Evolution of single celled organisms

Jack

How did single celled orgainsims evolve into multicelular organisms because I just can't imagine them making that step. Evolution is due to mutations in organisms that makes them better at survival but how could such a large mutation have occured?

Also, does anyone know what they evolved into?

marcus

this is one of the all-time most interesting questions

I have no hard info for you, only that I share the curiosity

I've read that fossil evidence shows it happened around 600 million years ago

Like....in extremely crude terms singlecell began 3.6 billion and went on being single cell for 3 billion years (!!!!!) and then got
the idea Hey why dont we try cooperating! and....

A few years back I read an article by a "Snowball Earth" theorist who tried to argue from some geological evidence that 600 or 700 years ago there was a runaway freeze that completely froze the oceans. Go figure.
This runaway freeze created a high albedo so very little solar energy stuck to the earth and so the iceball was stable
And the freezeover caused a mass extinction
(apparently there was one of those mass extinctions 600 or 700 million years ago, a major one)
And this mass extinction somehow triggered multicell life maybe by forcing cells to clump together for survival and clearing out a lot of ecological niches so that evolution could radiate and proceed rapidly when the ice finally melted.

Probably this "Snowball Earth" theory is unacceptable for some reason. most theories get shot down. but I thought it was cute.

Why, you may ask, did the ice eventually melt? because of
volcanos gradually building up CO2!!!
There wasnt much photosynthesis so the greenhouse gasses just stayed in the atmosphere until the greenhouse effect was so overwhelming that even despite the high albedo the ice melted.

Am I telling you old stuff? Did you know of this theory already?

BTW I have no trouble picturing the actual step itself because lots of singlecells form colonies that actually involve cooperation.

like mold, and lichen on rock, and plaque on your teeth and all that stuff. they work collectively to change the chemistry and even geometry around them to their collective benefit, and cooperate to build up spore spreading structures and send out filaments and all that.
so an active colony is not all that different from say a sponge, or coelenerate or jellyfish
which is also a sort of coalition of single cells.

the thing that is hard for me to imagine is how did we get stuck on the one-cell level (with singlecells occupying all the ecological niches) for almost 3 billion years?

and if that was so obviously stable, then what finally changed? how can there have been no decisive evolutionary advantage to coalescence for 3 billion years and then suddenly a very big
evolution-driving reproductive/survival advantage?

Another God

It's easy to imagine when you realise that a multicell organism is just a 'society' of single celled organisms. Just as animals may form societies, they may also be individuals. Humans are a collection of individual cells, organised into a complex society. In the begining, the societies weren't complex, they were just together. Over time, 'laws' evolved, where the societies of cells worked together to make more and more effective 'societies'.

It is accepted that the sponge style organism was pretty much the type of organism which first got on the of Multicellular life bandwagon
.
Chances are it was 'happening' over all that time. Seriously, 'fossil evidence' of single celled organisms isn't the most reliable of sources. Cells don't 'fossilize' very well at all, what with have no bones or anything, so if any can find out anything about early cels, then its impressive, but I doubt anyone can really say anything certain about them.

Chances are, those 3 billion years were spent clumping and unclumping, and different version of intercellular communications were being tried and aborted etc... all that time.

Unfortunately, evolution theory is so damn good at what it does, that it can really explain anything.

iansmith

What I remember from comparitve zoology course is that sponce and sea anemodes were not the first organism to have a basic multicellar structure. I remember some protozoan (i don't the familly or the name) could form a "society" were some individual would only reproduce sexually and asexually, and some would form the "outer wall" for protection. Some cells had other function.

Edit: the microorganism I talking about is not a protozoan it is a unicellular green algae

There is other factor than enviromental pressure and mutation. Single cell organism can acquire genetic information in the enviroment such as transposon and plasmid.

You rigth but mother nature is a b***h, so migth come kick us in the *** and proves us wrong.

marcus

Much truth to what you say about all these things but this may be a case where evolution theory has so far failed to explain the fossil record.

As I understand it, the record is very peculiar. There are a great many multicell fossils after 6 or 700, and none before!

As I understand it (and I'm not well informed) there is at present no explanation, from evolution theory or any other widely accepted model, why this should be.

