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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 ...
End Ordovician: 440 million years ago, 86% of all species lost, including graptolites. Late Devonian: 375 million years ago, 75% of species lost, including most trilobites. End Permian, The Great Dying: 251 million years ago, 96% of species lost, including tabulate corals, and most trees and synapsids.
Sustainable Development Goal 2 (SDG 2 or Global Goal 2) aims to achieve " zero hunger ". It is one of the 17 Sustainable Development Goals established by the United Nations in 2015. The official wording is: "End hunger, achieve food security and improved nutrition and promote sustainable agriculture ". [1][2] SDG 2 highlights the "complex inter ...
Understanding planetary habitability is partly an extrapolation of the conditions on Earth, as this is the only planet known to support life. Planetary habitability is the measure of a planet 's or a natural satellite 's potential to develop and maintain environments hospitable to life. [1] Life may be generated directly on a planet or ...
[17] [18] Estimates on the number of Earth's current species range from 10 million to 14 million, [19] of which about 1.2 million are documented, but over 86 percent have not been described. [ 20 ] The Earth's crust has constantly changed since its formation, as has life since its first appearance.
Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis, organisation, metabolism, growth, adaptation, response to stimuli, and reproduction. All life over time eventually reaches a state of ...
Repeating decimal. A repeating decimal or recurring decimal is a decimal representation of a number whose digits are eventually periodic (that is, after some place, the same sequence of digits is repeated forever); if this sequence consists only of zeros (that is if there is only a finite number of nonzero digits), the decimal is said to be ...
t. e. The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.