how did life begin ?

Question

tell me the theories but dont use the god excuse do it scientifical.. thanks (K)

Answer 1

There are a few major theories. It's even possible that they all happen in the universe and that determining which one happened here may be all but impossible. But let's start with what they're not:

There exists a pretty good consensus among most biologists about life on Earth for a fair proportion of its history. This is the evolutionary view: that existing organisms tend to adapt and change to and with their environments, and as they are separated they can become different enough to become different species. Combined with geology, it seems that all life on Earth evolved at some point from primitive single-celled organisms somewhere around 3.5 billion years ago.

So the question of where life begins (to these guys, anyway) is pretty much the question of how do you get a primitive single-celled organism to show up from stuff that we know was lying around.

One theory suggests that there's a lot more stuff lying around than most would grant. Some scientists have found spectra of light from other stars which seem to suggest the presence of amino acids. If this is so, it may suggest that some of the basic building-blocks of life are actually quite common in the universe, which goes a long way to getting life started.

Another theory, called 'panspermia' suggests that not only amino acids but actually whole cells just naturally arise. If this were true, then it would be no more suprising to find life in the universe than it would be to find methane and water. And if life if pretty much universal among all the materials of the universe, then pretty much every planet that can support life is going to have some.

Since there isn't too much evidence of other life in the universe yet, most scientists seem to prefer theories that involve life being created here.

Some suggests that even if building-blocks of life can't form anywhere, they might easily have formed on Earth. Attempts to replicate primordial conditions have produced complex organic molecules from just simple ingredients and energy. So there's good support for this idea.

Of course, you need more than building blocks to build a model, so there's different ideas on how they might have assembled. Perhaps a string of RNA formed that was able to make copies of itself (not too farfetched - a lot of protein-making and duplication is done by RNA in cells even now). Some suggest that waves might have made tiny bubbles out of naturally occurring lipids, and if one bubble just happened to have the right stuff inside it then it could have been the first cell (and there's probably a couple billion years for the waves to pull this off, so it's not completely ridiculous). One theory suggests that clay might have formed a protective layer, so crystallized RNA or DNA trapped in clay could have had some access to materials but still be concentrated enough to produce cell-like structures. It has also been suggested that perhaps the first cells were formed not on the surface, but deep in the Earth's crust. These cells would have used less favorable chemical reactions to run themselves, but down there conditions would have been very constant, allowing a very slow initial adaptation speed and an accumulation of good things without having to worry about them all being 'washed away'.

There is a weaker version of panspermia which just suggests that instead of life-making processes occurring on Earth, they occurred somewhere else. If, say, some other planet had life on it when its star exploded, then chunks of that planet - perhaps with still-living things in them - might be spread to all kinds places... even Earth. If this is so, then unless we can find other traces of the origin planet we may never know what went on - conditions could have been completely different from Earth, so all our experiments would have been way off track.

Which is right? There's scarcely any evidence to say. Maybe all, maybe none. In science, doubt and belief are two sides of the same valuable coin.

Answer 2

No one knows. Stromatolites (fossils of bacterial mats) exist that have been dated close to 3 billion years old.

No multicellular organisms (metazoans) are known until around 650 million years ago.

We know that amino acids, the so-called "building blocks" of proteins, may form spontaneously under a wide variety of conditions. Clay may act as both a scaffold and catalyst for the formation of biologically active molecules. But even a prokaryote (single celled organism without a nucleus) is hideously complex. No one knows how the first of these originated.

One hypothesis is that there was a world of self replicating RNA that preceded our DNA world. Even if we succeed in replicating life through natural means in a laboratory, that does not necessarily mean that is how earth life originated.

So far, this is a scientifically unanswered question. The fact there is no answer, yet, should not be that big of a concern. Most questions do not yet have answers. For that matter, every time science answers a question, it tends to breed new questions. I find that the more questions an answer provokes, the better that answer tended to be. We may never catch up!

Then again, if we ever do, scientists will have nothing left to research.

Answer 3

It is believed that life started some 3.5-4 billion years ago. An experiment done in 1953 by Miller showed that it was possible to spontaneously create simple amino acids and such from the primeval "soup" that existed back then. This would occur in the abscence of oxygen. There are many, many theories, some that life came from extra-terrestial origins, that life began as phospholipid bilayers, or that metabolic pathways developed and became "trapped" in vesicles. There is no evidence that DNA or RNA could self-polymerize in the abscence of enzymes, although many theories include that. It is clear, though, that life goes against entropy and disrupts the local entropy of a system.

Answer 4

God made the world universe the galaxy--------- and us.

Answer 5

osmosis?