What biological classification system are you using?

Plant, animal, or mineral?

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knobren
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What biological classification system are you using?

Postby knobren » Mon Nov 05, 2007 6:36 pm

The old five kingdom system of classification disappeared from college texts a number of years ago, but I suspect that it is still being taught in some high schools, and I don't know what you have in the resources that you are using.

The three domain system of classification - Bacteria, Archaea, and Eukarya - is the current system. There has been a blending of a three- domain/six-kingdom classifcation system for awhile now, but the six-kingdom system is about to kick the bucket, too. I attended a conference this weekend where there is also a push to eliminate the use of the term "prokaryote", because it is basically as bad as the old grouping of whatever wasn't a eukaryote into the kingdom Monera. (The Monerans were divided into the domains of Bacteria and Archaea, and the other 4 kingdoms were grouped into the Eukarya.) Also, there has been talk for some time about dividing the kingdom of Protista into at least three different kingdoms, because that is also a hodge-podge group of distantly related organisms.

The last universal common ancestor (LUCA) to all living things was not a member of any of these three domains. The Bacteria diverged from the lineage that led to to the Archaea and Eukarya, which last shared a common ancestor more recently in time. Genes have been passed between the three lines by viruses and other mechanisms. Also, it has been well established for some time now that the mitochondrion and chloroplast were originally bacteria that lived inside a host cell and later degenerated into organelles. (This is called the endosymbiotic theory, if you want to look it up.)

I just wanted to let you know that these are exciting times in the life sciences. I also wanted to let you know what you might expect your kids to learn if/when they get to college. :)

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Postby Theodore » Tue Nov 06, 2007 10:25 am

Is it heresy to say that anyone outside of a Biology major probably isn't going to care? :) I could discuss the shift from Pascal to C++ to Java, but I'm sad to say that only computer programmers would even know what I'm talking about.

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Postby knobren » Tue Nov 06, 2007 11:39 am

Theodore wrote:Is it heresy to say that anyone outside of a Biology major probably isn't going to care? :) I could discuss the shift from Pascal to C++ to Java, but I'm sad to say that only computer programmers would even know what I'm talking about.



We teach classification to NON-MAJORS, too. Also, this is revolutionary. It completely changes how we view living things and their evolutionary relationships. An elephant is more closely related to a single-celled yeast than a bacterium is to either an Archaean or a yeast. Also the amount of variation in the Bacteria and Archaea is vastly greater than that amoung the Eukarya. Most of the living things on earth are Bacteria or Archaean and far outnumber plants, animals, etc. combined.

It is not scientifically valid to have the Bacteria and Archaea lumped together in the "monera" and put on the same level as "protista", fungi, plantae, and animalia. Only in the last couple of decades have we had the tools to look at the genetic and biochemical differences among the "prokaryotes" and developed techniques to detect them in the environment. Only about 1% of bacteria/Archaea have been cultured and most of these are disease-causing bacteria, so we still don't know much about the majority of life on this planet. I would say that is vastly different than comparing two programming languages. The three domain system of biological classification is a revolution in how we think about life!

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Postby momo3boys » Tue Nov 06, 2007 4:02 pm

knobren respectfully I have no idea what you are talking about. I teach Herps, birds, mammals, invertabrits. I have no idea what those other names are. I assume Latin. I never memorized those. If you used common English I might be able to appreciate more of what you are saying.
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Postby Theodore » Wed Nov 07, 2007 7:27 am

knobren wrote:Also, this is revolutionary. It completely changes how we view living things and their evolutionary relationships. An elephant is more closely related to a single-celled yeast than a bacterium is to either an Archaean or a yeast. Also the amount of variation in the Bacteria and Archaea is vastly greater than that amoung the Eukarya.


At this risk of starting a whole other Creation vs evolution debate, does this mean that evolutionary theory is going to have to be revamped again, as it has every time more advanced scientific tools have been developed? How do you know that the latest way of looking at things is any better than the last one?

Personally, I'm all in favor of the reclassification (now that I've Googled a bit and discovered what on earth you mean), but it doesn't seem to reinforce existing evolutionary theory very much. It's more like validation for what Creationists have been saying the past few decades - the closer you look, the less of a logical evolutionary sequence there is.

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Postby knobren » Wed Nov 07, 2007 11:41 am

Theodore wrote:
knobren wrote:Also, this is revolutionary. It completely changes how we view living things and their evolutionary relationships. An elephant is more closely related to a single-celled yeast than a bacterium is to either an Archaean or a yeast. Also the amount of variation in the Bacteria and Archaea is vastly greater than that amoung the Eukarya.


