Evolution?

[[serious]]

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 appreciate you, Naraoia and few others talked about the genetic aspects of bacteria. I understand little. But I think it is fascinating.

We also, by linguistic convention, say the sun rises and sets. Of course, it isn't really the sun moving at all but the earth rotating. So why don't we say "the period of time during which the rotation of earth causes a given locality to be cast in shadow" instead of "sunset"? Well, one, it's shorter to just use "sunset" and two, everyone is already used to calling it "sunset". Likewise, everyone is used to saying "higher order life" and "lower order life" instead "species whose evolutionary path selected for/did not select for complexity" It's a linguistic throwback. Nothing more.

 

[juvenissun]

We also, by linguistic convention, say the sun rises and sets. Of course, it isn't really the sun moving at all but the earth rotating. So why don't we say "the period of time during which the rotation of earth causes a given locality to be cast in shadow" instead of "sunset"? Well, one, it's shorter to just use "sunset" and two, everyone is already used to calling it "sunset". Likewise, everyone is used to saying "higher order life" and "lower order life" instead "species whose evolutionary path selected for/did not select for complexity" It's a linguistic throwback. Nothing more.

No. It is more than that.

Sun rises/sets means the sun apparently rises or sets. Or, more precisely, it could mean the sun "relatively" rises or sets, which is scientifically correct.

Then what does the low/high order of life "apparently/relatively" mean?

 

[Vene]

Juv, set down the shovel before you hurt yourself.

And low/high order of life refers to when that variety first appeared. For example, reptiles appeared before mammals so mammals are referred to as a higher order.

 

[juvenissun]

Juv, set down the shovel before you hurt yourself.

And low/high order of life refers to when that variety first appeared. For example, reptiles appeared before mammals so mammals are referred to as a higher order.

You mean earlier/later?

 

[Wiccan_Child]

No. It is more than that.

Sun rises/sets means the sun apparently rises or sets. Or, more precisely, it could mean the sun "relatively" rises or sets, which is scientifically correct.

Then what does the low/high order of life "apparently/relatively" mean?

Relative complexity. Bacteria and ferns are, relatively speaking, less complex than cows and alligators.

 

[[serious]]

No. It is more than that.

Sun rises/sets means the sun apparently rises or sets. Or, more precisely, it could mean the sun "relatively" rises or sets, which is scientifically correct.

Then what does the low/high order of life "apparently/relatively" mean?

You really don't want to dig yourself deeper into a bad definition. "sunrise/sunset" is a throwback to when we thought that that is actually how things worked. Likewise, it was once thought that more complex life was "more evolved" than simple life. This is now known to be false but the convention of calling complex life a "higher order" of life is still occasionally used by those sloppy with their terms.

 

[juvenissun]

Likewise, it was once thought that more complex life was "more evolved" than simple life. This is now known to be false.

That is new to me. Why is it false?

If false, then the more complex life is NOT (or may not be) a result of evolution. If so, what is the origin?

This is the third time in this thread that I read argument seemingly made by a creationist.

 

[TheGnome]

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.

 

[Pete Harcoff]

That is new to me. Why is it false?

If false, then the more complex life is NOT (or may not be) a result of evolution. If so, what is the origin?

This is the third time in this thread that I read argument seemingly made by a creationist.

It's false because all life is equally "evolved" in terms of evolutionary time-frame. IOW, there is no such thing as "higher" or "lower" lifeforms in an evolutionary sense. Just a whole bunch of current lifeforms occupying various ecological niches as a result of ~4 billion years or so of evolution.

 

[Tomk80]

That is new to me. Why is it false?

Because genetic mutations happen in all organisms, even the ones that outwardly continue to appear the same.

If false, then the more complex life is NOT (or may not be) a result of evolution. If so, what is the origin?

More complex life is the result of evolution. Continuing evolution just doesn't automatically result in more complex life.

This is the third time in this thread that I read argument seemingly made by a creationist.

No, it's just one more demonstration that you should pick up a basic book on evolution.

 

[Wiccan_Child]

That is new to me. Why is it false?

Because everything is as evolved as everything else, roughly speaking. All modern day organisms are the descendants of a single common ancestor that lived 3.5 billion years ago; you don't think that bacterial species that lived, say, 2 billion years ago, are still around today, do you?

If false, then the more complex life is NOT (or may not be) a result of evolution.

How so?

If so, what is the origin?

Of complexity? Simple: evolution by natural selection.

This is the third time in this thread that I read argument seemingly made by a creationist.

That would only be the case if we were arguing against common descent.

 

[[serious]]

That is new to me. Why is it false?

If false, then the more complex life is NOT (or may not be) a result of evolution. If so, what is the origin?

This is the third time in this thread that I read argument seemingly made by a creationist.

Because increased complexity is not always evolutionarily favorable. We have all been evolving for ~3.5 billion years. Bacteria have been evolving for 3.5 billion years. We've both got 3.5 billion years of evolution behind us. Bacteria, by the way, are much more flexible as far as where and how they can live.

