From Wikipedia, the free encyclopedia

Life (Biota)
Life on a rocky peak in the Waitakere Ranges
Scientific classification
Domains and Kingdoms
Life on Earth: Non-cellular life (viruses) ** Cellular life Bacteria Archaea Eukarya Protista Fungi Plantae Animalia

Life (cf. biota) is a characteristic that distinguishes objects that have self-sustaining biological processes from those that do not^[1][2]–either because such functions have ceased (death), or else because they lack such functions and are classified as inanimate.^[3]

In biology, the science of living organisms, life is the condition which distinguishes active organisms from inorganic matter, including the capacity for growth, functional activity and the continual change preceding death.^[4][5] A diverse array of living organisms (life forms) can be found in the biosphere on Earth, and properties common to these organisms—plants, animals, fungi, protists, archaea, and bacteria—are a carbon- and water-based cellular form with complex organization and heritable genetic information. Living organisms undergo metabolism, maintain homeostasis, possess a capacity to grow, respond to stimuli, reproduce and, through natural selection, adapt to their environment in successive generations. More complex living organisms can communicate through various means.^[1][6]

In philosophy and religion, the conception of life and its nature varies. Both offer interpretations as to how life relates to existence and consciousness, and both touch on many related issues, including life stance, purpose, conception of a god or gods, a soul or an afterlife.

Early theories about life

Materialism

Plant life

Herds of zebra and impala gathering on the Masai Mara plain

An aerial photo of microbial mats around the Grand Prismatic Spring of Yellowstone National Park.

Some of the earliest theories of life were materialist, holding that all that exists is matter, and that all life is merely a complex form or arrangement of matter. Empedocles (430 B.C.) argued that every thing in the universe is made up of a combination of four eternal 'elements' or 'roots of all': earth, water, air, and fire. All change is explained by the arrangement and rearrangement of these four elements. The various forms of life are caused by an appropriate mixture of elements. For example, growth in plants is explained by the natural downward movement of earth and the natural upward movement of fire.^[7]

Democritus (460 B.C.), the disciple of Leucippus, thought that the essential characteristic of life is having a soul (psychê). In common with other ancient writers, he used the term to mean the principle of living things that causes them to function as a living thing. He thought the soul was composed of fire atoms, because of the apparent connection between life and heat, and because fire moves.^[8] He also suggested that humans originally lived like animals, gradually developing communities to help one another, originating language, and developing crafts and agriculture.^[9]

In the scientific revolution of the seventeenth century, mechanistic ideas were revived by philosophers like Descartes.

Hylomorphism

Hylomorphism is the theory (originating with Aristotle (322 BC)) that all things are a combination of matter and form. Aristotle was one of the first ancient writers to approach the subject of life in a scientific way. Biology was one of his main interests, and there is extensive biological material in his extant writings. According to him, all things in the material universe have both matter and form. The form of a living thing is its soul (Greek 'psyche', Latin 'anima'). There are three kinds of souls: the 'vegetative soul' of plants, which causes them to grow and decay and nourish themselves, but does not cause motion and sensation; the 'animal soul' which causes animals to move and feel; and the rational soul which is the source of consciousness and reasoning which (Aristotle believed) is found only in man.^[10] Each higher soul has all the attributes of the lower one. Aristotle believed that while matter can exist without form, form cannot exist without matter, and therefore the soul cannot exist without the body.^[11]

Consistent with this account is a teleological explanation of life. A teleological explanation accounts for phenomena in terms of their purpose or goal-directedness. Thus, the whiteness of the polar bear's coat is explained by its purpose of camouflage. The direction of causality is the other way round from materialistic science, which explains the consequence in terms of a prior cause. Modern biologists now reject this functional view in terms of a material and causal one: biological features are to be explained not by looking forward to future optimal results, but by looking backwards to the past evolutionary history of a species, which led to the natural selection of the features in question.

Vitalism

Vitalism is the belief that the life-principle is essentially immaterial. This originated with Stahl (17th century), and held sway until the middle of the nineteenth century. It appealed to philosophers such as Henri Bergson, Nietzsche, Wilhelm Dilthey, anatomists like Bichat, and chemists like Liebig.

Vitalism underpinned the idea of a fundamental separation of organic and inorganic material, and the belief that organic material can only be derived from living things. This was disproved in 1828 when Wöhler prepared urea from inorganic materials. This so-called Wöhler synthesis is considered the starting point of modern organic chemistry. It is of great historical significance because for the first time an organic compound was produced from inorganic reactants.

Later, Helmholtz, anticipated by Mayer, demonstrated that no energy is lost in muscle movement, suggesting that there were no vital forces necessary to move a muscle. These empirical results led to the abandonment of scientific interest in vitalistic theories, although the belief lingered on in non-scientific theories such as homeopathy, which interprets diseases and sickness as caused by disturbances in a hypothetical vital force or life force.

