Chapter 1: The Living World

Chapter 1: The Living World

  • What is Living?
  • Diversity in the living world
  • Systematics vs Taxonomy
  • Taxonomic Categories
  • Taxonomic Aids

What is LIVING?

Living means which shows life process such as growth, respiration, nutrition, reproduction.

  • All living organisms grow, increase in mass and increase in number of individual are twin characters of growth. A multi-cellular organism grows by cell division. In plants, this growth by cell division occurs continuously throughout their life span. In animals, this growth is seen only upto a certain age. However, cell division occur in certain tissue to replace lost cells. Unicellular organism also grow by cell division.
  • Reproduction, likewise a character of living organisms
  • Another characteristic of life is metabolism
  • Cellular organisation of the body is the defining feature of life forms
  • Consciousness therefore, becomes the defining property of living organisms


The number of species that are known and described range between 1.7-1.8 million. This refers to biodiversity or the number and types of organism present on earth. There is a need to standardize the naming of living organism such that a particular organism is known by the name all over the world. This process is called nomenclature. Obviously, nomenclature  or naming is only possible  when the organism is described correctly and we know to what organism the name is attached to. This is identification. In order to facilate the study, number of scientists have established procedures to assign a scientific name to each known organism. This is acceptable to biologists all over the world.


A process by which an organism is recognised from the others by already known organism and is assigned to a particular taxonomic group called identification.


Naming of organism according to international scientific rules is called nomenclature. For plants, scientific names are based on agreed principle and criteria, which are provided in International  Code for Botanical Nomenclature (ICBN). Animal taxonomists have evolved International Code of Zoological Nomenclature (ICZN). The scientific name ensure that each organism has only one name.

Carolus linnaeus gives binomial system. Each name has two components- the generic name and the specific epithet. This naming system given by  is being practised by biologists all over the world. Linnaeus proposed scientific name of plants in his book “Species plantarum” and name of animals in his book “Systema naturae”.

Universal rule of nomenclature:

  1. According to binomial system name of any organism consists of two components or words: Generic name (name of genus) and Specific epithet (name of species).
  2. In plant nomenclature tautonyms are not valid i.e. generic name and specific epithet should not be same. But tautonyms are valid in animal nomenclature. eg. Naja naja (Indian cobra) and Rattus rattus (Rat).
  3. First letter of generic name should be in capital letter and first letter of specific epithet should be in small letter.
  4. Scientific name should be derived from latin or greek languages because they are dead languages.
  5. When written with free hand or typed, then generic name and specific epithet should be separately underlined. But during printing name should be in italic to indicate their latin origin.
  6. Name of the scientist (who proposed nomenclature) should be written in short after the species name. But name of scientist should be neither underlined nor written in italics. eg. Mangifera indica Linn.


Classification is the process by which anything is grouped into convenient categories based on some easily observable characters. There are different types of classification.

  1. Practical Classification: In this plants are classified on the basis of their economic importance or human use. Example: Oil yield plants, medicinal plants, fiber yield plants etc.
  2. Artificial Classification: In this plants are classified on the basis of one or two morphological characters. Example: Linnaeus gives a classification on the basis of stamen.
  3. Natural Classification: In this plant are classified on the basis of complete morphological characters. Example: Classification of Bentham and Hooker.
  4. Phenetic Classification: This classification based on number of similarities and dissimilarities. Also known as numerical classification.
  5. Cladistic Classification: Classification based on phylogenetic relationship.

Systematics vs Taxonomy

Taxonomy deals with the identification and classification of the organism. Systematics is the scientific study of the kinds and diversity of living organism and the existing relationship among them. It is the science of diversity of organisms. Some taxonomists treat taxonomy and systematics as similar terms but in reality these are two different terms. Taxonomy deals with the study of living organism and their classification whereas systematics deals with the study of living organisms and their relationship.

Taxonomic Categories

Taxonomic categories

Classification involves hierarchy of steps. Each categories in classification represent unit of classification or taxon. Pleural term of taxon is taxa. Taxonomic categories is also called Linnaean hierarchy or taxonomical hierarchy. It is the classification of organism in a definite sequence of categories in a definite sequence of categories from kingdom to species or from species to kingdom. There are seven categories:

Species: Smallest unit of classification. A group of individual with fundamental similarities (morphological and some time reproductive).

Genus: Group of related species which has more characters in common in comparison to species of other genera.

Family: Group of related genera with still less number of similarities as compared to genus and species.

Order: Assemblage of families which exhibit a few similar characters.

Class: Group of closely related orders.

Phylum: Group of closely related classes with few common characters.

Kingdom: Highest level of classification system.

Taxonomical Aids

Biologists have established certain procedures and techniques to store and preserve the information as well as the specimen, some of these ar explained to help you understand the usage of these aids.

  1. Herbarium: Herbarium is the store house of collected plant specimens that are dried, pressed and preserved on sheet. Standard size of herbarium sheet is 11.5×16.5 inches. Further these sheets are arranged according to a uniformly accepted system of classification. These specimens, along with their descriptions on herbarium sheets, become a store house or repository for further use. The herbarium sheets also carry a label providing information about date and place of  collection, english, local and botanical games, family, collector’s name,etc. Herbaria also serve quick referral systems in taxonomical studies.
  2. Botanical gardens: These specialized gardens have collections of living plants for reference. Plant species in these gardens are grown for identification purposes and each plant is labelled indicating its botanical scientific name and its family. The famous botanical gardens are at Kew (england), Indian botanical garden, Howrah (India) and at National Botanical Research Institute, Lucknow(India).
  3. Museums: Biological museums are generally setup in educational institutes such as schools and colleges. Museums have collections of preserved plant and animals specimen for study and reference. Specimens are preserved in the containers or jars in preservative solutions. Plant and animal specimens may also be preserved as dry specimen. Insects are preserved in insect boxes after collecting, killing and pinning. Large animals like birds and mammals  are usually stuffed and preserved . Museums often collections of skeletons of animals too.
  4. Zoological parks: These are the places where wild animals are kept in protected environments under human care and which enable us to learn about their food habits and behaviour. all animals in a zoo are provided, as far as possible, the conditions similar to their natural habitats. Children love visiting these parks, commonly called zoos.
  5. Key: Key is used for identification of plants and animals based on the similarities and dissimilarities.
    • The key are based on the contrasting characters generally in a pair called couplet. It represent the choice made between the two opposite options. This result in acceptance of only one and rejection of the other.
    • Separate taxonomic keys are required for each taxonomic category such as family, genus and species for identification purpose.
    • Each statement of a couplet in the key is called a lead.
    • Keys are generally analytical in nature.
  6.  Catalogue: It is a small booklet which gives account for books related to botanical titles, full name of author and their publication.
  7. Flora: It contain the actual account of habitat and distribution of plants of a given area.
  8. Fauna: It contain the actual account of habitat and distribution of animals of a given area.

8.Manuals- They are useful in providing information for identification of names of species found in an area.

9.Monographs- They contain information on any one taxon.

Dharmendra Gaur

Dharmendra Gaur (Msc. Zoology) aka DRGP. I love to learn and teach biology. By this blog I want to increase my knowledge and share my knowledge with others. Feel free to ask what ever you want to ask related to biology, I try my best to help you.

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