Evolution?

[Tomk80]

Oh, that is what the class you are talking about. Yes, biologist will disagree with you.

Where is he wrong then, juvenissun. I'm sure you, in all your infinite wisdom, will be able to point that out.

Among 50+ chicken I raised in my yard, I can classify them in to "classes" too.

Can you do it in a meaningful classification?

 

[Naraoia]

Yes, another head of evolution monster emerged: The variation of environment.

If something seemingly evolved, it was caused by the changing of environment. If something did not evolve, it was caused by the stability of environment. If something evolved fast, the environment must have changed fast. And there are A LOT, A LOT different environments, in conditions, in size of area, in distribution/association, in duration, etc. So, either a life change, or not change, there is ALWAYS a good reason for it.

What's wrong with that, IF what happens to the organism doesn't contradict what happens to its environment? (Contradictions would be something like a place turning into a desert and a local animal sprouting swimming adaptations)

So, the environment is a convenient, and is usually a perfect shield/tool, which could be used to defend/interpret virtually ANY feature of evolution. It seems that the environmental factor is used in the argument as a consequence, rather than a cause of evolution: "if a life changed this way, then the environment must have been that way."

Unless I'm very much mistaken, such hypotheses tend to get tested sooner or later.

Romer's "drying pond" scenario comes to mind as an example - up to a few decades ago the main idea concerning why/how fish came onto land was that the Devonian was the age of massive droughts, and fish that could move better on land to get from a drying pond to one that still had water in it would be at an advantage* - hence legs from fins, etc. Only when people looked at various Devonian sediments, they didn't find those parched lands. (Or that's what I remember of the story, anyway )

Homo Sapients has not evolved for one million years.

I think palaeoanthropologists would dispute that. H. sapiens isn't nearly a million years old, let alone unchanged for one million years.

If you think this is what evolution relies on, you are no better than a creationist in science.

If you think this is what evolution relies on, you should study evolution a wee bit more.

*I thought this was far-fetched but it actually isn't. Common eels, for example, can cover considerable distances on land (though they do best on damp nights).

 

[Naraoia]

Oh, that is what the class you are talking about. Yes, biologist will disagree with you.

Which biologist?

(I'm curious if Juvenissun's prediction will be confirmed )

Among 50+ chicken I raised in my yard, I can classify them in to "classes" too.

Yeah, you can, since class denotes a perfectly arbitrary level of "differentness". But call them what you want, your groups of chickens will still be much more closely related than two classes of bacteria. A rose by any other name...

 

[Wiccan_Child]

Ha ha .. You hit yourself on the foot.

No. By "relatively speaking" I mean, speaking relative to geological time periods. The time periods across which populations speciate. The environment on my bed is pretty stable, relative to a time period of a few seconds.

 

[Vene]

Which biologist?

(I'm curious if Juvenissun's prediction will be confirmed )

This student of biology has no problem with Radagast's post.

 

[juvenissun]

Which biologist?

(I'm curious if Juvenissun's prediction will be confirmed )

Yeah, you can, since class denotes a perfectly arbitrary level of "differentness". But call them what you want, your groups of chickens will still be much more closely related than two classes of bacteria. A rose by any other name...

On a comparable scale, the classes of bacteria will be much more closely related than two classes of animals.

 

[Tomk80]

On a comparable scale, the classes of bacteria will be much more closely related than two classes of animals.

Wrong. In fact, on a comparable scale, genetic distance, two classes of bacteria are often much less closely related than two classes of animals. I showed you the graph on that already, more to the beginning of this thread.

 

[juvenissun]

Wrong. In fact, on a comparable scale, genetic distance, two classes of bacteria are often much less closely related than two classes of animals. I showed you the graph on that already, more to the beginning of this thread.

If so, why do people still put them into "class"? And how different phylla could be among bacteria?

 

[Radagast]

And how different phylla could be among bacteria?

Wikipedia lists these bacterial phyla:

Acidobacteria
Actinobacteria
Aquificae
Bacteroidetes/Chlorobi
Chlamydiae/Verrucomicrobia
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres
Firmicutes
Fusobacteria
Gemmatimonadetes
Nitrospirae
Planctomycetes
Proteobacteria
Spirochaetes
Synergistetes
Tenericutes
Thermodesulfobacteria
Thermotogae

 

[Vene]

If so, why do people still put them into "class"? And how different phylla could be among bacteria?

You know that different animals eat different things, right? You know that animals that are in the same grouping have similar diets and digestive systems, right? (Ex. order carnivora are all carnivores, mammals all have the same digestive organs) Well, bacteria 'eat' too. Cyanobacteria are photosynthetic, they obtain their energy from the sun. Whereas thermodesulfobacteria metabolize sulfur. Compare any two animals of any two classes (mammal, bird, reptile, amphibian, fish, cephalopods, etc) and they can only break down nucleic acids, protein, sugar, and/or* fat (all carbon based molecules). There is a greater difference between those two classes of bacteria than there is between two classes of animals.

I guess you could argue that I'm being myopic only looking at metabolism, but metabolism is one of the absolutely essential characteristics of life (other major ones are reproduction and development). It is one of the most important aspects of a living thing because it completely dictates which niche it fills.