Definitions

It is still a challenge for scientists and philosophers to define life in unequivocal terms.^[12][13][14] Defining life is difficult —in part— because life is a process, not a pure substance.^[15] Any definition must be sufficiently broad to encompass all life with which we are familiar, and it should be sufficiently general that, with it, scientists would not miss life that may be fundamentally different from earthly life.^[16]

Biology

Since there is no unequivocal definition of life, the current understanding is descriptive, where life is a characteristic of organisms that exhibit all or most of the following phenomena:^[15][17][18]

1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
2. Organization: Being structurally composed of one or more cells, which are the basic units of life.
3. Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
4. Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
5. Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and by chemotaxis.
7. Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.

Proposed

To reflect the minimum phenomena required, some have proposed other biological definitions of life:

• Living things are systems that tend to respond to changes in their environment, and inside themselves, in such a way as to promote their own continuation.^[18]
• A network of inferior negative feedbacks (regulatory mechanisms) subordinated to a superior positive feedback (potential of expansion, reproduction).^[19]
• A systemic definition of life is that living things are self-organizing and autopoietic (self-producing). Variations of this definition include Stuart Kauffman's definition as an autonomous agent or a multi-agent system capable of reproducing itself or themselves, and of completing at least one thermodynamic work cycle.^[20]
• Life is a self-sustained chemical system capable of undergoing Darwinian evolution.^[21]
• Things with the capacity for metabolism and motion.^[15]

Viruses

Viruses are most often considered replicators rather than forms of life. They have been described as "organisms at the edge of life",^[22] since they possess genes, evolve by natural selection,^[23] and replicate by creating multiple copies of themselves through self-assembly. However, viruses do not metabolise and require a host cell to make new products. Virus self-assembly within host cells has implications for the study of the origin of life, as it may support the hypothesis that life could have started as self-assembling organic molecules.^[24][25]

Biophysics

Biophysicists have also commented on the nature and qualities of life forms—notably that they function on negative entropy.^[26][27] In more detail, according to physicists such as John Bernal, Erwin Schrödinger, Eugene Wigner, and John Avery, life is a member of the class of phenomena which are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form (see: entropy and life).^[28][29][30]

Living systems theories

Some scientists have proposed in the last few decades that a general living systems theory is required to explain the nature of life.^[31] Such general theory, arising out of the ecological and biological sciences, attempts to map general principles for how all living systems work. Instead of examining phenomena by attempting to break things down into component parts, a general living systems theory explores phenomena in terms of dynamic patterns of the relationships of organisms with their environment.^[32]

Gaia hypothesis

The idea that the Earth is alive is probably as old as humankind, but the first public expression of it as a fact of science was by a Scottish scientist, James Hutton. In 1785 he stated that the Earth was a superorganism and that its proper study should be physiology. Hutton is rightly remembered as the father of geology, but his idea of a living Earth was forgotten in the intense reductionism of the nineteenth century.^[33] The Gaia hypothesis, originally proposed in the 1960s by scientist James Lovelock,^[34][35] explores the idea that the life on Earth functions as a single organism which actually defines and maintains environmental conditions necessary for its survival.^[36]

Nonfractionability

Robert Rosen (1991) built on the assumption that the explanatory powers of the mechanistic worldview cannot help understand the realm of living systems. One of several important clarifications he made was to define a system component as "a unit of organization; a part with a function, i.e., a definite relation between part and whole." From this and other starting concepts, he developed a "relational theory of systems" that attempts to explain the special properties of life. Specifically, he identified the "nonfractionability of components in an organism" as the fundamental difference between living systems and 'biological machines.'^[37]

Life as a property of ecosystems

A systems view of life treats environmental fluxes and biological fluxes together as a "reciprocity of influence",^[38] and a reciprocal relation with environment is arguably as important for understanding life as it is for understanding ecosystems. As Harold J. Morowitz (1992) explains it, life is a property of an ecological system rather than a single organism or species.^[39] He argues that an ecosystemic definition of life is preferable to a strictly biochemical or physical one. Robert Ulanowicz (2009) also highlights mutualism as the key to understand the systemic, order-generating behavior of life and ecosystems.^[40]

Origin of life

For religious beliefs about the creation of life, see creation myth.

Evidence suggests that life on Earth has existed for about 3.7 billion years.^[41] All known life forms share fundamental molecular mechanisms, and based on these observations, theories on the origin of life attempt to find a mechanism explaining the formation of a primordial single cell organism from which all life originates. There are many different hypotheses regarding the path that might have been taken from simple organic molecules 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 that combine both categories.^[42]

There is no scientific consensus as to how life originated and all proposed theories are highly speculative. However, most currently accepted scientific models build in one way or another on the following hypotheses:

• The Miller-Urey experiment, and the work of Sidney Fox, suggest that that conditions on the primitive Earth may have favored chemical reactions that synthesized some amino acids and other organic compounds from inorganic precursors.
• Phospholipids spontaneously form lipid bilayers, the basic structure of a cell membrane.