I suppose that under some circumstances permanent fossils *can* form from multicell beasties, as shown by the record after 700. But apparently as yet no earliers have been found.

Plus there was a great extinction around 700-600 which was then followed by a great radiation of multicell species.

It seems to me that what you imagine happening---a wealth of earlier experiments with multicell life---is exactly what there is no evidence for!

iansmith

Having no proof that a wealth of earlier experiments with multicell life does not mean that it did not happen. There is also no proof that only unicellular life happen. We are taking about microscopic fossil, and it can easily be overlook. There also specicial condition for fossil to be creat. Number of multicellular organism migth of not be significant to leave traces. We could argue for long how to prove or disprove any theory but I don't think multicellular organism arise overnigth and some earlier ewxperiment could have happen but there were not successfull. Fossils only show the successfull experiment maybe multicellular organism became extremely successfull at around 700 Million years ago. its only a theory and it will be debated untill proven rigth or wrong.

O Great One

The answer is, they didn't. It's sad that in 2003, we still have people believing in the fairy tale of evolution. Eventually evolution will be discarded just like the theories of phlogiston and the earth being flat.

Another God

HAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHAHHAHAHAHAHAHAHAHAHAHAHAH

OH LOL...LOL..LOL...HAHAHAHAHHAHAHAHAHAHAHAHAHAHHAHA

*sniff*

hehe..hahah.

HAHAHAHHAHAHHAHHAHAHHAHAHAHHAHHAHAHAHAHAHAHHAHA

That line cracks me up everytime...
hehehee

enigma

LOL,

I'm with AG...

so what will the "fairy tale" of evolution be replaced by?

fairy tales written by 4000 year old goat-herders, I suppose...

Mentat

And what fairy tale do you prefer to Evolution?

Mentat

By that you mean that a new hypothesis can be devised to explain each new concept? If so, I agree, and I say the previous sentence in no derogatory sense. Evolutionary theories can probably answer all of those questions: such as "where did the first cell come from?", or "what caused single-celled organisms to evolve into multicellular organisms?

sage

i think evolution of multicellar societies were caused by decreasing nutrition density in the oceans. as earth became more tectonically stable amount of nutrition belching in the form of minerals decreased a lot. this coupled with the worst global cooling in earths history were impetus enough enough for a radical evolutionary innovation. by the way edicarian fauna have shown that multicellular life had began in precambrian itself,no doubt discoveries in future will show that such a radical step was not as sudden as made out to be.

FZ+

Interesting hypothesis...

However, didn't the evolution of multicellular life appear after the cyanobacteria started emmiting oxygen? Then, the ecosystem would already have shifted out of reliance on mineral nutrition...

drag

Greetings !

I know these quotes are completely out of context,
but that's REALLY funny ! [:D]
[:D]

Anyway, Jack I got this thread on this
forum called "evolution of complex life"
and I got a link there to a recent spaceref
article with a relevant to this subject
recent discovery that you may be intrested in.

Live long and prosper.

Another God

I dont' get it Drag

sage

two things to find out.first compared to today how vigorous was geothermal activity on the seafloor.it is true that cyanobacter had opened up a new way of living but that does not mean the old way had been completely overwhelmed.it is possible(if the ocean floor was active enough of course)that the former way was still dominant.its a little like divergence between marine and terrestrial life.emergence of terrestrial life did not mean the end of marine ways of existing did it?it may be that a crisis in the unicellular life dependant on geothermal energy may have accentuated the need for mass cooperation.if that was what actually happened the first multicells would be of a distict stock from cyanobacters.so this is the second thing that needs investigation.one thing going for this theory(if you can call this wild surmise that)is in pockets of geothermal energy great densities of living things subsisting in similar ways must live together giving rise to fierce competition and fruitful liasions.but one needs proof and i have none to offer.

Phobos

Ah, c'mon. Give us more to work with. Tell us why you think evolution is a fairy tale. I'm up for a good debate. Are we talking in the line of Morris? Ham? Johnson? Behe?

(mentor: better start a new topic for that, unless you want to discuss it in light of single celled organisms only)