Protozoans – Animal–like Protists
Protozoa are one–celled eukaryotes. That implies that protozoa are unicellular microbes whose cells
have membrane–bound nuclei that commonly show characteristics usually associated with animals – mobility and heterotrophy. Protozoan Protists (Animal-like protists) : The name ‘protozoan’ (singular form of Protozoa) is derived from the Greek words (in Greek proto = first and zoa = animals) meaning ‘first animal’.
Protozoa are one–celled eukaryotes. That implies that protozoa are unicellular microbes whose cells have membrane–bound nuclei that commonly show characteristics usually associated with animals – mobility and heterotrophy. The single cell of the animal is capable of performing all the functions of life like nutrition, respiration, excretion, locomotion and reproduction. In size, they range from 2 to 200 microns. Ex: Amoeba, Paramecium, Euglena, Plasmodium, Trypanosoma.
Protozoa live nearly everywhere on earth, in water and moist soil. They are found in ponds and puddles. They are also found on decaying leaves and dead organic matter as saprophytes. Some of them may also be found living inside the body of other organisms as parasites. They obtain their food from other living things. The parasitic forms absorb digested food from the host. Amoeba is the simplest and most common of all protozoa. Some protozoa are oval, spherical or elongated, while others, like the Amoeba lack any definite shape. Protozoa are often included in the animal kingdom as they do not possess cell wall and lack chlorophyll. A typical protozoan cell contains a definite nucleus along with mitochondria and other membrane– bound cell organelles.