its pretty simple, life of the reactions of life represent a constant effort to avoid or deter the equilibrium state.
equillibrium conditions represents death
Dear Sanjoy Datta,
This is a tricky question. Maybe you should be more accurate: you are referring to an "object" that makes the answer very difficult. For example. Is a virus particle considered an object? But those "particle" are for definition not a living "object".
its pretty simple, life of the reactions of life represent a constant effort to avoid or deter the equilibrium state.
equillibrium conditions represents death
Life is the complex condition for continuously interacting system. Is virus living object or not, for me, question for existence of that condition.
There are few criteria which need to be full filled for one object to consider as living. These are :1) Growth (but even nonliving things grow eg mountains via accumulation), 2) reproduction (some living dont reproduce eg mule, worker honey bee though they are living), 3) All sum of metabolism (very important criteria as all living things show metabolism) and 4) Environmental response (another very imp criteria as all living respond to different environmental stimulus).
Hope this can be useful for what you r looking.
"struggle for survival" is the key feature for a thing to be classified as living, for survival an organism need to interact with different things in surrounding and possesses metabolic process within, that's how life continues. a non living thing has nothing to do with survival and so on. so in short "survival" is the exact base for differentiation.
life is a self-organizing bounded local environment that is at disequilibrium with its surroundings. When people die they become at equilibrium with their surroundings, the body will cool to the temperature of the surroundings and such. That is the chemistry definition of life. The philosophical definition is consciousness. If you do not know you are alive, are you really living?
Life is a special form that is capable to do work and enable to cganges by development, growth and reproduction.
As a geneticist, I prefer the following definition: Life is a complex and evolving pattern (the genetic material) capable of interfacing with its environment to ensure its own reproduction.
To Andrew Jenkins: crystals, eg clays and hydroxyapatite, can fulfil those criteria too.
The meaning of life as we perceive it is derived from philosophical and religious contemplation of, and scientific inquiries about existence, social ties, consciousness, and happiness. Many other issues are also involved, such as symbolic meaning, ontology, value, purpose, ethics, good and evil, free will, the existence of one or multiple gods, conceptions of God, the soul, and the afterlife. Scientific contributions focus primarily on describing related empirical facts about the universe, exploring the context and parameters concerning the "how" of life.
To @Roger Bayston. That's why I put in the word 'complex'. Crystals and clays are not complex. Neither does their pattern evolve.
To Elham Bilal: most of the criteria that you list would not apply to an amoeba (so far as we know), so is the amoeba dead? Also, re God and the soul: are atheists also dead?
I think this is more a philosophical question than anything else. Many ancient philosphers used to debate on the meaning of life and even today we cannot really define it by means of biology, chemistry or genetics (or else). Even a rock has life. It is subjected to weather erosion, therefore it interacts with the environment and it changes. It doesn't reproduce, not like other organisms do, but when it loses bits, could that be considered a sort of reproduction? I am being intentionally ridiculous now, with that, but the concept I am trying to put through is that life is really hard to define. For every definition we may find, there are others who could object with valid arguments. And that goes for the scientific community as well. Life can be defined differently, according to the field of specialization.
Re Valeria. This may seem like a philosophical question, but it actually has a practical side. Mankind is exploring space looking for life. In all probability, if we find life as we know it (Carbon-water based) then we will be able to recognize its signature. On the other hand, if it is 'Life, Jim, but not as we know it', we may not know how to look for it or fail to recognize or - more importantly - to respect it.
Andrew, you say that clays and crystals do not evolve. Crystals do change their structures from one generation to another, and carry unique surface microtopographies, so a moot point?
Roger, if the microtopology is 'heritable', then this is close to being an information system. If some microtopologies reproduce better under different environments, then the crystals would satisfy my definition of life. At that point I either have to accept that my definition is too broad or say that the crystals are alive.
Exit Andrew Jenkins, humbler, but wiser.
