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Author Topic:   Cell Division
Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 4 of 32 (605276)
02-18-2011 7:36 AM
Reply to: Message 1 by Drevmar
02-17-2011 11:55 PM


Lipids will spontaneously form liposomes --- (roughly) spherical cells with bilipid layers, and these will spontaneously divide and fuse. (When I say spontaneously, I mean that no biological mechanism is required, it's just down to the physics of the lipids.) Note that fission does not spill the contents of the liposomes.

So you could perfectly well have cell fission, in this sense, before you actually had life! --- and then life co-opted this ready-made process. The challenge then would be how best to regulate it.

In this paper, the author comments:

Because liposomes undergo spontaneous fission and fusion, and are subject to osmotic forces, size regulation in the earliest protocells would essentially have been liposome physics. For successful protocells, averting osmotic lysis would have been the first order of business. However, from the outset size mattered too, because of sex and reproduction (i.e., genome mixing and genome copying in entities with phenotypes). Protocell fission and fusion would have blended seamlessly into protocell sex and reproduction, making any gene product that furnished control over protocell size changes doubly adaptive.

So protocells didn't have to be programmed to divide, as such --- but once life started using these membranes, it was adaptive to acquire control over the process of division. It seems reasonable that any control would have been better than none, and more better than less, making this adaptation a prime candidate for evolution.

Edited by Dr Adequate, : No reason given.


This message is a reply to:
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Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 12 of 32 (605552)
02-20-2011 8:01 PM
Reply to: Message 10 by shadow71
02-20-2011 7:21 PM


Re: To RAZD
Incredulity is not an argument. Do you have any specific and science-based criticism, or do the fact that you laughed and an irrelevant quotation from Dr Flew constitute all you have to say for yourself?

We can watch liposomes dividing in a laboratory; we know it happens. If, as I suspect, you have a magic-based hypothesis, I should like you to produce equally strong evidence for the occurrence of magic. Otherwise I shall prefer the reality-based hypothesis to yours unless and until I have further data.

Edited by Dr Adequate, : No reason given.


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 Message 10 by shadow71, posted 02-20-2011 7:21 PM shadow71 has responded

Replies to this message:
 Message 13 by Drevmar, posted 02-21-2011 12:36 AM Dr Adequate has not yet responded
 Message 18 by shadow71, posted 02-21-2011 7:13 PM Dr Adequate has responded

  
Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 21 of 32 (605745)
02-21-2011 10:08 PM
Reply to: Message 18 by shadow71
02-21-2011 7:13 PM


Re: To RAZD
Do you label Szostak's video and the article by Ricardo and Szostak " life on earth" Scientific America sept. 2009 a:

Theory?
Hypothesis?
Speculation?
Wishful thinking?
Magic based hypothesis?

I can't access the article. The video presents a non-magical hypothesis as to the way in which abiogenesis took place and some facts about biochemistry that support its plausibility.

As no-one has observed magical processes in biology, this in my judgment makes the hypothesis superior to magic-based hypotheses.


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 Message 18 by shadow71, posted 02-21-2011 7:13 PM shadow71 has acknowledged this reply

Replies to this message:
 Message 22 by Bolder-dash, posted 02-21-2011 11:16 PM Dr Adequate has responded

  
Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 24 of 32 (605759)
02-22-2011 12:06 AM
Reply to: Message 22 by Bolder-dash
02-21-2011 11:16 PM


So you don't believe in magic.

Well, incredulity is not an argument.

Observation, however, is an argument. I have never seen magic any more than I have seen a pig with wings. Unless and until I do, the scientific method constrains me to disbelieve in both.

An argument from incredulity would be saying that magic is too ridiculous to be true. Whereas what I say is that it is too unevidenced to be plausible. Like winged pigs.


This message is a reply to:
 Message 22 by Bolder-dash, posted 02-21-2011 11:16 PM Bolder-dash has responded

Replies to this message:
 Message 26 by Bolder-dash, posted 02-22-2011 12:11 AM Dr Adequate has responded

  
Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 28 of 32 (605766)
02-22-2011 12:12 AM
Reply to: Message 25 by Bolder-dash
02-22-2011 12:07 AM


Re: Dr. A believe in magic
So you are saying that he does believe in magic?

Of course he isn't.

Is there any statement that you can't misunderstand?


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 Message 25 by Bolder-dash, posted 02-22-2011 12:07 AM Bolder-dash has not yet responded

  
Dr Adequate
Member (Idle past 78 days)
Posts: 16112
Joined: 07-20-2006


Message 32 of 32 (606138)
02-23-2011 9:19 PM
Reply to: Message 26 by Bolder-dash
02-22-2011 12:11 AM


Do you also mean like the evolution of the eye through random mutations? You haven't actually seen that happen have you?

Or of abiogenesis? You were there? Wow.

No, that is not what I mean.

I believe that I actually meant what I said. I realize that this concept may be foreign to you.


This message is a reply to:
 Message 26 by Bolder-dash, posted 02-22-2011 12:11 AM Bolder-dash has not yet responded

  
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