Summary: The state that distinguishes organisms from inorganic matter, manifested by growth, metabolism, reproduction, and adaptation. It includes the course of existence, the sum of experiences, the mode of existing, or the fact of being. Over the centuries inquiries into the nature of life have crossed the boundaries from philosophy to biology, forensic medicine, anthropology, etc., in creative as well as scientific literature. (Random House Unabridged Dictionary, 2d ed; Dr. James H. Cassedy, NLM History of Medicine Division)

Top Publications

  1. Wilson R, Barnes L, Krueger K, Hoganson G, Bienias J, Bennett D. Early and late life cognitive activity and cognitive systems in old age. J Int Neuropsychol Soc. 2005;11:400-7 pubmed
    ..The results suggest that past cognitive activity contributes to current cognition principally through its association with cognitive activity in old age. ..
  2. Caetano Anolles G, Caetano Anolles D. Universal sharing patterns in proteomes and evolution of protein fold architecture and life. J Mol Evol. 2005;60:484-98 pubmed
  3. Penzlin H. The riddle of "life," a biologist's critical view. Naturwissenschaften. 2009;96:1-23 pubmed publisher
    To approach the question of what life is, we first have to state that life exists exclusively as the "being-alive" of discrete spatio-temporal entities...
  4. Catling D, Glein C, Zahnle K, McKay C. Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time". Astrobiology. 2005;5:415-38 pubmed
    b>Life is constructed from a limited toolkit: the Periodic Table. The reduction of oxygen provides the largest free energy release per electron transfer, except for the reduction of fluorine and chlorine...
  5. Moreira D, López García P. Ten reasons to exclude viruses from the tree of life. Nat Rev Microbiol. 2009;7:306-11 pubmed publisher
    ..Here, we contend that there is strong evidence against the notion that viruses are alive and represent ancient lineages of the tree of life.
  6. Ling G. Nano-protoplasm: the ultimate unit of life. Physiol Chem Phys Med NMR. 2007;39:111-234 pubmed
    ..century was the recognition that the laws governing the dead world also govern the world of the living and that life has a physical basis called protoplasm...
  7. McRobbie A. Vulnerability, violence and (cosmopolitan) ethics: Butler's Precarious Life. Br J Sociol. 2006;57:69-86 pubmed
    This article proposes that Butler's Precarious Life: The Powers of Mourning and Violence provides a valuable contribution to the sociology of cosmopolitanism on the basis of a perspective which forcefully addresses the new sovereign power ..
  8. Schulze Makuch D, Irwin L. The prospect of alien life in exotic forms on other worlds. Naturwissenschaften. 2006;93:155-72 pubmed
    The nature of life on Earth provides a singular example of carbon-based, water-borne, photosynthesis-driven biology...
  9. Lindahl S. Oxygen and life on earth: an anesthesiologist's views on oxygen evolution, discovery, sensing, and utilization. Anesthesiology. 2008;109:7-13 pubmed publisher
    ..photosynthesis and the accumulation of oxygen in our atmosphere opened up new possibilities for the development of life on Earth...

More Information


  1. Oehler S, Müller Hill B. High local concentration: a fundamental strategy of life. J Mol Biol. 2010;395:242-53 pubmed publisher
    ..The structures and functions of two central molecules of life-the linear polymers DNA and protein-are particularly illuminating examples...
  2. Vinson G. The adrenal cortex and life. Mol Cell Endocrinol. 2009;300:2-6 pubmed publisher
    ..Perhaps we should re-examine other targets at the physiological level. At the present time, some of these seem to be out of fashion. ..
  3. Juhas M, Eberl L, Glass J. Essence of life: essential genes of minimal genomes. Trends Cell Biol. 2011;21:562-8 pubmed publisher
    ..Determination of the universal minimal set of genes needed to sustain life is, therefore, expected to contribute greatly to our understanding of life at its simplest level, with applications ..
  4. Hou C, Bolt K, Bergman A. A general life history theory for effects of caloric restriction on health maintenance. BMC Syst Biol. 2011;5:78 pubmed publisher
    ..have been made to understand the underlying mechanisms from the viewpoint of energy tradeoffs in organisms' life histories...
  5. Aller M, Arias J, Sanchez Patan F, Arias J. The inflammatory response: an efficient way of life. Med Sci Monit. 2006;12:RA225-34 pubmed
  6. Manapat M, Chen I, Nowak M. The basic reproductive ratio of life. J Theor Biol. 2010;263:317-27 pubmed publisher
    ..We call this phenomenon "subcritical life." Subcritical life suggests that sequences long enough to be ribozymes can become abundant even if replication ..
