Define life | Dictionary and Thesaurus

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Syriac: ܚܝܐ(khayē) m|pHebrew: חיא(khayē) m|pArmenian: կյանք(kyank‘)Catalan: vidaCzech: životDanish: livDutch: levenEsperanto: vivoFinnish: elämäFrench: vieGerman: LebenGreek: ζωή(zoí)Hebrew: חיים(ħayim) m|pHopi:qatsiItalian: vitaJapanese: 生命Norwegian: livPolish: życiePortuguese: vidaRomanian: viaţăRussian: жизнь(žizn’)Serbian: življenjeSlovene: življenjeSpanish: vidaSumerian:Swedish: livthe essence of the manifestation and thefoundation of the beingArmenian: կյանք(kyank‘)Danish: livDutch: levenFinnish: elämäGerman: LebenJapanese: 存在Polish: życiePortuguese: vidaRussian: жизнь(žizn’)Spanish: vidaA worthwhile existenceArmenian: կյանք(kyank‘)Bosnian: životCzech: životDanish: livDutch: levenEsperanto: vivoFinnish: elämä, eläminenFrench: vieGerman: LebenGreek: ζωή(zoí)Hebrew: חיים(ħayim) m|pPolish: życiePortuguese: vidaRussian: жизнь(žizn’)Serbian: живот, životSlovene: življenjeSpanish: vidaSwedish: livinheritantly part of a person's existencettbc Arabic: (ħayā)ttbc Afrikaans:lewettbc Bulgarian:живот(život)ttbc Basque: bizi, bizitza, existentziattbc Breton: buhezttbc Estonian: eluttbc Guarani: tekovettbc Hawaiian: ola, nohona, noho ʻanattbc Ido:vivottbc Indonesian:hidup, kehidupanttbc Interlingua:vitattbc Irish: saol , beathattbc Japanese: 命 (いのち,inochi), 生命(せいめい, seimei)ttbc Latin: vitattbc Lingala: bomɔittbc Lithuanian:gyvybė(1,2); gyvenimas (4,ttbc Maori: ora, koiora, wairua ora,tauorangattbc Persian: (zendegi)ttbc Slovak: život (1-5),doživotieTupinambá: tekobéttbc Turkish: yaşam, hayatttbc Welsh: bywydExternal linksBiologicallifePhenomenologicallifePhilosophyof the lifeExtensive DefinitionLife is a condition that distinguishes organisms from non-livingobjects, such as non-life, anddeadorganisms, being manifested by growth through metabolism and reproduction. Some livingthings can communicate and many canadapt to their environmentthrough changes originating internally. A physical characteristic of lifeis that it feeds on negativeentropy. In more detail, according to physicists such asJohnBernal, ErwinSchrödinger, EugeneWigner, and JohnAvery, life is a member of the class of phenomena which areopen or continuous systems able to decrease their internal entropy at the expense ofsubstances or freeenergy taken in from the environment and subsequently rejectedin a degraded form (see: entropyand life).A diverse array of living organisms can be foundin the biosphere onEarth. Properties common to these organisms—plants, animals, fungi, protists, archaea and bacteria—are a carbon-and water-basedcellularform with complex organization and heritablegenetic information. Theyundergo metabolism,possess a capacity to grow, respond to stimuli, reproduce and, throughnaturalselection, adapt to their environment in successivegenerations.An entity with the above properties is consideredto be a living organism, that is an organismthat is alive hence can be called a life form. However, not everydefinition of life considers all of these properties to beessential. For example, the capacity for descent with modificationis often taken as the only essential property of life. Thisdefinition notably includes viruses, which do not qualifyunder narrower definitions as they are acellular and do notmetabolize.DefinitionsThere is no universal definition of life; thereare a variety of definitions proposed by different scientists. Todefine life in unequivocal terms is still a challenge forscientists.Conventional definition: Often scientists saythat life is a characteristic of organisms that exhibit thefollowing phenomena:Homeostasis:Regulation of the internal environment to maintain a constantstate; for example, sweating to reduce temperature.Organization: Being composed of one or more cells,which are the basic units of life.Metabolism: Consumption of energy by converting nonlivingmaterial into cellular components (anabolism) and decomposingorganic matter (catabolism). Living thingsrequire energy to maintain internal organization (homeostasis) andto produce the other phenomena associated with life.Growth:Maintenance of a higher rate of synthesis than catalysis. A growingorganism increases in size in all of its parts, rather than simplyaccumulating matter. The particular species begins to multiply andexpand as the evolution continues to flourish.Adaptation: The ability to change over a period of time inresponse to the environment. This ability is fundamental to theprocess of evolutionand