Classification

"Father! Father! / Tell me what ails thee...

“Father! Father! / Tell me what ails thee? / With dismay thou art filling thy child!” (Photo credit: Wikipedia)

Oh, wow, drat and other words of dismay. I haven’t thought of a topic for this week and it is time to write my post. Time to get started.

OK, people seem to like classifying things. This can be so that they can find one item in a large collection of things, or it may be simply a means of bolstering prejudices that they might have. Or any of a myriad number of other reasons.

Garbage Can

Garbage Can (Photo credit: Wikipedia)

When faced with a profusion of things, the human impulse is to classify them. One of the most famous classification systems is that of Carl Linnaeus, whose classification system is used for the not so trivial task of classifying all living things. His system, with modifications is still the basis for biological classification of all organisms.

Digitally improved version of Alexander Roslin...

Digitally improved version of Alexander Roslin’s painting of Carl von Linné. This particular version has had dust and missing specs of paint deleted. (Photo credit: Wikipedia)

When Linnaeus started his classification, it is likely that partial schemes would likely have been in place to classify small groups of organisms, but Linnaeus extended this to all organisms, in an organised way. When someone states that mankind’s scientific name is “Homo Sapiens”, he or she is using the Linnaeus system, at least partially.

“Homo” represents mankind’s Genus, and “Sapiens” is mankind’s  Species, but the species is merely a leaf on the classification tree, which is rooted in the Animalia Kingdom, and descends through Phylum, Class, Order, Family, and Tribe, (which I’m not going to list here) and finally to the Genus and Species.

Darwin's tree of life

Darwin’s tree of life (Photo credit: Wikipedia)

Linnaeus’ system is still in use today, but the emphasis has changed somewhat. When he was doing his work, the classification was based on appearance, and while that is often a good guide to an organism’s place in nature, emphasis has now shifted to the genetic make up of organisms to determine their correct classification.

Agapornis phylogeny

Agapornis phylogeny (Photo credit: Wikipedia)

This has sometimes resulted in whole chunks of the classification tree being moved from one branch to another as knowledge of the genetics of the organisms has come to light. It is obvious that if two organisms have similar genetic make ups, then they must be closely related. Also, it implies that they almost certainly have a common ancestor, and such an ancestor is also fitted into the tree of life and given a species name.

Horned Dinosaur Phylogeny

Horned Dinosaur Phylogeny (Photo credit: Scott Wurzel)

This adds a time dimension to the genetic tree, turning it from a static representation of living organisms into a dynamic picture of all life over all time. The tree of life is evolving.

Another great classification system is the Dewey Decimal Classification system, a proprietary library classification system used to classify books. Every book in a library is assigned a number, which in most cases would not be unique. The number consists of two parts separated by a period (‘.’). Most library users would be aware of the system, and will have used it to locate books.

Spine Books Label show Call Number for Dewey D...

Spine Books Label show Call Number for Dewey Decimal Classification. (Photo credit: Wikipedia)

While the system can classify books in great detail, merely by extending the number after the period to many decimal points, most libraries classify their books in much less detail, using only two or three digits as a suffix. This results in groups of books receiving the same number, with the books in a group sharing a common topic, while differing in detail.

get to know the dewey decimal system

get to know the dewey decimal system (Photo credit: susannaryan)

For instance a particular number may be assigned by the library whose topic might be the geography of the country of Bolivia. (The actual number is 918.4). The library might have only one or two books on the subject of the country of Bolivia, so that number is sufficient to locate any of them.

In the country of Bolivia itself, however, there will almost certainly be many more books on the topic and the Dewey Decimal Classification almost certainly contains more detailed classification numbers which would have to be used in Bolivia libraries to classify the geography books. (I’ve not checked this “factoid” but it is probably true).

Shelf of Books on South America

Shelf of Books on South America (Photo credit: pkdon50)

So the Dewey Decimal Classification system can be hair-splittingly  accurate or broadly general in its application and this flexibility is ideal for libraries. Sometime libraries use a sort of hybrid system, probably driven by the need for a sub-classification where some books have been already more generally classified, where some books are classified as “something.12” and other books are classified as “something.123”. In most cases this inconsistency doesn’t matter.

Topographic map of Bolivia. Created with GMT f...

Topographic map of Bolivia. Created with GMT from public domain GLOBE data. (Photo credit: Wikipedia)

I’ve just realised on writing that, that it may not be inconsistency at all. Instead the “something.123” books may be more specific than the “something.12” books, which would therefore be more general.

An obvious difficulty with the Dewey Decimal Classification system is that there is no cross-reference possible. In the Bolivia example, a book may cover the topic of the geographic causes of distribution of various related Bolivian species of some organism or other. Is this to be classified as biology and be assigned to a class in the 500s (Pure Science), or should it be classified as geography and assigned to a class in the 900s?

English:

English: (Photo credit: Wikipedia)

Nowadays one can do a computer search and come up with a bunch of numbers that fit the topic that is being researched. In the days before computers there were card-based “Topic Catalogs” which would also provide the searcher with a bunch of numbers. The trouble is, many searches would result in multiple numbers, either as a result of a card search or a computer search.  One would then have to go to several locations to decide if the required topic was covered by this Dewey Decimal Classification number or one of the others. I make it sound bad, but really, it wasn’t, and the issue is more a user confusion about what was covered by each topic in the system rather than an issue with the system itself.

Banner for Wikipedia:WikiProject Lists of topics

Banner for Wikipedia:WikiProject Lists of topics (Photo credit: Wikipedia)

A computer search (on Google for example) will provide a list of possible references to a search term, but as anyone has used a computer search is aware, a search term can refer to many topics. A search for the word Socrates gave me a list including a Wikipedia article on the philosopher himself, a list of quotes taken from his work, a biography of the philosopher and a site where his philosophies could be discussed. And that is just the first four items out of an estimated 6 million or so.

Google

Google (Photo credit: warrantedarrest)

Classification of things seems to be a trait of humans. I think that we classify things to simplify things for ourselves, to make it easy to identify threats and possibilities. As such, it is probably an inherited trait possessed by at least the more developed organisms on the planet. However classification can add complexity if one is searching for something, so it is something of a trade off.

google_logo

google_logo (Photo credit: keso)

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