  7. Gayon J. Defining life: synthesis and conclusions. Orig Life Evol Biosph. 2010;40:231-44 pubmed publisher
    The first part of the paper offers philosophical landmarks on the general issue of defining life. Section 1 defends that the recognition of "life" has always been and remains primarily an intuitive process, for the scientist as ..
  8. Tsokolov S. Why is the definition of life so elusive? Epistemological considerations. Astrobiology. 2009;9:401-12 pubmed publisher
    A central question of astrobiology concerns the origin and distribution of life in the Universe. For this reason, astrobiology can be considered to fall within the science called transitional biology...
  9. Westerhof G, Bohlmeijer E, van Beljouw I, Pot A. Improvement in personal meaning mediates the effects of a life review intervention on depressive symptoms in a randomized controlled trial. Gerontologist. 2010;50:541-9 pubmed publisher
    The purpose of the study was to assess the impact of a life review intervention on personal meaning in life and the mediating effect of personal meaning on depressive symptoms as the primary outcome of this form of indicated prevention...
  10. Deamer D, Weber A. Bioenergetics and life's origins. Cold Spring Harb Perspect Biol. 2010;2:a004929 pubmed publisher central to our understanding of living systems, yet has attracted relatively little attention in origins of life research...
  11. Odronitz F, Kollmar M. Drawing the tree of eukaryotic life based on the analysis of 2,269 manually annotated myosins from 328 species. Genome Biol. 2007;8:R196 pubmed
    ..Here, we have reconstructed the tree of eukaryotic life based on the analysis of 2,269 myosin motor domains from 328 organisms...
  12. Ripperger J. The rhythms of life. Genome Biol. 2007;8:313 pubmed
  13. Shapiro R. A simpler origin for life. Sci Am. 2007;296:46-53 pubmed
  14. Cronin L, Krasnogor N, Davis B, Alexander C, Robertson N, Steinke J, et al. The imitation game--a computational chemical approach to recognizing life. Nat Biotechnol. 2006;24:1203-6 pubmed
  15. Williams R. Life, the environment and our ecosystem. J Inorg Biochem. 2007;101:1550-61 pubmed
    ..In the last two hundred years change has become fast and the adaptive process rests not with genes but with mankind's physical-chemical control. ..
  16. Kleidon A. Life, hierarchy, and the thermodynamic machinery of planet Earth. Phys Life Rev. 2010;7:424-60 pubmed publisher
    Throughout Earth's history, life has increased greatly in abundance, complexity, and diversity...
  17. Alavian K, Scholz C, Simon H. Transcriptional regulation of mesencephalic dopaminergic neurons: the full circle of life and death. Mov Disord. 2008;23:319-28 pubmed
    ..Throughout life, transcription factors determine the fate of this neuronal population and control essential processes such as ..
  18. Gluckman P. Epigenetics and metabolism in 2011: Epigenetics, the life-course and metabolic disease. Nat Rev Endocrinol. 2011;8:74-6 pubmed publisher
    Clinical and experimental studies suggest that early life experiences, perhaps spanning multiple generations, affect lifelong risk of metabolic dysfunction through epigenetic mechanisms...
  19. Klein N, Sander P, Stein K, Le Loeuff J, Carballido J, Buffetaut E. Modified laminar bone in Ampelosaurus atacis and other Titanosaurs (Sauropoda): implications for life history and physiology. PLoS ONE. 2012;7:e36907 pubmed publisher
    ..The large titanosaur Alamosaurus, on the other hand, retained the plesiomorphic bone histology of basal neosauropods. ..
  20. Singh Manoux A, Ferrie J, Chandola T, Marmot M. Socioeconomic trajectories across the life course and health outcomes in midlife: evidence for the accumulation hypothesis?. Int J Epidemiol. 2004;33:1072-9 pubmed
    ..has established the importance of considering the accumulation of advantage and disadvantage across the life course when examining adult health outcomes...
  21. Macklem P, Seely A. Towards a definition of life. Perspect Biol Med. 2010;53:330-40 pubmed publisher
    This article offers a new definition of life as a "self-contained, self-regulating, self-organizing, self-reproducing, interconnected, open thermodynamic network of component parts which performs work, existing in a complex regime ..
  22. Looser C, Wheatley T. The tipping point of animacy. How, when, and where we perceive life in a face. Psychol Sci. 2010;21:1854-62 pubmed publisher
    ..b>Life and mind were perceived to "appear" at a consistent location on the morph continuum, close to the human ..
  23. Kurakin A. The self-organizing fractal theory as a universal discovery method: the phenomenon of life. Theor Biol Med Model. 2011;8:4 pubmed publisher
    ..An application of the new discovery method to life sciences reveals that moving electrons represent a keystone physical force (flux) that powers, animates, informs, ..
