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|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | 4533 Ma
| align="RIGHT" nowrap | 4533 Ma
| According to one plausible theory, the planet Earth and the planet [[Theia (planet)|Theia]] collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the [[Moon]]. The gravitational pull of the new Moon stabilises the Earth's fluctuating [[axis of rotation]] and sets up the conditions for the formation of life.<ref>[http://www.psi.edu/projects/moon/moon.html Planetary Science Institute page] on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.</ref>
| According to one plausible theory, the planet Earth and the planet [[Theia (planet)|Theia]] collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the [[Moon]]. The gravitational pull of the new Moon stabilises the Earth's fluctuating [[axis of rotation]] and sets up the conditions in which life formed.<ref>[http://www.psi.edu/projects/moon/moon.html Planetary Science Institute page] on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.</ref>
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | 4100 Ma
| align="RIGHT" nowrap | 4100 Ma
| The surface of the Earth cools enough for the [[crust (geology)|crust]] to solidify. The [[Earth's atmosphere|atmosphere]] and the [[ocean]]s form.<ref>"<cite>However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development.</cite>" [http://www.oceansonline.com/ocean_form.htm How the Oceans Formed] (URL accessed on January 9, 2005)</ref>[[PAH world hypothesis|PAH]] infall, and [[Iron-Sulfide World|Iron-Sulfide]] synthesis along deep ocean platelet boundaries, may have led to the [[RNA world]] of competing organic compounds.
| The surface of the Earth cools enough for the [[crust (geology)|crust]] to solidify. The [[Earth's atmosphere|atmosphere]] and the [[ocean]]s form.<ref>"<cite>However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development.</cite>" [http://www.oceansonline.com/ocean_form.htm How the Oceans Formed] (URL accessed on January 9, 2005)</ref> [[PAH world hypothesis|PAH infall]]<ref>*[http://nai.nasa.gov/nai2005/abstracts/616%20-%20S.N.Platts%20PAH_World.doc.pdf The 'PAH World']</ref>, and [[Iron-Sulfide World|Iron-Sulfide]] synthesis along deep ocean platelet boundaries, may have led to the [[RNA world]] of competing organic compounds.
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | Between 4500 and 2500 Ma
| align="RIGHT" nowrap | Between 4500 and 2500 Ma
| The [[origin of life|earliest life]] appears, possibly derived from [[RNA world hypothesis|self-reproducing]] [[RNA]] molecules. The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition. [[Natural selection]] favours those molecules which are more efficient at replication. [[DNA]] molecules then take over as the main replicators. They soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: [[Cell (biology)#Evolution|proto-cells]].
| The [[origin of life|earliest life]] appears, possibly derived from [[RNA world hypothesis|self-reproducing]] [[RNA]] molecules.<ref>{{cite journal|title=The RNA World|journal=[[Nature (Journal)|Nature]]|first=Walter|last=Gilbert|authorlink=Walter Gilbert|month=February|year=1986|pages=618|volume=319|doi=10.1038/319618a0}}</ref><ref>{{cite journal |author=Joyce, G.F. |title=The antiquity of RNA-based evolution |journal=Nature |volume=418 |issue=6894 |pages=214–21 |year=2002 |pmid=12110897 |doi=10.1038/418214a}}</ref> The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with [[natural selection]] favouring those molecules which are more efficient at replication. [[DNA]] molecules then take over as the main replicators and these archaic [[genome]]s soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: [[Cell (biology)#Evolution|proto-cells]].<ref name="Hoenigsberg2003SelectionWithoutSpeciation">{{cite journal
| author=Hoenigsberg, H. | date=December 2003)
| title=Evolution without speciation but with selection: LUCA, the Last Universal Common Ancestor in Gilbert’s RNA world