Life as we know it today synthesizes proteins, which are polymers of amino acids using instructions encoded by cellular genes—which are polymers of deoxyribonucleic acid (DNA). Protein synthesis also entails intermediary ribonucleic acid (RNA) polymers. One possibility is that genes came first^[43] and then proteins. Another possibility is that proteins came first^[44] and then genes. However, because genes are required to make proteins, and proteins are required to make genes, the problem of considering which came first is like that of the chicken or the egg. Most scientists have adopted the hypothesis that because DNA and proteins function together so intimately, it's unlikely that they arose independently.^[45] Therefore, many scientists consider the possibility, apparently first suggested by Francis Crick,^[46] that the first life was based on the DNA-protein intermediary: RNA.^[45] In fact, RNA has the DNA-like properties of information storage and replication and the catalytic properties of some proteins. Crick and others actually favored the RNA-first hypothesis^[47] even before the catalytic properties of RNA had been demonstrated by Thomas Cech.^[48]

A significant issue with the RNA-first hypothesis is that experiments designed to synthesize RNA from simple precursors have not been nearly as successful as the Miller-Urey experiments that synthesized other organic molecules from inorganic precursors. One reason for the failure to create RNA in the laboratory is that RNA precursors are very stable and don't react with each other under ambient conditions. However, the successful synthesis of certain RNA molecules under conditions hypothesized to exist prior to life on Earth has been achieved by adding alternative precursors in a specified order with the precursor phosphate present throughout the reaction.^[49] This study makes the RNA-first hypothesis more plausible to many scientists.^[50]

Recent experiments have demonstrated true Darwinian evolution of unique RNA enzymes (ribozymes) made up of two separate catalytic components that replicate each other in vitro.^[51] In describing this work from his laboratory, Gerald Joyce stated: "This is the first example, outside of biology, of evolutionary adaptation in a molecular genetic system."^[52] Such experiments make the possibility of a primordial RNA World even more attractive to many scientists.

Conditions for life

The diversity of life on Earth today is a result of the dynamic interplay between genetic opportunity, metabolic capability, environmental challenges,^[53] and symbiosis.^[54][55][56] For most of its existence, Earth's habitable environment has been dominated by microorganisms and subjected to their metabolism and evolution. As a consequence of such microbial activities on a geologic time scale, the physical-chemical environment on Earth has been changing, thereby determining the path of evolution of subsequent life.^[53] For example, the release of molecular oxygen by cyanobacteria as a by-product of photosynthesis induced fundamental, global changes in the Earth's environment. The altered environment, in turn, posed novel evolutionary challenges to the organisms present, which ultimately resulted in the formation of our planet's major animal and plant species. Therefore this 'co-evolution' between organisms and their environment is apparently an inherent feature of living systems.^[53]

Range of tolerance

The inert components of an ecosystem are the physical and chemical factors necessary for life – energy (sunlight or chemical energy), water, temperature, atmosphere, gravity, nutrients, and ultraviolet solar radiation protection.^[57] In most ecosystems the conditions vary during the day and often shift from one season to the next. To live in most ecosystems, then, organisms must be able to survive a range of conditions, called 'range of tolerance'.^[58] Outside of that are the 'zones of physiological stress', where the survival and reproduction are possible but not optimal. Outside of these zones are the 'zones of intolerance', where life for that organism is implausible. It has been determined that organisms that have a wide range of tolerance are more widely distributed than organisms with a narrow range of tolerance.^[58]

Extremophiles

Deinococcus radiodurans can resist radiation exposure.

Life has evolved strategies that allow it to survive even beyond the physical and chemical limits to which it has adapted to grow. To survive, some microorganisms can assume forms that enable them to withstand freezing, complete desiccation, starvation, high-levels of radiation exposure, and other physical or chemical challenges. Furthermore, some microorganisms can survive exposure to such conditions for weeks, months, years, or even centuries.^[53] Extremophiles are microbial life forms that thrive outside the ranges life is commonly found in. They also excel at exploiting uncommon sources of energy. While all organisms are composed of nearly identical molecules, evolution has enabled such microbes to cope with this wide range of physical and chemical conditions. Characterization of the structure and metabolic diversity of microbial communities in such extreme environments is ongoing. An understanding of the tenacity and versatility of life on Earth, as well as an understanding of the molecular systems that some organisms utilize to survive such extremes, will provide a critical foundation for the search for life beyond Earth.^[53]

Classification of life

---

The hierarchy of biological classification's eight major taxonomic ranks. Life is divided into domains, which are subdivided into further groups. Intermediate minor rankings are not shown.

