Prokaryote to Eukaryote, why?

[Jimlarmore]

If life evolved from a single celled life form one could ask why this would happen. The most successful life form on earth is certainly single celled. What could make this happen and if it actually did happen that way why didn't all of the single celled life forms evolve to eukaryote status?

God bless
Jim Larmore

 

[Mallon]

Anyone else notice the tendency for neocreationists to ask questions reaching deeper and deeper back in time? It used to be "what good is half a wing?" and now it's "how did the first cell evolve?"
Could it be that as scientists slowly uncover the answers these questions, the neocreationists are forced to reach further into the abyss of time to find gaps in our knowledge where God might reside?

Who cares that we don't know the answers to some questions pertaining to life's early evolution. With God's guidance, we'll get there someday. And I'm sure the answers will only futher His glory.

But to answer your question more directly, you should do some reading about the Left Wall of Minimal Complexity. Gould wrote a lot about it. See also:

http://en.wikipedia.org/wiki/Eukaryote#Origin_and_evolution

 

[Jimlarmore]

Could someone define what a neocreationist is?

God Bless
Jim Larmore

 

[Mallon]

Neocreationism is the fundamentalist revival movement started by Seventh Day Adventist George McCready Price to oppose evolution. See:

http://en.wikipedia.org/wiki/Young_Earth_creationism#Revival

The history of neocreationism is well-documented in Numbers' book The Creationists.

 

[gluadys]

If life evolved from a single celled life form one could ask why this would happen. The most successful life form on earth is certainly single celled. What could make this happen and if it actually did happen that way why didn't all of the single celled life forms evolve to eukaryote status?

God bless
Jim Larmore

First, let me ask you a question. Why do you think, based on the theory of evolution, that all prokaryote forms would be expected to become eukaryotes? Please cite what in the theory of evolution, as you envision it, would suggest this prediction.

 

[sago]

Although we don't know, a good current hypothesis is that eukaryotes evolved from the capture of prokaryotic cells in other prokaryotic cells.

However it happened eukaryotic cells, like multi-cellular organisms have higher modularity.

Modularity is a very common tendency of evolving systems (in fact any system with sufficently complex interdependencies: the immune system, the US economy, human language, etc). Modularity is favoured because it allows vastly increased complexity from less complex components.

It is easier to assemble your plumbing from pipe components than make a single copper pipe that ties everything together perfectly.

Because there are many times more potential complex solutions to a problem than there are simple ones, the likelihood of finding and continuing to optimize a complex solution is greater. And so more complex solutions tend to be favored, unless the complexity is somehow detrimental to the solution itself.

This is seen in bloat in genetic programming (a type of evolution used to create computer programs).

It is seen all over nature. It is the same reason why all the air in your room doesn't suddenly head over into one corner and leave you asphyxiated.

So why are there more bacteria? Well to pay the price of complexity you need to have more complex reproductive apparatus. Eukaryotic reproduction is more complex than prokaryotic reproduction, when you get to complex multi-cellular life with lots of differentiated cell types it gets really quite tricky indeed. By the time you get to large mammals it is a many-year extravaganza of biology.

So bacteria can reproduce faster, and have much larger populations than other life. But they don't occupy a clear majority of ecological niches.

 

[Jimlarmore]

But they don't occupy a clear majority of ecological niches.

This is a new one on me. I understood that they did. What significant ecological niches don't they occupy that eukayotes do?

God Bless
Jim Larmore

 

[Jimlarmore]

Neocreationism is the fundamentalist revival movement started by Seventh Day Adventist George McCready Price to oppose evolution. See:

http://en.wikipedia.org/wiki/Young_Earth_creationism#Revival

The history of neocreationism is well-documented in Numbers' book The Creationists.

I was unaware of this. I have not been an sda all that long and had not read this. I began my philosophy of truth about macro-evolution long before becoming an sda.

God Bless
Jim Larmore

 

[Jimlarmore]

First, let me ask you a question. Why do you think, based on the theory of evolution, that all prokaryote forms would be expected to become eukaryotes? Please cite what in the theory of evolution, as you envision it, would suggest this prediction.

