Forums

ForumsWorld Events, Politics, Religion, Etc.

Edge Of Life

Posted May 27, '14 at 7:11am

HahiHa

HahiHa

5,473 posts

Knight

Ok then, can anyone explain this paragraph i got from wiki?

[quote] ........Basin Groups 1-9 (which collectively make up the Pre-Nectarian), and the Nectarian and Lower Imbrian. The first lifeforms (self replicating RNA molecules, see RNA world hypothesis) may have evolved on earth around 4 bya during this era.

..... especially the bolded sentence, because according to most of your posts, they shouldn't qualify as a "lifeform" or be "alive", yet why do they write this? [/quote]
In my modest opinion, qualifying RNA as the first lifeforms is arguably false.

First, I would not qualify them as lifeforms; they are organic molecules that can both contain information as well as act enzymatically; such molecules were certainly vital for the first lifeforms, but it isn't a lifeform by itself.

Second, the RNA we know today was likely not the very first of that molecule category. There are a wide variety of bases, the ones modern genetic information is made of (U,G,C,A,T) were not necessarily the first.

what about immortalized cell lines? are they not living, because they can't die by natural means? more explanation is in here, but if you are too lazy to read it, what i infer from them is that they include cancerous cells.

Good point. I guess this is a weak spot in the definition of life by death.

Then again, those immortal cells still perform "processes that keep it alive". If an individual cell would stop those processes, which is still possible (deleterious mutations in vital parts of the genome, lack of resources for growth) this cell would still die. Remember that cancerous cells induce angiogenesis in the surrounding tissue to sustain their increased growth rates.

A virus, as opposed to an immortal cell line, never performed those processes to begin with. In a way it doesn't even have the possibility to die.


last edited May 27 2014 07:13 am by HahiHa
 

Posted May 28, '14 at 8:08am

Kennethhartanto

Kennethhartanto

248 posts

In a way it doesn't even have the possibility to die.


I found this in Moe's links.

Most scientists agree that viruses are alive because of what happens when they infect a host cell.


According to your comment, you said that virus can't die, because it wasn't living to begin with. But here we got a statement that "most scientist agree that viruses ARE alive". so it must also be able to die, right? In my opinion, maybe a virus "dies" when it has already inserted itself to the cells genetic code.

First, I would not qualify them as lifeforms; they are organic molecules that can both contain information as well as act enzymatically; such molecules were certainly vital for the first lifeforms, but it isn't a lifeform by itself.


About RNA not being a lifeform by itself, that i can agreed on. but after i study this in a biology lecture textbook, i think that by "RNA world hypothesis", whoever write the article must meant RNA's that was enveloped by a lipid membrane and was able to multiply itself in a tidal pool, or inside clay deposits that can serve as a "cell membrane". a little difficult to explain it, but from there i found again the word "first lifeform", because in that it stated that it can both "multiply", "feed itself" ( by assimilating other organic compounds it got into contact ), and also "store information" ( using RNA's). would that enough to qualify as a lifeform?
 

Posted May 31, '14 at 3:56pm

HahiHa

HahiHa

5,473 posts

Knight

Most scientists agree that viruses are alive because of what happens when they infect a host cell.

Well, I disagree with the term "alive". A virus, as I already said, has no metabolism and no homeostasis to keep. What happens when a virus infects a cell is that a structure snaps mechanically, inserts the viral genome and all the proteins into the cell, cell which will do all the work and produce new viruses with new genomes and new proteins.

Actually I would rather prefer the term "undead" for viruses. It is definitely a biological structure with a genome, but no cell. It is not alive but neither is it dead anorganic matter. And it infects host cells. Seriously, viruses are the zombies of the cellular world.

About RNA not being a lifeform by itself, that i can agreed on. but after i study this in a biology lecture textbook, i think that by "RNA world hypothesis", whoever write the article must meant RNA's that was enveloped by a lipid membrane and was able to multiply itself in a tidal pool, or inside clay deposits that can serve as a "cell membrane". a little difficult to explain it, but from there i found again the word "first lifeform", because in that it stated that it can both "multiply", "feed itself" ( by assimilating other organic compounds it got into contact ), and also "store information" ( using RNA's). would that enough to qualify as a lifeform?

That would qualify as a lifeform, because it is not just an RNA molecule. It is a whole unit with many components.

Maybe what you are describing is something like this?
The Origin of Life - Abiogenesis
 

Posted Jun 1, '14 at 5:24am

Kennethhartanto

Kennethhartanto

248 posts

Well, I disagree with the term "alive". A virus, as I already said, has no metabolism and no homeostasis to keep


It seems we have a bit of a disagreement, as you defined life with having the capability to metabolize and had an homeostasis to keep. i however defined life as anything that is capable of storing information and also having a negative entropy ( as in that lifeform "desires" to become complex not becoming simplistic, unlike computers which can store information but over time will break down to it's constituent elements). your point of view is from the basic view of life, but mine is from thermodynamics and biophysics. maybe that is why those scientist believe the virus are "alive" in a sense.

So, which point of view is more right in your opinion and why? if you can explain which are more right and why that i can agree on, we can reach a consensus to the problem. for my alternative view, look at the wikipedia for the definition of life.

That would qualify as a lifeform, because it is not just an RNA molecule. It is a whole unit with many components.


what i explained earlier doesn't have a lot of components, just RNA's and a makeshift "cellular membrane". that's it. but is that a lifeform in your opinion if it has the properties i mentioned before? and also, what i was referring to is the same on your links
 

Posted Jun 1, '14 at 6:31am

HahiHa

HahiHa

5,473 posts

Knight

Biology is the science of life, hence biological definitions should be established and not ones based on entropy (of course thermodynamics play a huge role in organic processes, but also in anorganic processes). Organic molecules occur naturally without being alive. Lipid vesicles appear naturally without containing anything.

Also, viruses don't keep their entropy low by themselves. The single bits self-assemble, but it's the cell that produces them. The low entropy of viruses is guaranteed by the living cell because a virus just lacks the reactions to ensure its entropy by itself.

Metabolism and homeostasis are just two of a list of characteristics usually found in life, and which ones are the more important is still unsure. I just have a hard time of qualifying a single unit as alive if it doesn't have an inner physiology. And viruses are basically complex looking sacs full of molecules doing nothing. Yes, they are biological/organic structures, and they are certainly somehow linked to the origins of life, or just similar; but they are not living units in my eyes.

Of course, what I just said also implies that those very early units described in the abiogenesis video are not yet alive, as they have no inner physiology. But I think the transition of non-life to life was not a sudden, clearly defined jump anyway, but involved primitive structures performing reactions and swallowing other structures that would add to the range of reactions, eventually leading to a basic unicellular organism like we know them.


last edited Jun 01 2014 06:40 am by HahiHa
 
Reply to Edge Of Life

You must be logged in to post a reply!