*I say and/or because not all animals can break down all of the molecules in each category. Like how humans can't digest cellulose.

 

[Tomk80]

If so, why do people still put them into "class"?

What do you even mean here? What people generally call bacteria are put into two kingdoms, if that is what you mean, archaea and eubacteria, but such classifications are inherently arbitrary. They are based more on historical conventions than anything else. We also we put all mice in the same genus (Mus) while we put chimps and humans in a different genus (either Homo or Pan) but in the same family (Hominidae), which may also be inconsistent if you look at genetic distances.

That we can classify organisms in consistent, twin-nested hierarchies is a highly significant find, and strongly supports common ancestry. But the names we give to the different levels of relatedness (genus, family, class, fylum, kingdom) are for a large part arbitrary if we look at the level of relatedness.

And how different phylla could be among bacteria?

What Radagast said.

 

[TheGnome]

We also we put all mice in the same genus (Mus) while we put chimps and humans in a different genus (either Homo or Pan) but in the same family (Hominidae), which may also be inconsistent if you look at genetic distances.

This is not true. There are several genera for mice, one example being Ochrotomys and another being Peromyscus.

 

[Tomk80]

This is not true. There are several genera for mice, one example being Ochrotomys and another being Peromyscus.

Yeah, you're right.

However, the genetic diversity between different mice in the genus Mus is as large as the genetic diversity between humans and chimps. But humans and chimps are put in a different genus. Which was my point. And you could make the point that to be consistent, at least as far as genetic similarity is concerned, you either should divide the genus Mus into more classes, or put humans and chimps in the same genus.

I hate the differences between nomenclature and daily language. It's horribly confusing.

 

[Naraoia]

On a comparable scale, the classes of bacteria will be much more closely related than two classes of animals.

Really? I would love to see your reasoning. (EDIT: Although Vene pretty much shot it down, I think)

My guess (hypothesis ) is that it's some variation of "animals look soooo much more different!"

 

[Tomk80]

This is not true. There are several genera for mice, one example being Ochrotomys and another being Peromyscus.

Looking a bit further, Ochrotomys and Peromyscus aren't even in the same family as Mus. Heck, rats are more closely related to Mus than those two mice are. The difference being that those mice are native to the Americas, while Mus is native to Australia, Asia, Europe and Afrika. Similar to the difference between old world and new world monkeys. Perhaps old and new world mice also diverged at the same time that old and new world monkeys did? Do you know?

 

[juvenissun]

You know that different animals eat different things, right? You know that animals that are in the same grouping have similar diets and digestive systems, right? (Ex. order carnivora are all carnivores, mammals all have the same digestive organs) Well, bacteria 'eat' too. Cyanobacteria are photosynthetic, they obtain their energy from the sun. Whereas thermodesulfobacteria metabolize sulfur. Compare any two animals of any two classes (mammal, bird, reptile, amphibian, fish, cephalopods, etc) and they can only break down nucleic acids, protein, sugar, and/or* fat (all carbon based molecules). There is a greater difference between those two classes of bacteria than there is between two classes of animals.

I guess you could argue that I'm being myopic only looking at metabolism, but metabolism is one of the absolutely essential characteristics of life (other major ones are reproduction and development). It is one of the most important aspects of a living thing because it completely dictates which niche it fills.



*I say and/or because not all animals can break down all of the molecules in each category. Like how humans can't digest cellulose.

Thanks. I understand what you said. But for the sake of argument in this thread, I am going to twist it a little bit:

From your point of view, are you saying the evolution of eukaryotic cells are backward (i.e. become less and less diverse, and have fewer and fewer functions)

 

[juvenissun]

That we can classify organisms in consistent, twin-nested hierarchies is a highly significant find, and strongly supports common ancestry. But the names we give to the different levels of relatedness (genus, family, class, fylum, kingdom) are for a large part arbitrary if we look at the level of relatedness.

That is good. So, the fact that we classify bacteria does not mean bacteria evolved.

 

[Vene]

Yes, eukaryotes are less diverse than bacteria. This is what Tom mentioned earlier about genetics (these pathways are a direct result of genes).

Evolution can only build on what already exists. When a system of organs is already in place, there is only so much that can be modified. When a metabolic pathway already exists, the amount of modification is limited. This (link for huge) is a simplistic model of human metabolism and
this (link for huge) is the model for E. coli metabolism. It's pretty plain to see that eukaryotic metabolism is a lot more involved and as such, harder to safely modify.

 

[Tomk80]

That is good. So, the fact that we classify bacteria does not mean bacteria evolved.

What do you even mean to ask with this question. It doesn't make any sense.

No, the fact that we have observed their evolution in the lab and in nature means they have evolved.

That we can classify organisms in a twin-nested hierarchy means that they have a common ancestry.

edited to add: To further clarify this, if God had created all organisms (including bacteria) separately, we could still classify them in different ways. That we can classify something in itself does not mean that group of things has evolved. That still doesn't take away that the group of bacteria is more genetically diverse than the animals, plants and fungi together.

 

[Pete Harcoff]

On a comparable scale, the classes of bacteria will be much more closely related than two classes of animals.

No, I pointed this out pages back.

There is more genetic difference between certain bacteria than between you and a tree.