At this risk of starting a whole other Creation vs evolution debate, does this mean that evolutionary theory is going to have to be revamped again, as it has every time more advanced scientific tools have been developed? How do you know that the latest way of looking at things is any better than the last one?

Personally, I'm all in favor of the reclassification (now that I've Googled a bit and discovered what on earth you mean), but it doesn't seem to reinforce existing evolutionary theory very much. It's more like validation for what Creationists have been saying the past few decades - the closer you look, the less of a logical evolutionary sequence there is.



No, it doesn't. We are able to see farther down towards the root of the tree of life than ever before. The three domains of life all evolved from a common ancestor, but it wasn't a bacterium or an Archaean - it was a single-celled organism that we call the last universal common ancestor.

It is very "logical". In the past, we called all cells without a nucleus "prokaryotes". We just didn't have the tools to adequately compare these single-celled organisms, so we lumped them all together until the tools became available to study them better. Now we know that there are two distinctly different groups of "prokaryotes", so we need to lose the vague tag we've been using.

All cells use DNA to carry their genetic information. All cells decode the information in genes the same way (use the same codon table, except for a couple of minor variations), although the machinary to do so differs a bit. (All cells use ribosomes, but the ribosomes in the three domain are someone different. All have rRNA in their ribosomes though, so we can compare the genes that tell how to make rRNA to see how living things have evolved.) ETC....

Do you expect science to sit still? The germ theory of disease has only been around for about 150 years. Doctors used to go from autopsies to delivering babies without santitizing their hands.

DNA wasn't identified as the molecule that carried genetic information until 1944, and the structure of DNA has only been known for about 50 years.

The nature of science is that it changes when new evidence becomes available.

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Postby knobren » Wed Nov 07, 2007 11:59 am

momo3boys wrote:knobren respectfully I have no idea what you are talking about. I teach Herps, birds, mammals, invertabrits. I have no idea what those other names are. I assume Latin. I never memorized those. If you used common English I might be able to appreciate more of what you are saying.


Those are all eukaryotes (they have cells that contain a nucleus and other membrane-bound organelles). Furthermore, they are only a subset of the eukaryotes; those are all in the kingdom of animals. Yet, animals make up only a rather small number of the living things on this planet. Other eukaryotic kingdoms include the plants, fungi, and a diverse group of distantly-related, mostly single-celled organisms referred to as the protista. Some protists are plant-like, some are animal-like, and some are fungus-like. A few protists cause diseases in humans such as giardiasis, African sleeping sickness, and malaria.

The term "prokaryote" literally means "before the nucleus" and has been used to refer to single-celled organisms that don't have a nucleus or other membrane-bound organelles. We used to call them Monera or bacteria. Now we know that there are two very different groups of "bacteria". They differ in their cell membrane composition, the type of ribosomes they have, the chemical processes they use to "make a living", and evolutionarily based on gene sequences. So the "bacteria" are now split into two domains called Bacteria and Archaea. All eukaryotes make up the third domain and are called Eukarya. The Archaea are more closely related to the Eukarya (plants, animals, etc.) than to the Bacteria.

I used InfoTrak at our university library to pull up a paper from "The Science Teacher" (published by the National Science Teachers Association) that you might find helpful. It was in the October 2007 edition on p. 46. It is called "current taxonomy in classroom instruction: how to teach the new understanding of higher-level taxonomy" and was written by Laura K. Baumgartner and Norman R. Pace.

Also you can Google "Archaea" for more information. Also, here is a website that you might find useful:

http://www.ucmp.berkeley.edu/archaea/archaea.html
http://www.ucmp.berkeley.edu/archaea/archaeasy.html

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Postby seekingmyLord » Wed Nov 07, 2007 12:17 pm

I appreciate the info, but I also agree with Theodore--I have yet to run across any one of those "classifications" in our reference books nor on any educational shows. However, since you are a biologist and feel it is significant, I will consult a homeschooling friend of mine, who is also a biologist, for her opinion if this should be a concern for those of us teaching our children K-12 science/biology.

By the way, don't major changes like this take years before seen in textbooks typically anyway?

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Postby knobren » Wed Nov 07, 2007 1:12 pm

seekingmyLord wrote:I appreciate the info, but I also agree with Theodore--I have yet to run across any one of those "classifications" in our reference books nor on any educational shows. However, since you are a biologist and feel it is significant, I will consult a homeschooling friend of mine, who is also a biologist, for her opinion if this should be a concern for those of us teaching our children K-12 science/biology.

