Speciation And Continental Drift

Speciation can be defined as a process by which alterations in the gene pool of segments within a population is achieved either due to prezygotic or post zygotic mechanisms that ultimately leads to reproductive isolation between members of the population (Learning Evolution,2006).

Continental drift: # In the period between 1912 and 1930,Alfred Wegener proposed the theory that all continents of the world were fused together in a single land mass called Pangaea with a single ocean Panthalassa which became evident when the fit of the continents were checked. # Exact geographical correlations were discovered east coast of South America and West coast of Africa. Besides, the similarity in the rocks, fossils, and glaciations has led the geologists to suggest the existence of a massive southern continent Gondwana that included Australia. # The studies in paleo magnetism also supported the concept of a common continent.(Strickberger,2000). # In the 1960s and 1970s, the concept of Plate tectonics was postulated which stated test the Earth`s outermost layer, the Lithosphere, was broken down into 7 large hard plates, namely the African, North American, South American, Eurasian, Antarctic, Pacific .and Australian plates. There can be coexistence between plates also like Philippines plate, Arabian plate, and Nazca plate. # These plates are moving at different directions with different speeds in relation to each other, so sometimes the y are colliding, otherwise they are continuously moving away from each other.(Plate tectonics,2011). # Such a movement is possible since the plates are floating on the magma occupying the core of the earth producing convergent(,colliding), divergent (pulling apart) or sideswiping(Transform boundaries). # It is due to this plate tectonics that the landmasses have separated and are presently also moving in specific directions with respect to each other. Role of continental drift in speciation: a) If we now look at the aspect of evolution, keeping in mind the plate tectonics, then it comes to light that the parental populations were also separated and they migrated too with the continent, b) As a consequence, over millions of years, the difference between the previous landmasses has increased considerably and their individual ecological conditions along with the environmental factors transformed the landmasses . c) This resulted in rise of adaptations in the animals/plants that were not present in the original population .When such mutations became heritable and were beneficial for the part of the population`s inclusive fitness, then they produced sufficient reproductive isolation from other such groups to produce a new species. d) The most prominent example of the role of continental drift in speciation is the unique collection of primitive mammals found in Australia and South America. Australia doesn`t have any placental mammal in spite of having two families of monotones (Duck billed Platypus) and thirteen of marsupials(Kangaroos etc). e) Later researches have indicated that the evolution of mammals in isolated islands of South America is unique until South America joined North America by the Panama isthmus. Conclusion So in summary, we can state that continental drift subjected the moving landmasses to different climatic conditions, enabling the inhabitants for evolutionary adaptations, and eventually speciation is produced. species and thus speciation.(Speciation 2004, Strickberger,2000)

REFERENCES 1) Learning Evolution[internet].Berkeley(US)> The University of California Museum of Paleontology,Berkeley,and the Regents of University of California.Evolution101:Speciation. Obtained from http://www.evolution.berkeley.edu/evosite/evo101/index.html

2) Strickberger,W,M.` Evolution .Jones And Bartlett Publishers. New York 2000.

3)Exploring The Environment c1997-2001[ internet] Wheeling(US) Earth Floor: Plate tectonics. Obtained fromhttp://www.cotf.edu/ete/modules/msese/earthsysflr/plates1.html

4) Speciation and Mass Extinction. N 100: Speciation. Obtained from http://www.biology.iupui.edu/biocourses/N100/2K4ch17 spec.html