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I did. Speciation. That is the key. No speciation, no evolution.
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juvenissun, do give us your definition of evolution.
Let me first notice that this is a nonsense definition, as has been pointed out multiple times in this thread. Evolution does not automatically lead to speciation, although it often does. The normal definition is "a change in allele frequencies in a population over time". Speciation is not necessary for that to occur.I did. Speciation. That is the key. No speciation, no evolution.
I did. Speciation. That is the key. No speciation, no evolution.
I also suspect there's something about the genome. Generally more DNA, alternative splicing, more complex regulation of gene expression, in many cases, more genes... I can't imagine that has nothing to do with organismal complexity. And it's probably intimately linked with larger, more complex cells, too.Perhaps the most important difference between the three domains is the cellular compartmentalization in eukaryotes.
No problem.Sorry if I missed the reply to your point. And thank you for reminded me again.
Why? What makes one timescale different from another? Why can't a solution work for a billion years? Where's the point where we should start asking questions?The problem is on the scale. If 100 things evolved for 10 million years. Some evolved a little and some evolved more. Then I have no problem on that. If the same 100 things evolved 1 billion years. Some evolved a lot, some evolved some, but some evolved very little. Then there should be questions.
In a way, the very fact that bacteria are still with us shows that unicellularity is not an "under-evolved" state that should've gone out of fashion billions of years ago. If that were the case there wouldn't be so many bacteria. So I guess I vote for the "nearly perfect" option.Now, given 4 billion years, and bacteria is still extremely "under-evolved" (my convenient terminology !). Then either they are nearly perfect at the beginning, or they do not evolve, which works under the same principle (don't ever say that evolution has no working principle) to every living things.
Bacteria contributed a lot to us eukaryotes. They are our mitochondria (without which we wouldn't have much energy to power our large and complex bodies), they are plants' chloroplasts. A few years ago it was even proposed that eukaryotes came from a genome fusion between bacteria and archaea. So it's almost definitely wrong to say that they didn't evolve into anything, even if you disregard the diversity of bacteria themselves (biochemically and habitat-wise they trump eukaryotes by far) that must have evolved since they first came into being.Cockroach did not evolve over a few hundred million years. No problem. Some species evolved from the cockroach (possible error here, the common ancestor thing. Don't pick on this, it is not the point) and the process continued. However, the key feature is that NOTHING evolved out of bacteria.
I don't think it's an exception any more than crocodiles are an exception.And, the main argument is: this exception should be taken more seriously on the concept of evolution.
Please do define "species" for bacteria. I'm curious if you can come up with anything meaningful because I don't like any of the definitions biologists made upI did. Speciation. That is the key. No speciation, no evolution.
Let me first notice that this is a nonsense definition, as has been pointed out multiple times in this thread. Evolution does not automatically lead to speciation, although it often does. The normal definition is "a change in allele frequencies in a population over time". Speciation is not necessary for that to occur.
But even then, speciation has happened in bacteria. See Vulic et al for example.
From the article:
"We tested several lines of Escherichia coli, derived from a common ancestor and evolved for 20,000 generations, for their recombination ability."
And the results:
"These results demonstrate the establishment of an incipient genetic barrier between formerly identical lines, and they support a model in which the mismatch repair system can influence speciation dynamics through its simultaneous effects on mutation and recombination."
There are estimated to be 10 million to a billion different species of bacteria. I'd say that indicates a lot of speciation, so even by your definition, bacteria have evolved.
http://www.wisegeek.com/how-many-species-of-bacteria-are-there.htm
Your statement is illogical. You conflate your own bizarre definition of 'evolution' with the scientific definition, and you conflate 'speciation' with 'evolved to become multicellular'.because my statement is logical.
And that, sir, is why your definition is unscientific: the scientific definition is "Evolution is a change in the frequency of inherited traits in a given population over time". In other words, if allele frequency in a population changes over time, then the population has evolved. Your definition is entirely unlike this, and is thus unscientific.I did. Speciation. That is the key. No speciation, no evolution.
Please do define "species" for bacteria. I'm curious if you can come up with anything meaningful because I don't like any of the definitions biologists made upThey are all bloody arbitrary as far as I can tell. (The biological species isn't, but that doesn't apply to bacteria.)
