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The carbon cycle is a biogeochemical cycle that is important in maintaining life on Earth over a long time span. The cycle includes carbon sequestration and carbon sinks. [4] [5] Plate tectonics are needed for life over a long time span, and carbon-based life is important in the plate tectonics process. [6]
[10] [11] Carl Zimmer has speculated that the chemical conditions, including boron, molybdenum and oxygen needed to create RNA, may have been better on early Mars than on early Earth. [12] [13] [14] If so, life-suitable molecules originating on Mars would have later migrated to Earth via meteor ejections.
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 ...
More than 99 percent of all species that ever lived (over five billion) [1] are estimated to be extinct. [ 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 ]
Cyanobacteria dramatically changed the composition of life forms on Earth by leading to the near-extinction of oxygen-intolerant organisms. The diversity of life on Earth is a result of the dynamic interplay between genetic opportunity, metabolic capability, environmental challenges, [95] and symbiosis.
They are extremely important for understanding the evolutionary history of life on Earth, as they provide direct evidence of evolution and detailed information on the ancestry of organisms. Paleontology is the study of past life based on fossil records and their relations to different geologic time periods.
The Arecibo message (1974) sent information into space about basic chemistry of Earth life. A shadow biosphere is a hypothetical microbial biosphere of Earth that uses radically different biochemical and molecular processes than currently known life.
Molecular biology is the study of the fundamental chemistry of life, while cellular biology is the examination of the cell; the basic building block of all life. At a higher level, anatomy and physiology look at the internal structures, and their functions, of an organism, while ecology looks at how various organisms interrelate.