what belief led to the original classification of organic molecules?

ORIGIN OF LIFE

J. Bailey , in Encyclopedia of Geology, 2005

Development of Ideas on the Origin of Life

The idea that all life on World has a common origin became well established only in the twentieth century. Early ideas on the evolution of life were most conspicuously expressed by Lamarck, who described the process as one of progression from simpler to more complex and advanced forms (see EVOLUTION). The observation that both uncomplicated and complex organisms are currently present therefore required that simple organisms are appearing even today from inorganic matter by a process of 'spontaneous generation' (a concept that has its origins in antiquity). Thus, the ideas of transformism (evolution) and spontaneous generation were closely linked in the early nineteenth century and put Lamarck and his followers in disharmonize with the religious and scientific establishment, who argued for the immutability of species, which were divinely created in their current forms. Lamarck'due south ideas were criticized by scientists such as Cuvier (come across FAMOUS GEOLOGISTS | Cuvier) (in a celebrated debate with Geoffroy Saint-Hilaire in 1830) and later by Pasteur, who carried out his famous 'swan-necked flask' experiments to discredit the thought of spontaneous generation.

Darwin's theory of evolution past natural option opened the mode for the modern view of the origin of life ( see FAMOUS GEOLOGISTS | Darwin). In Darwin's theory there is not necessarily a ladder of progress from simple to more complex forms. Simple organisms can be as evolutionarily successful as complex ones. This allowed the idea that all life, simple and complex, had a single origin in the distant past. While the subject of the origin of life is hardly mentioned in Darwin's published writings, the following quote (from a letter to his botanist friend Joseph Hooker) gives us an inkling of his thoughts on the field of study at that time:

If (and oh! what a large if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity present, that a protein compound was chemically formed, ready to undergo nonetheless more complex changes… .

Oparin and Haldane in the early twentieth century developed the thought that chemic reactions on the early Earth could take led to the production of a range of organic compounds, forming a 'primordial soup' in which the required building blocks for life would have been nowadays.

Simply it was not until 1953 that these ideas received experimental back up. Stanley Miller, then a graduate student working in the laboratory of Harold Urey, gear up upward his famous experiment in which electric discharges were passed through a mixture of gases (marsh gas, ammonia, hydrogen, and water vapour) simulating a thunderstorm on the archaic Earth. The experiment produced a mixture of several amino acids, the building blocks of proteins. Miller speculated that this was how organic compounds had been fabricated on the early on Earth. In the aforementioned twelvemonth, Crick and Watson published their structure for Dna, the get-go step in elucidating the primal molecular basis of life. These 2 discoveries meant that we had both a plausible way of generating unproblematic organic building blocks and an understanding of the macromolecules on which life depends. A detailed experimental and theoretical study of the origin of life was at present possible.

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Foreword

In Investigating Seafloors and Oceans, 2017

The origin of life is a long-standing and controversial subject field, and dissimilar processes have been proposed. Co-ordinate to one, lightning in the early atmosphere and the consequent production of amino acids, when combined in long polymer chains, provided the basic constituents of life. The second concerns chemical processes at submarine volcanic vents which are thought to have been mutual in the Archean menses (four–two.5 BYA), and life at those depths would have been shielded from the ultraviolet radiations that then existed due to the absence of an ozone layer. The third proposed mechanism has life originating from the carbon and hydrocarbons in comets and meteorites every bit they burned in the atmosphere. It has also been suggested life may accept originated in inter-tidal pools that were repeatedly flooded and stale out under the sun—a process for which the geological record provides evidence.

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Coenzyme Earth Model of the Origin of Life

Alexei A. Sharov , in Habitability of the Universe Earlier Earth, 2018

Abstract

The origin of life means the emergence of heritable and evolvable self-reproduction. However, the mechanisms of primordial heredity were dissimilar from those in contemporary cells. Here, I fence that primordial life had no nucleic acids; instead, heritable signs were represented by isolated catalytically active self-reproducing molecules, similar to extant coenzymes, which presumably colonized surfaces of oil aerosol in water. The model further assumes that coenzyme-like molecules (CLMs) changed surface properties of oil aerosol (eastward.g., past oxidizing last carbons), and in this way, created and sustained favorable weather for their own self-reproduction. Such niche-dependent self-reproduction is a necessary status for cooperation between different kinds of CLMs because they have to coexist in the same oil droplets and either succeed or perish together. Additional kinds of hereditary molecules were acquired via coalescence of oil droplets conveying dissimilar kinds of CLMs or via modification of already existing CLMs. Eventually, polymerization of CLMs became controlled by other polymers used as templates; and this kind of template-based synthesis eventually resulted in the emergence of RNA-similar replicons. Apparently, oil aerosol transformed into the outer membrane of cells via engulfing water, stabilization of the surface, and osmoregulation. In consequence, the metabolism was internalized allowing cells to accrue free-floating resource (east.g., animoacids, ATP), which was a necessary condition for the development of protein synthesis. Thus, life originated from unproblematic only already functional molecules, and its gradual evolution towards higher complexity was driven by cooperation and natural pick.

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Astronomical and Biological Organizational Relationships

Dr. Antony Joseph , in Investigating Seafloors and Oceans, 2017

five.5.2 Two Opposing Views on Origin of Life

"Origin of Life" is a very complex subject, and frequently controversial. Two opposing scientific theories that existed on this complex subject for a long time were the then-called intelligent design and creationism. As indicated earlier, the satisfactory explanation offered by the large blindside theory of the origin of the Universe gave a new dimension to the give-and-take on the topic of biological evolution. It has been hypothesized that circuitous life-forms on Earth, including humans, arose over a period of fourth dimension from unproblematic bacteria-similar tiny cells by a process of self-arrangement akin to the evolution of the Universe by self-organisation of unproblematic material structures (ie, primal particles produced by the big bang) toward more than and more circuitous structures.

