Multicellular Evolution

[foodchain]

I was just wondering if anyone thought the action of virus material and or plasmids could be part of what lead to multicellular life. I know bacterial mats exist, but beyond that nucleated cells seem special in being multicellular.

 

Again I wonder that if early on in evolution the action of viruses and plasmids could have been what fostered an environment for being multicellular.

 

If selection had only brought single celled on so far, maybe reproduction keep it that way. Thus maybe beneficial traits existed in pockets or populations and would have to radiate.

 

I think another example would be that such could have had the advantage of generating bacterial mats, which maybe then allowed for mutation to develop organisms more prone to feeding on each other or some other trait based interaction that was beneficial or at least neutral.

 

Basically my idea is that if selection lead to single celled organisms, that via population density alone that multicellular traits were allowed to evolve via plasmids or other molecular interactions between bacteria.

[Moontanman]

I think multicellular life evolved when it did because it could, the advent of oxygen in the atmosphere allowed the development of complex life, no amount of virus particles or plasmids could have caused it to happen before free oxygen became available.

[Mr Skeptic]

Multicellularity has evolved several times independently. The basic thing is specialization, which (like in our society) can increase efficiency. The basic idea is single cell--> small colonial --> large colonial --> multicellular.

[Moontanman]

I was under the impression that multicellular complex life had only evolved once and then speciated from that one time. Can you give examples of how multicellular life has evolved more than once?

[Mr Skeptic]

I was under the impression that multicellular complex life had only evolved once and then speciated from that one time. Can you give examples of how multicellular life has evolved more than once?

 

In prokaryotes, brown algaes, some red algaes, plants, animals, and fungi.

[Moontanman]

Ok, I got my idea twisted, when I was thinking of complex life animals were on my mind, but multicellular prokaryotes? Bio-films are not multicellular organism by what most consider multicellular, this is how ever very interesting http://en.wikipedia.org/wiki/Myxobacteria

 

I guess my definition is a bit less inclusive, I know plants and animals and fungi are complex life with fungi being more closely related to animals than plants but I still think my contention that oxygen was the factor that allowed complex life to evolve. By my definition protists are on the border of complex life, bacteria are not although the before mentioned Myxobacteria show I might need to rethink that.

 

But If I read the link correctly myxobacteria are oxygen life forms as well. Quite possibly the idea that if not for Eukyrotes there would be no animals needs to be rethought but so far Eukarotes seem to be the first animals and bacteria and archea are still looking to get in the race, lol

[foodchain]

I am not interested in high details so much, just that for instance genetic material can also be transfered via virus behavior and plasmids. Not to each denotes some homology to the other, but I am looking at it sort of from that perspective.

 

Basically life had evolved to the point of bacteria, and for what its worth its when the population levels of that get high enough that it allowed for selection to influence differently perhaps, and that via variation in transfer of genetic material that some organisms can more interactive with fellow organisms. Either by food or whatever, and this specialization is what drove the complexity that is eukaryote structure, and why pigs are not bacteria.

 

Basically that complexity of eukaryote structure was a product of individual cells evolving in ways that aided cell to cell interactions.

[Moontanman]

I think it's safe to say that genetic material can be transfered via plasmids and virus but until there was oxygen it mattered very little in relation to complex life. Complex life required oxygen to get started, with out our oxygen there is just not enough energy to support anything but bacteria.

[Mr Skeptic]

Ah yes, oxygen is very useful. Oxygen granted two things:

1) it allows for the ozone layer and therefore terrestrial and near-surface life.

2) it allows carbohydrates to become very energy-dense storage for energy.

 

I think the presence of oxygen gives much more value to predation. I don't think oxygen is a prerequisite for multicellularity, but for us larger animals it is essential as otherwise we wouldn't be able to get enough energy to sustain ourselves.

[foodchain]

I think it's safe to say that genetic material can be transfered via plasmids and virus but until there was oxygen it mattered very little in relation to complex life. Complex life required oxygen to get started, with out our oxygen there is just not enough energy to support anything but bacteria.

 

 

I think its hard to equate oxygen to life when you can have metabolism that varies. All oxygen could be is a way life did manage to come to use in some way, but that oxygen itself is not the limit of what can be for life to exist in some form, how is that?

