THE LIVING WORLD

Taxonomic Categories

Narinder Singh, Academic Content Writer at Edumarz

A. What is Taxonomic Category and Hierarchy?

Hierarchy of steps as involved in classification, in which each step Represents a rank or a category.
Being part of an overall taxonomic arrangement, the category is referred

All the taxonomic categories together constitute the taxonomic hierarchy.
Each category which is the unit of classification is representing a rank Known as the taxon.
For instance, a group of organisms, like insects, sharing common Features like three pairs of jointed legs. So, insects are recognisable concrete objects, which can be classified and given a rank or a category.
The taxonomic groups or categories are distinct biological entities and not just morphological aggregates.

Taxonomic studies of all known organisms → Development of common Categories like Kingdom, Phylum or Division, Class, Order, Family, Genus and Species.
To place an organism in various categories, basic requirement is the knowledge of characters of individuals or group of organisms.
It helps in identifying similarities and dissimilarities amongst Individuals of same kind of organisms as well as of other kinds of organisms.

Species:

They are a group of individual organisms with fundamental similarities.
One species can be distinguished from the other closely related species based on distinct morphological differences.
For instance, Lion belongs to the species leo which is grouped in the genus Panthera. So, its scientific name is Panthera lio.

Also, the first word of the scientific name is the genus which is the Higher level of taxon or the category while the second word represents the specific epithet.

Furthermore, each genus can have one or more than one specific epithets Representing different organisms, but having morphological similarities.

Genus:

A group of related species having more characters in common in comparison to species of other genera.
Genus comes above species and below family in the hierarchy of biological classification.
For instance, Solanum tuberosum(potato) and Solanum nigrum(black nightshade) are two species within the genus Solanum. Solanum is a genus within the family Solanaceae.
Again, tiger(Panthera tigris), leopard(Panthera Pardus) and Lion(Panthera Lio), having several common features are all species of genus panthera.

Family:

Family comprises a group of related genera with still less number of similarities as compared to genus and species.
They are characterised on the basis of both vegetative and reproductive features of plant species.
According to wikipedia, “Carl Linnaeus used the word familia in his Philosophia botanica(1751) to denote major groups of plants: trees, herbs, ferns, palms and so on. He used this term only in the morphological section of the book, discussing the vegetative and generative organs of plants.
Additionally, the naming of families as codified by various international bodies include the “suffixes” as mentioned below:

1. In Algae, Fungal and botanical nomenclature, family names of fungi, algae and Plants end with the suffix “-aceae”.
2. In Zoological nomenclature, family names of animals end with the “-suffix”.

- - For instance, the three genera, Petunia, Solanum and Datura are placed in the family Solanaceae.
  - Families can be used for evolutionary, genetic and palaeontological studies because they are more stable than lower taxonomic levels like genera and species.

Order:

Order and other higher taxonomic categories are named based on the the aggregates of characters. Also, it is the assemblage of families exhibiting a few similar characters.
Also, the similar characters are less in numbers compared to a different genera included in a family.
For instance, the animal order, Carnivora includes families like Felidae and Canidae while the Plant families like Convolvulaceae, and Solanaceae are included in the order Polymoniales, mainly based on the Floral characters.

Taxonomic categories showing hierarchial arrangement in descending order:

Class:

It includes related orders.
Kingdom animalia includes 108 classes including class mammalia, reptilia, aves etcetera. Also, the classes used today are different from those proposed by Linnaeus and are not used frequently.
For example, order primata comprising monkey, gorilla, and gibbon is placed in Class Mammalia along with order Carnivora that includes animals like Dog, Cat and Tiger. Besides, class Mammalia has other orders also.

Phylum:

It includes mammals and classes comprising animals like fishes, amphibians, reptiles, birds etcetera.
On the basis of common features like, presence of notochord, and dorsal hollow neural system, all of these are included in Phylum chordata.
Whereas, classes with less similar characters, are assigned to a higher category, called division, in case of Plants.
Depending upon definitions, the Plant kingdom Plantae contains 14 phyla, animal kingdom Animalia contains 31 and fungus Kingdom Fungi contains about 8 Phyla.

Kingdom:

Kingdom animalia contains all animals belonging to various Phyla. In contrast, Kingdom Plantae is distinct and comprises all plants from various divisions.
In addition to this broad category of division in the taxonomic category, taxonomists have also developed sub-categories in this hierarchy to promote more sound and scientific placement of various taxa.