| journal=Genetic and Molecular Research | volume=2 | issue=4 | pages=366–375 | pmid=15011140
| url=http://www.funpecrp.com.br/gmr/year2003/vol4-2/gmr0070_full_text.htm | accessdate=2008-08-30
}}(also available as [http://www.funpecrp.com.br/gmr/year2003/vol4-2//pdf/gmr0070.pdf PDF])</ref><ref>{{cite journal |author=Trevors, J. T. and Abel, D. L. |title=Chance and necessity do not explain the origin of life |journal=Cell Biol. Int. |volume=28 |issue=11 |pages=729–39 |year=2004 |pmid=15563395 |doi=10.1016/j.cellbi.2004.06.006}}</ref><ref>{{cite journal |author=Forterre, P., Benachenhou-Lahfa, N., Confalonieri, F., Duguet, M., Elie, C. and Labedan, B. |title=The nature of the last universal ancestor and the root of the tree of life, still open questions |journal=BioSystems |volume=28 |issue=1-3 |pages=15–32 |year=1992 |pmid=1337989 |doi=10.1016/0303-2647(92)90004-I}}</ref>
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | 3900 Ma
| align="RIGHT" nowrap | 3900 Ma
| [[Late Heavy Bombardment]]: peak rate of [[impact event]]s upon the inner planets by meteors. This constant [[disturbance]] probably obliterated any life that had already evolved, as the oceans boiled away completely; conversely, life may have been [[panspermia|transported to Earth]] by a meteor.<ref>"<cite> Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across</cite>" [http://news-service.stanford.edu/news/1998/december2/marsunder122.html Geophysicist Sleep: Martian underground may have harbored early life] (URL accessed on January 9, 2005)</ref>
| [[Late Heavy Bombardment]]: peak rate of [[impact event]]s upon the inner planets by meteors. This constant [[disturbance|disturbance (ecology)]] probably obliterated any life that had already evolved, as the oceans boiled away completely; conversely, life may have been [[panspermia|transported to Earth]] by a meteor.<ref>"<cite> Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across</cite>" [http://news-service.stanford.edu/news/1998/december2/marsunder122.html Geophysicist Sleep: Martian underground may have harbored early life] (URL accessed on January 9, 2005)</ref>
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | Somewhere between 3900 - 2500 Ma
| align="RIGHT" nowrap | Somewhere between 3900 - 2500 Ma
| [[Cell (biology)|Cells]] resembling [[prokaryote]]s appear. These first organisms are [[chemotroph|chemoautotrophs]]: they use [[carbon dioxide]] as a [[carbon]] source and [[redox|oxidize]] inorganic materials to extract energy. Later, prokaryotes evolve [[glycolysis]], a set of chemical reactions that free the energy of organic molecules such as [[glucose]]. Glycolysis generates [[Adenosine triphosphate|ATP]] molecules as short-term energy currency, and ATP continue to be used in almost all organisms, unchanged, to this day.
| [[Cell (biology)|Cells]] resembling [[prokaryote]]s appear.<ref>[[Carl Woese]], [[J Peter Gogarten]], "[http://www.sciam.com/askexpert_question.cfm?articleID=000C32DD-60E1-1C72-9EB7809EC588F2D7&catID=3&topicID=3 When did eukaryotic cells (cells with nuclei and other internal organelles) first evolve? What do we know about how they evolved from earlier life-forms?]" ''[[Scientific American]]'', October 21, 1999.</ref> These first organisms are [[chemotroph|chemoautotrophs]]: they use [[carbon dioxide]] as a [[carbon]] source and [[redox|oxidize]] inorganic materials to extract energy. Later, prokaryotes evolve [[glycolysis]], a set of chemical reactions that free the energy of organic molecules such as [[glucose]] and store it in the chemical bonds of [[Adenosine triphosphate|ATP]]. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.<ref>Romano AH, Conway T. (1996) Evolution of carbohydrate metabolic pathways. ''Res Microbiol.'' 147(6-7):448-55 PMID 9084754</ref><ref>{{cite journal |author=Knowles JR |title=Enzyme-catalyzed phosphoryl transfer reactions |journal=Annu. Rev. Biochem. |volume=49 |issue= |pages=877–919 |year=1980 |pmid=6250450 | doi=10.1146/annurev.bi.49.070180.004305}}</ref>
|}
|}


