Life. What exactly is 'life'? I'm doing an independant study in my extention class at the moment, and one of the big questions I need to answer for myself is 'how life began,' so I figured that learning the basic components of 'life' could lead me to the answer. What atoms are necessary? What energy is necessary? How do all of these factors bond together? I know this is serious stuff, so please keep any answers relatively simple.
Any information would be appreciated. Thank you!
First of all, I'll tell you that I can't answer the question. However, you might think about viruses in the context of your study. Although they contain DNA/RNA, there is huge debate about whether they are technically "alive" . They replicate rather than reproduce (but what are the criteria for saying replication isn't reproduction??) and don't move independently (but neither do some plants) so the debate rolls on. Good luck, Big Ma
As Big ma has responded, this is actually a much more difficult question to answer than it might at first seem and - as far as I am aware - there hasn't yet been a wholly satisfactory answer to the question.
In terms of biochemical components though, all 'life' as we know it has in common some form of genetic material (either RNA or DNA), proteins, carbohydrates and lipids (consisting of carbon, oxygen, hydrogen, phosphorus, sulphur, and metal ions such as iron and zinc).
As for the origins of life, I would do some reading into the RNA world hypothesis (where RNA is thought to precede DNA as the original genetic material due to its ability to catalyse chemical reactions in the absence of proteins - DNA is to all intents and purposes inert and dependent on proteins for its function).
The first question, “What is life?” partly depends on how we choose to define it. We probably all remember the school Biology list of “What living things do”. We can simply make a list or use an existing one; and say that anything that does what is on our list is alive.
That is fine as a general rule of thumb. We can see that most living things grow, move respire, reproduce etc. Even though some of these activities are less obvious in plants they can still be found.
But then we come to viruses, which are unable, by themselves, to do most of the things on the usual list. Yet they are exquisitely adapted to invade the cells of more complex organisms and make use of them to perform the functions of life. Maybe viruses are alive, but are extreme forms of obligate parasites that have perhaps lost the ability to perform some or most of the usual functions of living things? Or maybe they are non-living bits of specially packaged DNA or RNA, that may be useful or harmful. (Viruses can transfer genetic material in some cases, so enrich the genome of their host).
However, “life” as most people understand it is something mysterious, something apparently much more than what is in our list.
The answer we give to the second question, “How did life originate?” depends less on science and more on our worldview, philosophy of life, belief system, religion, whatever you want to call it.
These beliefs make certain basic assumptions (which may or may not be true) about the origins of life, the universe etc. Such beliefs have little or nothing to do with science, but do profoundly influence our thinking, often without us being aware of it. It is possible to build a whole, apparently science-based, edifice on such assumptions, but (because of dealing with the unobserved past) they cannot be scientifically tested. Any evidence or data not fitting our beliefs may be ignored or reinterpreted to support the belief. In spite of the best efforts of even intellectually honest scientists (probably not too many are), scientific objectivity is largely a myth.
I could give you my personal belief on the origin of life in one word – “God” - and give ample scientific and historical evidence to support it as being the most likely explanation for the origin of life. But not many on this forum would accept that because their own beliefs are so strongly (in some cases fanatically) opposed and “cannot allow a divine foot in the door” as someone put it. That is mainly why I gave up debating evolution here.
On the other hand, Jonathan’s comments suggest that his worldview, like that of many, is naturalistic, with evolution as its starting assumption. (I too was "brought up" to accept Evolution as unquestionable fact, though encouraged to question everything else in science, so understand the hold this idea can have.)
Yet the RNA hypothesis merely takes things back one step; there is still no biochemical evidence that RNA, and especially the DNA/RNA Code itself, could have arisen spontaneously either – let alone that it actually did! It is still a matter of faith rather than science, and the “Origin of Life Prize” remains unclaimed! [http://www.us.net/life/]
I was once asked by a biology tacher at high school to argue why fire wasn't alive. It blew my mind!
Subjectively, life for me is any point in which molecules 'behave' to protect their own exhistence. The ability to perform the '7 functions' are nearly always disregarded, ie. torpor or hybrid sterility. Conscience and life are exclusive and shouldnt be considered part and parcel, although humanity I think likes to consider itself the most worthy life form to exhist on this earth by the wealth of its conscience - hence how genocide of any life form is an insuffarable human condition where the ethos of life as sacred is not impressed.
Also the virus conundrum makes me go loopy. On the one hand the single unit is a mutagen, but on the other hand - isn't the function of reproduction?! All molecules of the unit up until the point of it's break down are provided by the one single host cell previously, where as most living things require a soup of mixed host sources to provide an incorporation of molecules to increase it's own mass. Do viruses require sustainance? Do they have an expiration date if they left to exhist in an inert environment?
Objectively I think this question is impossible. Purely hypothetical and anyone claiming they knew the answer is claiming they were there at the start and that they are aware of every 'living' entity to account for a single working argument.
I don't think I've helped you out here, I've just spent a long time thinking about it on and off and sometimes its nice to get it off your chest and having a resource of independent responses like a social study can't bee too ba a thing??.. Philosophy burns me out! haha. Good luck on your paper!!!
The comment about trying to show if fire is "Alive" or not was food for thought, and the answer not obvious.
However, the complexity you see in the way fire moves, "breathes" and "reproduces", or in the growth and behaviour of crystals, is nothing like the complexity of living things. Living things are not only much more complex but of a different order or realm of of complexity altogether - sometimes called "Specified complexity"
Living things reproduce themselves, not in the chemical-mechanical way that fire or a crystal does; but as a result of coded information.
Fire replicates and reproduces itself in a sense. Crystals "give birth" to more crystals. But none of them does so by means of a sophisticated and highly interdependent system, including - at least in the case of DNA - more than one code operating at the same time, and multiple layers of meta-information (information about information) that even experts in the field struggle to properly understand.
This code-complex is not directly related to the actual end product of the use of this code, any more than writing, musical notation, or the computer binary code is directly related to the information it carries.
What resemblance has the code "D.O.G." to the hairy creature that barks and wags its tail and is found in many of our homes?
What resemblance have black marks on a page to beautiful orchestral music or information about any number of subjects? What resemblance have the words I am typing to the thoughts they convey? What difference would it make to the meaning if I typed the same words in some other script such as Russian or Hebrew letters?
What resemblance does the double hellix of DNA have to the specific individual flower, tree, moss, fungus, bacterium, animal, bird, insect or human that it gives rise to?
Just some thoughts...