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An important question that arises when we are studying organisms is why are living organisms classified? The classification of living organisms helps to eliminate confusion regarding the study of organisms.
- Studying about living organisms helps us understand the relationship between various organisms.
- The classification of living organisms helps determine the characteristics of living organisms.
- It will also determine how a particular type of organism is known differently in different parts of the world.
- Living organisms differ in terms of size, shape, mode of nutrition and methods of reproduction.
- They are divided into kingdoms, phyla and classes.
- We are surrounded by different types of plants, insects, birds and animals.
- Another reason why are living organisms classified is to determine organisms mode of nutrition and life cycle.
Key Terms: Living Organisms, Nutrition, Reproduction, Plants, Insects, Animals, Classification, Kingdom, Phylum, Class, Order, Family, Species, Genus
Why are Living Organisms Classified?
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It is essential to classify living organisms into different categories to study microorganisms easily by avoiding confusion and defining proper relationships between different living organisms.
- Species are classified into different categories based on their character, names, mode of nutrition, life cycle, and habitat.
- It also avoids confusion about the genetic and physical qualities of living organisms.
- Classification makes the study of different organisms easier in this huge and complex diversity.
- Organisms are classified into seven levels, which include kingdom, class, order, phylum, family, species, and genus.
Classification of Living Organisms
Advantages of Biological Classification
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The following are the advantages of biological classification of living organisms:
- It will help understand the relation between plants, animals, and other species.
- Biological classification helps in understanding the usefulness of organisms in relation to humans.
- Inter-relationships between different organisms will be enhanced with the help of classification.
- An important advantage of biological classification includes the detection of present and extinct organisms.
- The organisms are classified according to their features.
- We can learn about the evolution of any organism.
Read More:
| Chapter Related Concepts | ||
|---|---|---|
| Phenotype | Anagenesis | Genetics and Evolution |
| Ecology | Speciation | Speciation |
What is Classification?
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Classification is a process of dividing organisms on the basis of similarities and dissimilarities. The manner of classification of living organisms keeps changing as scientists discover new physiological qualities of animals every day.
- The binomial nomenclature is a modern system of classification which was created by Carl Linnaeus.
- It consists of characteristics such as the type of cell, the type of body organization, and the type of food generation.
- The difference between plants and animals and plants and algae display clear differences at the body organization level.
- Unicellular organisms such as cyanobacteria are different from plants and algae.
- Genetic qualities are also included in the classification system.
- Phylogenetic trees show the relationship between different organisms.
- As you move higher in the classification hierarchy towards plants and animals, the branching becomes more complex and diverse.
Basis of Classification of Organisms
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The classification of organisms is based on three categories which are as follows:
Type of Cell
Organisms are classified on the basis of eukaryotic or prokaryotic cell on the basis of organization of the nucleus or the cell organelles.
Type of Body Organization
Organisms are divided into unicellular organism or multicellular organisms category depending upon the type of functions carried out of the cell of organisms.
Type of Food Organization
Plants and animals comes into the category of food organization. These organisms are divided on the basis of their ability to make their own food.
Modern System of Classification
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There are seven levels of classification of living organisms which are as follows:
Kingdom
There are five kingdoms founded by Robert Whittaker in which living being is classified into. The categorization of living being in different kingdoms are based on many factors such as
- Type of cell which makes up their body
- Food habits.
- The number of cells they contain.
- The five kingdoms are protista, monera, Plantae, Fungi, and Animalia.
Phylum/division
There are many physical similarities between kingdom and phylum. The word and concept of the phylum are used in the animal kingdom while the concept of division is used in the plant kingdom.
- The animal kingdom contains 30 phyla.
- Insects are part of the Arthropoda phylum and humans belong to the Chordata phylum.
Class
The organisms of the phylum are further divided into classes. Class display more similarities than that of the phylum.
- There are a total of 87 classes of organisms in the animal kingdom.
Order
Order is a list of characteristics that decides the group of the organism. Each class is further broken down in order.
Family
Families are the more specific and detailed form of order. There are more similarities among the organisms in the family than any other classifications above.
- The family of humans is Hominidae.
Genus
The genetic name of an organism is known as the genus. There are limited organisms within each genus and there exists a wide variety of genera among plants and animals because the classification in the genus is very specific.
- The first part of the two-part name of any organism is determined by the genus.
Species
Species are the lowest and the strictest part of classifying organisms. The ability of a particular species to reproduce with the other organisms of the same species the basic factor.
- The second part of the two-part name of an organism is determined by the species of an organism.
Taxonomy
Read More:
| Class 12 Biology Related Concept | ||
|---|---|---|
| Reproduction in Plants | Heredity and Evolution | Charles Darwin Theory |
| Origin of Life | Life Process | Natural Selection |
Things to Remember
- Classification of living organisms is based on their ability to reproduce.
- Herbarium is a taxonomical aid where dried plant specimens are stored and preserved on sheets.
