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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 ...
539 Ma – present. The Phanerozoic Eon (Greek: period of well-displayed life) marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, with major mass extinctions at division points.
Panspermia is the hypothesis that life exists throughout the universe, distributed by meteoroids, asteroids, comets [ 1] and planetoids. [ 2] It does not attempt to explain how life originated, but shifts the origin to another heavenly body. The advantage is that life is not required to have formed on each planet it occurs on, but rather in a ...
For decades, scientists have theorized that volcanic lightning on an early Earth played a crucial role in kickstarting life on the planet by breaking molecules into useful, biological components ...
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 ...
In short, God has disposed some human beings as a cause of life for others, and likewise, he has disposed the latter as a cause of the death of the former." [39] Al-Jāḥiẓ also wrote descriptions of food chains. [40] Some of Ibn Khaldūn's thoughts, according to some commentators, anticipate the biological theory of evolution. [41]
According to the nebular hypothesis, the formation and evolution of the Solar System began 4.6 Gya with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun , while the rest flattened into a protoplanetary disk out of which the planets , moons , asteroids ...
The timeline of human evolution outlines the major events in the evolutionary lineage of the modern human species, Homo sapiens, throughout the history of life, beginning some 4 billion years ago down to recent evolution within H. sapiens during and since the Last Glacial Period . It includes brief explanations of the various taxonomic ranks in ...