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=== Biomarker === |
=== Biomarker === |
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Cholestane in the fossil record is often interpreted as an indicator ([[Biomarker (petroleum)|biomarker]]) of ancient animal life and is often used by geochemists and geobiologists to reconstruct animal evolution (particularly in the [[Precambrian]] Earth history; e.g., [[Ediacaran]],<ref name=":0" /> [[Cryogenian]] and [[Proterozoic]] in general<ref name=":1">{{Cite journal|last1=Brocks|first1=Jochen J.|last2=Jarrett|first2=Amber J. M.|last3=Sirantoine|first3=Eva|last4=Hallmann|first4=Christian|last5=Hoshino|first5=Yosuke|last6=Liyanage|first6=Tharika|date=August 2017|title=The rise of algae in Cryogenian oceans and the emergence of animals|journal=Nature|volume=548|issue=7669|pages=578–581|doi=10.1038/nature23457|pmid=28813409|issn=0028-0836|bibcode=2017Natur.548..578B|s2cid=205258987}}</ref><ref>{{Cite journal|last1=Summons|first1=Roger E|last2=Brassell|first2=Simon C|last3=Eglinton|first3=Geoffrey|last4=Evans|first4=Evan|last5=Horodyski|first5=Robert J|last6=Robinson|first6=Neil|last7=Ward|first7=David M|date=November 1988|title=Distinctive hydrocarbon biomarkers from fossiliferous sediment of the Late Proterozoic Walcott Member, Chuar Group, Grand Canyon, Arizona|journal=Geochimica et Cosmochimica Acta|volume=52|issue=11|pages=2625–2637|doi=10.1016/0016-7037(88)90031-2|issn=0016-7037|bibcode=1988GeCoA..52.2625S}}</ref>). Molecular oxygen is required to produce cholesterol;<ref>{{Cite web|url=https://pharmaxchange.info/2013/09/biosynthesis-and-regulation-of-cholesterol-animation/|title=Biosynthesis and Regulation of Cholesterol (with Animation) {{!}} Animations|last=Mehta|first=Sweety|date=2013-09-17|website=PharmaXChange.info|access-date=2019-06-04}}</ref> thus, the presence of cholestane suggests some trace of oxygen in the paleoenvironment. Cholestane is not exclusively derived from diagenesis of animal-derived steroid molecules; cholestane may also be associated with the presence of e.g., [[Red algae|rhodophytes]] and [[ |
Cholestane in the fossil record is often interpreted as an indicator ([[Biomarker (petroleum)|biomarker]]) of ancient animal life and is often used by geochemists and geobiologists to reconstruct animal evolution (particularly in the [[Precambrian]] Earth history; e.g., [[Ediacaran]],<ref name=":0" /> [[Cryogenian]] and [[Proterozoic]] in general<ref name=":1">{{Cite journal|last1=Brocks|first1=Jochen J.|last2=Jarrett|first2=Amber J. M.|last3=Sirantoine|first3=Eva|last4=Hallmann|first4=Christian|last5=Hoshino|first5=Yosuke|last6=Liyanage|first6=Tharika|date=August 2017|title=The rise of algae in Cryogenian oceans and the emergence of animals|journal=Nature|volume=548|issue=7669|pages=578–581|doi=10.1038/nature23457|pmid=28813409|issn=0028-0836|bibcode=2017Natur.548..578B|s2cid=205258987}}</ref><ref>{{Cite journal|last1=Summons|first1=Roger E|last2=Brassell|first2=Simon C|last3=Eglinton|first3=Geoffrey|last4=Evans|first4=Evan|last5=Horodyski|first5=Robert J|last6=Robinson|first6=Neil|last7=Ward|first7=David M|date=November 1988|title=Distinctive hydrocarbon biomarkers from fossiliferous sediment of the Late Proterozoic Walcott Member, Chuar Group, Grand Canyon, Arizona|journal=Geochimica et Cosmochimica Acta|volume=52|issue=11|pages=2625–2637|doi=10.1016/0016-7037(88)90031-2|issn=0016-7037|bibcode=1988GeCoA..52.2625S}}</ref>). Molecular oxygen is required to produce cholesterol;<ref>{{Cite web|url=https://pharmaxchange.info/2013/09/biosynthesis-and-regulation-of-cholesterol-animation/|title=Biosynthesis and Regulation of Cholesterol (with Animation) {{!}} Animations|last=Mehta|first=Sweety|date=2013-09-17|website=PharmaXChange.info|access-date=2019-06-04}}</ref> thus, the presence of cholestane suggests some trace of oxygen in the paleoenvironment. Cholestane is not exclusively derived from diagenesis of animal-derived steroid molecules; cholestane may also be associated with the presence of e.g., [[Red algae|rhodophytes]] and [[Embryophyte|embryophtes]],<ref>{{Cite journal|last1=Summons|first1=Roger E.|last2=Erwin|first2=Douglas H.|date=2018-09-20|title=Chemical clues to the earliest animal fossils|journal=Science|volume=361|issue=6408|pages=1198–1199|doi=10.1126/science.aau9710|pmid=30237342|issn=0036-8075|bibcode=2018Sci...361.1198S|hdl=1721.1/134716.2|s2cid=52306517|hdl-access=free}}</ref><ref name=":3" /> although the abundance of such non-metaozan cholestane is unknown. Embryophytes generally produce a variety of sterols, which are collectively known as [[Phytosterol|phytoterols]],<ref>{{Cite journal|last1=Darnet|first1=Sylvain|last2=Blary|first2=Aurélien|last3=Chevalier|first3=Quentin|last4=Schaller|first4=Hubert|date=2021|title=Phytosterol Profiles, Genomes and Enzymes – An Overview|journal=Frontiers in Plant Science|volume=12|pages=878|doi=10.3389/fpls.2021.665206|issn=1664-462X|pmc=8172173|pmid=34093623|doi-access=free}}</ref> and cholesterol remains a minor component. In contrast, [[bacteria]] produce other cyclic triterpenoids such as [[hopanoids]] and their diagenetic products [[hopane]]s are utilized as bacterial biomarkers. |
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== Natural preservation in fossils == |
== Natural preservation in fossils == |
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Greek: Ά ά Έ έ Ή ή Ί ί Ό ό Ύ ύ Ώ ώ Α α Β β Γ γ Δ δ Ε ε Ζ ζ Η η Θ θ Ι ι Κ κ Λ λ Μ μ Ν ν Ξ ξ Ο ο Π π Ρ ρ Σ σ ς Τ τ Υ υ Φ φ Χ χ Ψ ψ Ω ω {{Polytonic|}}
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