The "warm little pond" paradigm neatly described by the celebrated naturalist Charles Darwin, and documented in The Life And Messages of Charles Darwin has played a pregnant role in shaping our view of bacterial origins. However, according to Woese (1987), Darwin'south "warm little pond" paradigm has never been intended to exist a prescription for life's ancestry; probably, it was rather intended to requite his successors a guiding principle. It is believed that Darwin understood that the subject field of "life's beginnings" belonged to the future.

The existence of thermophilic bacteria probably compels microbiologists to believe that the setting in which bacteria arose may well accept been warm, just it was not the hospitable warmth implicit in the "pond" Darwin pictured. The collection of images associated with the prokaryote-eukaryote dichotomy, the Oparin Ocean scenario, and, to a lesser extent, Darwin's "warm little pond" form the starting point and dictate the direction of our thinking near bacterial development.

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Depositional environs and lithofacies estimation

Paul C.H. Veeken , Bruno van Moerkerken , in Seismic Stratigraphy and Depositional Facies Models, 2013

4.5.2 Meteorites and extra-terrestrial origin of life

The origin of life on Earth could have resulted from asteroid impacts, conveying life forms and molecules from far away planets and fifty-fifty from dissimilar solar systems ( Figure 4.209). The Murchison meteorite (carbonaceous chondrite), that came down in 1969 in Australia, demonstrates the validity of such a type of interplanetary transportation mechanism. Several fragments have been collected, upward to a total weight of 100   kg. The meteorite textile has been studied extensively and is proven to contain 18-carat amino acids from outer space (Figure four.210). It contains more than than hundred amino acids, among which the edifice rock for organic life. Contamination of the sample used in the analysis from an earthy source has been excluded by scientists (Wikipedia August 2012). Presence of surface water in the past on Mars seems nowadays no longer a far-fetched scenario. It is considered past many researchers a rather likely option in the history of our neighbouring planet (Bhattacharya et al. 2005, Grotzinger and Milliken 2010). The ripple laminated sands on Mars are thought to be water laid deposits (Effigy 4.211; Bhattacharya et al. 2012). Several reasons tin exist given:

Figure four.209. Extra-terrestrial meteoric impact might provide a vehicle to transport life from outer space to the Globe, or possibly it also even came from within our own solar organisation. Water on Mars has been demonstrated past several NASA infinite missions. Sedimentary cross-bedding on Mars has been documented by the rover missions. Canyon systems did exist at some point in time on the ruby-red planet and a fluidized phase was abundant. Building stones for life could have been transferred from Mars to the Earth via cosmic debris, mobilised during a severe impact on the red planet. The asteroid touch at the K/T boundary shows that large objects have been intercepted by the Earth in the past on its elliptic trajectory around the sun

Veeken 2007.

Effigy four.210. The Murchison meteorite came down in Australia in 1969 and has been studied in slap-up detail for its chemic contents. It contains many organic components and therefore it is believed that life is probably more widespread in the universe. Meteorites may provide a means of transport for organic cloth through the universe

Wikipedia, September 2012.

Figure iv.211. Ripple laminated clastic deposits on Mars seen on aerial photographs made by the Opportunity Mars vehicle (NASA / JPL). The rounded particles probably stand for reworked concretion nodules and this would explain the eccentric bi-modal grainsize distribution. The ripples signal traction of some sort by a fluidized menstruum. Eolian origin is excluded based on variation in grainsize. It is an other slice of prove for the existence of h2o in the very far by of our neighbour planet Mars

modified after J. Grotzinger / Bhattacharya et al. 2012.

•

Bimodal grainsize distribution.

•

Sedimentary lamination due to erosion and transportation.

•

Traction of particles in a fluidized medium.

•

Eolian origin is excluded by the peculiar grainsize distribution and sorting.

Hematite globules are thought to exist formed under the influence of water. Jarosite also needs water for its growth. Goethite has been proven by the Mossbauer Spectrometer mounted on the Spirit rover that besides needs water for its germination. Opal and ancient hydrothermal system is nowadays in the Gusev crater. Moreover, the aerial photographs of Mars show the presence of channels and canyons. In many cases the meandering channels illustrate a radial distributary drainage pattern that corresponds to a fan-type configuration. Several sequential lobes are distinguished on the aerial photographs of NASA/JPL (Figure 4.212). Life on Mars is therefore no longer a far fetched option (McKay et al. 1996, Frankel 1999), but can be considered an interesting issue that warrants further research.

Figure 4.212. Meandering channels in a fan type of setting or mayhap even a detaic environs could be envisaged. The lobes are active in different times. The distributary geometry is evident and also the radial overall shape of the sedimentary body can be recognised in this aerial photograph from Mars

Bhattacharya et al. 2012.

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The Role of Oceans in the Origin of Life and in Biological Development

Dr. Antony Joseph , in Investigating Seafloors and Oceans, 2017

4.i.1 Origin of Unmarried-Jail cell Organisms in Oceans

The origin of life is a long-standing and controversial subject area concerned with how the first known single-prison cell organisms called prokaryotes probably originated in the Archean period (four–2.5  BYA) and about 3.8   BYA in the oceans when chemical limerick of the bounding main and the atmosphere was very different from what it is today (see Dostal et al., 2009). I candidate machinery involves lightning in the early atmosphere and the consistent production of amino acids that, when combined in long bondage, provided the bones constituents of life. A second machinery concerns chemic processes at submarine volcanic vents. Such vents, like to the "black smokers" of today (see Rona et al., 1986), are thought to have been common in the Archean period, and life at those depths would have been shielded from the ultraviolet radiations that existed at that time due to the absence of an ozone layer. A third mechanism has life originating from the carbon and hydrocarbons in comets and meteorites equally they burned in the atmosphere. Nonetheless, a process that mostly concerns the states is the possibility that life originated in intertidal pools that were repeatedly flooded and dried out nether the Sun, a process for which the geological record provides testify (see Dostal et al., 2009).