is determined by the organism's heredity as well as thecomposition of metabolized substances, and external factorspresent.Response to stimuli: A response can take many forms, from thecontraction of a unicellular organism when touched to complexreactions involving all the senses of higher animals. A response isoften expressed by motion, for example, the leaves of a plantturning toward the sun or an animal chasing its prey.Reproduction: The ability to produce new organisms.Reproduction can be the division of one cell to form two new cells.Usually the term is applied to the production of a new individual(either asexually,from a single parent organism, or sexually,from at least two differing parent organisms), although strictlyspeaking it also describes the production of new cells in theprocess of growth.However, others cite several limitations of thisdefinition. Thus, many members of several species do not reproduce,possibly because they belong to specialized sterile castes (such asant workers), these are still considered forms of life. One couldsay that the property of life is inherited; hence, sterile orhybrid organisms such as mules, ligers, and eunuchs are alive although theyare not capable of self-reproduction. However, (a) The species as awhole does reproduce, (b) There are no cases of species where 100%of the individuals reproduce, and (c) specialized non-reproducingindividuals of the species may still partially propagate their DNAor other master pattern through mechanisms such as kinselection.Viruses and aberrant prion proteins are oftenconsidered replicators rather than forms of life, a distinctionwarranted because they cannot reproduce without very specializedsubstrates such as host cells or proteins, respectively. Also, theRickettsia andChlamydiaare examples of bacteria that cannotindependently fulfill many vital biochemical processes, and dependon entry, growth, and replication within the cytoplasm of eukaryotic host cells.However, most forms of life rely on foods produced by otherspecies, or at least the specific chemistry of Earth'senvironment.The systemicdefinition of life is that living things are self-organizing andautopoietic(self-producing). These objects are not to be confused withdissipativestructures (e.g. fire).Variations of this definition include StuartKauffman's definition of life as an autonomousagent or a multi-agentsystem capable of reproducing itself or themselves, and ofcompleting at least one thermodynamicwork cycle.Proposed definitions of life include:Living things are systems that tend to respond to changes intheir environment, and inside themselves, in such a way as topromote their own continuation.Life (a living individual) is defined as a network of inferiornegative feedbacks (regulatory mechanisms) subordinated to asuperior positive feedback (potential of expansion, reproduction)Life is a characteristic ofself-organizing,self-recycling systemsconsisting of populations of replicators that are capableof mutation, aroundmost of which homeostatic, metabolizing organismsevolve.Type of organization of matter producing various interactingforms of variable complexity, whose main property is to replicatealmost perfectly by using matter and energy available in theirenvironment to which they may adapt. In this definition "almostperfectly" relates to mutations happening during replication oforganisms that may have adaptive benefits.Life is a potentially self-perpetuating open system of linkedorganic reactions, catalyzed simultaneously and almost isothermallyby complex chemicals (enzymes) that are themselves produced by theopen system.Origin of lifeAlthough it cannot be pinpointed exactly,evidence suggests that life onEarth has existed for about 3.7 billionyears.There is no truly "standard" model for the originof life, but most currently accepted scientific models build in oneway or another on the following discoveries, which are listedroughly in order of postulated emergence:Plausible pre-biotic conditions result in the creation of thebasic small molecules of life. This was demonstrated in theMiller-Urey experiment, and in the work of SidneyFox.Phospholipidsspontaneously form lipidbilayers, the basic structure of a cellmembrane.Procedures for producing random RNA molecules canproduce ribozymes,which are able to produce more of themselves under very specificconditions.The Panspermiahypothesis proposes that life originated elsewhere in the universeand was subsequently transferred to Earth perhaps via