My concept of species and speciation came from the knowledge of biology and biological evolution. I am using it in this thread on bacteria. I knew it could be inappropriate. But that was exactly the original intention. An inevitable question then is: why doesn't this concept apply any more? In this discussion, I realized that even the idea of sex becomes different in the system of bacteria.
The problem isn't serious. Who cares about a species beyond defining a particularly similar group of organisms as a matter of convenience? It's just for classification. There are many kinds of organisms that do many kinds of things that reproduce in many different ways. As an aspiring evolutionary biologist, I'm one semester away from graduating with a bachelor's and I've been getting trained in population genetics techniques, I don't care so much for the organisms themselves as much as I care about the factors that made them develop that way. Not to say that particular organisms aren't inherently cool, but they are fleeting and will probably evolve into something else. That is the point, actually. Organisms are ephemeral, and that's what makes classifying them so hard. It's easier with sexually reproducing organisms than unisexual, substantially, but it's not perfect.
You're picking on prokaryotes right now, an amazingly diverse and complex set of organisms. Why are prokaryotes still prokaryotes? Because evolution is a local event and not a global event. You're only competing against those you're sharing resources with. Develop a new enzyme that can utilize an untapped resource and some kind of environmental event limits the previous resource and all of a sudden you're ahead of the game in that local area.
So, there is a huge gap (differences) between the lives of bacteria and plants/animals. My OP simply want to make these differences stand out as clearly as possible. So, I said the bacterial did not evolve. It may not be a precise description. But it effectively pointed out where the problem is.
The second paragraph of mine kind of addressed this, but let me say something more important. Evolution is the change in allele frequency in one generation to the next. I say this as a hopeful population geneticist, because that is our (their) definition. Substantial changes in allele frequencies lead to macroevolution. Microevolution is discrete, but macroevolution is subjective. If
D. melanogaster (species of fruit fly) is separate into two populations, and after several generations can no longer produce viable offspring with the other population, is that macroevolution? Under the biological species concept, they're two different species. Is speciation macroevolution? They just can't breed together, but morphologically, they're probably the same! What if they have different shapes? What if one is flightless and the other not? What if the flightless one is a completely different color and size, as well as different behavioral traits and sexual patterns? Then I would say that's macroevolution, but there's nothing particularly magical about macroevolution other than a series of microevolutionary changes.
I may be called a layman in biology or in cell biology. Exactly because I know little about gene, DNA stuff, I only see these life forms in a much bigger picture. As I talked to biologists, they don't hesitate to use the word "low level life" to describe bacteria, in contrast to other (highly evolved) "high level lives". Again, the question is that why use these terms like "low" or "high"? Do they obviously imply the "degree of evolution"? If bacteria sit low in the evolution history, then what is (are) the correspondent "higher level life" evolved from bacteria? No matter how do bacteria "change", they are still confined as the "low level" lives. Aren't they?
I don't know any biologists who say that, and I'm surrounded by them. I also don't see that kind of language in the literature. Low level and high level may be some residual language left over from the great chain of being days, but there are no traces of that kind of language in textbooks and research articles. I don't even hear it in speech over here. Hell, the organism with the largest genome is the
Amoeba dubia, while not a prokaryote, is still nothing like a human. What does that even mean? Hell if I know, maybe a lot of parasitic DNA.