Basics of Evolution

What we need for evolution ...-

A system that replicates.

Variation within the replication.

An environment that selects (at least slightly) for a particular replication.

-If we have this as our basis, then to get a complex system we need a long time and perhaps a variety of environments.

3722 views

Romansh: What we need for evolution ...
> 
>

A system that replicates.
>
Variation within the replication.
>
An environment that selects (at least slightly) for a particular replication.
>

> 
> If we have this as our basis, then to get a complex system we need a long time and perhaps a variety of environments.-But first you have to have a system that replicates with almost perfect accuracy, and so far it is not described, and how it is formed is not understood. Yet it happened.

Post reply

3669 views

Romansh: What we need for evolution ...
	A system that replicates.
	Variation within the replication.
	An environment that selects (at least slightly) for a particular replication.
If we have this as our basis, then to get a complex system we need a long time and perhaps a variety of environments.-DAVID: But first you have to have a system that replicates with almost perfect accuracy, and so far it is not described, and how it is formed is not understood. Yet it happened.-For evolution to take place, it's the variations that are essential. Otherwise the process will stick at replication. I would have thought the variety of environments was also essential, since a single uniform environment would limit potential ways of life, and hence the potential variety of species. I'm not sure where this is heading!-Romansh, I'll reply to your Random post tomorrow.

Post reply

3677 views

dhw: For evolution to take place, it's the variations that are essential. Otherwise the process will stick at replication.-Of course we are stuck at replication, no matter what the environmental variations!-In Koonin's famous article for a multiworlds scenario he produced a back of the envelop calculation for the odds of a accurately replicating RNAzyme:- http://www.biologydirect.com/content/2/1/15#sec8-"A ribozyme replicase consisting of ~100 nucleotides is conceivable, so, in principle, spontaneous origin of such an entity in a finite universe consisting of a single O-region cannot be ruled out in this toy model (again, the rate of RNA synthesis considered here is a deliberate, gross over-estimate). -"The requirements for the emergence of a primitive, coupled replication-translation system, which is considered a candidate for the breakthrough stage in this paper, are much greater. At a minimum, spontaneous formation of: -"- two rRNAs with a total size of at least 1000 nucleotides-"- ~10 primitive adaptors of ~30 nucleotides each, in total, ~300 nucleotides-"- at least one RNA encoding a replicase, ~500 nucleotides (low bound)is required. In the above notation, n = 1800, resulting in E <10-1018. -"In other words, even in this toy model that assumes a deliberately inflated rate of RNA production, the probability that a coupled translation-replication emerges by chance in a single O-region is P < 10-1018. Obviously, this version of the breakthrough stage can be considered only in the context of a universe with an infinite (or, in the very least, extremely vast) number of O-regions. -"The model considered here is not supposed to be realistic by any account. It only serves to illustrate the difference in the demands on chance for the origin of different versions of the breakthrough system and hence the connections between these versions and different cosmological models of the universe.-Comment: This is smaller chance than Morowitz 10^40,000 estimate of many years ago. It directly supports my initial response to Romansh's post. Life MUST start with accurate replication. Varying environmental locations offer a tiny hope to improve chances, but no much at the odds quoted.

Post reply

3716 views

Here is a question ... what are the chances of a smaller replicator occurring?
Say a chain of 30 amino acids.-And if it does form what are the chances of complexity increasing after that?-and dhw ... all three are required for evolution to occur. 
I am not sure how good the fidelity is required for the replication, but it is sure very high in what we describe as life.

Post reply

3675 views

Romansh: Here is a question ... what are the chances of a smaller replicator occurring?
> Say a chain of 30 amino acids.
> 
> And if it does form what are the chances of complexity increasing after that?
> 
> and dhw ... all three are required for evolution to occur. 
> I am not sure how good the fidelity is required for the replication, but it is sure very high in what we describe as life.-To my knowledge of the studies the small replicators are reproducing with fidelity in the high 90's%, for up to 2oo generations, but these are made in the labs after computer studies of trillions of possible molecules. This will not make life with the necessary fidelity. And finally short replicators are not seen in current life. Is ancient life so different? We will never know.

Post reply

3696 views

dhw: For evolution to take place, it's the variations that are essential. Otherwise the process will stick at replication. I would have thought the variety of environments was also essential, since a single uniform environment would limit potential ways of life, and hence the potential variety of species. I'm not sure where this is heading!-DAVID: This is smaller chance than Morowitz 10^40,000 estimate of many years ago. It directly supports my initial response to Romansh's post. Life MUST start with accurate replication. Varying environmental locations offer a tiny hope to improve chances, but no much at the odds quoted.
Of course we are stuck at replication, no matter what the environmental variations!
-There seems to have been a misunderstanding here. I thought Romansh was dealing with the basics of evolution, not with the odds against chance. By stuck at replication I meant that evolution would never have taken place: the first cells would have stayed as they were. The ability to vary is therefore the key to evolution (as opposed to the existence and survival of one type of cell) - but of course you are right that first you have to have the ability to replicate. Environmental variations also seem to me to be an essential factor, for the reason given above. But I wrote that I didn't know where this was heading, and your subsequent exchange with Romansh suggests that his concern is indeed with the odds for and against chance.
 
ROMANSH: dhw...all three are required for evolution to occur.-Agreed.

Post reply

3707 views

Evolution from single cell to multi-cell animals simpler than previously thought.-http://www.nytimes.com/2016/01/12/science/genetic-flip-helped-organisms-go-from-one-cell-to-many.html?_r=0-You don't need some elaborate series of thousands of mutations in just the right order.

--
GPJ

Post reply

3713 views

George: Evolution from single cell to multi-cell animals simpler than previously thought.
> 
> http://www.nytimes.com/2016/01/12/science/genetic-flip-helped-organisms-go-from-one-cel... 
> You don't need some elaborate series of thousands of mutations in just the right order.-Thank you! Fascinating article. Of course it doesn't tell us how the single cells started. I'm sure they did this all by computer simulations, so there are some assumptions and what they found may not be exactly as they proclaim. -"The evolution of a molecular carabiner did not by itself give rise to the animal kingdom, of course. Other adaptations were needed in order to grow multicellular bodies. Dr. Thornton said that it might be possible to resurrect other ancestral molecules in order to figure out how those adaptations evolved, as well.-"And if GK-PID is any guide, Dr. Thornton said, their evolution may have been surprisingly simple. A single mutation might have been enough to switch a molecule from one job to another."-That is a big IF.

Post reply

3642 views

RSS Feed of thread

AgnosticWeb.com

Basics of Evolution (Evolution)