The five kingdom classification, that is proposed by RH Whittaker is based upon cell structure, body structure (unicellular, multicellular), nutrition (autotrophic, heterotrophic) reproduction and way of living either aquatic, terrestrial, or arial and phylogenetic relationship. So, it is more useful as compared to two kingdom system of classification which does not distinguish between prokaryotes and eukaryotes and no other kingdom except plant and animal are identified.

Polluted water bodies possess high algal growth due to the presence of nutrient. These nutrients increase the rapid growth of water plants, i.e., algae especially Nostoc and Oscillitoria, etc., and result in colonies. These colonies are generally surrounded by a gelatinous sheath and furtherleads to the formation of blooms in water bodies.

Chemosynthetic bacteria are capable of oxidising various inorganic substances such as nitrates, nitrites and ammonia and use the energy released for their ATP production. So, they are autotrophs and not heterotrophs.

The common or vernacular names changes with the change in place, causing confusion regarding the identification of specific specimen, whereas the complex scientific names are in latin and universally accepted and understood. Hence, scientific names are preferred over the common vernacular names.

Viruses are considered as living when they are inside a host but outside any host they are referred to as non-living due to their

(a) inert nature

(b) inability to reproduce

(c) lack of cellular organisation

(d) inability for growth and cell division

These characters potraited by viruses make them identical to non-living organisms. Viruses are considered a connecting link between living and non-living organisms.