3) Classification of Organisms

Classification of organisms started as early as premedieval times when scientists try to classify organisms into various classifications based on observable features. Carl Linnaeus's method of classification took popularity in the 18th century who grouped species according to shared physical characteristics (eg presence or absence of vertebral column).

Portrait of Carl Linnaeus, 1707 - 1778. Source: National Portrait Gallery Gallery, London

Besides shared physical characteristics, current classifications have taken into consideration other factors like descendency of the organism as well as genetic factors. Each organism can be classified into various degree of specificity with life being the most general and the species being the most specific. Naming of an organism usually begins with GENUS followed by SPECIES.  Eg. Scientific name of humans is Homo sapiens, dogs would be Canis familiaris.

                              Modern biological classification of living things.

The diagram shows the various approaches to classifying organisms used by scientists. The most current one is the use of the three domain systems - Bacteria, Archae and Eukarya. Eukarya would then consist of kingdoms - PLANTAE, ANIMALIA, PROTISTA and FUNGI. 

Click on link to find out the total no of species in this world.

Group Discussion:

Do you think the method of classification is constant? Support your answers with appropriate examples.