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|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | 3500 Ma
| align="RIGHT" nowrap | 3500 Ma
| Lifetime of the [[last universal ancestor]];<ref>Doolittle, W. Ford (February, 2000). [http://shiva.msu.montana.edu/courses/mb437_537_2004_fall/docs/uprooting.pdf Uprooting the tree of life]. Scientific American 282 (6): 90–95.</ref><ref>Nicolas Glansdorff, Ying Xu & Bernard Labedan: The Last Universal Common Ancestor : emergence, constitution and genetic legacy of an elusive forerunner. Biology Direct 2008, 3:29.</ref> the split between [[bacteria]] and [[Archaea]] occurs.<ref>{{cite journal |last=Hahn |first=Jürgen |coauthors=Pat Haug |year=1986 |title=Traces of Archaebacteria in ancient sediments |journal=System Applied Microbiology |volume=7 |issue=Archaebacteria '85 Proceedings |pages=178&ndash;83}}</ref>
| Lifetime of the [[last universal ancestor]]; the split between the [[bacteria]] and the [[Archaea]] occurs.


Bacteria develop primitive forms of [[photosynthesis]] which at first do not produce [[oxygen]]. These organisms generate [[Adenosine triphosphate|ATP]] by exploiting a [[electrochemical gradient|proton gradient]], a mechanism still used in virtually all organisms.
Bacteria develop primitive forms of [[photosynthesis]] which at first do not produce [[oxygen]].<ref>{{cite journal |author=Olson JM |title=Photosynthesis in the Archean era |journal=Photosyn. Res. |volume=88 |issue=2 |pages=109–17 |year=2006 |month=May |pmid=16453059 |doi=10.1007/s11120-006-9040-5}}</ref> These organisms generate [[Adenosine triphosphate|ATP]] by exploiting a [[electrochemical gradient|proton gradient]], a mechanism still used in virtually all organisms.
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | 3000 Ma
| align="RIGHT" nowrap | 3000 Ma
| Photosynthesizing [[cyanobacteria]] evolve; they use water as a [[reducing agent]], thereby producing [[oxygen]] as waste product. The oxygen initially oxidizes dissolved iron in the oceans, creating [[iron ore]]. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The [[moon]] is still very close to the earth and causes [[tide]]s 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See [[Oxygen Catastrophe]])
| Photosynthesizing [[cyanobacteria]] evolve; they use water as a [[reducing agent]], thereby producing [[oxygen]] as waste product.<ref>{{cite journal |author=Buick R |title=When did oxygenic photosynthesis evolve? |journal=Philos. Trans. R. Soc. Lond., B, Biol. Sci. |volume=363 |issue=1504 |pages=2731–43 |year=2008 |month=August |pmid=18468984 |doi=10.1098/rstb.2008.0041}}</ref> The oxygen initially oxidizes dissolved iron in the oceans, creating [[iron ore]]. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The [[moon]] is still very close to the earth and causes [[tide]]s 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See [[Oxygen Catastrophe]])
|}
|}


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| pmid = 16754612
| pmid = 16754612
}}
}}
</ref> Eukaryotes contain membrane-bound [[organelle]]s with diverse functions, probably derived from [[prokaryote]]s engulfing each other via [[phagocytosis]].
</ref> Eukaryotes contain membrane-bound [[organelle]]s with diverse functions, probably derived from [[prokaryote]]s engulfing each other via [[phagocytosis]]. (See [[Endosymbiosis]])
|- valign="TOP"
|- valign="TOP"
| align="RIGHT" nowrap | By 1200 Ma
| align="RIGHT" nowrap | By 1200 Ma

Revision as of 17:46, 11 July 2009

For the history of evolutionary biology, see History of evolutionary thought.

