Biological classification is the scientific procedure of arrangement of living organism into groups. It is done on the basis of their similarities and dissimilarities and placing the groups in a hierarchy of categories.
The first pioneer work on biological classification was done by Linnaeus. He classified living organisms into the two kingdoms, i.e Plantae and Animalia. But this classification system proved to be inadequate as there were many organisms that did not fall into any of the categories. Afterwards, the classification system for living organisms has undergone several changes. However, the place of plant and animal kingdoms remains consistent under all different systems.
In the ancient (Vedic) times, the living organisms were classified into three classes and these were(BCECE 2015).
- Jivaja (Born from the worm or viviparous).
- Andaja (Born from egg or oviparous).
- Udbhija (Born from sprouts).
According to the five kingdom system of classification of living beings, Archaebacteria are monerans which live under extremely adverse conditions, Euglenoids are one of the protists, Phycomycetes is one of the classes of Fungi, and the algae belong to the kingdom Plantae(Kerala CEE 2011).
Mode of nutrition of kingdom – Animalia is heterotrophic. The prokaryotic kingdom monera lack nuclear envelope while Protists are eukaryotic (Kerala CEE 2012).
Mycoplasma is the smallest living cell which is devoid of the cell wall(AIIMS 2012).
Green phytoplanktons are photosynthetic and have chloroplast for carrying out photosynthesis. Since these are unicellular eukaryotic organisms, they are placed in the kingdom – Protista, e.g. Chlorella, Chlamydomonas, etc(Chhatisgarh PMT 2015).