- The study of different relationships between an organism through evolution is known as systematics.
- The scientific names of the organisms have two parts- generic names and specific epithets.
- Binomial nomenclature is the system of giving scientific names to the two components of organisms.
- The process of grouping organisms according to different characteristics is known as classification.
- The classified organisms are grouped in different categories known as taxa.
Sample questions
Ques. What is taxonomy? (2 marks)
Ans. Taxonomy is the study of naming and classifying organisms. It is prone to changing nature because of innovations and discoveries in the field every day.
- Taxonomy includes all the plants, animals, and microorganisms present in this world.
- Various species are named and classified on the basis of similarities and dissimilarities present in them which is possible through taxonomy as it is a huge branch of biological sciences.
Ques. Who are the notable biologists in the field of classification? (2 marks)
Ans. Besides carl Linnaeus who is the founder of the modern system of classification. There are many other notable biologists in the field of classification which includes Robert Whittaker, Ernst Haeckel, and carl woese who have already made an impactful contribution to modern classification.
Ques. What is a taxon? Explain with examples? (3 marks)
Ans. Taxon is the unit or category of classification which represents a rank. The different categories of classification of a species in ascending order are termed taxon. For eg:
| Phylum/division | Class | Order | Family | Genus | species |
|---|---|---|---|---|---|
| Green alga | Fern | Mushroom | Grass | Eucalyptus | neem |
| Roundworm | Bird | Lizard | Elephant | Wolf | dog |
Ques. What is key and how Is it helpful in the identification and classification of an organism? (3 marks)
Ans. In order to identify and classify the organisms easily and properly, biologists and scientists take the help of a taxonomical key. Similarities and dissimilarities in a character are detected by the keys generally in a couplet pair.
- Lead is identified as each statement in the taxonomical key.
- Keys are essential to identify unknown organisms and categorize each taxonomical rank such as family, species, genus, etc.
- The two major types of keys are- intended and bracketed keys.
Ques. Illustrate the taxonomical hierarchy of man? (2 marks)
Ans. Following is the illustration of taxonomical hierarchy of man:
- kingdom – Animalia
- Phylum – chordate
- Class – Mammalia
- Order – primate
- Family – Hominidae
- Genus – homo
- Species – sapiens
Ques. Why living organisms are divided into different category? (3 marks)
Ans. The reason why living organisms are classified are as follows:
- Classification of organisms help in the identification of living organisms.
- It provide deep analysis about relationship between different groups of organisms.
- The process also explains how complex organisms are divided into simpler organisms.
- It is used for development of other biological sciences.
- It determines difference in characteristics, similarities, and differences between plants and animals.
Ques. What are the advantages of biological classification? (3 marks)
Ans. The advanatages of biological classification are as follows:
- Biological Classification involves deep understanding about evolution of organisms.
- It divide organisms based on their features.
- It help in the identification of organisms that are present and extinct.
- Biological classification help determine the usefulness for human welfare.
Ques. What is the difference between prokaryotic and eukaryotic cells? (5 marks)
Ans. The difference between prokaryotic and eukaryotic cells are as follows:
| Prokaryotic Cells | Eukaryotic Cells |
|---|---|
| Prokaryotic cells are unicellular in nature. | Eukaryotic cells are both unicellular and multicellular in nature. |
| The DNA are arranged in circular fashion. | The DNA are arranged in linear fashion. |
| In these cells, mitochondria are absent. | In these cells, mitochondria are present. |
| It consists of small ribosomes. | It consists of large ribosomes. |
| The cells produce asexually. | The cells produce asexually and sexually. |
Ques. How organisms are classified? (3 marks)
Ans. Organisms are classified on the basis of three categories which are as follows:
- Based on type of cell: Organisms are classified on the basis of eukaryotic or prokaryotic cell on the basis of organization of the nucleus or the cell organelles.
- Based on type of body organization: Organisms are divided into unicellular or multicellular category depending upon the type of functions carried out of the cell of organisms.
- Based on type of food organization: Plants and animals comes into the category of food organization. These organisms are divided on the basis of their ability to make their own food.
Ques. Why scientists need to classify organisms? (3 marks)
Ans. There are billions of species on our planet; we only know the names of the plants and animals that are visible to us. Within a nation, these regional or colloquial names differ from one location to another.
- This makes it difficult to distinguish between and research several species.
- Therefore, in order to standardize language and the study of organisms, it must be referred to by its scientific name globally.
- Organisms are named and grouped based on their traits in order to fulfill this purpose.
Ques. Explain the different rules of nomenclature? (4 marks)
Ans. The different rules of nomenclature are as follows:
- Biological names are derived from Latin and written in italics.
- They are named irrespective of their origin.
- The first section of the word represents the genus and starts with a capital letter.
- The second section of the word represents specific epithet and starts with a small letter.
- Both the words are underlined or written in italics to indicate their nature.
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