This timeline of the evolution of life outlines the major events in the development of life on the planet Earth (See Organism). For a thorough explanatory context, see the history of Earth, and geologic time scale. The dates given in this article are estimates based on scientific evidence.

In biology, evolution is the process by which populations of organisms acquire and pass on novel traits from generation to generation. Its occurrence over large stretches of time explains the origin of new species and ultimately the vast diversity of the biological world. Contemporary species are related to each other through common descent, products of evolution and speciation over billions of years.

Basic timeline

The basic timeline is a 4.5 billion year old Earth, with (very approximate) dates:

  • 300 million years of reptiles,
  • 200 million years of mammals,
  • 150 million years of birds,
  • 130 million years of flowers,
  • 65 million years since the non-avian dinosaurs died out,
  • 2.5 million years since the appearance of the genus Homo,
  • 200,000 years since humans started looking like they do today,
  • 25,000 years since Neanderthals died out.

Detailed timeline

Note that Ma, megaannum, means "million years ago".

Hadean eon

3800 Ma and earlier.

Date Event
4600 Ma The planet Earth forms from the accretion disc revolving around the young Sun.
4533 Ma According to one plausible theory, the planet Earth and the planet Theia collide, sending countless moonlets into orbit around the young Earth. These moonlets eventually coalesce to form the Moon. The gravitational pull of the new Moon stabilises the Earth's fluctuating axis of rotation and sets up the conditions in which life formed.[1]
4100 Ma The surface of the Earth cools enough for the crust to solidify. The atmosphere and the oceans form.[2] PAH infall[3], and Iron-Sulfide synthesis along deep ocean platelet boundaries, may have led to the RNA world of competing organic compounds.
Between 4500 and 2500 Ma The earliest life appears, possibly derived from self-reproducing RNA molecules.[4][5] The replication of these organisms requires resources like energy, space, and smaller building blocks, which soon become limited, resulting in competition, with natural selection favouring those molecules which are more efficient at replication. DNA molecules then take over as the main replicators and these archaic genomes soon develop inside enclosing membranes which provide a stable physical and chemical environment conducive to their replication: proto-cells.[6][7][8]
3900 Ma Late Heavy Bombardment: peak rate of impact events upon the inner planets by meteors. This constant disturbance (ecology) probably obliterated any life that had already evolved, as the oceans boiled away completely; conversely, life may have been transported to Earth by a meteor.[9]
Somewhere between 3900 - 2500 Ma Cells resembling prokaryotes appear.[10] These first organisms are chemoautotrophs: they use carbon dioxide as a carbon source and oxidize inorganic materials to extract energy. Later, prokaryotes evolve glycolysis, a set of chemical reactions that free the energy of organic molecules such as glucose and store it in the chemical bonds of ATP. Glycolysis (and ATP) continue to be used in almost all organisms, unchanged, to this day.[11][12]

Archean eon

3800 Ma – 2500 Ma

Date Event
3500 Ma Lifetime of the last universal ancestor;[13][14] the split between bacteria and Archaea occurs.[15]

Bacteria develop primitive forms of photosynthesis which at first do not produce oxygen.[16] These organisms generate ATP by exploiting a proton gradient, a mechanism still used in virtually all organisms.

3000 Ma Photosynthesizing cyanobacteria evolve; they use water as a reducing agent, thereby producing oxygen as waste product.[17] The oxygen initially oxidizes dissolved iron in the oceans, creating iron ore. The oxygen concentration in the atmosphere subsequently rises, acting as a poison for many bacteria. The moon is still very close to the earth and causes tides 1000 feet high. The earth is continually wracked by hurricane force winds. These extreme mixing influences are thought to stimulate evolutionary processes. (See Oxygen Catastrophe)