Precellular systems called liposomes take been identified in which the encapsulation of DNA has been achieved using dehydration-hydration cycles like to those that may have occurred in an intertidal setting on the early Globe (see Oro et al., 1990). Once self-replication of life was established, then evolution to more than complicated forms of life could take taken place past Darwinian selection (run into Benn, 2001). The ocean could accept played farther roles in human development, for example via the aquatic ape hypothesis, although that detail theory is not widely accepted (see Hoare, 2013).

About 3   BYA, something similar to modern photosynthesis adult and oxygen was produced. Over time, it transformed Earth's temper to its electric current state. Some of the oxygen reacted to class ozone, which collected in a layer near the upper part of the atmosphere. By blocking the ultraviolet radiation, it allowed cells to colonize the surface of the sea and ultimately the land. Fish, the earliest vertebrates, evolved in the oceans effectually 530   MYA.

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Volume 3

Humberto Fifty.S. Reis , Evelyn A.M. Sanchez , in Encyclopedia of Geology (Second Edition), 2021

The Origin of Life

The origin of life is certainly one of the almost intriguing and fundamental questions asked by humanity. Several settings, biochemical mechanisms and paleoenvironmental conditions have been proposed to explain the emergence of life, making necessary an interdisciplinary approach to understand such a unique event. Laboratory experiments and modeling, the analysis of the stone record and the observation of outer space are among the primary techniques practical to investigate this subject, which demands a different and non-actualistic approach to (bio)chemical systems.

For life to flourish, the evolution of different and intrinsically interconnected compartments was first necessary: the cosmos, the Solid World, the Earth's temper-hydrosphere, and its chemical systems. The evolution of these compartments and their mechanisms took time and resulted, ultimately, in the auto-organized and auto-replicating chemical molecules referred to as life. Once established, life persisted on our planet and likely never completely disappeared.

Available information suggests that, by the time life originated, World went through a series of bolide bombardments (described above). In a general panorama, information technology seems that life may have originated and become extinct many times during the sterilizing collisions of the Hadean Early Heavy Bombardment and probably due to the heating up and ecosystem-destroying impacts of the Tardily Heavy Bombardment upshot. Alternatively, available reckoner modeling has as well indicated that much of the Earth's surface may take not experienced the heating effects of pocket-size- to medium-sized impacts. Instead, the heated areas (to a higher place 110   °C) would accept not been large enough to completely extinguish life or the oceans, and habitable weather remained. The same models also advise that pocket-size portions of Globe'due south chaff might have been metamorphosed by impacts, reaching temperatures near 500   °C. Possibly, the Tardily Heavy Bombardment offered important weather for helping life (re-)establish. Together with extreme volcanism rates, they might have contributed to create subaqueous hydrothermal systems, paleosettings widely accepted as the cradle of life.

The influence of asteroid impacts has as well been used to address an additional paradox on the Hadean to early Archean life's origin. If one considers the Faint Immature Sunday paleoenvironmental model (Fig. 3), information technology is viable that the impacts of both planetesimals and other extraterrestrial bodies may have been of great importance for life's origin. Impacts would accept represented a determinant cistron to solve this paradox, producing heat and releasing greenhouse gases into the atmosphere, which melted the any existing frozen ocean and allowed life to plant and disperse in subaqueous systems.

A complex scenario because energy and carbon sources and ideal paleoenvironmental conditions was fundamental to build the starting time biomolecules (the earliest forms of life). The Heavy Bombardment Events, geothermal energy, atmospheric discharges, and solar radiation may have represented get-go-order energy sources, while carbon and other of import chemical elements were likely sourced past interstellar dust, chondrite meteorites and organic compounds released through magmatic events. These ingredients combined in a scenario with an early temper and a primitive magnetic shield (equally depicted by Hadean zircons), in what may have been both shallow water conditions and terrestrial ponds or hydrothermal vents in the deepest parts of the earliest oceans. The latter take been accepted as the nigh suitable for life's cradle, one time they fit all the basic needings such as a wide range of temperatures, free energy sources, and organic compounds. In addition, the fossil record, in some way, is in agreement with this hypothesis, since the oldest microfossil occurrences have been plant in rocks formed in deep h2o hydrothermal settings. These records include possible 3.viii–iii.7   Ga organic remains found in chemical metasedimentary rocks of the Isua supracrustal belt and the Nuvvuagittuq greenstone belt. Estimates of the terminal impact large enough to vaporize global oceans at c. four.3   Ga seem to provide an upper limit for the origin and subsequent establishment of life, an assumption supported by contempo molecular clock analyses indicating the origin of marsh gas-based metabolism during this flow. Although the early Earth most likely held all the necessary ingredients and environmental settings for life to originate, an extraterrestrial origin cannot exist ruled out. Asteroids and other extraterrestrial surfaces, such as on Mars, may also have presented all of the features necessary for life's origin.

Irrespective of the major controlling mechanisms, information technology is already known that life rapidly arose subsequently the last severe bear upon episode in the Eoarchean. Regardless of the very poor preservation of ancient life remnants due to resurfacing processes and late geological events, this fact opens new perspectives on the time necessary for life to originate and evolve and, lastly, become the biosphere. This may too be extrapolated for astrobiological purposes, allowing new approaches and expectations in the search for past and present life in the universe.

