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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 ...
The earliest evidence for life on Earth includes: 3.8 billion-year-old biogenic hematite in a banded iron formation of the Nuvvuagittuq Greenstone Belt in Canada; [30] graphite in 3.7 billion-year-old metasedimentary rocks in western Greenland; [31] and microbial mat fossils in 3.48 billion-year-old sandstone in Western Australia.
Evolutionary biology is the subfield of biology that studies the evolutionary processes (natural selection, common descent, speciation) that produced the diversity of life on Earth. It is also defined as the study of the history of life forms on Earth. Evolution holds that all species are related and gradually change over generations. [1]
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 .
A life form (also spelled life-form or lifeform) is an entity that is living, [1] [2] such as plants , animals , and fungi . It is estimated that more than 99% of all species that ever existed on Earth, amounting to over five billion species, [3] are extinct. [4] [5] Earth is the only celestial body known to harbor life forms. No form of ...
Over time these evolutionary processes lead to formation of new species , changes within lineages , and loss of species . "Evolution" is also another name for evolutionary biology , the subfield of biology concerned with studying evolutionary processes that produced the diversity of life on Earth.
This process is responsible for the many diverse life forms in the world. The modern understanding of evolution began with the 1859 publication of Charles Darwin's On the Origin of Species. In addition, Gregor Mendel's work with plants helped to explain the hereditary patterns of genetics. [11]
In 1785, he stated that Earth was a superorganism and that its proper study should be physiology. [12]: 10 The Gaia hypothesis, proposed in the 1960s by James Lovelock, suggests that life on Earth functions as a single organism that defines and maintains environmental conditions necessary for its survival. [13] [14]