Earlier quoted context omitted.
DNA doesn’t help as much as you think with single celled organisms thanks to HGT. Bacteria, at least, share DNA and thus we can’t use it to determine a linear evolutionary sequence.
HGT?
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Mitochondria and the origin of eukaryotes
41–50 of 85 posts
Re: Mitochondria and the origin of eukaryotes
#42How simple are Prokaryotic Cells really? Like "simple" enough that we understand all the intricate workings of it, or "simple" enough to be made from scratch?
Imagine giving a scientist in 1900 a modern CPU. He may be able to disassemble and study it, but it’s impossible to make it from scratch because it takes a chain of steps that lead to complicated modern factories that then produce the chip. It’s hard to skip those steps. We can swap DNA in living cells and produce modified cells, but we lack the tools to create such complicated and microscopic structures in a pure synthetic way.
Re: Mitochondria and the origin of eukaryotes
#43If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the length of time involved here before eukaryotes, can we estimate how many planets in the galaxy have eukaryotes? Or how long it will be before some do? Presumably increasing the length of time increases the probability of occurrence as would increasing the number o…
You make a big assumption, that there must be only two kinds of cells, "simple" and "complex", like on earth. That could well be an accidental fact. Maybe on some planets we have a gradient of cell complexity. Also, we don't really know what even simpler kinds existed on earth but were lost, since bacteria, the "simple" kind, it's obviously too complex to have been the first ever life form.
That's not even true on earth. Archaea exist, and eukaryotes span a pretty wide range of complexity themselves.
Re: Mitochondria and the origin of eukaryotes
#44If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the length of time involved here before eukaryotes, can we estimate how many planets in the galaxy have eukaryotes? Or how long it will be before some do? Presumably increasing the length of time increases the probability of occurrence as would increasing the number o…
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Re: Mitochondria and the origin of eukaryotes
#45If we assume single celled life is common, and exists in either all star systems, or in all systems without a hot Jupiter close to the star; then given the length of time involved here before eukaryotes, can we estimate how many planets in the galaxy have eukaryotes? Or how long it will be before some do? Presumably increasing the length of time increases the probability of occurrence as would increasing the number o…
Maybe, but there are other narratives that are easy to spin. Our solar system has 3 planets all of which might have had single-celled organisms, at some point: Venus, Earth, and Mars. And for the first 3.7 billion years, the 3 planets might have followed a similar path. And then all 3 planets reach old age and basically die, Venus becoming too hot, while Earth and Mars become mostly dead ice covered snow balls. And maybe that is the normal history of most planets, even planets that develop single-celled life.
In that narrative, the emphasis is on the extraordinary re-birth of Earth, after the end of Snowball Earth. Almost everything that we regard as interesting about Earth happens after this late-in-its history revival. That raises some other questions, such as, why did Snowball Earth end? Why does multicellular life take off then, but not before? What is it that makes the Earth/moon system so unusually dynamic that it hasn't settled down to some dead equilibrium, even after 3.7 billion years? What allows Earth to have such an extraordinary additional era?
Re: Mitochondria and the origin of eukaryotes
#46Earlier quoted context omitted.
> can we estimate how many planets in the galaxy have eukaryotes? Not yet. In the history of life on Earth, this has happened once. Knowing what we know about cellular biology, it’s stupidly unlikely. Beyond our present theories’ ability to quantify. By the way, I think this is one of—if not the—great filters. It’s unlikely to happen, to not promptly get smote by its primordial planet’s tantrums and to get it so righ…
per the article, endosymbiosis has happened a bunch of times. multiple different kinds of chloroplasts, several prokaryotes, a parasite etc. this was all when eukaryotes engulfed prokaryotes, but still, how does this mean unlikely? it seems imminently likely, since.. it happened a bunch of times. seems to me like prokaryotes evolve a strategy of engulfing others for their resources, then one day engulf a prokaryote i…
Yes, this (nonsense) discuassion is when you have computer progammers discuss biology. Is strange because they know nothing but all seem to think they must be experts of evrything because they get paid a lot to sit infront of a computer all day.
Re: Mitochondria and the origin of eukaryotes
#47Earlier quoted context omitted.
> can we estimate how many planets in the galaxy have eukaryotes? Not yet. In the history of life on Earth, this has happened once. Knowing what we know about cellular biology, it’s stupidly unlikely. Beyond our present theories’ ability to quantify. By the way, I think this is one of—if not the—great filters. It’s unlikely to happen, to not promptly get smote by its primordial planet’s tantrums and to get it so righ…
per the article, endosymbiosis has happened a bunch of times. multiple different kinds of chloroplasts, several prokaryotes, a parasite etc. this was all when eukaryotes engulfed prokaryotes, but still, how does this mean unlikely? it seems imminently likely, since.. it happened a bunch of times. seems to me like prokaryotes evolve a strategy of engulfing others for their resources, then one day engulf a prokaryote i…
> how is this more of a filter than abiogenesis?
Common chemistries get us very close to molecular systems subject to evolutionary pressure. (Simplest: RNA world hypothesis.) We are missing links. But the pathway is plausible.
Chloroplasts, as you mention, are a potent counter argument. But once you have surplus cellular energy, additional endosymbiosis has a lower threshold. Based on current research, all life has a similar mitochondria. Different kingdoms didn’t nom their own and go. That uniqueness suggests difficulty.
Re: Mitochondria and the origin of eukaryotes
#48Earlier quoted context omitted.
> can we estimate how many planets in the galaxy have eukaryotes? Not yet. In the history of life on Earth, this has happened once. Knowing what we know about cellular biology, it’s stupidly unlikely. Beyond our present theories’ ability to quantify. By the way, I think this is one of—if not the—great filters. It’s unlikely to happen, to not promptly get smote by its primordial planet’s tantrums and to get it so righ…
per the article, endosymbiosis has happened a bunch of times. multiple different kinds of chloroplasts, several prokaryotes, a parasite etc. this was all when eukaryotes engulfed prokaryotes, but still, how does this mean unlikely? it seems imminently likely, since.. it happened a bunch of times. seems to me like prokaryotes evolve a strategy of engulfing others for their resources, then one day engulf a prokaryote i…
The thing that only happened once on Earth and that's a prerequisite to developing complex life forms is not endosymbiosis, it's life going multi-cellular. They are not the same thing.
Endosymbiosis is not identical with going multi-cellular, and it seems that all but perhaps one of the known instances of endosymbiosis didn't play any role in us going multi-cellular anyway. In fact this article makes the case that it may not have been critical at all.
Re: Mitochondria and the origin of eukaryotes
#49[deleted]
Re: Mitochondria and the origin of eukaryotes
#50An accessible and incredibly insightful read 100% on this topic is "Power, Sex, Suicide: Mitochondria and the Meaning of Life"- despite the flashy title a thorough scientific read and analysis, working through various possible arguments and teaching fundamentals along the way.
My favourite book I read in the past five years or so