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Organic Geochemistry

Thou. Grice , C. Eiserbeck , in Treatise on Geochemistry (Second Edition), 2014

12.3.ane Introduction

The origin of life on Earth and its potential beingness on other planets present one of science'south greatest unresolved mysteries. Information technology is now widely accustomed that biomarkers (molecular fossils) are derived from lipids and other natural products such every bit photosynthetic pigments. In sedimentary systems, lipids tin be reduced to biomarkers. Biomarkers can exist in sediments and oils over hundreds of millions of years. Many of the biomarkers encountered in sediments and oils have been related to lipids and other biochemicals of present-day biological systems, thus allowing their biomarker–precursor relationships to exist established. They bridge the 3 domains of life: eukaryotes, bacteria, and archaea ( Brocks and Grice, 2011; Brocks and Pearson, 2005; Brocks and Summons, 2004; Grice and Brocks, 2011). Lipids including sterols, hopanols, alcohols, phospholipids, and ether-lipids are the molecular components of cell membranes. The identity, isomeric arrangement, and stable isotopic limerick of biomarkers have been widely used in studies of oils and sedimentary organic affair (OM) to appraise the source of OM and provide paleoenvironmental depositional information. In the nineteenth century, many scientists supported an inorganic source for hydrocarbons nowadays in oil. In 1866, Marcellin Berthelot suggested that oil was formed past the reaction of h2o with inorganic carbides (Berthelot, 1866), and in 1878, Dmitri Mendeleev (1878) contended that oil is abiogenic and is formed within World'south chaff. However, the first fundamental basis for sedimentary rocks and oils containing biomarkers was presented by Alfred Treibs. In 1934, Treibs separated a vanadyl-porphyrin complex (I) begetting a similar structure to chlorophyll a (Two) present in eukaryotes (plants and algae) from an OM-rich black shale. Alfred Treibs (1936) later on elucidated the degradation pathway of chlorophyll a in sedimentary environments, and is now regarded as the 'prominent father' of biomarker geochemistry. In his retentivity, the Alfred Treibs Medal is awarded by The Organic Geochemistry Division of the Geochemical Guild and European Association of Geochemistry for major achievements over a period of years in the discipline of organic geochemistry.

The rapid development of chemical separation and detection techniques such as GC (gas chromatography), GC-MS (gas chromatography-mass spectroscopy) and elemental analysis in the 1960s and 1970s facilitated the analysis of such complex mixtures as petroleum and stone extracts. Some early biomarker studies were motivated by the search for evidence of early life on Earth (Barghoorn, 1957; Barghoorn et al., 1965; Burlingame et al., 1965; Eglinton et al., 1964; Hoering, 1965; Kvenvolden and Hodgson, 1969; Meinschein et al., 1964; Oró and Nooner, 1967). Delight too encounter Chapter 12.2 in this volume. Later in the mid-to-tardily twentieth century, the focus of geochemistry shifted toward the petroleum industry. Biomarkers were applied to study and understand the transformation of OM into petroleum, including secondary processes such as thermal maturity, biodegradation, and the estimation of the geological age of reservoired oil (Albrecht and Ourisson, 1969; Chase, 1979; Peters et al., 2005; Philippi, 1965; Tissot and Welte, 1984).

With oil prices declining in 1998, organic geochemistry shifted to a inquiry-focused subject field in academic institutions. More recently, the focus has moved toward the report of organisms and metabolisms (including stable carbon and hydrogen isotope studies) that otherwise rarely leave a fossil record (e.grand., Chikaraishi and Naraoka, 2006; Chikaraishi et al., 2004a,b; Collister et al., 1994; de Leeuw et al., 1980; Eglinton and Hamilton, 1967; Goericke et al., 1994; Grice et al., 1998a, 2008; Hayes, 1993, 2001; Hinrichs et al., 1999; Jasper et al., 1994; Kuypers et al., 2001; Laws et al., 1995; Massé et al., 2004; Melzer and Schmidt, 1987; Moldowan and Talyzina, 1998; Monson and Hayes, 1982; Popp et al., 1998; Rechka and Maxwell, 1988; Schouten et al., 1998; Schwender et al., 1996; Sessions et al., 1999; Sinninghe Damsté et al., 2004a; Smith and Freeman, 2006; Summons et al., 1994, 1999; van der Meer et al., 1998; Volkman, 2003; Volkman et al., 1980; Werne et al., 2002; Zhou et al., 2010, 2011), and paleoenvironmental and paleoclimatic proxies (Audino et al., 2001a; Boetius et al., 2000; Brassell et al., 1986; Castañeda and Schouten, 2011; Coolen et al., 2004; Freeman et al., 1990; Grice et al., 1996a,b, 1998c, 2001; Hartgers et al., 1994; Hinrichs et al., 1999; Huang et al., 2000; Jaraula et al., 2010; Kashiyama et al., 2008; Meyers, 1997; Murray et al., 1998a; Pagani et al., 2006; Schefuss et al., 2003; Schoell et al., 1994; Schouten et al., 1997, 2002; Sinninghe Damsté et al., 1989, 1993; Smith et al., 2007; Summons and Powell, 1986; Wiesenberg et al., 2004).

