Everybody knows the story of the dinosaur and the various speculations about what happened to them and they become extinct. Extinction is the drastic decrease on the number of species in a short period of time. Mass extinctions may happen to every taxonomic group in the world. Based on the conventional geological sciences, mass extinctions is a type of major catastrophic event in the world biosystems (Thomas, n. d. ). Mass extinction is a term that is quite difficult to define for it incorporates “catastrophe”, which usually refers to human life and property loss.
However, recent mass extinction events occur not within human experiences and not influenced by any other human activity. The definition of mass extinctions includes the following; (1) It is a rapid event; (2) The significant part of life in Earth become extinct; (3) The life forms that became extinct must belong to different phyla that lived and located in various part of the world (Thomas, n. d. ). It means that mass extinction is a sudden annihilation of large number of life forms in different locations. Mass extinctions are brought about by many causes such as external and internal causes.
External causes include inability of the species to adapt on the change of habitat. The external causes are divided into terrestrial and extraterrestrial causes. Terrestrial causes of mass extinctions include moving continents which is characterized by the “kangaroo effect” lowering the biodiversity when there is a single continent than when there are various continents. Globally low sea-level is another form of terrestrial causes of mass extinction where in some creature living underwater loss their habitat. Extreme climate change significantly affects the various species and their living conditions.
Another terrestrial cause of mass extinctions is the lacks of oxygen or anoxia which often happens in oceans like the Black Sea. Low levels of oxygen in the sea and oceans will deliberately lower the number of underwater life forms (Thomas, n. d. ). Extraterrestrial causes of mass extinctions, on the other hand, are causes that occur or may be brought about by non-Earth materials and phenomena. This includes impact of large asteroids which can annihilate large number of life forms in an instant. Some meteorites may measure kilometers in diameter.
Same happens on the impact of comets on the Earth like what could have happened in southeastern Siberia in 1908, though there is no concrete evidence about the explosion of a comet. Supernova explosions may also be a cause of mass extinctions, however, there is no concrete and clear evidence that it influence the various life forms on earth (Thomas, n. d. ). Internal causes of mass extinction include the evolution of bacteria and viruses that may greatly affect the different species from different phyla (Thomas, n. d. ).
It may also be the development of pathogens or disease-carrying organisms that may be the cause of worldwide epidemic with no available cure. The contemporary society also experience mass extinctions but brought about by causes of human intervention such as hunting especially in the periods when large mammals disappeared in North America and Australia upon the inception f human beings. Direct human-induced habitat destruction is also a cause of contemporary mass extinction wherein people destroy the natural habitat of organisms and species for their own benefit and industrial development.
Mass extinction is truly a catastrophic event in the world as species and life forms disappeared on earth’s surface that affects the natural biodiversity of the world. It is also a significant event in the world’s history as mass extinctions give rise for the evolution of another species. Reference Thomas, E. (n. d. ). Biodiversity – Invasive Species – Mass Extinctions. Retrieved March 27, 2009, from http://ethomas. web. wesleyan. edu/ees123/mass_extinctions. htm.