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ALmom
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| Posted: Aug 28 2007 at 4:33pm | IP Logged
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Ok back to my taxonomy panic. I have managed to find a bit in my dd high school science book (Prentis Hall). I'm not trying to put anyone on the spot about evolution, etc. I am so ignorant that all I can say for sure is what is in Humanis Generis - God directly created the soul and Adam and Eve didn't have ape (or any other sort) parents. I will say my little mind finds it very difficult to see a major evolution between species - but I'm not saying that this is some deep conviction or well thought out decision - it is a gut feeling based on what I know to be ignorance of all but the very rudimentaries. I'm willing to be educated.
Now that being said, I'm reading in dd high school book that a lot of the taxonomy charts are being driven by evolutionary assumptions (ie we are grouping these things together because we think they have more recent common ancestors). Ok, is this assumption being driven by similiarities and differences found in the animals themselves (ie something that would make sense and be useful to someone who didn't believe in evolution or at least isn't ready to have that underneath every other thing you do) or is it driving the taxonomy charts? It makes a difference to me.
I have no problem teaching my children that currently scientists are using 3 domains and 6 kingdoms if that is really based on true differences in living things that are observable. I don't even mind saying that some of this is used to support conclusions about evolution and who is closely related to whom. I have a problem if the assumption is driving the whole chart - ie true scientific perspective is being clouded by something that is held almost as a tenet of faith in the scientific world. Obviously what someone considers an important difference or similiarity will be influenced by what they believe about evolution - so I'm sure these charts are not totally without that influence. I'd just like to know to what extent the one drives the other.
Can anyone shed light on this so I can go about deciding whether to teach 5 or 6 kingdoms (certainly my children will know that this whole thing is a matter of sorting and classifying to make the study of these things more productive and as more and more is learned and discovered, these classifications change - and scientists are not currently even in agreement about how it should be done, so they are free to differ in opinion from whatever I come up with as long as they have good, substantiated evidence and justification for their proposals though they should know what most scientists agree on (whatever that is at the moment). Am I off my rocker?
Lapazfarm, would you feel on the spot if I asked why you decided to go 3 domains and 5 kingdoms instead of 6? (I don't mind a PM if that is a better forum). I'm just trying to become educated here and feel once again, hopelessly lost. Are you putting things in groupings based on some certain criteria? At the moment, I'm really just about ready to make cards for the divisions (we gotta learn the names of the groups first - ie kingdom, phylum, etc....and be able to put them in order from most inclusive to most restrictive) - then plan to start with mammals (I'm still trying to get a handle of where I am on the taxonomy chart - ie I think mammals is class (in phylum chordata) and then we can break that down into orders. I guess you can see how really uneducated I am when it comes to science - but I'm desperately trying to learn. What happened to vertebrata? My last science class was as a college freshman (non-science major, obviously) and that was a long, long time ago so there are vague things floating around in my mind that seem to have totally disappeared off the science map. I've avoided this subject like the plague at home for far too long simply because I am not sure how to sort through what is out there and was really turned off by most of what I saw in the way of science texts(either anti-science and young earthish or anti-religion and every believer is an idiot or full of agenda driven drug and s* education) - so my poor dc have been virtually on their own here with only field guides (that I cannot help them figure out because I cannot see the detail that well) and our backyard. We're either hopelessly ignorant or so science wired that nothing will stop the learning (one son) and tearing apart and rebuilding whatever electronic/mechanical stuff we have around - but nothing that comes close to my ideal basic education for those of us obviously not geared for the major pursuit of science. (Those folks seemed to have taken my poor example and simply avoided it until high school when we have to have the credit - and then we don't have a clue what we're doing  ). I'm trying to break the cycle and become educated).
Anyways, any insight here would be appreciated. Thanks.
Janet
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ALmom
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| Posted: Aug 28 2007 at 10:01pm | IP Logged
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Ok, sorry to double post, but going back to the previous post about number of kingdoms, I think I finally have wrapped my brain around why the bacteria and archaebacteria are divided (ie new molecular data indicates that archaebacteria aren't really bacteria). Of course I really don't have a clue what makes a bacteria a bacteria but I'll trust the scientists here. Ok that makes sense - but it seems too hard for me to divide out 3 domains that do nothing but divide the monera into 2 groups - why not just make them 2 kingdoms unless you want to highlight a relationship.
