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Eukaryogenesis, the process which created the eukaryotic cell and lineage, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The process is widely agreed to have involved symbiogenesis , in which an archeon and a bacterium came together to create the first eukaryotic ...
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 ...
A multicellular organism is an organism that consists of more than one cell, unlike unicellular organisms. [1] All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium. [2] [3]
As duplex DNA became the predominant form of the genetic material, the mechanism of genetic recovery evolved into the more complex process of meiotic recombination, found today in most species. It thus appears likely that sexual reproduction arose early in the evolution of cells and has had a continuous evolutionary history.
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.
The origin of the eukaryotic cell, or eukaryogenesis, is a milestone in the evolution of life, since eukaryotes include all complex cells and almost all multicellular organisms. The last eukaryotic common ancestor (LECA) is the hypothetical origin of all living eukaryotes, [ 71 ] and was most likely a biological population , not a single ...
The result of four billion years of evolution is the diversity of life around us, with an estimated 1.75 million different species in existence today. [71] [72] Usually the process of speciation is slow, occurring over very long time spans; thus direct observations within human life-spans are rare.
A tree of life, like this one from Charles Darwin's notebooks c. July 1837, implies a single common ancestor at its root (labelled "1"). A phylogenetic tree directly portrays the idea of evolution by descent from a single ancestor. [3] An early tree of life was sketched by Jean-Baptiste Lamarck in his Philosophie zoologique in 1809.