 

[juvenissun]

Because increased complexity is not always evolutionarily favorable. We have all been evolving for ~3.5 billion years. Bacteria have been evolving for 3.5 billion years. We've both got 3.5 billion years of evolution behind us. Bacteria, by the way, are much more flexible as far as where and how they can live.

Here is my layman question: How does one measure the biological "complexity" of a life? For example, are we more complex than dinosaur? or than dog?

 

[juvenissun]

Because genetic mutations happen in all organisms, even the ones that outwardly continue to appear the same.


More complex life is the result of evolution. Continuing evolution just doesn't automatically result in more complex life.

If we take a look of the life-tree in any textbook, does it present a picture which suggests that evolution made life more complex through time? There may be variations which could not be seen on the simple life-tree diagram. But that is exactly the point: the life-tree shows the general trend: evolution makes life form more complex.

 

[Tomk80]

Here is my layman question: How does one measure the biological "complexity" of a life? For example, are we more complex than dinosaur? or than dog?

We don't. When people, including biologists it is usually as a qualitative terms, usually in terms of number of functions or organs. Single celled animals are less complex than multicellular organisms, parasites have lost many organs and thus are less complex than non-parasitic organisms. I have yet to see an objective, quantitative measure for these and do think it is not helpfull to talk in terms of complexity precisely because of that.

 

[Tomk80]

If we take a look of the life-tree in any textbook, does it present a picture which suggests that evolution made life more complex through time?

Depends. This one doesn't:

edited to add: And that tree of life is based on the genetic difference between organisms based on genetic analysis. Note that the blue part is bacteria, the red part eukaryotes and the green part archaea. Note that the genetic difference between bacteria is much greater than between any of the eukaryotes.

There may be variations which could not be seen on the simple life-tree diagram. But that is exactly the point: the life-tree shows the general trend: evolution makes life form more complex.

That life tends to evolve in the direction of more complex organisms does not mean that more complex organisms are more evolved. A currently living bacteria has about 3.5 to 3 billion years of evolution behind it, just as a currently living human has. 3 billion years of continuing mutation and selection in it's ancestors. In a way, given that mutation rates and reproduction rates are generally higher in bacteria, these might even be "more evolved" than humans. Meaning that they may have had more mutations and have had more selective forces working on them.

A currently living bacteria definitely has had a longer evolutionary lineage than a Tiktaalik living millions of years in the past. Yet it is less complex.

That the history of evolution seems to show a picture towards more complexity is most likely an artifact of life's simple beginnings. Meaning that as a start there was no way but up, less complex was not possible. In later stages we see that lineages tend to go in both ways.

Answer me this completely hypothetical scenario. If a barnacle at some point splits into two groups, one evolving via 6 mutations into a more complex mobile predator and the other with 6 mutations into a less complex parasite, is the parasite than less evolved than the predator? Both have had the exact same time of evolution, the exact same number of evolutionary steps.

 

[[serious]]

Here is my layman question: How does one measure the biological "complexity" of a life? For example, are we more complex than dinosaur? or than dog?

One doesn't measure biological complexity. It is yet another example of a common term that has survived in the scientific discussion even though it doesn't have a well defined meaning. There are a wealth of words in scientific discourse that are pretty much only used out of habit. There are also many explanations of phenomena that get thrown around that are either erroneous simplifications (such as the common explanations of hawking radiation) or lend themselves to misunderstanding (explanations of entropy).

Any way, to sum up, "complexity" should only be used in cases where it can be given a definite meaning or when the implied meaning can be broadly agreed on. It's fine to say "bacteria aren't as complex as mammals" because everyone can agree on it. Trying to hash out relative complexity of animals and plants is essentially impossible though.

 

[Tomk80]

One doesn't measure biological complexity. It is yet another example of a common term that has survived in the scientific discussion even though it doesn't have a well defined meaning. There are a wealth of words in scientific discourse that are pretty much only used out of habit. There are also many explanations of phenomena that get thrown around that are either erroneous simplifications (such as the common explanations of hawking radiation) or lend themselves to misunderstanding (explanations of entropy).

Any way, to sum up, "complexity" should only be used in cases where it can be given a definite meaning or when the implied meaning can be broadly agreed on. It's fine to say "bacteria aren't as complex as mammals" because everyone can agree on it. Trying to hash out relative complexity of animals and plants is essentially impossible though.

Note that these statements are only helpful if you can indeed agree on some kind of metric. Most people would call an amoeba less complex than a human. But if you look at the genetic material, one could argue about this, given that Amoeba dubia has a genome 700 times larger than that of a human (yes, I had to look that up).

 

[Bombila]

I suspect you can only measure complexity in terms of gross systems, like counting the chambers of a heart, or noting the processing organs of a digestive tract. Which last would likely imply that a cow is, superficially at least, more complex than a human.

 

[Wiccan_Child]

Here is my layman question: How does one measure the biological "complexity" of a life? For example, are we more complex than dinosaur? or than dog?

It depends on just what you mean by 'complexity'. The fern, for instance, has thousands of chromosomes (compare this to our meagre 23). What does it mean to be 'complex'?