What are the theories on the origin of life on earth?

Question

It's really important! I need to know the answers badly. I'm making a project out of it

Answer 1

We know from fossil stromatolites that life on earth began more than 3 billion years ago.

There are a number of competing ideas on how life might have begun. There are no concrete answers, however. It is a complex problem. "Panspermia" suggests life was seeded on earth from elsewhere in the galaxy--perhaps drifting down on board some meteorite with a slow trajectory. We have found meteorites from arctic ice to wheatfields. This simply pushes back the origin of life question, however.

Another idea suggests that before our DNA based world there was a simpler RNA based world. Self replicating RNA would have been replaced by self replicating DNA when the latter mutated into existence. Although we have synthesized self replicating RNA through natural means in laboratories, that is still a big step from DNA and cells, and no clear pathway has yet been discerned for cellular abiogenesis.

A third hypothesis suggests there may be simpler self replicating organic molecules which served as percursors to self replicating DNA. You can find an article about this in a recent edition of Scientific American.

A popular hypothesis (none of these are really fleshed out as full fledged "theories") is that life began near deep ocean hydrothermal vents. We find that amino acids occur naturally in such environments--just as they do in the Miller/Urey experiments, and even out in space (back to "panspermia.") Amino acids to archaeobacteria is still such a huge gulf, however.

Many biologists suspect there is some as yet unknown phenomenon that makes the origin of life next to inevitable given proper environmental conditions. Precisely what this might be remains unclear at this time. The reason this is suspected is because life started on this planet very early, when conditions for its existence as we find it were not particularly favorable.

One problem is that biologists continue to lack a particularly good, simple definition of "life." Are viruses alive? Fire consumes and grows, but most folks reject the notion it is alive.

Answer 2

Well, first of all start with the experiments done by a PhD named Miller back in the 1950's. He set up an experiment to duplicate the conditions on this planet at the time life formed. Having done this, he eventually made some of the components to life in a "test tube" from the bare essentials. What he found in short is that the basic components of the outer membrane layer of a cell are self assembling/ self organizing.

From there also look at resent work that the basic materials/ building blocks of life can and may form in the space around the stars and planets, coming together from the material ejected from dying stars and ice globs and the like. This material periodically rains down on the planets like "Lego's of life". It seems to that with the findings of possible fossil life blasted from the Mars surface and finding it's way here, that this probably has happened before and will happen again here and in other parts of the universe.
Look also at the theory of how the basic cellular components first appeared. The four different molecules that make up our DNA, adenine, thymine, guanine, and cytosine, may actually be found in full or in part in interstellar space. The article below cites research that has found 140 molecules alone, some of which are complex organic molecules and found in interstellar space. Is this the basics to form small chunks of DNA or RNA like material? If that and the basic cell membranes found in the 1950's Miller experiment came together in the primordial soup of our sea then maybe viruses, viroids, prions, etc? Once that far and some basic simple cell like materials form, then it is thought that some of the different ones, specialized ones, came together inside of the first membranes to work together as a cell would but as a community, with a nucleus like object in it's own membrane, and other organelle like objects that found a great protected home in a membrane. Some of them had their own genetic material, like pre-mitochondria. Once this "cell" found a way to split and multiply, and with differences in environment and the constant rain of radiation and chemical deposition, the "soup" was done.
A lot of research points to that kind of scenario, and it is all available to read. And though the research is frequently dry, the concept of life evolving from the star dust that was is a really amazing thing, and one just lives for any new research. It has been a thing that has held my rapt attention my whole life. Life is precious. The thing that caused me to take nearly an hour to write this short piece is that, yesterday my son brought home a sea sponge from the beach. Last night the little things that called it home crawled out looking for the sea. I had to collect them and return them to the ocean, because life is precious and only a huge respect will do, especially when you think about all it went threw to get to a little crab that lives on a sponge on my back deck.

Answer 3

A scientific theory starts with an idea, and researchers then look for evidence to support OR refute the idea. Creationists look only for data to support their idea so creationism is not a scientific theory. Panspermia (the idea that life arises somewhere else in the cosmos and drifts to Earth and other planets) might be a scientific idea, depending on how it's advocates approach it. Zvi

Answer 4

The two primary theories are:

Serendipity. A lucky, mindless accident. Conditions and chemistry was "just right" and inorganic matter spawned organic material which evolved, changed, multiplied and diversified randomly based on natural conditions, environment and other factors.

The second theory is creation by an advanced or "supereme" being (God is a good generic name) who engineered it somehow with intent, design, will, intelegence and a plan (to some degree at least). Much like the engineers at Apple who created the Ipod.

