Polluted water bodies (Ponds, ditches and rivers etc.) have usually nutrient contents (such as nitrate, phosphates) domestic sewage primarily contains biodegradable organic matter. Presence of large amount of nutrients in waters also causes excessive growth of Planktonic (free floating algae) called an algal bloom, which imparts a distinct colour to water bodies. Algal bloom causes deterioration of the water quality and fish mortality. Some bloom forming algae mainly Nostoc and Oscillitoria are extremely toxic to human beings and animals.

Cysts formation helps to overcome unfavourable condition for reproduction.

Due to the presence of rapid asexual reproduction.

It occurs by conjugation. It involves transfer of genetic material from one bacterium to another through cell to cell contact.

Parasites have phagotrophic and absorptive type of nutrition.

Euglene, dinoflagellates and zooflagellates.

Cell wall in diatoms is made up of cellulose and pectin compounds. It is two-valved layer called frustule.

Halophiles contains a chemical called  halorhodopsin that pumps chlorides into the cells and prevents cellular dehydration.

Halophiles live in habitats having high salinity and high light intensity. Examples are Halobacterium and  Halococcus.

Plantae, Protista, and Animalia

Ernst Haeckel (1866)

Linnaeus proposed the two kingdom classification in  1758

Aristotle divided animals in two groups. These are Enaima (with red blood ) and Enaima (without red blood)

Anisogamy, it occurs in Ceratium, a dinoflagellate.

Slime moulds are saprophytic protists that possess all these characteristics.