SYSTEMS OF CLASSIFICATION

     SYSTEMS OF CLASSIFICATION

Artificial system of classification;- One or two morphological characters (habit, colour, number, form etc) is used for grouping of organism.

Many taxonomists proposed artificial system of classification. Theophrastus (Tyrtamus) divided plants into four groups (trees, shrubs, sub-shrubs and herbs). Albertus Magnus (doctor universalis) (1193-1280) dealt with the medicinal plants. He was the first to recognize monocots and dicots. He separated vascular and nonvascular plants. John Ray (1627-1705) in his book historia plantrum divided plants into Herbae (herbs) and Arborae (trees).

C. Linneus (1753) divided flowering plants into 24 classes on the basis of no. and arrangement of sexual parts also called sexual system.

In artificial system no affinities or relationships were involved. It was not based on hierarchial system. In this only few plants were included and unrelated plant species were grouped by common criteria.

Natural system of classification;- this system Takes into consideration comparable study of a number of characters so as to bring out natural similarities and dissimilarities and hence natural relationships among the organisms. The natural system of classification was started by Adanson and culminated by Bentham and Hooker.

Benthum and Hooker system of classification;- G. Bentham and J.D Hooker classified seed plants (phanerogames) in their book genera plantrum into 202 families, 7569 genera and 97205 species.

Merits;-

• Great practical value and easy to follow.
• It was based on comparative study of actual specimens.
• Gymnosperms were raised to class level.
• Renales are placed at top.
• Dicots were put before monocotyledons.

Demerits;-

• There was no involvement of phylogeny.
• Gymnosperms were put before dicots and monocots
• Monochalamydae included unnatural assemblage of taxa.
• Some well known genera were placed in order anomaly.

Phylogenetic System of Classification;- Based on the evolutionary relationship of organisms. In this system organism are classified on the basis of their evolution on earth from primitive to highly evolved. After the Darwin’s origin of species de Candolle and Bentham and hookers system of classification was found inadequate.

Engler and Prantl classification;- A. Engler and K.A Prantl devised classification of entire plant kingdom based on progressive complexity or level of advancement(transitional system).

They divided plant kingdom into 13 divisions;

01-11th division dealt with thalophytes- (algae and fungi)

12th division dealt with embryophyta asiphonogama- (bryophytes and pteridophytes)

13th division dealt with embroyophyta siphonogama (gymnosperms and angiosperms).

Hutchinson classification;- it was the intentional phylogenetic system. John Hutchinson gave a system of classification of plants based upon 24 principles. He concluded that;

Most primitive ---- -- most advanced

Trees   ---------------  shrubs --------------       herbs

Perennials ---------biannual-------------       annuals

Dicots ------ -------------      monocots

More stamens ------- -------------      less stamens