Biomarkers derived from an extinct organism tin constrain the minimum age of a sedimentary rock. Some biomarkers specific for a source organism that was known to take evolved at a certain geological era can signify the maximum age of the sedimentary rock. Some biomarkers are age-specific and the organisms that give ascension to these components are conservative in their lipid biochemistry and their resulting stable isotopic compositions. Historic period-specific biomarkers are used to acquire information about the composition of aboriginal microbial ecosystems or to determine the initial occurrence of organisms in the geologic record. Since well-nigh organisms accept a preference for specific environments, and because lipid compositions of private organisms are often attuned to changing atmospheric condition (e.thou., salinity, temperature, and oxygen), biomarkers may also serve as paleoenvironmental proxies (see Department 12.three.2 ). Different stages of degradation and thermal maturation (diagenesis, catagenesis, metagenesis; e.g., Brocks and Grice, 2011; Peters et al., 2005) influence the biomarker skeleton and have to be considered when relating the biomarker to its biological source, age, and paleoenvironment of degradation. The benefit of biomarkers over macrofossils is their occurrence in both sedimentary rocks and oil. Thus, biomarkers have been successfully applied to oil–oil and oil–source correlation research studies (east.one thousand., Aboglila et al., 2011; Al-Arouri et al., 1998; Cai et al., 2009; Chen et al., 2003; Curiale, 2008; Eneogwe, 2004; Farrimond et al., 2004; Fowler and Douglas, 1984; George et al., 2004; Grosjean et al., 2009; Li et al., 2008; Ocampo et al., 1993).

The following summary contains a discussion of the virtually essential biomarkers in relation to the reconstruction of paleoenvironments ( Tabular array 1 ) and age(south) of deposition ( Table 2 ). Additional references can be establish, for example, in Peters et al. (2005), Brocks and Summons (2004), Brocks and Grice (2011), and Grice and Brocks (2011). Furthermore, the give-and-take includes the application of biomarker distributions associated with major extinction events in geological history and frontier developments in selected analytical techniques for the analyses of biomarkers in different sample types.