Traditionally, people have divided organisms into the classes of plants and animals, based mainly on their ability of movement. The first known attempt to classify organisms was conducted by the Greek philosopher Aristotle (384-322 BC). He classified all living organisms known at that time as either a plant or an animal. Aristotle distinguished animals with blood from animals without blood (or at least without red blood), which can be compared with the concepts of vertebrates and invertebrates respectively. He divided the blooded animals into five groups: viviparous quadrupeds (mammals), birds, oviparous quadrupeds (reptiles and amphibians), fishes and whales. The bloodless animals were also divided into five groups: cephalopods, crustaceans, insects (which also included the spiders, scorpions, and centipedes, in addition to what we now define as insects), shelled animals (such as most molluscs and echinoderms) and "zoophytes". Though Aristotle's work in zoology was not without errors, it was the grandest biological synthesis of the time and remained the ultimate authority for many centuries after his death.^[59]

The exploration of the American continent revealed large numbers of new plants and animals that needed descriptions and classification. In the latter part of the 16th century and the beginning of the 17th, careful study of animals commenced and was gradually extended until it formed a sufficient body of knowledge to serve as an anatomical basis for classification.

In the late 1740s, Carolus Linnaeus introduced his method, still used, to formulate the scientific name of every species.^[60] Linnaeus took every effort to improve the composition and reduce the length of the many-worded names by abolishing unnecessary rhetoric, introducing new descriptive terms and defining their meaning with an unprecedented precision. By consistently using his system, Linnaeus separated nomenclature from taxonomy. This convention for naming species is referred to as binomial nomenclature.

The fungi were originally treated as plants. For a short period Linnaeus had placed them in the taxon Vermes in Animalia. He later placed them back in Plantae. Copeland classified the Fungi in his Protoctista, thus partially avoiding the problem but acknowledged their special status.^[61] The problem was eventually solved by Whittaker, when he gave them their own kingdom in his five-kingdom system. As it turned out, the fungi are more closely related to animals than to plants.^[62]

As new discoveries enabled us to study cells and microorganisms, new groups of life were revealed, and the fields of cell biology and microbiology were created. These new organisms were originally described separately in protozoa as animals and protophyta/thallophyta as plants, but were united by Haeckel in his kingdom protista, later the group of prokaryotes were split off in the kingdom Monera, eventually this kingdom would be divided in two separate groups, the Bacteria and the Archaea, leading to the six-kingdom system and eventually to the current three-domain system.^[63] The classification of eukaryotes is still controversial, with protist taxonomy especially problematic.^[64]

As microbiology, molecular biology and virology developed, non-cellular reproducing agents were discovered, such as viruses and viroids. Sometimes these entities are considered to be alive but others argue that viruses are not living organisms since they lack characteristics such as cell membrane, metabolism and do not grow or respond to their environments. Viruses can however be classed into "species" based on their biology and genetics but many aspects of such a classification remain controversial.^[65]

Since the 1960s a trend called cladistics has emerged, arranging taxa in an evolutionary or phylogenetic tree. It is unclear, should this be implemented, how the different codes will coexist.^[66]

Extraterrestrial life

Panspermia hypothesis

Earth is the only planet in the universe known to harbour life. The Drake equation, which relates the number of extraterrestrial civilizations in our galaxy with which we might come in contact, has been used to discuss the probability of life elsewhere, but scientists disagree on many of the values of variables in this equation. Depending on those values, the equation may either suggest that life arises frequently or infrequently.

Panspermia, also called exogenesis, is a hypothesis proposing that life originated elsewhere in the universe and was subsequently transferred to Earth in the form of spores perhaps via meteorites, comets or cosmic dust. However, this hypothesis does not help explain the ultimate origin of life.

Death

Death is the permanent termination of all vital functions or life processes in an organism or cell.^[75][76] After death, the remains of an organism become part of the biogeochemical cycle. Organisms may be consumed by a predator or a scavenger and leftover organic material may then be further decomposed by detritivores, organisms which recycle detritus, returning it to the environment for reuse in the food chain.
One of the challenges in defining death is in distinguishing it from life. Death would seem to refer to either the moment at which life ends, or when the state that follows life begins.^[77] However, determining when death has occurred requires drawing precise conceptual boundaries between life and death. This is problematic, however, because there is little consensus over how to define life. The nature of death has for millennia been a central concern of the world's religious traditions and of philosophical inquiry. Many religions maintain faith in either some kind of afterlife, reincarnation, or resurrection.

