Taxonomical Hierarchy | Class 9 Biology

An organism with a different sizes, shapes, modes of nutrition, reproduction mode, habitat, etc. exists on the planet earth. In every species, there are hundreds of similar species which are found to show similar characteristics. Diversity among the living species increases day by day as every day new species are getting discovered so to make their study easy it is very important to categorize these species in an order in which we can remember them that’s why the hierarchy groups are formed to make a better understanding of the species. All the animals may vary in many things like shape, size, nutrition, reproduction, habitat, etc. but they all carry one thing in common i.e., cells. As we all know that all the functions and metabolic activities in our body are performed by cells and these are the building blocks of the body. Tissue is formed from a group of cells that perform similar functions as a group together. The level of organization varies in every organism. The more advance the animal is more advanced its level of organization will be. Diversity can be seen on the basis of many different things like temperature, land, water, etc. Some species can look alike but the genetic makeup of every species is different even if they belong to the same group. This genetic material makes every species unique in its own way. In the evolution over million years, a wide variety of diversity has developed in living species. Human beings have now become homo sapiens from ape-like creatures. To divide species into categories similarities in species are considered.

 Taxonomical Hierarchy

This classification is given by Carolus Linnaeus for the first time. In this, there are groups from top to bottom on the basis of their similarities. As we go down this classification the similarity in species among groups increases. These are taxonomic groups at different levels. If we go in the history of hierarchy classification then on the basis of characteristics, habitat, etc. the animals were first classified by Aristotle who was a Greek philosopher. After him, Carolus Linnaeus classified the animals and introduced Taxonomic Hierarchy Categories. To the modern date this classification is followed. Arranging the categories in increasing and decreasing order is called as Taxonomic Hierarchy. Here the highest rank is Kingdom and the Hierarchy is the lowest. Let’s get started with the highest rank category.

Kingdom

In the modern classification according to Carl Linnaeus, the highest rank is given to Kingdom but actually, it comes in second place after Domain. In the five-kingdom classification, mainly five kingdoms are made that are Animalia, Plantae, Fungi, Protista, and Monera. The Kingdom includes all the species without any categorization of animals all the animals have included dogs, cats, insects, sponges, etc. but when we go deeper into the classification, we can differentiate the animals on the basis of their similarities and differences.

Phylum

Next in the line, we have Phylum. As compared to the kingdom, the phylum is more specific. Instead of division, the phylum term is used in botany. There are 31 phyla in the animal kingdom whereas 14 phyla in the kingdom Plantae and for fungi, we have 8 phyla and all these phyla are divided on the basis of their similar characteristics. For e.g., in the phylum Porifera, all those animals are kept which have pores on their body which is also the distinguishing feature of this phylum. And so, all these phyla are made to make the classification easy for us. Ernst Haeckel was the person who coined the term phylum in 1866. Basically, based on the general specialization of body plan the group of organisms is called phyla.

Class

This is a taxonomic rank that comes between phylum and order while decreasing the order of life. It is also considered as a rank, unit, and taxon in the language of biology. In 1694 French botanist whose name was Joseph Pitton de Tournefort coined the term class in his book which was on the classification of plants. By the subjective judgment of taxonomists composition of every class is determined. Different taxonomists taking different positions don’t have any proper agreement in Kingdoms of Nature which is the first edition of Systema Naturae in 1735 written by Carl Linnaeus. In this book for the first time, he divided minerals, animals, and plants into classes. Until the phyla by Ernst Haeckel is introduced in the early nineteenth-century class was the highest rank in the hierarchy.

Order

In the Linnaean taxonomy order is eight major hierarchical taxonomic ranks. In between family and class falls order category. On the basis of nomenclature codes organisms are divided into different orders (taxonomic rank). There’s a higher rank than the order which is used very rarely above order i.e., superorder and there is one rank lower than the order which is suborder. These two categories are used very rarely in some organisms only. The similarity in the species occupying the same order is much more than it is in Kingdom or any other category. A taxonomist is the one who decides the traits of a particular order so that it can be recognized as a separate order. An exact agreement doesn’t exist for different positions taken by the different taxonomists. Not all the orders are accepted universally only some are accepted while others are recognized rarely. The reason behind this is that there are some hard-core rules for taxonomists have to follow during the formation of any separate orders. There are some suffixes that make it easier to recognize order in classification and these are as follows- Fungi, plants, and algae use the suffix- ales. For e.g., Dictyotales Fishes and birds use the suffix- i. For e.g., Passeriformes Invertebrates and mammals are not consistent in using these suffixes. For e.g., Primates, Actiniaria, Artiodactyla, etc.

