TAXONOMIC CATEGORIES
There are 7 main taxonomic categories. They are obligate or broad categories i.e. they are essentially used at the time of any plant classification. However, taxonomists have also developed sub categories or extra categories to facilitate more sound placement of various taxa, like sub division, sub order, etc. They are not regularly used. They are used only when they are needed.
Taxonomic hierarchy - Descending or ascending
arrangement of taxonomic categories is known as taxonomic hierarchy. Classification of mango
|
CATEGORIES |
MANGO |
|
Kingdom |
Plantae |
|
Division |
Angiospermae |
|
Class |
Dicotyledonae |
|
Order |
Sapindales |
|
Family |
Anacardiaceae |
|
Genus |
Mangifera |
|
Species |
Mangifera indica |
Classification is not a single step process but
involves hierarchy of steps in which each step represents a rank or category.
Since the category is a part of overall taxonomic arrangement, it is called the
taxonomic category and all categories together constitute the taxonomic
hierarchy. Each category referred to as a unit of classification, in fact,
represents a rank and is commonly termed as taxon (Pl.: taxa)
Remember, groups represent category, Category
further denotes rank. Each rank or taxon, in fact, represents a unit of
classification.
Wheat, rice, plants, animals and mammals are
convenient categories or taxa we use to study organism. Animals, mammals and
dogs are different taxa at different level.
All living organism including those in plant and
animal kingdom have species as lowest category. It is basic unit of
classification.
Taxonomic groups/categories are distinct biological entities and are not merely morphological aggregates.
(A) Species:
Taxonomic studies consider a group of individual
organisms with fundamental similarities. as a species. One should be able to
distinguish one species from the other closely related species based on the
distinct morphological differences. For example, Mangifera indica can easily be
identified from any another species on the basis of morphological differences.
(B) Genus:
Genus comprises a group of related species which
has more characters in common in comparison to species of other genera. We can
say that genera are aggregates of closely related species. Each genus may have
one or more than one specific epithets representing different organisms but
having morphological similarities. For example, Solanum tuberosum (Potato),
Solanum melongena (Brinjal) and Solanum nigrum (Makoi) are three different but
related species, hence they all belong to the same genus Solanum. (C) Family:
Family has a group of related genera with still
less number of similarities as compared to genus and species. Families are
characterised on the basis of both vegetative and reproductive features of
plant species.
For example three different
genera Solanum, Petunia and Datura are placed in the family Solanaceae.
(D) Order:
Order being a higher category is
the assemblage of related families which exhibit a few similar character. For
example convolvulaceae and solanaceae are related and included in the order
polymoniales and are mainly characterised by floral characters. Order has less
number of similarities as compared to family, genus and species. Order and
other higher taxonomic categories are identified on the basis of aggregates of
characters.
(E) Class:
A class includes organisms of
related orders having less similarities than orders. For example Sapindales and
Polymoniales are related, so they are included in one class Dicotyledonae.
(F) Division:
Division
include all organisms belonging to different classes having a few common
characters.
(G) Kingdom:
The
kingdom plantae is distinct and comprises all plants from various divisions.
As we go higher from species to kingdom , number of common characters decrease.
Lower the taxa , more are the characteristics that the member with in the taxon
share. Higher the category , greater is the difficulty of determining the
relationship to other taxa at the same level.
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