Thread: class system

can you help me find info on what the current class system is and exaplain cladism to me I was just wondering and I read Dawkins books on evolution resently

Originally Posted by Kenny Klassen

can you help me find info on what the current class system is and exaplain cladism to me I was just wondering and I read Dawkins books on evolution resently

Welcome to the forum, Kenny.

I have no idea what the current class system is, and in a cladistic sense it actually becomes irrelevant.

Regarding cladistics itself, two books that help provide good introductions to it are Colin Tudge's The Variety of Life and Henry Gee's Deep Time (the latter a bit more polemic, providing a history of how cladistics swept through biology over the last three or four decades).

I presume wiki will have some info on it as well.

If you've tried these sources and still have questions, I'm sure the biologists here will be more than happy to help. (I too might be able to chip in usefully from time to time. )

I believe classification schemes are somewhat controversial. Five kingdoms is generally recognised as wrong, but still widely used because it is a decent first approximation.

Seven and eight kingdoms have been suggested (breaking protista into animal-like, plant-like, and a few other groups) and are sometimes considered the proper way to think about things until we understand things better, but are still recognised as an approximation.

Cavalier-Smith has the most developed system to my knowledge, but it is so bulky as to be generally hard to grasp in introductory courses (and beyond!) He recommends 22 or so kingdoms.

Originally Posted by free radical

I believe classification schemes are somewhat controversial. Five kingdoms is generally recognised as wrong, but still widely used because it is a decent first approximation.

Seven and eight kingdoms have been suggested (breaking protista into animal-like, plant-like, and a few other groups) and are sometimes considered the proper way to think about things until we understand things better, but are still recognised as an approximation.

Cavalier-Smith has the most developed system to my knowledge, but it is so bulky as to be generally hard to grasp in introductory courses (and beyond!) He recommends 22 or so kingdoms.

The best system is the phylogenetic system proposed by Woese: Archaea, Bacteria, and Eukarya.

Originally Posted by i_feel_tiredsleepy

Originally Posted by free radical

I believe classification schemes are somewhat controversial. Five kingdoms is generally recognised as wrong, but still widely used because it is a decent first approximation.

Seven and eight kingdoms have been suggested (breaking protista into animal-like, plant-like, and a few other groups) and are sometimes considered the proper way to think about things until we understand things better, but are still recognised as an approximation.

Cavalier-Smith has the most developed system to my knowledge, but it is so bulky as to be generally hard to grasp in introductory courses (and beyond!) He recommends 22 or so kingdoms.

The best system is the phylogenetic system proposed by Woese: Archaea, Bacteria, and Eukarya.

That leaves out viruses.

Originally Posted by spuriousmonkey

That leaves out viruses.

Bring it to the virus and bacteria thread if you want to continue this argument lol

thank you

I personally don't count anything that meet the requriments of a living thing only in reproduction and DNA I belive the Caviler-Smith system is the best and is really not that hard to follow and I am only a high school senior

I got a tip for you then:

throw out that whole belief thing.

It is actually possible to base your biological thinking on logic and application of logic.

I don`t really belive it I just think its the best basis I have found I have no absolute beliefs there usally consdiered wrong 10 years later but since there is no absolute system and no standard then I wil go with the one which I feel is proably best

Let's apply some logic will we.

We have a myriad of organisms occupying the biosphere of our little planet. It's called life.

We want to classify it.

How do we classify it?

A. Create a classification system based on only a part of this life because of historical and cultural reasons.
B. Try to classify all life in a meaningful manner.


I go for B.

I can't see how you can go for A and maintain you are not applying belief instead of logic.

Originally Posted by spuriousmonkey

Let's apply some logic will we.

We have a myriad of organisms occupying the biosphere of our little planet. It's called life.

We want to classify it.

How do we classify it?

A. Create a classification system based on only a part of this life because of historical and cultural reasons.
B. Try to classify all life in a meaningful manner.


I go for B.

I can't see how you can go for A and maintain you are not applying belief instead of logic.

You are operating under the principle that viruses are undeniably life. Which they are not. Being a product of life does not make something alive. Individual proteins couldn't exist without organisms, but they are not alive. A strand of DNA can't exist without organisms, but it is not alive. Being dependent on life for it's replication does not automatically make a virus alive.

Edit: Since classifications must be based on a quality all members of that class have. Please provide what you would base viruses being life on.

Of course viruses are part of life!

What else are they supposed to be classed under?

Rocks?

Planetary systems?

Carparts?

Gaseous molecules?

Originally Posted by spuriousmonkey

Of course viruses are part of life!

What else are they supposed to be classed under?

Rocks?

Planetary systems?

Carparts?

Gaseous molecules?

Why not abiotic self-replicators?

Actually virus aren't even truly capable of self-replication and I personally think of them as organic compounds that just happen to excist outside of being living things like methane alchol etc....

I'm not going to get into this life/non-life thing with viruses. However, they are highly pertinent to biological study, and despite the way in which they replicate, they clearly possess evolving nucleotide sequences by which their degree of phylogenetic relatedness to other organisms can be evaluated. Granted, it may be possible that the lineage of organic molecules that originally gave rise to viruses may be separate from the one that gave rise to the rest of life on this planet, but I think it's unlikely. If they arose from the same lineage as other forms of life then at the very least they deserve a place in a taxonomic tree that describes the evolutionary descent and relationships of organisms. In this sense trying to decide whether or not they fit into our definition of "life" is moot.

Excellent post Paralith!

Originally Posted by spuriousmonkey

Excellent post Paralith!

Seconded

I am not saying they are not part of Biology they are as much part of the study of living things as fossils even if they are not living themselves

Originally Posted by Kenny Klassen

I am not saying they are not part of Biology they are as much part of the study of living things as fossils even if they are not living themselves

Fair enough. Now perhaps we can consider whether having such a definition of 'life' (that excludes viruses) is useful, or simply another attempt to continue to distinguish ourselves from the rest of the universe.

of course its useful otherwise people would be even more confused when taking to biolgist no other real reason[/code]

It is usually the other way around. Biologists get confused when talking to normal people.

Originally Posted by Kenny Klassen

of course its useful otherwise people would be even more confused when taking to biolgist no other real reason

The utility should not lie in 'our' thinking it a convenience but in biologists' ability to use it, surely?

Really I found normal people very easy to confuse and rather symple to understand and as for the class system but really we have taxonmy keys for our convience when it comes write down to it they don't truly follow the class system that well most of them are still based on the class system