  24. Steiner U, Tuljapurkar S. Neutral theory for life histories and individual variability in fitness components. Proc Natl Acad Sci U S A. 2012;109:4684-9 pubmed publisher
    Individuals within populations can differ substantially in their life span and their lifetime reproductive success but such realized individual variation in fitness components need not reflect underlying heritable fitness differences ..
  25. Sankaran N. How the discovery of ribozymes cast RNA in the roles of both chicken and egg in origin-of-life theories. Stud Hist Philos Biol Biomed Sci. 2012;43:741-50 pubmed publisher
    Scientific theories about the origin-of-life theories have historically been characterized by the chicken-and-egg problem of which essential aspect of life was the first to appear, replication or self-sustenance...
  26. McKay C, Stoker C, Glass B, Davé A, Davila A, Heldmann J, et al. The Icebreaker Life Mission to Mars: a search for biomolecular evidence for life. Astrobiology. 2013;13:334-53 pubmed publisher
    The search for evidence of life on Mars is the primary motivation for the exploration of that planet...
  27. Deamer D. A giant step towards artificial life?. Trends Biotechnol. 2005;23:336-8 pubmed
    Step by step, the components of an artificial form of cellular life are being assembled by researchers. Lipid vesicles the size of small bacteria can be prepared and under certain conditions are able to grow and divide, then grow again...
  28. Jaarsma T, Pool G, Ranchor A, Sanderman R. The concept and measurement of meaning in life in Dutch cancer patients. Psychooncology. 2007;16:241-8 pubmed
    ..consisting of 39 of the 57 original items, divided into 5 factors, labeled 'relation with God'; 'dedication to life'; 'fairness of life'; 'goal-orientedness' and 'relations with other people', which can be summed to a total score ..
  29. McKaughan D. The influence of Niels Bohr on Max Delbrück: revisiting the hopes inspired by "light and life". Isis. 2005;96:507-29 pubmed
    The impact of Niels Bohr's 1932 "Light and Life" lecture on Max Delbrück's lifelong search for a form of "complementarity" in biology is well documented and much discussed, but the precise nature of that influence ..
  30. Bhutkar A. Synthetic biology: navigating the challenges ahead. J Biolaw Bus. 2005;8:19-29 pubmed
    ..These recommendations include an improved framework for patentability testing, ethical principles to guide work in this area, a controlled approval process, and reference frameworks for regulation. ..
  31. O Meara B, Ane C, Sanderson M, Wainwright P. Testing for different rates of continuous trait evolution using likelihood. Evolution. 2006;60:922-33 pubmed
    Rates of phenotypic evolution have changed throughout the history of life, producing variation in levels of morphological, functional, and ecological diversity among groups...
  32. Ramchandani N, Arya S, Ten S, Bhandari S. Real-life utilization of real-time continuous glucose monitoring: the complete picture. J Diabetes Sci Technol. 2011;5:860-70 pubmed
    ..A questionnaire was designed to assess real-life use of and issues surrounding RT-CGM...
  33. Bruylants G, Bartik K, Reisse J. Is it useful to have a clear-cut definition of life? On the use of fuzzy logic in prebiotic chemistry. Orig Life Evol Biosph. 2010;40:137-43 pubmed publisher
    ..Many scientists, including one of the authors of the present paper, have devoted time to try to find a definition for life (Bersini and Reisse 2007)...
  34. Szyf M. The early life social environment and DNA methylation: DNA methylation mediating the long-term impact of social environments early in life. Epigenetics. 2011;6:971-8 pubmed publisher
    ..We propose that modulation of DNA methylation in response to environmental cues early in life serves as a mechanism of life-long genome "adaptation" that molecularly embeds the early experiences of a ..
  35. Eisner D, Venetucci L, Trafford A. Life, sudden death, and intracellular calcium. Circ Res. 2006;99:223-4 pubmed
  36. Taubman Ben Ari O, Weintroub A. Meaning in life and personal growth among pediatric physicians and nurses. Death Stud. 2008;32:621-45 pubmed publisher
    ..The current study sought to examine 2 positive outcomes, meaning in life and personal growth, among physicians and nurses working with hospitalized children and exposed to different levels ..
  37. Danchin A, Fang G, Noria S. The extant core bacterial proteome is an archive of the origin of life. Proteomics. 2007;7:875-89 pubmed
    ..This remarkable organisation reflects the evolution of life from small molecules metabolism to the RNA world, suggesting that extant microorganisms carry the marks of the ..
  38. Saakian D, Biebricher C, Hu C. Lethal mutants and truncated selection together solve a paradox of the origin of life. PLoS ONE. 2011;6:e21904 pubmed publisher
    Many attempts have been made to describe the origin of life, one of which is Eigen's cycle of autocatalytic reactions [Eigen M (1971) Naturwissenschaften 58, 465-523], in which primordial life molecules are replicated with limited ..