Extinction

Extinction is the gradual process by which a group of taxa or species dies out, reducing biodiversity.^[78] The moment of extinction is generally considered to be the death of the last individual of that species. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively after a period of apparent absence. Species become extinct when they are no longer able to survive in changing habitat or against superior competition. Over the history of the Earth, over 99% of all the species that have ever lived have gone extinct.^[79]

Fossils

Fossils are the preserved remains or traces of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossil-containing rock formations and sedimentary layers (strata) is known as the fossil record. Such a preserved specimen is called a "fossil" if it is older than the arbitrary date of 10,000 years ago.^[80] Hence, fossils range in age from the youngest at the start of the Holocene Epoch to the oldest from the Archaean Eon, a few billion years old.

See also

References

Further reading

• Kauffman, Stuart. The Adjacent Possible: A Talk with Stuart Kauffman
• Nealson KH, Conrad PG (December 1999). "Life: past, present and future". Philos. Trans. R. Soc. Lond., B, Biol. Sci. 354 (1392): 1923–39. doi:10.1098/rstb.1999.0532. PMID 10670014. PMC 1692713. http://journals.royalsociety.org/content/7r10hqn3rp1g1vag/. 
• Walker, Martin G. LIFE! Why We Exist...And What We Must Do to Survive Dog Ear Publishing, 2006, ISBN 1598582437

External links

• Wikispecies - a free directory of life
• "The Adjacent Possible: A Talk with Stuart Kauffman"
• Stanford Encyclopedia of Philosophy entry
• Life under extreme conditions An in depth look at how life can form under the most extreme conditions and circumstaces.

Basic topics in evolutionary biology Evidence of common descent Processes of evolution Adaptation · Macroevolution · Microevolution · Speciation Population genetic mechanisms Genetic drift · Gene flow · Mutation · Natural selection Evolutionary developmental biology (Evo-devo) concepts Canalisation · Modularity · Phenotypic plasticity The evolution of... Aging · Birds · Dinosaurs · DNA · Dolphins and whales · The Ear · The Eye · Flight · Fungi · Horses · Humans · Human intelligence · Insects · Life · Molluscs · Plants · Sex · Sirenians (sea cows) · Spiders Modes of speciation Anagenesis · Catagenesis · Cladogenesis History of evolutionary thought Charles Darwin · On the Origin of Species · Modern evolutionary synthesis · Gene-centered view of evolution · Life (classification trees) Other subfields Ecological genetics · Molecular evolution · Phylogenetics · Systematics List of evolutionary biology topics · Timeline of evolution

From Wikiquote

Life is a state that distinguishes organisms from non-living objects or dead organisms, being manifested by growth through metabolism and reproduction.

Sourced

• All who have meant good work with their whole hearts, have done good work, although they may die before they have the time to sign it. Every heart that has beat strong and cheerfully has left a hopeful impulse behind it in the world, and bettered the tradition of mankind. And even if death catch people, like an open pitfall, and in mid-career, laying out vast projects, and planning monstrous foundations, flushed with hope, and their mouths full of boastful language, they should be at once tripped up and silenced: is there not something brave and spirited in such a termination? and does not life go down with a better grace, foaming in full body over a precipice, than miserably straggling to an end in sandy deltas?
  • Robert Louis Stevenson in "Aes Triplex" (1878)

• Brief and powerless is man's life; on him and all his race the slow, sure doom falls pitiless and dark.
  • Bertrand Russell, Mysticism and Logic, ‘A free Man's Worship’

• I compare human life to a large mansion of many apartments, two of which I can only describe, the doors of the rest being as yet shut upon me.
  • John Keats, letter to J. H. Reynolds, 3rd May 1818

• Life is a pill which none of us can bear to swallow without gilding.
  • Samuel Johnson, in Anecdotes of Johnson by Mrs Piozzi.

• Life is a process of becoming, a combination of states we have to go through. Where people fail is that they wish to elect a state and remain in it. This is a kind of death.
  • Anaïs Nin, in D. H. Lawrence : An Unprofessional Study (1932)

• Life's but a walking shadow, a poor player that struts and frets his hour upon the stage, and then is heard no more: it is a tale told by an idiot, full of sound and fury, signifying nothing.
  • William Shakespeare in Macbeth

• Life is not measured by the number of breaths we take, but by the moments that take our breath away.
  • Claimed by Erica Frandsen in Kochmer, Casey; Erica Frandsen (2002). JSP and XML: Integrating XML and Web Services in Your JSP Application. Addison-Wesley Professional. pp. p. xv. ISBN 0672323540. Retrieved on 2008-01-23.  
  • Attributed to George Carlin in:
    • McCollister, John (2004). Echoes From The Smithsonian: America's History Brought to Life. Sports Publishing LLC. pp. p. 73. ISBN 1582612455. Retrieved on 2008-01-23.  
    • Conklin, Todd (2004). Simple Revolutionary Acts: Ideas To Revitalize Yourself And Your Workplace. iUniverse. pp. p. xiv. ISBN 0595320651. Retrieved on 2008-01-23.  
  • Commonly attributed to "Unknown"