Table 1. Environmental diagnostic markers

Biomarker	Biological source	Environmental estimation	Additional sources	References
Stratified waters, anoxia
Crocetane	Isorenieratene in anaerobic methane oxidisers (ANMO), green sulfur bacteria	Sub-sea gas sources, gas hydrates, mud volcanoes, photic zone euxinia	Deposition product of diaromatic carotenoids	Maslen et al. (2009), Thiel et al. (1999a), Pancost (2000), Hartgers et al., (1993), Requejo et al. (1992), Greenwood and Summons (2003)
Isorenieratane	Carotenoid isorenieratene of brown pigmented species, green sulfur bacteria	Photic zone euxinia	Some sponges, Actinomycetales	Bosch et al. (1998), Grice et al. (1996b, 1997), Hartgers et al. (1993), Koopmans et al. (1996a, b), Pancost et al. (1998), Putschew et al. (1998), Simons and Kenig (2001), Hartgers et al. 1994, Requejo et al. (1992), Melendez et al. (2013)
β-Isorenieratane	Carotenoid β-isorenieratene of chocolate-brown pigmented species, light-green sulfur leaner	Photic zone euxinia		Brocks and Schaeffer (2008), Grice et al., (1998b), see "isorenieratane" above)
ii,three,6-Trimethyl aryl isoprenoids	Cleavage products of above isorenieratanes	Photic zone euxinia	Aromatization and degradation of β-carotene	Hartgers et al. (1993), Koopmans et al. (1996b), Requejo et al. (1992), Summons and Powell (1986)
Palaerenieratane and 3,4,5-trimethyl aryl isoprenoids	Precursors unknown	Photic zone euxinia		Hartgers et al. (1993), Requejo et al. (1992), Grice et al. (1996b)
Okenane	Purple sulfur bacteria (Chromatiaceae)	Photic zone euxinia, planktonic conditions		Brocks et al. (2005), Brocks and Schaeffer (2008)
Chlorobactane	Green sulfur bacteria	Anoxic and sulfidic weather condition in the presence of light in microbial mats or planktonic environments (photic zone euxinia)		Brocks et al. (2005), Grice et al. (1998d, 2005), Schaeffer et al. (1997)
3-Isobutyl-four-methylmaleimide	Degradation product of BChl c, d and east	Photic zone euxinia	Chlorobi	Grice et al. (1996a, 1997), Pancost et al. (2002)
Gammacerane	Tetrahymanol in ciliates feeding on leaner	Chemocline of stratified waters	Tetrahymanol was too observed in a fungus, a fern and the ubiquitous a-proteobacterium Rhodopseudomonas	Sinninghe Damsté et al. (1995), ten Haven et al. (1989), BarbÕ et al. (1990), Harvey and McManus (1991),Ourisson et al. (1987)
Marine
24-n-Propylcholestane	Pelagophyte algae ('dark-brown tides' and Sarcinochrysidales)	Commonly merely establish in marine environments		Peters (1986), Moldowan et al. (1990), Peter et al. (2005)
Dinosterane (23,24-dimethylcholestane)	Dinoflagellates, haptophytes	Marine	Small-scale and rare in diatoms	Moldowan and Talyzina (1998), Robinson et al. (1984), Volkman et al. (1993)
Mid chain monomethylalkanes	Cyanobacteria	Hot springs, marine, mainly Precambrian		Summons and Walter (1990), Chiliad­ster et al. (1999), Shiea et al. (1990), Thiel et al. (1999b)
C25 and C30 highly branched isoprenoid (HBI) alkanes (precursors: HBI alkenes)	Axial diatoms (genus Rhizosolenia)	Marine	C25 HBI in pennate diatoms	Nichols et al. (1988), Sinninghe Damsté et al. (2004a), Volkman et al. (1994)
Crenarchaeol	Crenarchaeotes	Marine		Sinninghe-DamstÕ et al. (2002)
Lacustrine
3β-Methylhopanes	Type-I methanotrophic bacteria (Methylococcaceae), microaerophilic proteobacteria	Lacustrine	Methylotrophs, acetic acid bacteria	Farrimond et al. (2000), Summons and Jahnke, (1992), Zundel and Rohmer (1985a, 1985b, 1985c), Collister et al. (1992)
C30–C37 Botryococcanes, cyclobotryococcanes, polymethylsqualanes	Botryococcus braunii, race B(Chlorophyte alga)	Fresh to brackish water, third		Huang et al. (1988), Metzger et al. (1985), Metzger and Largeau (1999), Summons et al. (2002), Grice et al. (1998c,d), Maxwell et al. (1968)
Macrocyclic C15–C34 alkanes without carbon number preference	B. braunii	Fresh to stagnant water, 3rd		Grice et al. (2001), Audino et al. (2001, 2002, 2004)
Marine/lacustrine
iv-Methylergostane; 4-methylstigmastane	Dinoflagellates	Lacustrine or marine	Pocket-sized component in other eukaryotes	Volkman (2003)
four-Methycholestanes, 4,four-dimethylcholestanes	Dinoflagellates	Lacustrine or marine	Modest component in all eukaryotes	Bird et al. (1971), Brocks et al. (2005), Summons et al. (1988)
Cxx + C25 HBI alkanes	Pennate diatoms (phylogenetic cluster including Haslea, Pleurosigma, Navicula)	Marine, lacustrine	Axial diatoms (genus Rhizosolenia)	Nichols et al. (1988), Sinninghe Damsté et al. (2004a)
Terrigenous environments
due north-Alkanes >   C25 with odd-over-fifty-fifty carbon number preference	State plants in full general	Terrigenous	Non-marine algae	Hedberg (1968), Tissot and Welte (1984)
northward-Ctwoscore–due north-C100	Cuticular waxes inland lants	Terrigenous		del RÚo and Philp (1999), Nip et al. (1986), Tegelaar et al. (1995)
Dominant n-Cxiv and n-C19 (even numbered)	Land plants in general	Terrigenous		Kuhn et al. (2010), Zhou et al. (2010)
C27–C29 sterane	Algae and higher plants	Terrigenous (high C29%)		Grantham and Wakefield (1988), Huang and Meinschein (1979), Philp and Gilbert (1986), Moldowan et al. (1985)
Isopimarane, retene, simonellite, eudesmane, fichtelite	Conifers	Terrigenous	Possible occurrence in algae and microorganisms	Otto and Wilde (2001), Otto and Simoneit (2002), Blunt et al. (1988), Alexander et al. (1983), Noble et al. (1986), Zinniker (2005)
Phyllocladanes, beyerane, kaurane, atisane	Conifers	Terrigenous	Lower concentrations in other land plants and peradventure algae	Noble et al. (1985), (1986)
Oleananes, lupanes	Angiosperms	Terrigenous	Precursors also occur in lichen and ferns in pocket-sized concentrations	Moldowan et al. (1994), Riva et al. (1988), Ekweozor et al. (1988, 1990), Eiserbeck et al. (2011a,b), Murray et al. (1997), Rullk­tter et al. (1994,) ten Haven et al. (1992a,b, 1988), Freeman et al. (1994), Stout (1992), Peakman et al. (1991)
24-Norlupane, 24,28-bisnorlupane	Angiosperms	Terrigenous		Curiale (2006)
Cadinanes, bicadinanes	Angiosperms (east.thou., Dipterocarpaceae)	Terrigenous		Cox et al. (1986), van Aarssen et al. (1992)
Perylene	Uncertain, likely wood degrading fungi, lignin	Terrigenous		Wakeham et al. (1979), Wilcke et al. (2002), Jiang et al. (2000), Keppler et al. (2007), Grice et al. (2009), Suzuki et al. (2010)
Extreme environments
Abundant squalane	Archaea	Hypersaline	Leaner and eukaryotes, but commonly in lower concentrations
2,vi,10,15,19-Pentamethylicosane (PMI)	Archaea	Hypersaline, anoxic		Elvert et al. (1999), Schouten et al. (1997), Thiel et al. (1999a)
β-Carotane	Blue-green alga, algae	Barren, hypersaline		Koopmans et al. (1997)
Regular acyclic isoprenoids with 21 to 30 carbon atoms	Haloarchaea	Evaporitic environments, table salt lakes	Other Archaea	Grice et al., (1998b,d), Oren et al. (2002)
Isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs)	Archaea, crenarchaeota, thaumarchaeota, methanotrophic and methanogenic euryarchaeotes	Hot springs, cold lakes, also freshwater lakes and oceans		Schouten (2012), De Rosa and Gambacorta (1988), Bullpen et al. (2009), de la Torre et al. (2008), Pearson et al. (2004),Sinninghe Damsté et al. (2002), Kim et al. (2008)
Branched GDGTs	Bacteria, acidobacteria	Predominantly soils	Sediments and water column	Weijers et al. (2007b), Sinninghe Damsté et al. (2011), Blaga et al. (2009), Tierney et al. (2009, 2010a)