Yes, exactly the conundrum posed by Professor AG Cairns Smith in 1985 ("seven clues to the origins of life"
Re Andrew. While I agree with you entirely, we constantly fail to respect life forms here on earth, at this moment in time (but this is another topic). In my opinion, it is still a philosophical concept, which has needs to be translated into practical applications, such as the ability to recognise life which might sustain itself in different combinations than carbon-water, as you put it. Unless you are suggesting that we consider any possible combination of systems which could be qualified as "life", I guess it will have to be a trial-error kind of thing. We should approach space exploration with Star Trek in mind. The principles expressed through the Federation of Planets, could work great! And who knows, we might have already encountered alien life, say on Mars, and we might have not recognised it. I don't disagree with you. I am just saying that we do not have specific parameters to apply and therefore, any reasoning is purely conceptual.
Ability of growth and reproduction, sensing its self and its environment
I think the only sensible approach to the question "What is life?" is taken from thermodynamics. Read Erwin Schrödinger's little book "What is life?", and/or the slim 1995 volume of expert commentary on Schrödinger's book, entitled "What is life? The next fifty years. Speculations on the future of biology", and edited by Michael P. Murphy and Luke A. J. O'Neill. The bottom line is that a living entity is one that decreases entropy in an environment of increasing entropy.
The capacity for growth, reproduction, functional activity, and continual change
Re Gregg and Roger. I have a lot of time for the thermodynamic definition, though I think one should specify: living entity is one that decreases its own entropy in an environment of increasing entropy.
On the other hand: don't Roger's crystals do this too?
Thank's @Andrew Jenkins
The definition consider abbreviated for All metabolic and chemical reaction from the cell into the system
I acknowledge, and appreciate, Andrew's clarifying addition to the definition of life that I offered. As to the question of crystals, Schrödinger addresses that in his book, noting that crystals are periodic and living entities are aperiodic. It is this aperiodicity that leads to the complexity of living entities, versus the simplicity of crystals. This concept also led Schrödinger to postulate the existence of molecules in the cells of living organisms that were complex enough to encode information, years before the discovery that nucleic acids (DNA and RNA) serve that very function.
This leads to another addition to our proposed definition of life: A living entity is one that decreases its own entropy in an aperiodic form in an environment of increasing entropy.
It depends on the kind of organism. For example bacteria death is the inability to grow.For higher organisms is linked to organs dysfunctionality.
But inability to grow (ie reproduce) does not necessarily indicate death in bacteria. We are familiar with viable but non-culturable bacteria. Also, the ability to "grow" depends on environmental factors: some bacteria reproduce only inside cells, etc
I agree that inability of bacteria to grow is not decisive of death but there is no alternative approach.
An older person is not growing nor reproducing but I would argue still alive Be careful of your definitions!
The definition of death for humans and animals is based on body dysfunctionality for any reason which can be checked medically. For bacteria death concept is different and hard to deferintiate a dead bacterium from alive. Inability to grow on suitable medium is an empirical approach.perhaps a molecular based approach would be more decisive.
Amin, I agree with you but the original poster didn't specify they were only looking at bacteria. Any appropriate answer is going to need to address the entire spectrum of "living" organisms.
I already differentiate between higher organisms and bacteria as they present different realities and clear distinction of death phenomenon. Thank you
Adult people grow their cells because the definition involves a cellular level and not just appearnce @Michael j. Benedik
Life and death are incidents related to all organisms.
• A human with life thinks and acts whereas a human being that is dead does not think and act.
• Brain remains active when there is life and brain becomes inactive when a person dies.
• The two terms life and death are used as suggestive words too.
• The word life gives the meaning of ‘vital breath’ whereas the word death gives the meaning of ‘final moments’ in suggestion.
• Life implies survival whereas death implies end.
• Life implies essence whereas death implies decay.
• Life is also used to mean ‘vitality, vigour or energy.’
• Life is used to identify the period between birth and death of a living thing.
• Life is used as a synonym for biography in literature.
An organism becomes dead or considered dead when it is no longer showing signs of life as metabolism, movement, sensing, and reproduction due dysfunctionality at molecular, cellular,or organs level.
Organsim consider a life if it has characteristics of life, which included cellular orgnazation , movement , transport, regenaration, reproduction and homostatsis .
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