I think sago answered the question quite well. Depending on the situation more complex life forms can exploit their ecologies more efficiently. I guess my big question is that what ever caused the change to happen should have made all other life forms to change as well, shouldn't it?

God Bless
Jim Larmore

 

[Mallon]

I guess my big question is that what ever caused the change to happen should have made all other life forms to change as well, shouldn't it?

No, because selective pressures don't operate homogeneously across all taxa around the world. What's advantageous for a bacterium living adjacent to a deep-sea hydrothermal vent isn't necessarily advantageous for one living in the gut of a cow.

 

[Jimlarmore]

No, because selective pressures don't operate homogeneously across all taxa around the world. What's advantageous for a bacterium living adjacent to a deep-sea hydrothermal vent isn't necessarily advantageous for one living in the gut of a cow.

We need to focus on a time when there were no eukaryote life forms at all. The earth's ecosystems would vary for sure causing heterogenous systems world wide. However, eventually due to the dynamics of diffusion and equilbrium all of the species that survive would come to a similar pressure to evolve. However that happened to me should have stimulated all of them to eventually become the more complex form. So why do we still see prokaryotes?

God Bless
Jim Larmore

 

[Mallon]

However, eventually due to the dynamics of diffusion and equilbrium all of the species that survive would come to a similar pressure to evolve.

That's an awful big assumption to make.
1) Can you test that assumption?
2) Why do you equate "evolving" with "becoming prokaryotic"?
3) There's no more reason to believe that surviving lineages would follow the same evolutionary channel then than there is to believe they do today. Evolution doesn't happen that way.
Sorry, Jim, but I don't think your assumptions are tenable.

 

[Jimlarmore]

That's an awful big assumption to make.
1) Can you test that assumption?
2) Why do you equate "evolving" with "becoming prokaryotic"?
3) There's no more reason to believe that surviving lineages would follow the same evolutionary channel then than there is to believe they do today. Evolution doesn't happen that way.
Sorry, Jim, but I don't think your assumptions are tenable.

Sorry but I thought the concept fully aligns with known laws of physics. Diffusion and equilbrium exists not only in Chemical reactions but in the physical reality of all known things. For instance let's take the so-called primordial soup life arose from. Given any set of circumstances and eventually all of the component concentrations of that "soup" would be mixed homogenously. The atmosphere is the same way. You can take an air component reading anywhere on earth as long as you are about the same elevation and it will read the same for all of the major components that make up our air. When changes in the ecology came about it would take a while but eventually diffusion would make it all equal out.

What ever caused the first prokaryote to "evolve" to a eukaryote would eventually reach them all.

God Bless
Jim Larmore

 

[Mallon]

Sorry but I thought the concept fully aligns with known laws of physics. Diffusion and equilbrium exists not only in Chemical reactions but in the physical reality of all known things.

Make no mistake: we're talking about biology. And biological systems, like the weather systems you cite, are not only infrequently equilibriated, they're also rarely heterogeneous. In fact, if they were, no adaptation of any kind could proceed since everything would be perfectly suited to its unchanging environment. So that about kills your primary assumption there.
I would be willing to discuss this further if you were to present some concrete data that supported your position, Jim.

 

[gluadys]

I think sago answered the question quite well. Depending on the situation more complex life forms can exploit their ecologies more efficiently. I guess my big question is that what ever caused the change to happen should have made all other life forms to change as well, shouldn't it?

God Bless
Jim Larmore

In addition to mallon's answers, there are some other considerations to take into account.

One is that diversification helps to reduce the intensity of competition between populations. If all current species reacted to current evolutionary pressures in the same way, that benefit would not accrue: they would still all be competing on the same level for the same resources by the same means. Through diversification, different populations use different resources in different ways and so can continue to thrive beside other populations.

Second, we need to remember that the biosphere is its own environment and exerts its own selective pressures. Once you have a population of eukaryotes well-established, it becomes a competitor to any incipient eukaryote, and probably well-placed to eliminate it. Meanwhile, prokaryotes have already established many ways to survive.

Furthermore, the new eukaryotes are a new environment which prokaryotes can exploit as predators, parasites, symbionts, etc so there is no drive for them to become eukaryotes themselves.