Now, I may be really showing my ignorance and there probably is a reason for not doing what makes sense to me so please explain this:
Why couldn't there be 2 domains - Eukaryotes and Prokaryotes then you are comparing apples to apples instead of some arbitrary division of convenience. Then have 6 kingdoms the Eubacteria and Archaebacteria are both prokaryotes so there seems to be a real reason for the domains (maybe this is my English you don't have a major heading unless you break two things out in it).
I thought Monera was the old kingdom that included all bacteria. I guess you could still use Monera as a name but it seems confusing to me cause then I'll be putting all kinds of wrong stuff in the wrong place.
My dd high school biology text lists the 3 domains: Eukarya, Archaea, and Bacteria but then under Bacteria it only lists Eubacteria and under Archaea it only lists Archaebacteria. It is hard for me to figure out what is the distinguishing thing that seperates these 3 domains whereas it is clear that Eukaryotes and Prokaryotes are divided according to whether or not there is a nucleas. Then I can trust the scientists to say there is some molecular evidence that Archaea are not real bacteria so they wouldn't be in the same kingdom as real bacteria. At least there is some distinguishing feature here of some sort, I presume. I guess I don't mind the Protista lump just because it is Eukaryotic and understood that it is the rest of the Euckaryotes that haven't been studied enough yet to divide out better. Probably am more comfortable with this because of familiarity but at least it does seem to make some sense.
Now this is my laymans uneducated stab at trying to figure this out. Am I doing my dc a disservice if we organize things this way?
Janet
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lapazfarm
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| Posted: Aug 29 2007 at 8:08am | IP Logged
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Ok, I'm going to try to address these questions a little at a time, if I can.
Taxonomy is based on evolutionary relationships. These relationships are determined based on morphological (structural) similarities and differences, and genetics (which is, if you think about it, morphology on the smallest scale).
As the tools of science become more and more sophisticated, scientists can tease out relationships that were not well understood before based on more gross observations.
The Archeae are a good example of this. When they say the relationship is based on molecular data, what they typically mean is that they have been able to look at small sections of genetic material and "read" them to determine these similarities and differences. Through these more recent techniques, scientists are able to see relationships they simply could not previously. This is why science is ever-changing, as new technologies are developed, there may be (and I would venture to say "will" be) more changes yet.
As far as the whole evolution issue goes, you can look at these genetic relationships as having arisen evolutionarily or not. That does not alter the basic integrity of the information either way.
The next question is, then how do scientists determine whether this new information leads to designation of a new kingdom, phylum, or development of another scheme entirely (domains)? Here is where the subjectivity comes in, and hence the controversies. There is no good objective criteria for determining if a genetic difference is profound enough to merit a new kingdom or not, or if it is so profound as to place it above even the kingdom level. This is where we stand with archeae and with protista.
Some folks want to split protista up into many individual kingdoms because they feel the differences are that profound. Others don't. Some think archeae are so profoundly different that the entire scheme needs to be re-worked because of them. Others don't.In taxonomy circles these folks are termed "lumpers" and "splitters" and they tend to be pretty entrenched in their tendencies, thus the debates rage on.
So, I teach 3 domains because I think this view will be the one that is upheld in the long run as more data accumulates, and it is the prevailing opinion. I also teach 5 kingdoms because it is such a useful mental scheme for understanding the major lineages of life that most of us will encounter on a regular basis. But as I do, I also bring up the fact that while there are disagreements about the exact level of categorization, the basic facts of their differences and similarities remain. And it is these facts that are our subject matter in the long run.
I know I have not responded to all of your questions, and I hope to. But for now I am out of time and school here has to get going. If it would be helpful I would be glad to respond to more as time permits.
__________________
Theresa
us-schooling in beautiful Fairbanks, Alaska.
LaPaz Home Learning
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4Real Forums : Exploring God's Creation in Nature and Science
Topic: taxonomy
