 'Thermal Convecti on" generated in th e upper mantl e. The di stributi on of bi ologic al communities across different landscapes surel y corre spond s to th e th eo ry of pl ate moti on or plate tectonics. Early in th e Earth's hi story until Carboniferous, conti­ nents of the wo rld were once united to form a large super-c ontinent known as "Pangaea". The remainin g surface of Earth was covered by a large ocean called "Panthal asa". Due to so me causes in th e beginning of Mesozoic Era th e super continent Pangaea drifted apart into two large subcontinents called Gondwana Land and Laurasia. Consequently there was birth of a sea between th ese two subco ntin ent s called Tethys. The great so uth ern co ntin ent s such as South America, Africa, Arabia, Indi a, Australia and Antarctica united to form th e "Gond wa na land", while the great north ern continents such as North America, Europe, Greenland, As ia, Scandinavia, Canada resembled to form Laurasia. Gradually these co ntin ents drifted and moved to the present posi ti on. Bi ogeography is th e stud y of th e patt ern s of di stributi on of animals and plants. It lo oks for ge neral prin ci ples to ex pl ain how and why organisms are di stributed th e way they are locally or region­ all y as we ll world wide. Bi ogeography uses informati on from ecolo gy and evolution ary biology as we ll as fro m geology, palaeontology and climatol ogy. In spite of these environment al fac tors such as clim ate, physiography, mountain ranges and Human impac t, affect the di spersa l of organi sms and the coloniza­ tion of a region.