Monday, 7 June 2021

BIOLOGICAL CLASSIFICATION AND TAXONOMIC CATEGORIES [ CLASS XI LIVING WORLD ]

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BIOLOGICAL CLASSIFICATION AND TAXONOMIC CATEGORIES

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It is difficult to study and remember all living organisms, so there is need to classify them. CLASSIFICATION is the process in which anything can be grouped into convenient categories based on similarities and dissimilarities. 

External and internal structure, structure of cell, biochemical characters, ecological information can be used as characters for classification.

TAXONOMY is the branch of biology dealing with characterization, identification, classification and nomenclature of organisms.

SYSTEMATICS is the branch of biology that considers evolutionary relationships between organisms. Systema means systematic arrangement of organisms. This word was first used by Linnaeus in his title of publication 'SYSTEMA NATURAE'. SYSTEMATICS also deals with identification, classification and nomenclature while considering evolutionary relationships.

Taxonomy involves classification of organisms into groups i.e. TAXA. Smallest group or taxon is SPECIES. Similar species are grouped together to form GENUS. Similar genera are grouped to form FAMILY. Families showing similar characters are grouped into ORDER and similar orders to CLASS. In the same way similar classes form PHYLUM ( animals ) and DIVISION ( PLANTS ) and finally these  groups showing similar characters can be grouped to form largest group KINGDOM.

Each group in taxonomy is representing a RANK or CATEGORY. eg. Species is the lowest rank and kingdom is the highest rank. Each rank is also called taxonomic CATEGORY. So,                          SPECIES-->GENUS -->FAMILY-->ORDER-->CLASS-->PHYLUM or DIVISION-->KINGDOM forms step by step arrangement of groups called TAXONOMIC HIERARCHY. So, Taxonomic Hierarchy is the arrangement of taxa in ascending order from species to kingdom.

Let us understand it by one example, Panthera leo ( lion), Panthera tigris ( tiger) and Panthera pardus (Leopard) are representing three different SPECIES ( leo, tigris, pardus ) but based on similarities these species are grouped together to form GENUS ( Panthera ).

Genera similar to Panthera is the Felis ( Cat ). Both these genera are grouped to form FAMILY Felidae.

Family similar to Felidae ( Cat ) is Canidae ( Dog). These two families are grouped to form ORDER Carnivora.

Order Carnivora includes carnivorous animals mostly carnivorous mammals like cat, dog, tiger, lion etc. Similar Orders including mammals like Order Primata comprising monkey, gorilla are grouped together to form CLASS Mammalia.

Classes are Piesces ( Fish ), Amphibia ( Amphibians), Reptilia ( Reptiles ), Aves ( Birds ) and Mammalia ( Mammals ) form the larger group PHYLUM Chordata ( Animals with notochord ).

All phyla are grouped to form highest category or rank KINGDOM- ANIMALIA.

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