Taxonomical Categories and Taxonomical Aids - Class 11 PDF Download

What is Taxonomic Hierarchy?

• According to the history of biological classification, Aristotle, a Greek philosopher classified different animals based on the habitat, characteristics, etc. Later, a Swedish botanist Carolus Linnaeus introduced Taxonomic Hierarchy Categories during the 18th Century, and this system of classification is followed globally till date. 
• The word “Taxonomy” is derived from a Greek word – “taxis”, meaning arrangement or division, and “nomos”, meaning method. Taxonomy is a branch of Biology that refers to the process of classifying different living species. 
• A taxon is referred to as a group of organisms classified as a unit.
  Taxonomic Hierarchy
• Taxonomic hierarchy is the process of arranging various organisms into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.
• The kingdom is the highest rank and species is the lowest rank in the hierarchy.
• Each of these levels of the hierarchy is called the taxonomic category or rank.
• In this system of classification, the kingdom is always ranked the highest followed by division, class, order, family, genus, and species.

Taxonomic Hierarchy Categories

Following are the important taxonomic hierarchies in which different organisms are classified:
(i) Kingdom 

• The kingdom is the highest level of classification, which is divided into subgroups at various levels. 
• There are 5 kingdoms in which the living organisms are classified, namely, Animalia, Plantae, Fungi, Protista, and Monera. 

(ii) Phylum 

• This is the next level of classification and is more specific than the kingdom. 
• There are 35 phyla in the kingdom Animalia.
  Example: Porifera, Chordata, Arthropoda, etc. 

(iii) Class

• The class was the most general rank in the taxonomic hierarchy until phyla were not introduced. 
• Kingdom Animalia includes 108 classes including class mammalia, reptilia, aves, etc. However, the classes used today are different from those proposed by Linnaeus and are not used frequently. 

(iv) Order

• Order is a more specific rank than class. The order constitutes one or more than one similar families. 
• There are around 26 orders in class Mammalia such as primates, carnivora, etc. 

(v) Family 

• This category of the taxonomic hierarchy includes various genera that share a few similarities.
  Example: The families in the order Carnivora include Canidae, Felidae, Ursidae, etc. 

(vi) Genus 

• A group of similar species forms a genus. 
• Some genera have only one species and is known as monotypic, whereas, some have more than one species and is known as polytypic.
  Example: Lion and tiger are placed under the genus Panthera. 

(vii) Species 

• It is the lowest level of the taxonomic hierarchy. There are about 8.7 million different species on earth. 
• It refers to a group of organisms that are similar in shape, form, reproductive features. Species can be further divided into sub-species.

Table: Examples of Taxonomic Hierarchy

Taxonomical Aids

Taxonomical Aids

• Taxonomical aids are the collections of samples or preserved organisms which help in extensive research for the identification of various taxonomic hierarchy. 
• Classifying organisms into various categories needs a lot of field and laboratory study. This is an essential process because taxonomic categorization helps in identifying many organisms necessary in various fields like agriculture, industries, bioresources, etc.
• The taxonomical aids are the main source that helps us in studying the relative level of a group of organisms, their taxonomic hierarchy and the taxonomic rank.

Taxonomical Aids are required for:

• Taxonomic studies of various species of plants, animals, and other organisms, which require correct classifications and identification.
• Identification of organisms requires laboratory and field studies.
• Museum
• Herbarium
• Zoological Parks
• Botanical Gardens

Types of Taxonomical Aids

(i) Herbarium
Herbarium Sheets

• It is a store that houses a collection of preserved plant species. 
• Plant specimens are preserved in the forms of herbarium sheets which are prepared by drying, pressing and preserving the samples on sheets. These sheets are then arranged in their order of classification in the taxonomic hierarchy. 
• These herbarium sheets carry all the information about the respective specimen. 

(ii) Botanical Garden
Botanical Garden

• These are gardens in which specific plants are grown and are labelled according to their taxonomy. Thus, the labels carry their scientific names and family. 
• The main purpose of botanical gardens is to identify the plant species under consideration. 

(iii) Museum
Biological Museum

• Biological museums are found in schools and colleges; like the biology laboratory that we find in our schools. 
• In these museums, plants and animal species are preserved in jars and containers with the help of appropriate preservatives. They may also be dried and preserved. 
• Birds and larger animals are usually stuffed before preserving and insects are killed and pinned in the boxes. We sometimes find skeletons of various animals too.

(iv) Zoological Park

Zoological Park

• These are places where animals and birds are kept within protected boundaries. An attempt is made to provide them with a habitat closest to their natural habitats. 
• Thus, we get a chance to learn about their natural habits and behaviour. 
• Zoological parks are open for human visits. 

(v) Key 

• This is a taxonomical aid where plants and animals are recognized based on contrasting characteristics known as keys. 
• Two contrasting keys are generally kept as a pair, thus leading to acceptance of one and rejection of another.