Proterozoic eon

2500 Ma – 542 Ma

Date Event
By 2100 Ma Eukaryotic cells appear.[18] Eukaryotes contain membrane-bound organelles with diverse functions, probably derived from prokaryotes engulfing each other via phagocytosis. (See Endosymbiosis)
By 1200 Ma Sexual reproduction evolves, increasing the rate of evolution.[19]
1200 Ma Simple multicellular organisms evolve, mostly consisting of cell colonies of limited complexity.
850–630 Ma A global glaciation may have ocurred.[20][21] Opinion is divided on whether it increased or decreased biodiversity or the rate of evolution.[22][23][24]
580–542 Ma The Ediacaran biota represent the first large, complex multicellular organisms - although their affinities remain a subject of debate.
580–500 Ma Most modern phyla of animals begin to appear in the fossil record during the Cambrian explosion.
Around 540 Ma The accumulation of atmospheric oxygen allows the formation of an ozone layer. This blocks ultraviolet radiation, permitting the colonisation of the land.

Phanerozoic eon

542 Ma – present

The Phanerozoic eon, literally the "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, which are divided by major mass extinctions.

Paleozoic era

542 Ma – 251.0 Ma

Date Event
530 Ma The first known footprints on land date to 530 Ma, indicating that early animal explorations may have predated the development of terrestrial plants.[25]
434 Ma The first primitive plants move onto land,[26][citation needed] having evolved from green algae living along the edges of lakes.[27] They are accompanied by fungi, which may have aided the colonisation of land through symbiosis.
363 Ma By the start of the Carboniferous period, the Earth begins to be recognisable. Insects roamed the land and would soon take to the skies; sharks swam the oceans as top predators,[28] and vegetation covered the land, with seed-bearing plants and forests soon to flourish.

Four-limbed tetrapods gradually gain adaptations which will help them occupy a terrestrial life-habit.

251.4 Ma The Permian-Triassic extinction event eliminates over 95% of species. This "clearing of the slate" may have led to an ensuing diversification.

Mesozoic era

Date Event
From 251.4 Ma The Mesozoic Marine Revolution begins: increasingly well-adapted and diverse predators pressurise sessile marine groups; the "balance of power" in the oceans shifts dramatically as some groups of prey adapt more rapidly and effectively than others.
220 Ma
Eoraptor, an early dinosaur.

Gymnosperm forests dominate the land; herbivores grow to huge sizes in order to accommodate the large guts necessary to digest the nutrient-poor plants.[citation needed]

200 Ma The first accepted evidence for viruses (at least, the group Geminiviridae) exists.[29] Viruses are still poorly understood and may have arisen before "life" itself, or may be a more recent phenomenon.
130 Ma The rise of the Angiosperms: These flowering plants boast structures that attract insects and other animals to spread pollen. This innovation causes a major burst of animal evolution through co-evolution.

Cenozoic era

65.5 Ma – present

Date Event
65.5 Ma
An asteroid impact probably wiped out half of all animals species 65½ million years ago. Other life forms became extinct as well.
An asteroid impact probably wiped out half of all animals species 65½ million years ago. Other life forms became extinct as well.

The Cretaceous–Tertiary extinction event eradicates about half of all animal species, including all dinosaurs except the ancestors of modern birds[30]

35 Ma Grasses evolve from among the angiosperms; grassland dominates many terrestrial ecosystems.
200 ka
(200,000 years ago) 		Anatomically modern humans appear in Africa. Around 50,000 years before present they start colonising the other continents, replacing the Neanderthals in Europe and other hominins in Asia. The Holocene epoch starts 10,000 years ago after the Last Glacial Maximum, with continuing impact from human activity.
Present day With a human population approaching 6.76 billion,[31] the impact of humanity is felt in all corners of the globe. Overfishing, anthropogenic climate change, industrialization, intensive agriculture, clearance of rain forests and other activities contribute to a dramatically rising extinction rate.[32] If current rates continue, humanity will have seen the eradication of one-half of Earth's biodiversity over the next hundred years.[33]

