Biological Classification – Systems of Classification
Biological Classification is the process of grouping living organisms into convenient categories based on simple characters. It was first proposed by Aristotle who divided organisms into 2 groups: Plants and animals. He further classified animals into anaemia (without RBC) and enaima (with RBC). Later Theophrastus classified plants into herbs, shrubs and trees.
Types of Biological Classifications:
Systems of Classifications are as follows:
Artificial System of Classification:
· t is one of the earliest systems of classification based on one or few easily observable characters.
· These classifications focussed only on one characteristic and classified organism. For example, Linnaeus classified plants based on floral characters only and was called the Linnaeus sexual system.
· Gaius Plinius Secundus, known as Pliny the Elder classified animals on the basis of their habitat, e.g. land, air and water.
Natural System of Classification:
· The most important and last of natural systems for classification of seed plants was developed by Bentham (1800 - 1884) and Hooker (1817 - 1911).
· Natural classifications are based on a large number of characters. This enabled an understanding of the relationships amongst plants as they exist in nature.
· They classified plants as Gymnosperms (non – flowering) and Angiosperms (flowering). Angiosperms were further classified as monocots and dicots.
· Initially, natural classifications were based mainly on morphological features and overall similarities using as many taxonomic characters as possible. This helped in placing the closely related taxa together or close to one another.
· Natural classifications analyse the overall similarity for determining the relationship amongst the taxa.
· After Charles Darwin’s publication of “Origin of Species” (1859) there was a profound change in the outlook of taxonomists.
· The most significant aspect of the theory of evolution was the concept that “species are not static entities but are the products of evolution”.
· Therefore, all later classifications were mostly based on the course of evolutionary descent. These tried to reflect the evolutionary sequence /relationship between different groups of organisms and were usually constructed on the basis of natural classification.
· Such classifications are considered as phylogenetic because they are based on evolutionary history.
Modern system of classification:
· The, modern classifications are broad based, using data obtained from a number of branches such as morphology, anatomy, embryology, phytochemistry, ultrastructure etc. Hence, this is also referred as Phenetic relationship.