Classification of Living Organisms


Organisms differ in their form, structure and mode of living.  Hence, based on their similarities they should be grouped.  The grouping of related organisms helps us in studying their evolutionary relationships. Classification is the division of organisms on the basis of characteristics into groups and sub-groups. A characteristic may be a particular form or function.

History of classification
    •  Aristotle, the Greek philosopher, classified animals based on whether they live on land, in water or in the air.
    •  Charles Darwin put forward the idea of evolution in 1859, in his book, The Origin of Species.
    •  Ernst Haeckel, Robert Whittaker and Carl Woese have tried to classify living organisms into broad categories, called kingdoms.
    •  Carolus Linnaeus classified all the living organisms into two kingdoms namely, ‘Plantae’ and ‘Animalia’. 
    •  Robert Whittaker, in 1969 proposed ‘Five kingdom classification’ of living organisms. 

Hierarchical classification
The hierarchy can be represented as Kingdom subgrouping into Phylum for animals or Division for plants, Class, Order, Family, Genus and Species. Hence, the basic unit of classification is species. Species includes all the organisms that are similar to breed and produce fertile offspring.

The scientific naming of an organism is called as nomenclature. Binomial nomenclature, introduced by Carolus Linnaeus is the method of naming an organism with the genus name first and species name later.

Conventions followed while writing scientific names
    •  Name of the genus begins with a capital letter. 
    •  Name of the species should begin with a small letter. 
    •  Scientific name should be in Italics when printed. 
    •  Genus name and the species name should be underlined separately while handwritten.

Five kingdom classification
The five kingdom classification was proposed by R.H. Whittaker in 1969. The five kingdoms were formed on the basis of characteristics such as cell structure, mode of nutrition, source of nutrition and body organisation. It includes Kingdom Monera, Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.

Kingdom Monera:
It includes prokaryotic cells lacking organised nucleus and membrane bound cell organelles. Some of the Monerans are autotrophic and some of them are heterotrophic forms.Bacteria, cyanobacteria, blue-green algae, mycoplasma are some of the examples of Kingdom Monera.

Kingdom Protista:
It includes algae, diatoms and protozoans. These are unicellular and the simplest form of eukaryotes exhibiting both autotrophic and heterotrophic mode of nutrition. Locomotion and movement are possible by whip-like flagella and hair-like cilia or finger-like pseudopodia.

Kingdom Fungi:
These are multicellular, eukaryotic saprophytes. The cell wall of fungi is made up of chitin.
They feed on dead and decaying matter. They include mushrooms, rhizopus and mucor. Some fungi are symbiotic forming an association with algal cells. These symbionts are termed to be lichens.

Kingdom Plantae:
It includes all the plants that are non-motile, multicellular and eukaryotic organisms with their cell walls made up of cellulose.
These are complex organisms which can perform photosynthesis.
Plants comprise cells with thick cell walls.
Plant cells are rigid nd cannot be comprssed
Plants are immobile, they cannot move from one place to another.
Plants have unlimited growth.

Kingdom Animalia:
It includes all the animals that are motile, multicellular, eukaryotic organisms with their cells possessing no cell walls. It exhibits species diversity.
Members of this kingdom are complex oganisms with tissue differentiation.
Nutrition is heterotrophic .
Well developed organ systems with division of labour.
animals are ecologically meant to be consumers.


  • HD 10:34 Animated video Lecture for Classification of Living Organisms
    LearnNext Video
  • YouTube Video
  • YouTube Video
  • YouTube Video
  • YouTube Video

Activities & Simulations

Activity 1 has built a design to explain the concept of 'Diversity'. It is an user-friendly template which displays the classification of animals in the form of a 'Tree diagram'. By clicking on the buttons displayed in the tree diagram, student can know the base point which the organisms are categorised. By clicking on the images displayed, user can know the names of the organisms which serve as examples to that particular group.   
Go to Activity

Activity 2 has constructed a small game to make students familiar with organisms like fungi, protozoa and protista. Student can play video to know about these organisms. Student can also take a test under each topic displayed by clicking on 'Test yourself button'. Different aspect of playing karoake is also given to the student as a choice.
Go to Activity

Questions & Answers

1 . why are Bryophytes called the Amphibians of the plant kingdom?
Amphibians are those organisms which live on both land and in water. Bryophytes are called amphibians of the plant kingdom because these pla...
2 . Bring out any five differences between cryptogams and phanerogams.

Differences between cryptogams and phanerogams

Cryptogamae: This sub-kingdom includes plants which do not fl

3 . 9th class SA1 syllabus
4 . Why do bryophytes and pteridophytes grow well in moist and shady places ?
 they can't with stand to sunlight and they are adapted for shadow and moisture places
5 . how are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?
Animal Kingdom:  organisms that usually move around and find their own animals

Plant Kingdom: organi