• Life is the distance between dreams and reality.
  • Leonid S. Sukhorukov, All About Everything (2005)

• Life is what happens to you while you're busy making other plans.
  • John Lennon, in "Beautiful Boy (Darling Boy)" (1980)

• The Lives We try to make never seem to get Us anywhere but Dead.
  • Soundgarden in "The Day I Tried To Live" (1994)

• Now this is eternal life: that they may know you, the only true God, and Jesus Christ, whom you have sent.
  • Jesus, in John 17:3 (NIV)
  • Variants:
  • And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.
    • John 17:3 (KJV)
  • This means everlasting life, their taking in knowledge of you, the only true God, and of the one whom you sent forth, Jesus Christ.
    • John 17:3 (New World Translation)

• Every man's life is a train made of straw which tries to move on a track made of fire! The very next stop is ashes and dust.
  • Mehmet ildan, "Quotations"

• The cleverest amongst you is he who is the loyal apostle of life, the true disciple of existence and the devout follower of love.
  • Mehmet ildan, "Quotations"

• Life shrinks or expands according to one's courage.
  • Anaïs Nin, as quoted in French Writers of the Past (2000) by Carol A. Dingle, p. 126

• Living should be perpetual and universal benediction.
  • Wei Wu Wei in Why Lazarus Laughed : The Essential Doctrine, Zen — Advaita — Tantra (2003)

• The life so short, the craft so long to learn.
  • Hippocrates, Aphorisms, I. i
    Often translated in Latin as:
    Ars longa, vita brevis

• The sea is only beautiful if there's a shore. Life is like the sea. There'll be a direction to follow even if you sail more than one day or one life... the promise of a new land is your guide, because you know that the sea is a huge world that's beautiful only if there's a shore.
  • Patricky Field, as quoted in Beautiful if there's a shore (2008) song by Patricky Field

• To be what we are, and to become what we are capable of becoming, is the only end of life.
  • Robert Louis Stevenson in Familiar Studies of Men and Books (1882)

• God is a communist; He does not let us to own our life as our own property, because we did not earn it through working!
  • Mehmet ildan, "Quotations"

• We write to taste life twice, in the moment, and in retrospection. We write, like Proust, to render all of it eternal, and to persuade ourselves that it is eternal. We write to be able to transcend our life, to reach beyond it.
  • Anaïs Nin, entry for February 1954, in The Diary of Anaïs Nin, Vol. 5 as quoted in Woman as Writer (1978) by Jeannette L. Webber and Joan Grumman, p. 38

Dictionary of Burning Words of Brilliant Writers (1895)

Reported in Josiah Hotchkiss Gilbert, Dictionary of Burning Words of Brilliant Writers (1895).

• Life as we call it, is nothing but the edge of the boundless ocean of existence when it comes upon soundings.
  • Oliver Wendall Holmes, p. 380.

• Life is before you,— not earthly life alone, but life— a thread running interminably through the warp of eternity.
  • Josiah Gilbert Holland, p. 380.

• O thou child of many prayers!
  Life hath quicksands, Life hath snares!
  Care and age come unawares!
  • Henry Wadsworth Longfellow, p. 380.

• The grand question of life is, Is my name written in heaven?
  • Dwight L. Moody, p. 380.

• The end of life is to be like unto God; and the soul following God, will be like unto Him.
  • Socrates, p. 380.

• God help us! it is a foolish little thing, this human life, at the best; and it is half ridiculous and half pitiful to see what importance we ascribe to it, and to its little ornaments and distinctions.
  • Francis Jeffrey, p. 381.

• There is no life so humble that, if it be true and genuinely human and obedient to God, it may not hope to shed some of His light. There is no life so meager that the greatest and wisest of us can afford to despise it. We cannot know at what moment it may flash forth with the life of God.
  • Phillips Brooks, p. 381.

• Life is rather a state of embryo, a preparation for life; a man is not completely born till he has passed through death.
  • Benjamin Franklin, p. 381.

• As one climbs a mountain roadway, and looks off on the landscape through the forest trees or from some overtopping crag, at each step he sees more and more of the outlying beauty of field and lake and forest and hill and river, till he reaches the summit, where the whole vast scene opens to the view, and enthuses his soul with delight. So life should be a constant lookout, through the gray mists, through the falling shadows, through the running tears, till he comes to the shining top of life in God Himself, where the fogs lift, and the shadows fall, and the view is all undisturbed.
  • Theodore Bayard Romeyn, p. 381.

