Biological classification notes

Biological classification notes

Aug 09, 2022, 16:45 IST

Types of Systems of Biological Classification

There are three systems of classification

i) Artificial

ii) Natural

iii) phylogenetic

Artificial Systems of Classification

• In this system of classification, habit, habitat and a few morphological characters are used for grouping of organism.
• All early systems of classification (e.g. Given by Aristotle, Theophrastus, Pliny, Bauhin, John Ray, Linnaeus etc) were artificial.
• Linnaeus divided angiosperm on the basis of numerical strength of essential organs e.g. Cryptogamia, Monoandria, Diandria, Polyandria, Monoecia etc. For More Biology Doubts check out our biology doubts section.

There are several drawbacks

i) The grouping is based on external features which may appear due to parallel evolution retrogressive evolution or progressive evolution.

ii) Grouping on the basis of habit would put Pinus and Eucalyptus in one group.

iii) Organisms of different affinities may come in the same group e.g. Vitis (a dicot) and Asparagus (a monocot) in classification of Linnaeus.

iv) Closely related organisms get separated into different groups.

v) The traits used for artificial system are liable to change.

vi) Natural relationships are not brought out.

Natural systems of classification

• Here organisms are arranged according to their natural affinities through the use of all important permanent characteristics, especially structural, cytological (chromosomal) reproductive and biochemical.
• The first natural system of plant classification was proposed by Schimper followed by Eichler.
• The last natural systems of classification of phanerogams was developed by Bentham and Hooker in treatise Genera Plantarum (1862-1883).

Phylogenetic systems

These are the systems proposed after the publication of ‘Origin of Species’ and the announcement of ‘theory of evolution’ by charles Darwin. Hence they are also called ‘ Post-Darwinian classifications’ . They reflect the genetic and evolutionary relationships among the taxa and show them in the form of a phylogenetic tree. Classifications made by Eichler, Engler and Prantl, Rendle, Bessey, Hutchinson and others come under this category. More recent phylogenetic classifications made by Takhtajan (1980), Cronquist (1981), Goldberg (1986) and Thorne (1992) have used data from different branches of Botany apart from the vegetative and floral characters. Hence they are also known as ‘ Multidisciplinary or Synthetic systems’ .

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