By the way, don't major changes like this take years before seen in textbooks typically anyway?


The last posting I sent contained information about an article in a journal/magazine meant for high school science teachers.

I have been teaching in my current position for 11 years. It took a couple of years before our non-major textbooks switched from the five kingdom system to the mixed 3 domain/6 kingdom system - the system that I learned in graduate school several years before. Many of the non-majors that I teach are elementary and middle school education majors, and I have been teaching them the mixed 3 domain/6 kingdom system for several years. (High school teachers take majors classes in biology, or whatever they plan to teach.) I don't know what system is currently being taught in K-12, but I would imagine that they will be switching eventually, if they haven't already done so. If your child is a bit younger, by the time they reach high-school or college, I would think that they would encounter the new terminology. I just wanted folks to be aware of the changes in case they want to teach their kids what they will most likely encounter later on or if they would like to use this example to illustrate that science isn't just a static list of facts.

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Re: What biological classification system are you using?

Postby Ramona » Wed Nov 07, 2007 1:15 pm

To the very small extent that I have my 10th-grade bio students study taxonomy, we learn the really, really old stuff, before the word "moneran" was a part of it.

Since my kids read the Core Knowledge Series in grades 1-6, they are exposed to the word moneran and the concept that taxonomy has changed over time.

The idea that science changes is certainly a bedrock of their education.

I think that if I had a child who wanted to major in biology, s/he would be capable of coping with whatever should happen to be taught in college by the time s/he attended. (So far I haven't had one who's interested in science. I have a film-maker, a music teacher, and an interior designer.)

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Postby knobren » Wed Nov 07, 2007 3:17 pm

That's fine. Like I said, I'm just throwing the information out there for whoever might be interested. :)

I DO NOT want to debate evolutionary relationships or belief systems. :!:

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Postby Theodore » Thu Nov 08, 2007 12:13 pm

Personally, I'd like more emphasis on things large enough to see. Tiny organisms are all well and good, but very little use to anyone not specializing in biology, while the entire rest of the spectrum is given just a token once-over. Read any standardized test for biology and you'll see what I mean - there are probably more questions on Mendellian genetics than there are for plants or animals.

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Postby knobren » Thu Nov 08, 2007 1:00 pm

If you want to talk about how antibiotics work, it helps to understand how the drugs affect bacterial cells and not ours because bacterial cells are different than our cells. For example, penicillin interferes with forming new cell walls, but our cells don't have cell walls, so it doesn't affect our cells. (People can have an allergy to penicillin, but that is an immune response.) Streptomycin affects certain bacterial ribosomes, and therefore, inhibits protein production, but we have a different kind of ribosome, so it doesn't inhibit our ribosomes.

Do you go over cell structure? Bacteria and Archaea don't have membrane-bound organelles, such as chloroplasts and mitochondria. And yet, some bacteria and Archaeans can do photosynthesis and/or cellular respiration.

Plants wouldn't have a source of nitrogen that they could use if it weren't for nitrogen-fixing bacteria. Do you live in a place that has crop rotations of soybeans and corn? Legumes (peas, beans, peanuts, clover) have nitrogen-fixing bacteria in root nodules. Some of the ammonium and nitrates leak out into the soil and enrich it for the corn the next year.

Do you discuss nutrient cycling of nitrogen, phosphorus, and carbon through food chains? Do you discuss the roles of decomposer bacteria and nitrogen-fixing bacteria?

Do you talk about the normal flora in and on our bodies that act as a first line of defense against harmful bacteria?

Do you talk about how cheese, yogurt, and saurerkraut are made and the role of bacteria in these processes? Do you discuss "active cultures" in yogurt?

Did you know that animals can't digest the cellulose that makes up the cell walls of plants and that bacteria (and protists) digest it for termites and ruminants like cows and then the cows, etc. digest the bacteria?

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Postby Ramona » Thu Nov 08, 2007 1:27 pm

We do touch on most of those, but I don't find taxonomy to be necessary to the discussion.

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Postby knobren » Thu Nov 08, 2007 1:53 pm

Theodore wrote:Personally, I'd like more emphasis on things large enough to see. Tiny organisms are all well and good, but very little use to anyone not specializing in biology <snip>


Ramona: this is what my last post was addressing, not whether you needed to discuss taxonomy in order to discuss these other topics. Bacteria are of "very little use to anyone not specializing in biology," according to Theodore.


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