See also

Further reading

References

  1. ^ Planetary Science Institute page on the Giant Impact Hypothesis. Hartmann and Davis belonged to the PSI. This page also contains several paintings of the impact by Hartmann himself.
  2. ^ "However, once the Earth cooled sufficiently, sometime in the first 700 million years of its existence, clouds began to form in the atmosphere, and the Earth entered a new phase of development." How the Oceans Formed (URL accessed on January 9, 2005)
  3. ^ *The 'PAH World'
  4. ^ Gilbert, Walter (1986). "The RNA World". Nature. 319: 618. doi:10.1038/319618a0. {{cite journal}}: Unknown parameter |month= ignored (help)
  5. ^ Joyce, G.F. (2002). "The antiquity of RNA-based evolution". Nature. 418 (6894): 214–21. doi:10.1038/418214a. PMID 12110897.
  6. ^ Hoenigsberg, H. (December 2003)). "Evolution without speciation but with selection: LUCA, the Last Universal Common Ancestor in Gilbert's RNA world". Genetic and Molecular Research. 2 (4): 366–375. PMID 15011140. Retrieved 2008-08-30. {{cite journal}}: Check date values in: |date= (help)(also available as PDF)
  7. ^ Trevors, J. T. and Abel, D. L. (2004). "Chance and necessity do not explain the origin of life". Cell Biol. Int. 28 (11): 729–39. doi:10.1016/j.cellbi.2004.06.006. PMID 15563395.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ Forterre, P., Benachenhou-Lahfa, N., Confalonieri, F., Duguet, M., Elie, C. and Labedan, B. (1992). "The nature of the last universal ancestor and the root of the tree of life, still open questions". BioSystems. 28 (1–3): 15–32. doi:10.1016/0303-2647(92)90004-I. PMID 1337989.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  9. ^ " Between about 3.8 billion and 4.5 billion years ago, no place in the solar system was safe from the huge arsenal of asteroids and comets left over from the formation of the planets. Sleep and Zahnle calculate that Earth was probably hit repeatedly by objects up to 500 kilometers across" Geophysicist Sleep: Martian underground may have harbored early life (URL accessed on January 9, 2005)
  10. ^ Carl Woese, J Peter Gogarten, "When did eukaryotic cells (cells with nuclei and other internal organelles) first evolve? What do we know about how they evolved from earlier life-forms?" Scientific American, October 21, 1999.
  11. ^ Romano AH, Conway T. (1996) Evolution of carbohydrate metabolic pathways. Res Microbiol. 147(6-7):448-55 PMID 9084754
  12. ^ Knowles JR (1980). "Enzyme-catalyzed phosphoryl transfer reactions". Annu. Rev. Biochem. 49: 877–919. doi:10.1146/annurev.bi.49.070180.004305. PMID 6250450.
  13. ^ Doolittle, W. Ford (February, 2000). Uprooting the tree of life. Scientific American 282 (6): 90–95.
  14. ^ Nicolas Glansdorff, Ying Xu & Bernard Labedan: The Last Universal Common Ancestor : emergence, constitution and genetic legacy of an elusive forerunner. Biology Direct 2008, 3:29.
  15. ^ Hahn, Jürgen (1986). "Traces of Archaebacteria in ancient sediments". System Applied Microbiology. 7 (Archaebacteria '85 Proceedings): 178–83. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ^ Olson JM (2006). "Photosynthesis in the Archean era". Photosyn. Res. 88 (2): 109–17. doi:10.1007/s11120-006-9040-5. PMID 16453059. {{cite journal}}: Unknown parameter |month= ignored (help)
  17. ^ Buick R (2008). "When did oxygenic photosynthesis evolve?". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 363 (1504): 2731–43. doi:10.1098/rstb.2008.0041. PMID 18468984. {{cite journal}}: Unknown parameter |month= ignored (help)
  18. ^ Knoll, Andrew H. (2006). "Eukaryotic organisms in Proterozoic oceans". Philosophical Transactions of the Royal Society of London, Part B. 361 (1470): 1023–38. doi:10.1098/rstb.2006.1843. PMC 1578724. PMID 16754612. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  19. ^ "'Experiments with sex have been very hard to conduct,' Goddard said. 'In an experiment, one needs to hold all else constant, apart from the aspect of interest. This means that no higher organisms can be used, since they have to have sex to reproduce and therefore provide no asexual control.'