You can continue to apply these principles all along the history of phylogeny. There is seldom, if ever, a reason for all of a population to acquire the same adaptations. That is why a tree is a better image of evolutionary history than a ladder.

 

[Jimlarmore]

Make no mistake: we're talking about biology. And biological systems, like the weather systems you cite, are not only infrequently equilibriated, they're also rarely heterogeneous. In fact, if they were, no adaptation of any kind could proceed since everything would be perfectly suited to its unchanging environment. So that about kills your primary assumption there.
I would be willing to discuss this further if you were to present some concrete data that supported your position, Jim.

Biology and specifically life cannot exist apart from chemistry and physics but because of them. The natural laws that govern diffusion and equilbrium in a proto earth would have worked the same then as they do now. Weather works within a reference frame work of equilizing cycles , that is why it is fairly easy to predict. Atmospheric energies are highly predictable because of known laws that are all about seeking equilibrium and stasis, i.e. low pressure systems move away from high pressure systems etc.

We have nearly all species of bacterium/prokaryotes in every known niche and climate on earth right now. So we know they all survive in these predictable cycles yet they remained single celled. So to my way of thinking weather as a specific could be discounted as a causitive agent in stimulating evolution to a muliple celled form. No, I think we need to most likely stay within possible biochemical stimulations to change .

BTW, I am simply asking an honest question here. To my knowledge there is no published literature on why this happened. I am just trying to use simple logic and my knowledge base to determine the plausibility of the way some say life diversified from a single cell life form. If you don't want to participate that's ok. Thanks for what you have written so far.

God Bless
Jim Larmore

 

[Mallon]

Biology and specifically life cannot exist apart from chemistry and physics but because of them.

But you cannot atomize species-level processes down to fundamental laws of chemistry and physics. These are emergent properties of ecology that cannot be reduced the way you insist. Again, if you think otherwise, please provide some empirical data to support yourself.

BTW, I am simply asking an honest question here.

And I'm giving you an honest answer. Your assumptions are invalid.

To my knowledge there is no published literature on why this happened.

Do you have access to the scientific literature? Have you searched Google Scholar or PudMed or Web of Science for research pertaining to the evolution of prokaryotes? The papers are out there.

 

[gluadys]

We have nearly all species of bacterium/prokaryotes in every known niche and climate on earth right now. So we know they all survive in these predictable cycles yet they remained single celled.

Query: up to now you have been talking about the prokaryote/eukaryote transition. Now you speak of prokaryotes remaining "single-celled". It is true that multicellularity has occurred only in eukaryotes, but I am sure you are aware that many, if not most, eukaryotes are single-celled protists. IOW the emergence of eukaryotes per se and the emergence of multicellular eukaryotes are distinct events that did not occur simultaneously, nor under the same circumstances.

So to my way of thinking weather as a specific could be discounted as a causitive agent in stimulating evolution to a muliple celled form.

Don't be too quick to dismiss the weather, or rather the climate as a causative factor. And remember that the biosphere affects the atmosphere and the climate. James Lovelock, originator of the Gaia hypothesis, surmises that the production of free oxygen by photosynthesizing cyanobacteria may have precipitated the first Ice Age about 2.5 billion years ago. The higher levels of atmospheric oxygen were already a challenge to life that had arisen in relatively anoxic conditions, and together with the lowering of average temperature may have produced the conditions favoring nucleated cells.

Lynn Margulis has done a great deal of work on the possible symbiotic origin of eukaryotes and their organelles.

BTW, I am simply asking an honest question here. To my knowledge there is no published literature on why this happened. I am just trying to use simple logic and my knowledge base to determine the plausibility of the way some say life diversified from a single cell life form. If you don't want to participate that's ok. Thanks for what you have written so far.

So, as Mallon said, you need to check out what is available on the diversification of bacteria themselves. Why do we have cyanobacteria, proteobacteria, firmicutes, sulphur bacteria, methanogens and so many different types of bacteria. We need to remember that bacteria are as diverse if not more diverse than any vertebrate order.

Then, if you want to venture further, look at the work of Margulis and others on the emergence of eukaryotes.

And finally, at the origins of multi-cellular life.

The rest is pretty much a piece of cake.