Answer 5

There are NO theories about the origin of life. Evolution is a theory about the origin of SPECIES, not life.

Answer 6

Here is the basis of the leading, non-religious, basis of life on Earth, Abiogenesis, along with counter theories and problems associated with it. Even with its conjectural nature, it is the most likely explanation.

Answer 7

there are no theries on the origings of life, just guesses. A Theory needsto be proven with scientific fact. Creationism has not been proven, and Evolution tells us nothing about the origins of life, merely how life addapts to its surroundings

Answer 8

One is that life began some 3.8 billion years ago when advanced organic chemicals began replicating. These chemicals formed out of simpler substances such as aminoacids which in turn formed (in several steps) out of atmospheric nitrogen, methane, carbondixode, water, etc in the presence of substances like iron and aluminium oxides (catalysts), silica, phosphorous. All these substances would have been baked together in warm, shallow puddles where evaporation would have made it a concentrated stew. Every now and then the tide (the moon was much closer) would have washed these substances out into the oceans where the protolife forms would have mixed with other protolife forms formed in other puddles. And new substances and minerals would wash into new puddles. This process began as soon as earth was cool enough for water to condense and form oceans and it was able to go on like this, an endless mixing and blending with the sun and lightning and possibly even volcanoes and asteroid impacts giving energy. It is possible, since early earth was a very violent place, that impacts from comets may have jumpstarted the process since they too have a lot of the substances required for life already on the surface. Still, it took some 800 million years for this huge chemical experiment to yield life. (Urey and Miller did this experiment in a glass bottle with water, a primordial atmosphere and bolts of lightning. They only ran it for a short period and still got aminoacids which is the base chemical of life.)

The first organisms were very simple bacteria. They were chemotrophes meaning they simply "ate" organic chemicals that would rain down and that were dissolved in water. They would get energy from oxidizing the "food" with oxygen from a nitrate or sulphate ion, reducing them to ammonia and hydrogen sulphide. The energy they got from this metabolism they used to form chemicals of their own.

Soon the bacteria started feeding off each other instead. They became carnivorous. But eventually one bacteria would fail to digest another bacteria it had just eaten (possibly due to a new proteincoating). Instead the smaller bacteria, with properites of its own, kept on living inside the bigger one. They would pool their resources making up a whole new organism and evolution had gone from bacteria to single celled organisms. In modern cells, in humans and single celled organisms alike, we call these little half eaten bactera organelles. (The ribosome especially supports this theory. It has its own dna.)

Eventually the bacteria developed the ability to get their energy directly from the sun with photosynthesis. They began churning out oxygen as a byproduct. Oxygen was poisonous to all other life but since earth is basically a huge metalball in the oceans there were enourmus quantites of iron dissolved. This iron would react with the dissolved oxygen to form an insolluable iron oxide. As this reaction gives off heat bacteria evolved to capture that energysource and began doing this reaction for themselves. So as soon as a little oxygen formed it was immediatelly consumed. For two billion years this went on (creating the banded iron formations or BIFs that we get our iron ore from today) and the primordial atmosphere, which was mostly carbondioxide and 70 times as dense as it is today, was almost completely "eaten" by these iron bacteria (as well as by organisms that use carbonate for their shells). But finally the oceans ran out of iron and oxygen began building up, first in the oceans and then in the atmosphere. And organisms had now evolved to utilize the free oxygen where as before it had been poison. And the oxygen metabolism is much more energetic than non oxygen metabolism. With this whole new level of energy for life evolution was about to explode.

In the timeline we are now about 700 million years in the past. Until now life had reproduced by mitosis or celldivision. This cloning makes sure the offspring is identical to the parent. Only rarely does a change or a mutation sneak in. This is evolution at its slowest and for 3 billion years life hardly evolved beyond singlecelled organisms. There were some more advanced organisms but they too utilized mitosis.

And then there was sex. Sexual reproduction made sure the off spring is never identical to the parents and suddenly changes began appearing all over. Sex, along with the new oxygen rich environment, caused evolution to explode. It is called the Cambrian explosion and has also been nicknamed "the big bang of evolution". Pretty soon there were sharks, fishes and all kinds of possible and impossible lifeforms.

So that is a short summary of life on earth.

Answer 9

You need to specify your question. If you need to know the answers so badly, just google it or go to wikipedia ...
We here cannot know where you want to start from ... interstellar dust? amino acids? bacterias? or when life came to higher forms? You really need to specify what you want.

Answer 10

at the origin there was only Morgan Freeman. then he decided he was alone and bored so he began to develop what you call today humanity.