Author's note: these pages were written some years ago. I am not planning to update them. For a more current coverage, see the link to palaeos com Palaeos website (to which many links on these pages point to anyway. More info here

Author's note: these pages were written some years ago. I am not planning to update them. For a more current coverage, see the link to palaeos com Palaeos website (to which many links on these pages point to anyway. More info here

Systematics

Systematics
diagram from external linkUCMP Phylogenetics database

Systematics - a definition

Systematics is the branch of biology that deals with classifying living beings: the diversity and interrelationships of living beings, both current organisms ("neontology") and prehistoric ones ("palaeontology").  It can be divided into three parts.

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Systematics - history

Correspondences by Association
The Scala Natura
Aristotle and the dawn of science
The Linnean System
The Darwinian Revolution
The Cladistic revolution


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Correspondences by Association

In shamanistic cultures,  the world (including living organisms and inanimate objects) was classified according to the archetypal mandala - the four cardinal points, each associated with an element, a season, a deity, an animal, and so on, which constituted the underlying structure of the world (much as the elementary particles and forces in quantum physics is considered nowadays).  This system of correspondence by association, which is metaphysical rather than scientific,  reached great sophistication in the Chinese system of Five States of Change, the Indian doctrine of tattwas, and more recently (late 19th century) in Hermetic Qabalah.


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The Scala Natura

A different slant on things was given by Plato and his student Aristotle, who introduced the idea of the scala natura - the scale of nature - according to which the natural world is interpreted in terms of the principle of plenitude, the overflowing abundance of the first principle or Godhead which creates successive beings.  The further the beings are from the source the more ontologically impoverished they are.  So you have formless matter right at the bottom, then rocks, plants, lower animals, higher animals, man, and finally spiritual and divine beings.  This hierarchical view of the world - the Great Chain of Being, persisted through the middle ages and up until the scientific revolution of the seventeenth and eighteenth centuries, when it was replaced by a sort of monotheistic dualism - there is the material world or creation, and there is God in his heaven.


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Aristotle and the dawn of science

Though Aristotle's work in zoology was not without errors, it was the greatest biological synthesis of the time, and remained the ultimate authority for many centuries after his death.  Animals could be classified by their way of life, their actions, or by their parts.  His observations on the anatomy of octopus, cuttlefish, crustaceans, and many other marine invertebrates are remarkably accurate, and could only have been made from first-hand experience with dissection. Aristotle described the embryological development of a chick; he distinguished whales and dolphins from fish; he described the chambered stomachs of ruminants and the social organization of bees; he noticed that some sharks give birth to live young -- his books on animals are filled with such observations, some of which were not confirmed until many centuries later.

Aristotle's classification of animals grouped together animals with similar characters into genera (used in a much broader sense than the current Linnean definition) and then distinguished the species within the genera. He divided the animals into two types: those with blood, and those without blood (or at least without red blood). These distinctions correspond closely to our distinction between link to palaeos com vertebrates and Wikipedia link invertebrates. The blooded animals, corresponding to the vertebrates, included five genera: viviparous quadrupeds (mammals), birds, oviparous quadrupeds (reptiles and amphibians), fishes, and whales (which Aristotle did not realize were mammals).  This basic division (except for the whales) was to be adopted by Linneus (for whom the "genera" became classes). The bloodless animals were classified as cephalopods (such as the octopus); crustaceans; insects (which included the spiders, scorpions, and centipedes, in addition to what we now define as insects); shelled animals (such as most molluscs and echinoderms); and "zoophytes," or "plant-animals," (e.g. corals) which supposedly resembled plants in their form.


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The Linnean System

In the 18th century the Swedish botanist Carl von Linne, better known under the Latinised form of his name, Linnaeus, developed what's known as the binomial system of classification, in order to simplify the chaotic state of affairs around at his time.  (Some plants were given names ten words long for example).  He used Latin because that was the academic language of the time.  The modern system of classification in current widespread use is the binomial hierarchical system introduced by Linnaeus.

internal link The Linnean system

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The Darwinian Revolution

While Linneus founded taxonomy and classification, it was left to Charles Darwin in the 19th century to introduce the theory of evolution and hence make possible phylogenetic reconstruction; that is, the evolutionary relationships and history of the various groups of organisms through geological time (millions of years).  That's where things really get interesting, because life as a dynamic process is much more fascinating than life as a static series of unchanging types.

REVOLUTION AND EVOLUTION IN TAXONOMY: MAMMALIAN CLASSIFICATION BEFORE AND AFTER DARWIN - 131 kb of text, reviewing how classification and taxonomy changed through the publication of Darwin's Origin of Species.  Looks at Linneus, Cuvier, Owen, Huxley, Simpson, and others.

internal link Evolutionary Systematics

internal link "Vertical" and "Horizontal" Classification

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The Cladistic revolution

Over the last few decades there has been a major paradigm shift in biology and systematics, with the Linnean system being pretty much superseded by the cladistic one.  Cladistics is based not on morphological similarity (as in the Linnean system) but on ancestor and descent relationship (phylogeny).

internal link Cladistics

an example of the distinction between the Linnean and the Phylogenetic (cladistic) arrangements
The difficulty of reconciling the Linnean and the cladistic systems

Proceedings of a Mini-Symposium on Biological Nomenclature in the 21st Century - suggests replacing the Linnean system with a cladistic phylogenetic system of nomenclature.  However R. K. Brummitt in Quite Happy with the Present Code, Thank You - argues against the tendency to reduce the Linnean system to the Cladistic one by eliminating paraphyletic taxa.

Dinosaurs and Evolution part 4 - by Jeff Polling, Points out weaknesses of the linnean scheme and argues for the cladistic, with reference to Monohynchus, a prehistoric animal that, like Archaeopteryx, was transitional between dinosaurs and birds (note: this page is part of a longer discussion regarding evolution and creationism)

Phylogenetics Databases and Information Phylogenetics Databases and Information


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It should be pointed out here that - as with fields of science in general - all of these biotic classification schemes are in a sense arbitrary, dependent on the incomplete state of knowledge at present.   Systematic classifications are supposed to convey phylogenetic information according to ancestry and descent, as well as being names for organisms or groups of organisms.  But there still is (and perhaps never will be) a complete consensus on the phylogenetic relationships of organisms on Earth.  As research progresses, phylogenetic concepts change, and the names that are tied to these concepts change as well. Research also discovers numerous instances of wrongly applied labels, such as when two or more species are found hiding under a single species name, and identifies previously undescribed creatures and lineages for which new names are needed.


[note - part of above paragraph from external linkAbout Protist Image Data]

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Lunean taxonomy
evolutionary systematics
cladistics
 
The Scala Natura
The Linnean system
Evolutionary Systematics
Cladistics
Phenetics

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links

BIOLOGICAL DIVERSITY: CLASSIFICATION - very good non-technical intro - part of M.J. Farabee's On-Line Biology Book

Taxonomy: Classifying Life - John Kimball - excellent overview (part of Kimball's Biology Pages)

Taxonomy, Transitional Forms, and the Fossil Record - Keith B. Miller - online essay, makes some interesting observations


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Biological Systematics : Principles and Applications

by Randall T. Schuh

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content by M.Alan Kazlev
most recent update 31 May 2001, links updated 18 January 2010


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