• A picture without sky has no glory. This present, unless we see gleaming beyond it the eternal calm of the heavens, above the tossing tree tops with withering leaves, and the smoky chimneys, is a poor thing for our eyes to gaze at, or our hearts to love, or our hands to toil on.
  • Alexander Maclaren, p. 382.

• Life is great if properly viewed in any aspect; it is mainly great when viewed in connection with the world to come.
  • Albert Barnes, p. 382.

• There is no human life so poor and small as not to hold many a divine possibility.
  • James Martineau, p. 382.

• Life and religion are one, or neither is any thing.
  • George MacDonald, p. 382.

• Let the current of your being set towards God, then your life will be filled and calmed by one master-passion which unites and stills the soul.
  • Alexander Maclaren, p. 382.

• Man's life is so interwoven with the grand life of his Maker that it admits of no adequate or rational interpretation except when the Creator as Supreme and the creatures of His hand as subordinate, are seen working in unison.
  • Charles H. Anthony, p. 382.

• I believe that we cannot live better than in seeking to become better.
  • Socrates, p. 382.

• Making their lives a prayer.
  • John Greenleaf Whittier, p. 382.

• While we seek to fill up life in a way that will best secure the ends of our existence here, our whole plan and course of action should be such as will not hinder but serve our preparation for a future world.
  • Albert Barnes, p. 383.

• Pray for and work for fullness of life above every thing; full red blood in the body; full honesty and truth in the mind; and the fullness of a grateful love for the Saviour in your heart.
  • Phillips Brooks, p. 383.

• Act as if you expected to live a hundred years, but might die to-morrow.
  • Ann Lee, p. 383.

• Nor love thy life, nor hate; but what thou livest,
  Live well; how long, or short, permit to Heaven.
  • John Milton, p. 383.

• We live in deeds, not years; in thoughts, not breaths;
  In feelings, not in figures on a dial.
  We should count time by heart-throbs. He most lives
  Who thinks most, feels the noblest, acts the best.
  • Philip James Bailey, p. 383.

• I would not choose to go where I would be afraid to die, nor could I bear to live without a good hope for hereafter.
  • Charles Spurgeon, p. 383.

• Life is short, art long, opportunity fleeting, experiment uncertain, and judgment difficult.
  • Hippocrates, p. 384.

• A few years hence and he will be beneath the sod; but those cliffs will stand, as now, facing the ocean, incessantly lashed by its waves, yet unshaken, immovable; and other eyes will gaze on them for their brief day of life, and then they, too, will close.
  • Henry Parry Liddon, p. 384.

• They waste life in what are called good resolutions—partial efforts at reformation, feebly commenced, heartlessly conducted, and hopelessly concluded.
  • Charles Maturin, p. 384.

• It is infamy to die, and not be missed.
  • Carlos Wilcox, p. 384.

• And thus does life go on, until death accomplishes the catastrophe in silence, takes the worn frame within his hand, and, as if it were a dried-up scroll, crumbles it in his grasp to ashes. The monuments of kingdoms, too, shall disappear. Still the globe shall move; still the stars shall burn; still the sun shall paint its colors on the day, and its colors on the year. What, then, is the individual, or what even is the race in the sublime recurrings of Time? Years, centuries, cycles, are nothing to these. The sun that measures out the ages of our planet is not a second-hand on the great dial of the universe.
  • Henry Giles, p. 384.

• Oh, I believe that there is no away; that no love, no life, goes ever from us; it goes as He went, that it may come again, deeper and closer and surer, and be with us always, even to the end of the world.
  • George MacDonald, p. 384.

• The highest life is a broken column; the fairest life, a tar niahed gem; the richest life, an unripened fruit.
  • John Humpstone, p. 385.

• This earth will be looked back on like a lowly home, and this life of ours be remembered like a short apprenticeship to duty.
  • William Mountford, p. 385.

• This is life's greatest moment, when the soul unfolds capacities which reach beyond earth's boundaries.
  • Isaac Hecker, p. 385.

• Life! we've been long together
  Through pleasant and through cloudy weather;
  Tis hard to part when friends are dear,—
  Perhaps 'twill cost a sigh, a tear.
  Then steal away, give little warning.
  Choose thine own time,
  Say not "Good-night," but in some brighter clime,
  Bid me "Good-morning."
  • Anna Letitia Barbauld, p. 385.

External links

Wikipedia has an article about:

Life

From Wikiversity

'From Wikipedia, the free encyclopedia

Life is a characteristic of organisms that exhibit certain biological processes such as chemical reactions or other events that results in a transformation. Living organisms are
capable of growth and reproduction, some can communicate and many can adapt to their environment through changes originating internally.[1] A physical characteristic of life is
that it feeds on negative entropy. In more detail, according to physicists such as John Bernal, Erwin Schrödinger, Eugene Wigner, and John Avery, life is a member of the class of
phenomena which are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently
rejected in a degraded form (see: entropy and life).