meteorites, comets or cosmicdust.There are many different hypotheses regarding thepath that might have been taken from simple organicmolecules via pre-cellular life to protocells and metabolism.Many models fall into the "genes-first" category or the"metabolism-first"category, but a recent trend is the emergence of hybrid models thatdo not fit into either of these categories.Classification of lifeTraditionally, people have dividedorganisms into the classes of plants and animals, based mainly on theirability of movement. The first known attempt to classify organisms,as per personal observations, was conducted by the Greekphilosopher Aristotle.He classified all living organisms known at thattime as either a plant or an animal. Aristotle distinguishedanimals with blood from animals without blood (or at least withoutred blood), which can be compared with the concepts of vertebrates and invertebrates respectively.He divided the blooded animals into five groups: viviparousquadrupeds (mammals),birds, oviparous quadrupeds(reptiles and amphibians), fishes and whales. Thebloodless animals were also divided into five groups: cephalopods, crustaceans, insects (whichalso included the spiders, scorpions, and centipedes, in addition towhat we now define as insects), shelled animals (suchas most molluscs andechinoderms) and"zoophytes". ThoughAristotle's work in zoology was not without errors, it was thegrandest biological synthesis of the time, and remained theultimate authority for many centuries after his death. Hisobservations on the anatomy of octopus, cuttlefish, crustaceans,and many other marine invertebrates are remarkably accurate, andcould only have been made from first-hand experience withdissection.The exploration of parts of the New Worldproduced large numbers of new plants and animals that neededdescriptions and classification. The old systems made it difficultto study and locate all these new specimens within a collection andoften the same plants or animals were given different names becausethe number of specimens were too large to memorize. A system wasneeded that could group these specimens together so they could befound, the binomial system was developed based on morphologywith groups having similar appearances. In the latter part of the16th century and the beginning of the 17th, careful study ofanimals commenced, which, directed first to familiar kinds, wasgradually extended until it formed a sufficient body of knowledgeto serve as an anatomical basis for classification.CarolusLinnaeus is best known for his introduction of the method stillused to formulate the scientificname of every species. Before Linnaeus, long many-worded names(composed of a generic name and a differentia specifica) had beenused, but as these names gave a description of the species, theywere not fixed. In his Philosophia Botanica (1751) Linnaeus tookevery effort to improve the composition and reduce the length ofthe many-worded names by abolishing unnecessary rhetorics,introducing new descriptive terms and defining their meaning withan unprecedented precision. In the late 1740s Linnaeus began to usea parallel system of naming species with nomina trivialia. Nomentriviale, a trivial name, was a single- or two-word epithet placedon the margin of the page next to the many-worded "scientific"name. The only rules Linnaeus applied to them was that the trivialnames should be short, unique within a given genus, and that theyshould not be changed. Linnaeus consistently applied nominatrivialia to the species of plants in SpeciesPlantarum (1st edn. 1753) and to the species of animals in the10th edition of SystemaNaturae (1758). By consistently using these specific epithets,Linnaeus separated nomenclature from taxonomy. Even though theparallel use of nomina trivialia and many-worded descriptive namescontinued until late in the eighteenth century, it was graduallyreplaced by the practice of using shorter proper names combined ofthe generic name and the trivial name of the species. In thenineteenth century, this new practice was codified in the firstRules and Laws of Nomenclature, and the 1st edn. of SpeciesPlantarum and the 10th edn. of SystemaNaturae were chosen as starting points for the Botanical and Zoological Nomenclature respectively. This convention fornaming species is referred to as binomialnomenclature. Today, nomenclature is regulated by NomenclatureCodes, which allows names divided into ranks; separatelyforbotany and forzoology. Whereas Linnaeus classified for ease