Very good. I like you to correct my understanding:
My limited understanding on speciation is something like a population of one species is isolated into two populations. So the two groups stopped interbreeding and developed independently on their own traits. This is not a strict definition, but is a description. Biologist could phrase this idea by a more precise language.
So, bacteria split to populate. I am not sure how does algae or fungi populate themselves. But until they evolved into something which will "give birth" (bisexual?) to their offsprings, there is no speciation to me. Any life populated itself before the bisexual function kicked in, is grouped and labelled by me as a "life not evolved". I know there are/were a lot different life forms fall into this category and need some systems to subdivide. But that is a problem left to biologist, not to me. So if you don't like this definition, you are extremely welcome to replace it with another term of a similar meaning.
So, to me, bacteria are all in one species, which is the (non-sexual + single cell) species. I will be convinced in this thread that bacteria evolved if someone showed me some bacteria that is populated by a sort of sexual function, I guess, in that case, it must have been a multicellular creature. So, Naraoia, to your question, my thought is that the word species is not a proper word for the classification of bacteria. A different word should be used.
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My scheme on this biological issue is very primitive and simple. But unless I am corrected on the fundamental level of definition and process, my logic on this issue stands. I understand miscommunication happened due to the different content of definition. But until this post, nobody is asking me what is my definition of anything (big credit to Naraoia, excellent student). The only message I read is that my definition is wrong. If you do not know what it is, how could you say it is wrong?
Bacterial species are typically demarcated based on a combination of more than one criteria (Vandamme et al. 1996; Stackebrandt et al. 2002), with the criterion proposed by Wayne et al. being by far the most influential one and the reference point for the development of new standards for species. This criterion considers a species to be essentially a collection of strains that are characterized by at least one diagnostic phenotypic trait and whose purified DNA molecules show at least 70% cross-hybridization (DNA–DNA hybridization or DDH; Wayne et al. 1987). (SOURCE)
This post is just stupid. It's the forum equivalent of sticking your fingers in your ears and shouting "LALALALA I CAN'T HEAR YOU!" at the top of your voice.Very good. I like you to correct my understanding:
My limited understanding on speciation is something like a population of one species is isolated into two populations. So the two groups stopped interbreeding and developed independently on their own traits. This is not a strict definition, but is a description. Biologist could phrase this idea by a more precise language.
So, bacteria split to populate. I am not sure how does algae or fungi populate themselves. But until they evolved into something which will "give birth" (bisexual?) to their offsprings, there is no speciation to me. Any life populated itself before the bisexual function kicked in, is grouped and labelled by me as a "life not evolved". I know there are/were a lot different life forms fall into this category and need some systems to subdivide. But that is a problem left to biologist, not to me. So if you don't like this definition, you are extremely welcome to replace it with another term of a similar meaning.
So, to me, bacteria are all in one species, which is the (non-sexual + single cell) species. I will be convinced in this thread that bacteria evolved if someone showed me some bacteria that is populated by a sort of sexual function, I guess, in that case, it must have been a multicellular creature. So, Naraoia, to your question, my thought is that the word species is not a proper word for the classification of bacteria. A different word should be used.
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My scheme on this biological issue is very primitive and simple. But unless I am corrected on the fundamental level of definition and process, my logic on this issue stands. I understand miscommunication happened due to the different content of definition. But until this post, nobody is asking me what is my definition of anything (big credit to Naraoia, excellent student). The only message I read is that my definition is wrong. If you do not know what it is, how could you say it is wrong?
I guess that these two cultures of bacteria are the same thing, right Juv?
I don't know. You are hiding the scale bar of the bigger image. I guess it is an optical image. So the size are very different. I guess the smaller one is an image of some sub-cell particles? Would you give answer to your tricky question? Did you get me?
Whatever these two things are, can you explain the similarity on their morphology, which you used to trick me? Did I get you?
Conjugation:
en.wikipedia.org/wiki/Bacterial_conjugation
All right. Please tell me how to identify the two "different" sexes.
Furthermore: Is there an example that shows one type of bacteria changed into two types and there is no more conjugation between the two new groups of bacteria?
[serious];48705585 said:yes, the donor cell has the F-plasmid. It forms a pilus which allows gene transfer to other bacteria.
As far as your reproductive isolation question, you seem to miss that things work a little differently when an organism reproduces by binary fission.
You also seem to miss that sexual reproduction does not require two distinct sexes. There are numerous sexual hermaphrodites.
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