Family

Family is a taxonomic rank that falls after order and before genus. This rank usually has a sub-category that is widely used in classification i.e., subfamilies that fall between family and genus. The common name of the families is much more popular as the scientific name of families is in the Latin language. For e.g., Juglandaceae is the scientific name of a family which is commonly called hickory trees and walnut trees. This family is popularly known as the walnut family (which is its common name). Rules are set for the formation of any new family which has to be followed anyhow by the taxonomists who are working on it. The families that are made are then cross-checked by the team of experts before it is recognized by the universe to see whether the rules are followed or not. Sometimes it takes a lot of time to make a new family division with all the adjustments and consensus.

Genus

In the name of every organism, there are two parts the starting part is Genus in binomial nomenclature. All the similar species come under the same genus. This is a taxonomic rank that falls between family and species. This rank plays a very important role in the classification of an organism as it is the first name of any organism. For e.g., the genus of lion and jaguar is the same i.e., Panthera but the species are different i.e., the lion is Panthera leo and the jaguar is Panthera onca. As there are no specific codifies with the name of genus o different taxonomists sometimes give different names to organisms. There are basically three criteria that have to be fulfilled for the name of the genus and they are as follows.

• Group together all the heirs of the ancestral taxon.
• The name of the genus should not be extended especially when there’s no need for it.
• The name of genera should be composed of phylogenetic units of the same kind of genera or other.

Species

The basic unit of classification is known as species. This is the last rank of taxonomic classification if we move from top to bottom. The species name for every organism is different as every species is one of its own kind. There are approx. 8 to 8.7 million eukaryotic species. Out of these only, 14 % have been classified till 2011 and the rest are still unidentified. Except for viruses, the name of every organism in binomial nomenclature has two names and species is the second name of the organism which is unique for every organism. There are some organisms that also have subcategories in this rank known as subspecies. The concept of species also has some loopholes and which create some controversies in the names of the species like we can not differentiate between similar species and also the ones which are hybridized. Evolution causes a change in the species and due to this, the names of the species become debatable.

Uses of the Classification

• For the convenient study of organisms, around us, it is important to classify them.
• For better information about organisms, it is important to know the different varieties of organisms which can only be understandable by classification.
• To know the origin and evolution of organisms it is important to classify them.
• The exact position of an organism is determined by classification.
• Phylogenetic relation between another group of organisms can be determined by the classification of organisms.
• For the correct identification of organisms, it is very much needed to classify them in the proper classification system.
• Classification of organisms makes it easier for us to study and memorize them.

FAQs on Taxonomical Hierarchy 

Question 1: Explain the need for diversity in the environment.

Answer:

Change is a rule of the environment. For the balance of the ecosystem, evolution is important and evolution brings changes in the existing organisms which brings diversity. Diversity leads to creativity and it increases the curiosity of new organisms. For the research and development of organisms, diversity is very much needed.

Question 2: Give the advantages of classification.

Answer:

• Identification of organisms can be determined by classification.
• It gives new scope for the research of organisms and evolution.
• It also tells us the importance of evolution.
• The study of organisms becomes easy and now due to classification, it is easier to learn and memorize living organisms.

Question 3: What is the way to describe the hierarchy of classification.

Answer:

There is a proper sequence of classification from top to bottom in order of increasing the similarities in the organisms which is the Kingdom at the top continued by phylum, class, order, family, genus, and species. Any organism has a proper classification based on this flow. Through this, we can easily know that the organism belongs to which class or order or family.

Question 4: Give the key features of this classification.

Answer:

There are some features on the basis of which the classification is done which are mode of reproduction, presence of membrane-bound organelle, unicellular or multicellular organism, prokaryotic or eukaryotic, mode of nutrition, etc.

Question 5: Give the reason why system of classification changes with time.

Answer:

Due to evolution, there is a change in organisms. Moreover, day by day new organisms is getting discovered. To classify these new organisms, we have to adapt a new system of classification so that the new species can be adjusted in the classification system.