Tabular array 2. Age-diagnostic biomarkers

Biomarker or biomarker patterns	Biological source	Age range for loftier affluence	Further information
Dinosterane (23,24-dimethylcholestane)	Dinoflagellates?, haptophytes; small and rare in diatoms	Marine, Mostly Mesozoic and Cenozoic (minor concentrations in Paleozoic, possibly of 'protodinoflagellate' origin)	Moldowan and Talyzina (1998), Robinson et al. (1984), Volkman et al. (2003), Summons et al. (1987, 1992), Moldowan et al. (1996), Talyzina et al. (2000)
24-Norcholestane	Diatoms	Jurassic to Tertiary	Holba et al. (1998a), (1998b)
24-Isopropylcholestane/ 24-north-propylcholestane	Demospongiae, demosponges	latest Neoproterozoic to Ordovician, earliest detection between the Sturtian and the Marinoan glaciation events 713–635   Ma	Honey et al. (2009), McCaffrey et al. (1994), Kelly et al. (2011), Moldowan et al. (1990)
C25 and C30 HBIs	Centric diatoms (genus Rhizosolenia)	Upper Turonian, 91.5 ± one.5   Ma	Sininghe DamstÕ et al. (2005, 2004a), Volkman et al. (1994), MassÕ et al. (2004)
C30–C37 botryococcanes, cyclobotryococcanes, polymethylsqualanes	Botryococcus braunii, race B(Chlorophyte alga)	Cenozoic, fresh to stagnant water	Huang et al. (1988), Metzger et al. (1985, 1987, 1991), Metzger and Largeau (1999), Maxwell et al. (1968), Summons et al. (2002), Grice et al. (1998c), Tyson (1995), Niehaus et al. (2011)
Macrocyclic C15–C34 alkanes without carbon number preference	Botryococcus braunii	Cenozoic, fresh to brackish h2o	Grice et al. (2001), Audino et al. (2001, 2002, 2004), Derenne et al. (1988), Largeau et al. (1984), Boreham et al. (1994)
Outstanding concentrations of due north-Cxv, due north-C17 and n-Cnineteen	Marine alga Gloeocapsomorpha prisca	Early Paleozoic (Cambrian - Devonian)	Fowler (1992), Hoffmann et al. (1987), Blokker (2001)
due north-Alkanes→C25 with odd-over-even carbon number preference	Land plants in general	Late Cretaceaous to recent	Hedberg (1968), Tissot and Welte (1984)
northward-C40–n-C100	Cuticular waxes inland lants	Tardily Devonian onwards	del RÚo and Philp (1999), Nip et al. (1986), Tegelaar et al. (1995)
C28/C29 steranes	Algae, marine environments	Decreasing age with increasing ratio	Grantham and Wakefield (1988), Volkman (1986, 2003), Kodner et al. (2008)
C28/C29 steranes	Higher plants, terrigenous environments	Late Devonian onwards for low ratios (loftier C29 sterane content)	Grantham and Wakefield (1988), Huang and Meinschein (1979), Philp and Gilbert (1986), Moldowan et al. (1985)
Phyllocladanes, beyeran, kaurane, atisane	Conifers	Devonian to Cenozoic, often abundant in coal	Noble et al. (1985, 1986), Otto and Wilde (2001)
Bicyclic and tricyclic diterpanes (due east.k. isopimarane, eudesmane, simonellite)	Conifer resins	Belatedly Devonian onwards	Otto and Wilde (2001), Alexander et al. (1983), Noble et al. (1986), Zinniker (2005)
24-Norlupane, 24,28-bisnorlupane	Angiosperms	Late Cretaceaous to contempo	Curiale (2006)
Oleananes, lupanes	Angiosperms	Late Cretaceaous to recent	(Moldowan et al. (1994), Riva et al. (1988), Ekweozor et al. (1988, 1990), Eiserbeck (2011), Eiserbeck et al. (2011a), Friis et al. (2006, Crane et al. (1995), Muller (1981)
Cadinanes, bicadinanes	Angiosperms (e.g. Dipterocarpaceae)	Oligocene to recent	Cox et al. (1986), van Aarssen et al. (1992), Morley (2000)
Crenarchaeol	Crenarchaeota	Offset appearance in the Cretaceous	Kuypers et al. (2001)

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Biogeochemistry

E.G. Nisbet , C.1000.R. Fowler , in Treatise on Geochemistry, 2003

8.01.5.i Origin of Life

Over the origin of life, Nature has chosen to draw a veil. A basic criterion in science is that the result should be reproducible, falsifiable. Non one of the notions of the origin of life has led to reproduction, yet non one tin can be falsified. No doubtfulness success will soon come in the effort to understand the detailed step-by-footstep molecular controls of reproduction. At that place are many notions about the origin of life. Where there is little fact, imagination is allowable and assisting, only where at that place is no fact, so fifty-fifty imagination is best left unimagined here. Similarly, the question "what is life?" is peradventure best left to the consideration of Hades by trouser-function opera singers, of uncertain reproductive ability, seeking Eurydice. Life is more than than reproduction, which clay minerals too attain. Defining the boundary between life and nonlife is, to quote Due north. H. Slumber, similar searching for the world'due south smallest giant.

Nevertheless, despite these warnings, the questions are of supreme involvement. Given that life bends the rules, a slight digression is warranted. A definition of life is perchance best approached via thermodynamics (Nisbet, 1987). Life is growth—it is always in disequilibrium with its surroundings, and its actions are such as to increase that disequilibrium. Sustainable, equilibrium molecules are expressionless molecules. In practice the purlieus is fix between the cell and the virus: the cell tin can in principle reproduce and thus increment the scale of the disequilibrium, while in dissimilarity the virus tin can crystallize and thus set up itself in a fixed point on the entropy scale.

There are several favorite notions of the site of the origin of life (Nisbet, 1987). The best known is the Marxist hypothesis of the "primaeval soup"—that the early ocean was a soup of organic molecules that had fallen in from meteorites (which frequently contain circuitous carbon-chain compounds: organic chemicals, but made past prebiotic inorganic processes). In this soup, lipid blobs somehow evolved into living cells. The discovery of hydrothermal systems led to the realization that early oceans would have pervasively reacted with basalt, both in hydrothermal systems and besides with basalt ejecta after impacts. Thus, the tardily Hadean ocean was most unlikely to be a festering broth, but more likely a absurd clean ocean not greatly dissimilar to the modern bounding main: exit the primaeval soup.