    Goddard and colleagues instead turned to a single-celled organism, yeast, to test the idea that sex allows populations to adapt to new conditions more rapidly than asexual populations." Sex Speeds Up Evolution, Study Finds (URL accessed on January 9, 2005)
  20. ^ Hoffman, P.F. (1998-08-28). "A Neoproterozoic Snowball Earth". Science. 281 (5381): 1342. doi:10.1126/science.281.5381.1342. PMID 9721097. Retrieved 2007-05-04. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)CS1 maint: date and year (link) Full online article (pdf 260 Kb)
  21. ^ Kirschvink, J.L. (1992). "Late Proterozoic low-latitude global glaciation: The snowball Earth". In Schopf, JW, and Klein, C. (ed.). The Proterozoic Biosphere: A Multidisciplinary Study (PDF). Cambridge University Press, Cambridge. pp. 51–52.{{cite book}}: CS1 maint: multiple names: editors list (link)
  22. ^ http://researchpages.net/media/resources/2007/06/21/richtimhywelfinal.pdf
  23. ^ {cite journal | author = Corsetti, F.A. | coauthors = Awramik, S.M.; Pierce, D. | date = 2003-04-15 | title = A complex microbiota from snowball Earth times: Microfossils from the Neoproterozoic Kingston Peak Formation, Death Valley, USA | journal = Proceedings of the National Academy of Sciences | volume = 100 | issue = 8 | pages = 4399–4404 | doi = 10.1073/pnas.0730560100 | url = http://www.pnas.org/cgi/content/abstract/100/8/4399 | accessdate = 2007-06-28 | pmid = 12682298 }}
  24. ^ Corsetti, F.A. (2006). "The biotic response to Neoproterozoic Snowball Earth". Palaeogeography, Palaeoclimatology, Palaeoecology. 232 (232): 114–130. doi:10.1016/j.palaeo.2005.10.030. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  25. ^ "The oldest fossils of footprints ever found on land hint that animals may have beaten plants out of the primordial seas. Lobster-sized, centipede-like or slug like animals such as Protichnites and Climactichnites made the prints wading out of the ocean and scuttling over sand dunes about 530 million years ago. Previous fossils indicated that animals didn't take this step until 40 million years later." Oldest fossil footprints on land
  26. ^ "The oldest fossils reveal evolution of non-vascular plants by the middle to late Ordovician Period (~450–440 Ma) on the basis of fossil spores" Transition of plants to land
  27. ^ "The land plants evolved from the algae, more specifically green algae, as suggested by certain common biochemical traits" The first land plants
  28. ^ "The ancestry of sharks dates back more than 200 million years before the earliest known dinosaur. Introduction to shark evolution, geologic time and age determination
  29. ^ "Viruses of nearly all the major classes of organisms—animals, plants, fungi and bacteria/archaea—probably evolved with their hosts in the seas, given that most of the evolution of life on this planet has occurred there. This means that viruses also probably emerged from the waters with their different hosts, during the successive waves of colonisation of the terrestrial environment." Origins of Viruses (URL accessed on January 9, 2005)
  30. ^ . Chiappe, Luis M., & Dyke, Gareth J. (2002). "The Mesozoic Radiation of Birds". Annual Review of Ecology & Systematics. 33: 91–124. doi:10.1146/annurev.ecolsys.33.010802.150517. {{cite journal}}: Unknown parameter |quotes= ignored (help)CS1 maint: multiple names: authors list (link)
  31. ^ An United States Census Bureau estimate of the number of people alive on Earth at any given moment. United States census bureau
  32. ^ The American Museum of Natural History National Survey Reveals Biodiversity Crisis (URL accessed on February 23, 2006)
  33. ^ E. O. Wilson, Harvard University, The Future of Life (2002)

External links


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