Archea before Bacteria?

[Elite Engineer]

Since some Archea ar known to be hyperthermophiles, acidophiles, and halophiles, why are they placed AFTER bacteria in the evolutionary tree. Wouldn't these extreme climate tolerance characteristics allow them to live in an earlier Earth environment than bacteria? (i.e. high heat, acid environments).

[CharonY]

Nope they are not placed after bacteria. That would imply that archaea are a group of bacteria.

Current molecular (well, since Woese in the late 70s) evidence point to a common ancestor of archaea and bacteria, i.e they are different groups and are the result of an early split.

Also note that many archaea are not extremophiles and there are also bacteria that are.

[delboy]

Nope they are not placed after bacteria. That would imply that archaea are a group of bacteria.

Current molecular (well, since Woese in the late 70s) evidence point to a common ancestor of archaea and bacteria, i.e they are different groups and are the result of an early split.

Also note that many archaea are not extremophiles and there are also bacteria that are.

 

So did neither spring from within the other?

If so there must be another as yet undefined group?

[CharonY]

Well, the ancestor is not around anymore and for unicellular organisms it is highly unlikely that fossils will be found. I am not sure whether there is a misunderstanding, however. Consider humans and chimpanzees (different level of trees, similar principle), for example. Neither spring from each other, but both share a common node, or ancestor.

[delboy]

No misunderstanding I think. I realise we certainly didn't evolve from chimpanzees, but from another unidentified ancestor ape, the same as the chimpanzee's ancestor.

But the above evidence must mean the common ancestor to all life was neither archaea nor bacteria as defined at the moment.

[CharonY]

Yes most studies point towards a common ancestor between archaea and bacteria and would be the common ancestor to all. There is at least one proposed deviation from it, but to my knowledge it is not very well substantiated (though Arete may want to comment on this).

[Elite Engineer]

Nope they are not placed after bacteria. That would imply that archaea are a group of bacteria.

Current molecular (well, since Woese in the late 70s) evidence point to a common ancestor of archaea and bacteria, i.e they are different groups and are the result of an early split.

Also note that many archaea are not extremophiles and there are also bacteria that are.

but wouldn't their traits of tolerating harsh environments place them before bacteria. In fact a lost ancestor connecting the two would sound more logical if it were archea- *ancestor*- bacteria. Maybe the ancestor would have had traits less tolerant of high temperature and acidic environments than the archea, and more similar to bacteria. I guess what Im trying to say is, it doesnt make sense to have bacteria, a species that can tolerate regular environmental conditions come before a species that can tolerate very harsh conditions.

 

I think you said archea came before bacteria: http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Phylogenetic_tree.svg/450px-Phylogenetic_tree.svg.png

[chadn737]

but wouldn't their traits of tolerating harsh environments place them before bacteria. In fact a lost ancestor connecting the two would sound more logical if it were archea- *ancestor*- bacteria. Maybe the ancestor would have had traits less tolerant of high temperature and acidic environments than the archea, and more similar to bacteria. I guess what Im trying to say is, it doesnt make sense to have bacteria, a species that can tolerate regular environmental conditions come before a species that can tolerate very harsh conditions.

 

I think you said archea came before bacteria: http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Phylogenetic_tree.svg/450px-Phylogenetic_tree.svg.png

 

1) There are many extremophile bacteria.

 

2) Archaea are not all extremophiles, they are found in all the same places as bacteria.

 

3) This presumes a certain directionality in evolution from extreme environments to relatively benign ones and the impossibility of adaptation to extremes after the fact.

[CharonY]

but wouldn't their traits of tolerating harsh environments place them before bacteria. In fact a lost ancestor connecting the two would sound more logical if it were archea- *ancestor*- bacteria. Maybe the ancestor would have had traits less tolerant of high temperature and acidic environments than the archea, and more similar to bacteria. I guess what Im trying to say is, it doesnt make sense to have bacteria, a species that can tolerate regular environmental conditions come before a species that can tolerate very harsh conditions.

 

I think you said archea came before bacteria: http://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Phylogenetic_tree.svg/450px-Phylogenetic_tree.svg.png

 

In addition to what chadn737 said: check the tree again. You will see that archaea and bacteria have a common root (look at the red part and do not get confused by the branching of archaea and eukarya,

As a side note, bacteria are not species.

[chadn737]

The likely truth is that the first life resembled nothing like what we call bacteria or archaea.

[CharonY]

First life could be a bit trickier, even, depending on when we put the start point. But for the common ancestor the properties most have agreed upon are somewhat close to bacteria/archaea in a very general sense. This includes for example possession of DNA or RNA genome and protein expression system (ribosomes) with the common genetic code, lipid membrane with embedded proteins (though types of lipids are heavily discussed) and I am pretty sure a couple of other things that I cannot remember right now.