Other hypotheses annotation the properties of minerals, specially clay minerals (Bernal, 1951, 1967), iron oxides and zeolites. Hooker, in a letter to Darwin that provoked the "warm little pond" hypothesis (Darwin, 1959), noted the characteristics of modern hydrothermal systems: abiotic formation of hydrocarbons may occur today in mid-ocean ridge systems (Holm and Charlou, 2001). An interesting variant is the idea of "genetic take-over" (Cairns-Smith, 1982). This is based on the notion that some minerals are non greatly dissimilar from viruses—as Schrodinger (1944) pointed out, life is based on molecules that can be crystallized every bit aperiodic crystals. Mineral crystals reproduce, in a sense, when they abound—each crystal surface seeds new copies of itself. In one version of the genetic takeover hypothesis, the earliest replicating structures were simply minerals, that replicated just equally clays minerals grow. These structures jump proteins, which helped in the reproduction. Then nucleic acid took over the office of the mineral template, and occupied the central direction of the reproducing body (Figure six) .

Figure half-dozen. Models of the descent of life: (a) after Darwin's single illustration in Origin of Species (chapter IV) (Darwin, 1859, 1872) and (b) braided delta model, bold large-scale lateral gene transfers and boundaries of nonviability.

The "panspermia" hypothesis is elementary (Crick, 1981)—Earth was seeded by little green men from outer space, who spread life cells by sending rockets throughout the milky way. This hypothesis has the attraction of fugitive the incommunicable task of elucidating how life began on Earth by transferring the problem to another planet far away and long ago; it as well achieves a happy congruence with Star Trek'south Deoxyribonucleic acid-based universe. Withal, it is not discussed why the men were light-green, or why they were men: pan-oo would be perhaps more than likely than pan-sperm.

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Biogeochemistry

East.G. Nisbet , C.Yard.R. Fowler , in Treatise on Geochemistry (2d Edition), 2014

10.ane.5.i Origin of Life

Over the origin of life, nature has chosen to draw a veil. A bones criterion in science is that the result should be reproducible, falsifiable. Not one of the notions of the origin of life has led to reproduction, not i can be falsified. No doubt success volition soon come in the effort to understand the detailed footstep-by-pace molecular controls of reproduction. There are many notions most the origin of life. Where there is little fact, imagination is commanded and profitable, merely where there is no fact, then even imagination is best left unimagined here. Similarly, the question "what is life?" is perhaps best left to the consideration of Hades by trouser-office opera singers of uncertain reproductive status, seeking Eurydice. Life is more than reproduction, which dirt minerals also reach. Defining the boundary between life and nonlife is, to quote N. H. Sleep, like searching for the world'south smallest giant.

Nevertheless, despite these warnings, the questions are of supreme interest. Given that life bends the rules, a slight digression is warranted. A definition of life is mayhap all-time approached via thermodynamics (Nisbet, 1987). Life is growth – information technology is always in disequilibrium with its environs, and its actions are such as to increase that disequilibrium. Sustainable equilibrium molecules are dead molecules. In do, the boundary is set between the cell and the virus. The cell must be agile and tin in principle reproduce; it must maintain disequilibrium past increasing the universal anarchy. In contrast, the virus can crystallize and thus prepare itself in a fixed point on the entropy calibration.

In that location are several favorite notions of the site of the origin of life (Nisbet, 1987). The best known is the Marxist hypothesis of the 'primaeval soup' – that the early sea was a soup of organic molecules that had fallen in from meteorites (which oft contain circuitous carbon-chain compounds: organic chemicals merely made past prebiotic inorganic processes). In this soup, lipid blobs somehow evolved into living cells. The discovery of hydrothermal systems led to the realization that early oceans would take pervasively reacted with basalt, both in hydrothermal systems and also with basalt ejecta later on impacts. Thus, the late Hadean body of water was nearly unlikely to exist a festering broth, but more likely a cool make clean ocean not greatly dissimilar to the modern ocean: go out the primaeval soup.

Other hypotheses note the properties of minerals, especially clay minerals (Bernal, 1951, 1967), iron oxides, and zeolites. Hooker, in a letter to Darwin that provoked the 'warm little pond' hypothesis (Darwin, 1859, 1959 edition), noted the characteristics of modernistic hydrothermal systems: abiotic germination of hydrocarbons may occur today in MOR systems (Holm and Charlou, 2001). An interesting variant is the idea of 'genetic takeover' (Cairns-Smith, 1982). This is based on the notion that some minerals are not profoundly different from viruses – as Schrodinger (1944) pointed out, life is based on molecules that can be crystallized every bit aperiodic crystals. Mineral crystals reproduce, in a sense, when they grow – each crystal surface seeds new copies of itself. In one version of the genetic takeover hypothesis, the earliest replicating structures were simply minerals, which replicated simply equally clays minerals grow. These structures bound proteins, which helped in the reproduction. And so nucleic acrid took over the part of the mineral template and occupied the primal direction of the reproducing body.

The 'panspermia' hypothesis is unproblematic (Crick, 1981) – World was seeded past petty green men from outer infinite, who spread life cells by sending rockets throughout the milky way. This hypothesis has the allure of avoiding the impossible chore of elucidating how life began on World by transferring the problem to another planet far away and long ago; it besides achieves a happy congruence with Star Expedition'south DNA-based universe. Nonetheless, although littleness has great advantages, information technology is not discussed why the men were greenish or why they were men: pan-oo would be perchance more likely than pan-sperm.

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