ofidentification, it is now generally accepted that classificationshould reflect the Darwinian principle of commondescent.The Fungi have long beena problematic group in the biological classification: Originally,they were treated as plants. For a short period Linnaeus had placedthem in the taxon Vermes in Animaliabecause he was misinformed: the hyphae were said to have beenworms. He later placed themback in Plantae. Copelandclassified the Fungi in his Protoctista, thus partially avoidingthe problem but acknowledging their special status. The problem waseventually solved by Whittaker,when he gave them their own kingdom in his five-kingdom system. As it turned out, the fungi are moreclosely related to animals than to plants.As new discoveries enabled us to study cells andmicroorganisms,new groups of life where revealed, and the fields of cell biologyand microbiologywere created. These new organisms were originally describedseparately in Protozoa asanimals and Protophyta/Thallophytaas plants, but were united by Haeckel inhis kingdom Protista, laterthe group of prokaryotes were split of inthe kingdom Monera, eventuallythis kingdom would be divided in two separate groups, the Bacteria and theArchaea,leading to the six-kingdom system and eventually to the three-domainsystem. The 'remaining' protists would later be divided intosmaller groups in cladesin relation to more complex organisms. ThomasCavalier-Smith, who has published extensively on theclassification of protists, has recently proposed that the Neomura, the cladewhich groups together the Archaea andEukarya,would have evolved from Bacteria, moreprecisely from Actinobacteria.As microbiology, molecularbiology and virology developed,non-cellular reproducing agents were discovered, sometimes theseare considered to be alive and are treated in the domain ofnon-cellularlife named Acytota or Aphanobionta, which are virus.And thus all the primary taxonomical ranks were established: Domain,Kingdom,Phylum,Class,Order,Family,Genus,SpeciesSince the 1960s a trend called cladistics has emerged,arranging taxa in an evolutionaryor phylogenetic tree. If a taxon includes all the descendantsof some ancestral form, it is called monophyletic, asopposed to paraphyletic,groups based on traits which have evolved separately and where themost recent common ancestor is not included are called polyphyletic.A new formal code of nomenclature, the PhyloCode, to berenamed "International Code of PhylogeneticNomenclature" (ICPN), is currently under development, intendedto deal with clades, which do not have set ranks, unlikeconventional Linnaeantaxonomy. It is unclear, should this be implemented, how thedifferent codes will coexist.Extraterrestrial lifeEarth is the onlyplanet in the universeknown to harbour life. The Drakeequation has been used to estimate the probability of lifeelsewhere, but scientists disagree on many of the values ofvariables in this equation (although strictly speaking Drakeequation estimates relate the number of extraterrestrialcivilizations in our galaxy with which we might come in contact -not probability of life elsewhere). Depending on those values, theequation may either suggest that life arises frequently orinfrequently. Drake himself estimated the number of civilizationsin our galaxy with which we might expect to be able to communicateat any given time as equal to one.Relating to the origin of life on Earth, panspermia and exogenesis aretheories proposing that life originated elsewhere in the universeand was subsequently transferred to Earth perhaps via meteorites, comets or cosmic dust.For example, there is the meteorite ALH84001. Howeverthose theories do not help explain the origin of thisextraterrestrial life.See alsoArtificiallifeBiologicalkingdomBiology, thescientific study of lifeCarbon-basedlifeCellularautomaton, a discrete model of an infinite, regular grid ofcellsCellularlifeConway'sGame of Life, simple mathematical 'cellular automaton' thatmimicks the dynamics of an ecosystem.Death,the termination of lifeEcologicalliteracyEntropyand lifeExtraterrestriallifeExtremophile,organisms that live in so called 'extreme' conditions e.g. hydrothermalventsGaiahypothesisMeaning oflifeNature,in the original meaning, it is strongly associated with life.Non-cellularlifeNon-lifeOrganic lifeOrganismOrigin oflifePersonallifePhylogenetics,is the study of evolutionary relatedness among speciesPrehistoriclife, life from before the human history started on EarthQuality oflifeSyntheticlifeTaxonomy,the science