Biological Classification

[Lateral]

http://upload.wikimedia.org/wikipedia/commons/thumb/5/5f/Biological_classification_L_Pengo.svg/144px-Biological_classification_L_Pengo.svg.png
Could someone tell me what the two holes in the bottom classification (the one that says Life) represent? This has been bugging me for weeks. Thanks?

[AsteriskAmp]

There are three domains, Archae, Bacteria and Eukarya
Each hole represents the number of subdivisions.
Mind, there are several systems of sub-classification and the diagram is assuming Woese's system for domain subdivision.

[Lateral]

Well, I thought of that, but then what do the 4 holes in the one marked 'Domain' represent? There are 6 kingdoms.

[AsteriskAmp]

Well, I thought of that, but then what do the 4 holes in the one marked 'Domain' represent? There are 6 kingdoms.

Not if you go by the Copeland system. Again, there are several ways to subdivide and this diagram just shows one.

And as of now and the Cavalier-Smith system, there are two Empires instead of Domains

[Lateral]

Okay, fair enough. Thanks.

[VeisuItaTyhjyys]

At risk of being pedantic, I think the number of kingdoms is far less inaccurate than the number of families.

[AsteriskAmp]

At risk of being pedantic, I think the number of kingdoms is far less inaccurate than the number of families.

I think you are forgetting that we don't know from what creature this tree was made and that we also don't know which system was applied to each level.

Also, after certain point around phylum, graphing each possible hole just becomes ridiculous.

[grimbold]

I think you are forgetting that we don't know from what creature this tree was made and that we also don't know which system was applied to each level.

Also, after certain point around phylum, graphing each possible hole just becomes ridiculous.

really its kind of ridiculous trying to qualify most things biologically because every once in a while that completetely changes our view on biology
but i also believe that kingdoms are easier to classify than families

[mucat]

Well, I thought of that, but then what do the 4 holes in the one marked 'Domain' represent? There are 6 kingdoms.

But it wouldn't make sense to show all six at that level of the diagram; only the ones within the chosen domain. (Which is apparently Eukarya, since in the most common domain-based scheme, Eukarya includes four kingdoms.)

From there on down, the number of "holes" is pretty arbitrary, because it would depend on which kingdom, phylum, etc. we chose on the previous level.



really its kind of ridiculous trying to qualify most things biologically because every once in a while that completely changes our view on biology

A classification scheme is still useful, even if we might rework it later as our understanding improves.

[SDF]

really its kind of ridiculous trying to qualify most things biologically because every once in a while that completetely changes our view on biology
but i also believe that kingdoms are easier to classify than families

We never completely change classification. We gradually refine it and will restructure based on better data (mitochondrial DNA vs morphology)

[Don Julio Anejo]

I don't think holes themselves are meant to represent anything, it's only the actual level of pyramid is important.

To add on to the above, "life" is meant to distinguish living matter from non-living organic matter like viruses (which can't live on their own; they need a host to reproduce and don't have any metabolism whatsoever) or inorganic matter like rocks.

Eukaryotic kingdoms is a whole new can of worms right now. While three of them are pretty easy to classify and have distinct boundaries (plantae, animalia, fungi - plants, animals and mushrooms), protists are a completely different story. New (and a lot of old) DNA/mtDNA/morphology evidence shows that they're actually pretty different (and the only thing they have in common is that they're all unicellular or colonial instead of multicellular). Kinda like how humans and alligators are very, very different, despite both being 4-limbed vertebrates.