A brief History of Life on Earth.

Life is valuable to all(prenominal) of us, but how it began is not something many populate are interested in discussing. This is a brief sum-up of one version the history of life on Earth, concur on by most biologists.

The Earths crust formed some 4.5 trillion years ago. There are various theories as to what it was that caused the first prokaryotic cells to form 700 million years later. Unfortunately, Scientists get hold of not agreed on what it was. Roughly two billion years later, these prokaryotic cells combined to form the first eucaryotic cells.

The Cambrian period started about 543 million years ago, algae change and there was a huge evolutionary radiation therapy among our first ancestors. During the Ordovician period (510-440 mya) marine organisms radiated all over the globe, mosses and horsetails colonised wet terrestrial environments. As the Ordovician period came to a close, major environmental heightens caused widespread glacial formation, which, in turn, caused 75% of all marine species to become extinct. During the Silurian period (440-409 mya), marine life bounced okay after the major liquidation event at the give notice of the Ordovician. The first terrestrial arthropods appeared during this period. During the Devonian period (409-354 mya), rates of evolutionary change accelerated, the first forests appeared and the Northern and Southern continents slowly moved northward.



At the end of the Devonian there was another 75% mass extinction of all marine life due to climatic circumstances. The carbonous (354-290 mya) brought large amounts of glacial formation on Gondwana. Terrestrial animals diversified and some of the first reptiles appeared during Carboniferous period. During the Permian period (290-245 mya), all of the continents came in concert to form the super-continent Pangaea. Volcanic activity blocked out the suns rays, causing a broad ice age. At the end of the Permian period, massive lava flows released...

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