of describing, categorising and naming organismsgeneticsgeneticengineeringReferencesFurther readingKauffman, Stuart. The Adjacent Possible: A Talk with StuartKauffman. Retrieved Nov. 30, 2003 from http://www.edge.org/3rd_culture/kauffman03/kauffman_index.htmlWalker, Martin G. LIFE! Why We Exist...And What We Must Do toSurvive (BookPage) (Web Site),Dog Ear Publishing, 2006, ISBN 1-59858-243-7External linksWikispecies - afree directory of life"TheAdjacent Possible: A Talk with Stuart Kauffman"StanfordEncyclopedia of Philosophy entryLife under extreme conditions An in depth look at how life canform under the most extreme conditions.life in Arabic: حياةlife in Aymara: Jakañalife in Bosnian: Životlife in Bulgarian: Животlife in Catalan: Vidalife in Czech: Životlife in Welsh: Bywydlife in Danish: Livlife in German: Lebenlife in Estonian: Elulife in Modern Greek (1453-): Ζωήlife in Spanish: Vidalife in Esperanto: Vivolife in Basque: Bizitzalife in Persian: زندگیlife in French: Vielife in Galician: Vidalife in Korean: 생명life in Croatian: Životlife in Indonesian: Kehidupanlife in Icelandic: Líf (líffræði)life in Italian: Vitalife in Hebrew: חייםlife in Georgian: სიცოცხლეlife in Latin: Biotalife in Latvian: Dzīvībalife in Lithuanian: Gyvybėlife in Limburgan: Levelife in Hungarian: Életlife in Macedonian: Животlife in Malay (macrolanguage): Hidupanlife in Dutch: Levenlife in Japanese: 生命life in Norwegian: Livlife in Uzbek: Hayotlife in Polish: Życielife in Portuguese: Vidalife in Romanian: Viaţălife in Quechua: Kawsaylife in Russian: Жизньlife in Albanian: Jetalife in Simple English: Lifelife in Slovak: Životlife in Slovenian: Življenjelife in Serbian: Животlife in Serbo-Croatian: Životlife in Sundanese: Hiruplife in Finnish: Elämälife in Swedish: Livlife in Tagalog: Buhaylife in Thai: ชีวิตlife in Vietnamese: Sự sốnglife in Turkish: Yaşamlife in Ukrainian: Життяlife in Urdu: حیاتlife in Yiddish: לעבןlife in Chinese: 生命Synonyms, Antonyms and RelatedWordsAdamite, Clio, Muse of history, activator, activity, adventures, affairs, age, alacrity, an existence, animalspirits, animation,animator, annals, anxiety, anxiousness, appetite, ardor, arouser, autobiography, avidity, avidness, being, biographical sketch,biography, body, bounce, breathless impatience,breeziness, brio, briskness, bubbliness, capersomeness, casehistory, cat, chap, character, cheerful readiness,chronicle, chronicles, chronology, circumstances, coltishness, compulsion, concerns, condition of things,conditions, confessions, creature, critter, curriculum vitae,customer, dash, dazzle, dealings, diary, doings, duck, duration, eagerness, earthling, ebullience, effervescence, elan, elan vital, elasticity, energizer, energy, ens, entelechy, enthusiasm, entity, esprit, esse, essence, existence, experiences, exuberance, fellow, fixation, flair, flavor, fortunes, forwardness, freshness, friskiness, frolicsomeness, gaiety, gamesomeness, gayness, generation, get-up-and-go,glow, goings-on, groundling, gust, gusto, guy, hagiography, hagiology, hand, head, heartiness, historiography, history, homo, human, human being, human dynamo,impatience, impetuosity, impetus, individual, joie de vivre,joker, journal, keen desire, keenness, legend, life and letters, lifestory, lifeblood,lifetime, liveliness, living, living soul, lustiness, man, march of events, martyrology, materiality, matters, memoir, memoirs, memorabilia, memorial, memorials, mettle, monad, mortal, motivating force, motivepower, moving spirit, moxie, necrology, nose, obituary, object, obsession, occurrence, one, oomph, organism, party, passion, pep, peppiness, period ofexistence, perkiness,person, persona, personage, personality, pertness, photobiography, piss andvinegar, pizzazz,playfulness,preoccupation,presence, proceedings, profile, promptness, pungency, quickness, readiness, record, relations, resilience, restorative, resume, robustness, rollicksomeness,rompishness, run ofthings, sentience,single, skittishness, somebody, someone, something, soul, spark of life, spark plug,sparkle, spirit, spiritedness, spirits, sportiveness, sprightliness, spring, state of affairs,stimulant, stimulator, stimulus, story, subsistence, substantiality, survival, sustenance, tellurian, terran, the times, the world,theory of history, thing,time, tonic, unit, verve, viability, vigor, vim, vital spark, vitality, vivaciousness, vivacity, warmth, way of life, whathappens, worldling,zest, zestfulness, zing, zip

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