 

Biological thermodynamics are of interest to me, just as how closely related on the periodic table various elements common to life happened to be classified, but thats not really my questions.

 

If chromosomes in terms of euchromatin and heterochromatin single complex biochemical behavior occurring along various cell activities, then how much of that is cell to cell based behavior from a gene point of view. What about sexual reproduction, it in a reductionist sense touches gene material somewhere is all.

 

I also dont have a super discrete thinking when it comes to life and or species. In terms of reproduction the interaction of viruses have a diverse role just like maternal RNA. I happen to wonder if that continuous interplay or organisms in an environment also is at play early on in evolution to multicellular life.

 

Transformation allows genetic material to be absorbed by bacteria, the F plasmid is also well known for conjugation. Plus bacteria and archaea lacks true nucleus and instead have a much more "disorganized" nucleiod. Maybe this lack of organization is because these cells were not selected on criteria surrounding cell to cell behavior.

 

Having a gene based view here of a molecular question pertaining to evolution I guess.

[Moontanman]

Ah yes, oxygen is very useful. Oxygen granted two things:

1) it allows for the ozone layer and therefore terrestrial and near-surface life.

2) it allows carbohydrates to become very energy-dense storage for energy.

 

I think the presence of oxygen gives much more value to predation. I don't think oxygen is a prerequisite for multicellularity, but for us larger animals it is essential as otherwise we wouldn't be able to get enough energy to sustain ourselves.

 

There are no anaerobic complex life forms, anaerobic respiration does not provide enough energy for complex life forms. you will find no anaerobic fish or crustaceans or even worms or even protists. All animals need free oxygen, oxygen doesn't make prey animals more energy dense, it allows them to exist, predators follow prey but with no oxygen you have neither.

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I think its hard to equate oxygen to life when you can have metabolism that varies. All oxygen could be is a way life did manage to come to use in some way, but that oxygen itself is not the limit of what can be for life to exist in some form, how is that?

 

No one is saying there are no anaerobic life forms, there are lots of anaerobic bacteria and archea. Oxygen is actually bad for many life forms, when oxygen was released by photosynthesis it was a poison and wiped the Earth of many life forms but once it became possible for life to use oxygen complex life became possible until then bio films were as complex as life could get.

[foodchain]

There are no anaerobic complex life forms, anaerobic respiration does not provide enough energy for complex life forms. you will find no anaerobic fish or crustaceans or even worms or even protists. All animals need free oxygen, oxygen doesn't make prey animals more energy dense, it allows them to exist, predators follow prey but with no oxygen you have neither.

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No one is saying there are no anaerobic life forms, there are lots of anaerobic bacteria and archea. Oxygen is actually bad for many life forms, when oxygen was released by photosynthesis it was a poison and wiped the Earth of many life forms but once it became possible for life to use oxygen complex life became possible until then bio films were as complex as life could get.

 

Anaerobic metabolism is not as limited as you think and evolution of sea vent communities prove life is not dependent on the sun also. I dont think any particular rules exist or molecular laws exist for biological structure yet, or at least nothing absolute and or determined as to how you place the role of oxygen, you could say the same for carbon or even Iron if you wanted.

[Moontanman]

Anaerobic metabolism is not as limited as you think and evolution of sea vent communities prove life is not dependent on the sun also. I dont think any particular rules exist or molecular laws exist for biological structure yet, or at least nothing absolute and or determined as to how you place the role of oxygen, you could say the same for carbon or even Iron if you wanted.

 

Foodchain, you are mistaken, in the sea vent communities only the bacteria are anaerobes, the animals breath and metabolize oxygen just like you do. It's a mistaken idea that these communities of large animals are independent of the sun, they rely on oxygen from photosynthesis just like me and you. Only the bacteria are independent of the sun, not the animals.

 

No you cannot say the same thing about iron or carbon, free oxygen is not necessary for life, just animal life. a great many bacteria and archea do quite well with no oxygen. Oxygen to many of these life forms is poisonous, but to have animals, and complex plants too for that matter you have to have oxygen. Oxygen metabolism is necessary for animals.