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Diversity in Living Organisms

Tutormate > CBSE Syllabus-Class 9th Biology > Diversity in Living Organisms

01 Binomial Classification

  • The term “Biodiversity” was coined by Walter G. Rosen in 1986. Biodiversity refers to the diverse or varied forms of living beings which differ from one another in external appearance, size, colour pattern, internal structure, nutrition, habitat, behaviour, etc.
  • Currently, there are around 1.7-1.8 million organisms, all of which are different from one another.
  • Also the number is increasing since there are still species to be discovered especially in the tropics.
  • India is one of the 12 mega biodiversity countries in the world.
  • The country is divided into 10 biogeographical regions.

Binominal Classification: Taxonomy

  • In order to study the vast diversity of species, there was a need to classify them into groups.
  • Taxonomists, a group of biologists, carefully devised a plan to organize the myriad species into one group.
  • Carolus Linnaeus, a Swedish physician, and botanist, classified organisms with shared characteristics in the mid-1700s by the method called binomial nomenclature for biological classification.
  • Thereafter, the art of biological classification was introduced which basically puts organisms into groups and is a part of Scientific Taxonomy.
  • The classification system starts with a group having a wide variety of organisms and becoming more selective as the groups get more specific.
  • The eight groups are as follows:
    • Domain
    • Kingdom
    • Phylum
    • Class
    • Order
    • Family
    • Genus
    • Species


  • A domain is the highest rank of organisms.
  • Taxonomic ranks need to be capitalized, except for species as it helps people to distinguish between bacteria and Bacteria ((the organisms and the domain).
  • The three-domain system of taxonomy (Bacteria, Archaea, and Eukaryota) was designed by Carl Woese in the year 1990.


  • The next highest classification is Kingdom into which living organisms are grouped.
  • All the living species are grouped into specific kingdoms based on factors like the types of cellsthey are composed of, mode of their nutrition and the total number of cells they hold.
  • There are currently five known kingdoms, namely Animalia, Plantae, Fungi, Protista, and Bacteria.


  • The phylum or phyla is the next level after kingdom so that some physical similarities among various organisms within a kingdom could be classed.
  • There are 35 phyla in the kingdom Animalia.
  • Some phyla are phylum Arthropoda, phylum Porifera, phylum Chordata, etc.


  • The classes were the most common rank proposed by Linnaeus.
  • There are about 108 different classes in the kingdom Animalia that were introduced after the 19th century
  • The different classes are class Aves, class Mammalia, class Amphibians, class Reptilia and many others.


  • The organisms of a particular class are further distributed into orders which are much more accurate than the classes.
  • The art of taxonomymostly determines which order an organism belongs to.
  • There are about 18-26 orders of class mammalia which are based on the classification of organisms.
  • The different orders are Order Primates, Order Chiroptera, Order Carnivora, Order Cetaceans, etc.


  • Organisms are further grouped into families.
  • It is the 8th major taxonomic rank in biological classification which can be subdivided into subfamilies.
  • There are totally 15 families in the order Carnivora and 620 families in the Kingdom Plants.
  • The different families of Animal Kingdom are family Canidae, family Ursidae, family Felidae, family Mephitidae, etc.

Genus or genera

  • Genus is the first part of an organism’s scientific name using binomial nomenclature followed by the second part is the species name.
  • For example –Homo sapiens – it is the scientific name given to humans.
  • Homo– genus name and sapiens -species name.
  • In this way, the scientific name of an organism is always italicized, followed by the genus name which should be capitalized.
  • Both Genus and species are the only taxonomic ranks that are italicized.


  • Species is the last and major taxonomic rank which is subdivided into subspecies in certain cases only.
  • There are more than 8.7 millions of different species of organisms on planet Earth.
  • As each genus name is unique, the same species names can be used for different organisms.
  • The species determine the second part of the organism’s binomial nomenclature.
  • The species name should be always italicized, but never capitalized.
  • For example –  Bufo americanus and  Ursus americanus.

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