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The history of life on Earth traces the processes by which living and extinct organisms evolved, from the earliest emergence of life to the present day. Earth formed about 4.5 billion years ago (abbreviated as Ga, for gigaannum) and evidence suggests that life emerged prior to 3.7 Ga. [1] [2] [3] The similarities among all known present-day species indicate that they have diverged through the ...
[2] [3] Estimates on the number of Earth's current species range from 10 million to 14 million, [4] with about 1.2 million or 14% documented, the rest not yet described. [5] However, a 2016 report estimates an additional 1 trillion microbial species, with only 0.001% described. [6]
A variation of this analogy instead compresses Earth's 4.6 billion year-old history into a single day: While the Earth still forms at midnight, and the present day is also represented by midnight, the first life on Earth would appear at 4:00 am, dinosaurs would appear at 10:00 pm, the first flowers 10:30 pm, the first primates 11:30 pm, and ...
The age of Earth is about 4.54 billion years; [7] [33] [34] the earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago according to the stromatolite record. [35] Some computer models suggest life began as early as 4.5 billion years ago. [36] [37] The oldest evidence of life is indirect in the form of isotopic ...
c. 2.58 Ma – start of the Pleistocene epoch, the Stone Age and the current Quaternary Period; emergence of the genus Homo. Smilodon, the best known of the sabre-toothed cats, appears. c. 2.4 Ma – The Amazon River takes its present shape in South America. c. 2.0–1.5 Ma – The basin of the Congo River acquires its present shape.
But crucially, nitrogen (N 2) would’ve also converted into nitrates, nitrites, and ammonia. This is extremely important, as Earth’s early atmosphere would’ve been made up of nonreactive N 2 ...
The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth
A mass extinction event that brought about the rise of the dinosaurs more than 200 million years ago was believed to be caused by the planet’s warming. Now, scientists at Columbia University say ...