Please a Yes or a No...


by TenNen
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TenNen
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#1
Jun21-04, 09:49 PM
P: 109
May I ask you two questions ?
(1) Do self-assembly and directed assembly mean adaptation and natural selection respectively ?
(2) Are prebiotic assemblies chemical elements ?

Thanks a lot in advance
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Monique
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#2
Jun22-04, 03:35 AM
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Quote Quote by TenNen
May I ask you two questions ?
Yes
(1) Do self-assembly and directed assembly mean adaptation and natural selection respectively ?
(2) Are prebiotic assemblies chemical elements ?

Thanks a lot in advance
You need to explain yourself a little further to what you mean..
TenNen
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#3
Jun22-04, 03:57 AM
P: 109
Okay,(smile)

Matter evolved from prebiotic assemblies to multicellular organisms....etc
They developed to higher levels of organization by a means of self assembly and directed assembly
I thought they should be the same meanings as what I have said above but not really sure, therefore I raised some questions to hopefully receiving someone's answers, way of confirmation from a newie anyway...(smile)

TenNen
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#4
Jun22-04, 03:59 AM
P: 109

Please a Yes or a No...


I am reading an essay about evolution in which the writer used so many terms whose exact meanings I am not able to figure out...
Monique
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#5
Jun22-04, 04:33 AM
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Ok :) so
(1)Do self-assembly and directed assembly mean adaptation and natural selection respectively ?
No, I think what is meant is that sponges are able to self-assemble: if you pass them through a sieve so that they are all individuall celled, they will aggregate again to form an organism. Directed assembly must mean forming the different organs in an organism.
(2) Are prebiotic assemblies chemical elements ?
Everything is chemical elements the author might mean biochemical reactions or physical structures like a cell membrane.
TenNen
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#6
Jun22-04, 05:16 AM
P: 109
Thanks Monique, I misundertood them all, (*o*)
(smile)
loseyourname
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#7
Jun22-04, 12:53 PM
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Quote Quote by Monique
No, I think what is meant is that sponges are able to self-assemble: if you pass them through a sieve so that they are all individuall celled, they will aggregate again to form an organism. Directed assembly must mean forming the different organs in an organism.
I think this guy is talking about the self-assembly of protobionts, the 4th step in the standard model of abiogenesis. I'll just quote this piece from Biology by Campbell and Reese:

The properties of life emerge from an interaction of molecules organized into higher levels of order. Living cells may have been preceded by protobionts, aggregates of abiotically produced molecules. Protobionts are not capable of precise reproduction, but they maintain an internal chemical environment different from their surroundings and exhibit some of the properties associated with life, including metabolism and excitability.

Laboratory experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds. For example, droplets called liposomes form when the organic ingredients include certain lipids. These lipids organize into a molecular bilayer at the surface of the droplet, much like the lipid bilayer of cell membranes. Because the membrane is selectively permeable, the liposomes undergo osmotic swelling or shrinking when placed in solutions of different salt concentrations. Some of these protobionts also store energy in the form of a membrane potential, a voltage across the surface. The protobionts can discharge the voltage in nervelike fashion; such excitability is characteristic of all life (which is not to say that liposomes are alive, but only that they display some of the properties of life). Liposomes behave dynamically, sometimes growing by engulfing smaller liposomes and then splitting, other times "giving birth" to smaller liposomes. If enzymes are included among the ingredients, they are incorporated into the droplets. The protobionts are then able to absorb substrates from their surroundings and release the products of the reactions catalyzed by the enzymes

Unlike some laboratory models, protobionts that formed in the ancient seas would not have possessed refined enzymes, which are made in cells according to inherited instructions. Some molecules produced abiotically, however, do have weak catalytic capacities, and there could well have been protobionts that had a rudimentary metabolism that allowed them to modify substances they took in across their membranes.
TenNen
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#8
Jun22-04, 08:14 PM
P: 109
Many Thanks to you again for this thread and others in which you have helped me out....(smile)


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