Hey kids, want to know the facts behind the forming and beginning of the planet on which we live? Our earth is the most important planet as it supports life, because of which living beings can dwell on this planet and every moment the environment of earth helps in giving birth to new life. Our mother earth was different to a large extent from what it is now. There used to be constant bombardment by meteorites, intense volcanism, and a poisonous atmosphere, at the beginning.But the fossils known as stromatolites in rocks 3 to 3.5 billion years old that had been studied by geologists showed them that life evolved very early in the Earth’s history. During the time known as the Archean (~4 billion to 2.5 billion years ago) Stromatolite fossils are very rare. Stromatolites were formed by the growth of layer upon layer of Cyanobacteria, a single-celled photosynthesizing microbe growing on a sea floor which was ultimately responsible for one of the most important “global changes” that the Earth has undergone. Being photosynthetic, Cyanobacteria produce oxygen as a by-product. Photosynthesis is the only chief cause of free oxygen gas in the atmosphere. As stromatolites became more general 2.5 billion years ago, they slowly altered the Earth’s atmosphere from a carbon dioxide-rich mixture to the existing oxygen-rich atmosphere. This led to the appearance of life on earth.
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