  39. Elowitz M, Lim W. Build life to understand it. Nature. 2010;468:889-90 pubmed publisher
  40. Faussone Pellegrini M, Vannucchi M, Alaggio R, Strojna A, Midrio P. Morphology of the interstitial cells of Cajal of the human ileum from foetal to neonatal life. J Cell Mol Med. 2007;11:482-94 pubmed
    ..ICC-MP, the intestinal pacemaker cells, in spite of absence of food intake, are already present during the foetal life and the ICC-IM appear by pre-term life, thus ensuring neurotransmission...
  41. Brack A, Horneck G, Cockell C, Berces A, Belisheva N, Eiroa C, et al. Origin and evolution of life on terrestrial planets. Astrobiology. 2010;10:69-76 pubmed publisher
    ..exoplanets inside the habitable zone (HZ) of their host stars but also to address the major question as to whether life may have evolved on a habitable Earth-like exoplanet outside our Solar System...
  42. Garvie L, Knauth L, Bungartz F, Klonowski S, Nash T. Life in extreme environments: survival strategy of the endolithic desert lichen Verrucaria rubrocincta. Naturwissenschaften. 2008;95:705-12 pubmed publisher
    ..Biodeterioration of the caliche concomitant with biomineralization of a protective surface coating of micrite results in the distinctive anatomy of V. rubrocincta. ..
  43. Abel E, Kruger M. Precocity predicts shorter life for major league baseball players: confirmation of McCann's precocity-longevity hypothesis. Death Stud. 2007;31:933-40 pubmed
    ..Age at debut was the definition for precocity. We controlled for possible artifacts of life expectancy selection, the "healthy worker" effect, player position, and body-mass index...
  44. Juster R, Bizik G, Picard M, Arsenault Lapierre G, Sindi S, Trepanier L, et al. A transdisciplinary perspective of chronic stress in relation to psychopathology throughout life span development. Dev Psychopathol. 2011;23:725-76 pubmed publisher
    ..approach to comprehensively conceptualize and quantify chronic stress in relation to pathologies throughout the life cycle...
  45. Poole A, Willerslev E. Can identification of a fourth domain of life be made from sequence data alone, and could it be done on Mars?. Astrobiology. 2007;7:801-14 pubmed
    A central question in astrobiology is whether life exists elsewhere in the universe...
  46. Wiggins P. Life depends upon two kinds of water. PLoS ONE. 2008;3:e1406 pubmed publisher
    ..Bioactive enantiomorphs partition into low density water in which they polymerise spontaneously. The simplified model of water has great explanatory power. ..
  47. Troje N, Westhoff C. The inversion effect in biological motion perception: evidence for a "life detector"?. Curr Biol. 2006;16:821-4 pubmed
  48. Authier M, Bentaleb I, Ponchon A, Martin C, Guinet C. Foraging fidelity as a recipe for a long life: foraging strategy and longevity in male Southern Elephant Seals. PLoS ONE. 2012;7:e32026 pubmed publisher
    Identifying individual factors affecting life-span has long been of interest for biologists and demographers: how do some individuals manage to dodge the forces of mortality when the vast majority does not? Answering this question is not ..
  49. Kato K, Zweig R, Barzilai N, Atzmon G. Positive attitude towards life and emotional expression as personality phenotypes for centenarians. Aging (Albany NY). 2012;4:359-67 pubmed
    ..The results generated two personality characteristics/domains, Positive Attitude Towards Life (PATL: optimism, easygoing, laughter, and introversion/outgoing) and Emotional Expression (EE: expressing emotions ..
  50. Tosca N, Knoll A, McLennan S. Water activity and the challenge for life on early Mars. Science. 2008;320:1204-7 pubmed publisher
    ..Our calculations indicate that the salinity of well-documented surface waters often exceeded levels tolerated by known terrestrial organisms. ..
  51. Westerhoff H, Winder C, Messiha H, Simeonidis E, Adamczyk M, Verma M, et al. Systems biology: the elements and principles of life. FEBS Lett. 2009;583:3882-90 pubmed publisher
    ..Systems Biology is a science of its own, discovering own fundamental principles, some of which we identify here. ..
  52. Leisman G, Koch P. Networks of conscious experience: computational neuroscience in understanding life, death, and consciousness. Rev Neurosci. 2009;20:151-76 pubmed
    ..theory is enigmatic for explaining consciousness because the nature of subjective experience, or 'qualia'- 'inner life' - is a "hard problem" to understand; binding spatially distributed brain activity into unitary objects, ..
  53. Barbieri M. Biosemiotics: a new understanding of life. Naturwissenschaften. 2008;95:577-99 pubmed publisher
    Biosemiotics is the idea that life is based on semiosis, i.e., on signs and codes...