An entity with the above properties is considered to be a living organism, hence, a 'life form'. However, not every definition of life considers all of these properties to be essential. For example, the capacity for evolution is sometimes taken as the only essential property of life; this definition notably includes viruses, which do not qualify under narrower definitions as they are cellular and do not metabolize.

A diverse array of living organisms can be found in the biosphere on Earth. Properties common to these organisms—plants, animals, fungi, protists, archaea and bacteria—are a carbon- and water-based cellular form with complex organization and heritable genetic information. They undergo metabolism, possess a capacity to grow, respond to stimuli, reproduce and, through natural selection, adapt to their environment in successive generations. So far, there is no evidence of extraterrestrial life.

Definitions

There is no universal definition of life. To define life in unequivocal terms is still a challenge for scientists, as the definition must be sufficiently broad that would encompass all
life with which we are familiar. It should be sufficiently general that, with it, scientists would not miss life that may be fundamentally different from earthly life. In addition,
defining life requires measurable terms, and when derived from analysis of known organisms, life is usually defined at the cellular level.

Conventional definition: The consensus is that life is a characteristic of organisms that exhibit all or most of the following phenomena:

  1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
  2. Organization: Being structurally composed of one or more cells, which are the basic units of life.
  3. Metabolism: Consumption of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy
to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
  4. Growth: Maintenance of a higher rate of synthesis than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular
species begins to multiply and expand as the evolution continues to flourish.
  5. Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's
heredity as well as the composition of metabolized substances, and external factors present.
  6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of higher
animals. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and chemotaxis.
  7. 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 strictly speaking it also describes the production of
new cells in the process of growth.

From Wikisource

Life may refer to:

• Life, a biographical work on Samuel Johnson by James Boswell.
• Life, a poem by Samuel Taylor Coleridge. ("As late I journeyed o’er the extensive plain")
• Life, a poem by Charlotte Brontë. ("Life, believe, is not a dream,")
• Life, a poem by Paul Laurence Dunbar. ("A crust of bread and a corner to sleep in,")
• Life, a poem by Edith Wharton. ("Life, like a marble block, is given to all,")
• Life, a poem by Ella Wheeler Wilcox. ("Life, like a romping schoolboy, full of glee,")
• Life, a poem by Florence Earle Coates from Poems (1898). ("Before we knew thee thou wert with us ;")
• Life, another poem by Florence Earle Coates from Poems (1898). ("Thou art more ancient than the oldest skies,")
• Life, a poem by Robert Ervin Howard. ("They bruised my soul with a proverb,")

From LoveToKnow 1911

Definition from Wiktionary, a free dictionary

English

Proper noun

Life

1. (Christian Science) God.

Anagrams

• Anagrams of efil
• file
• lief

From BibleWiki

generally of physical life (Gen 2:7; Lk 16:25, etc.); also used figuratively (1) for immortality (Heb 7:16); (2) conduct or manner of life (Rom 6:4); (3) spiritual life or salvation (Jn 3:16, 17, 18, 36); (4) eternal life (Mt 19:16, 17; Jn 3:15); of God and Christ as the absolute source and cause of all life (Jn 1:4; 5:26, 39; 11:25; 12:50).

what mentions this? (please help by turning references to this page into wiki links)

From Wikia Gaming, your source for walkthroughs, games, guides, and more!

LIFE or The Game of Life is a board game produced by Milton Bradley Company that simulates life from adulthood to retirement. The goal of the game is to retire with the most money.

At the start of the game the player can choose to enter college or immediately start working. There is advantages and disadvantages to both: if you go to college you must borrow money but when you graduate you have a larger choice of careers that potentially pay more.

Players travel the board in a miniature car and eventually must stop to get married and buy a house. Over the course of the game players will have children, change jobs, pay taxes, and encounter pitfalls and windfalls that generally occur in life. Players also have the option of taking out loans which must be repaid with interest, buying home and automobile insurance to minimize the cost of some pitfalls, and buying stocks that pay out when any player's spin points to the same number as their stock card.

Some spaces on the board allow you to collect LIFE tiles that are kept face down until the end of the game. Each tile describes a special achievement such as "Compose a Symphony", and gives a monetary reward. When all the players reach retirement they may choose to retire at either "Countryside Acres" or "Millionaire Estates". Four LIFE tile are reserved at "Millionaire Estates" for the player with the most cash. If more than one player chooses to retire there, the players must add up their cash and the one with the most gets the last four LIFE tiles.

The winner is the player with the highest LIFE tile value and cash value.