Protozoa: Definition, Characteristics, Classification and their Types

Single-celled species are known as protozoa. They come in a variety of shapes and sizes, ranging from amoebae that can change shape to paramecium, which has a complicated structure and shape. They can survive in a wide range of habitats, including freshwater, coastal environments, and soils.

The main distinguishing features of Protozoa are given below.

They are devoid of a cell wall. Some, on the other hand, have a stiff inorganic shell outside the elastic layer, called a shell or cell membrane.
They are capable of being transmitted throughout their life via locomotive or a gliding mechanism.
It has a heterotrophic nutritional mode in which the free forms look at particles like bacteria, yeast and algae and their nutrition is derived from their hosts' body fluids.
They are unicellular with some colonial and multidimensional stages.
Most are microscopes.
All balances are present in group members.
No germ layer is present.
No organs or tissues are formed, but specialized organs perform many of these functions.

Protozoa classification:

The protozoan classification is mainly based on the means of migration. The succeeding four classes are grouped into (or sub files by some taxonomists). The species are described in detail with an asterisk.

1. Sarcodina

The movements are because of the ectoplasm's flow, which produces so-called pseudopodia projections (false feet). For instance: Amoeba protease* like the free life form and Entamoeba histolytica like the parasite form.

2. Mastigophora

One or more weight-like structures known as flagella are influenced by localisation. For instance: free live forms like Euglena Verdi's, Trichomonas langicada, heteronyms, parasite forms like Trichomonas vagina or Trypanosoma, Guardia lamblia. For instance: free live forms.


The location is made by short projections like the hair called cilia, which move the body when they are beaten together. Parasite forms such as cadmium pyrethrum, polymorphic stentors, bell ribs, and separate forms such as balantidium, for example.


Class members of Sporozoa do not have organelles at the maturation stage, contrary to the three classless protozoa noted above. Unintentional forms, however, denote movement of some sort. This group is all members of parasites.

Based on the style of nutrition, Protozoa are of the following two types:

1.Protozoa are self-contained living organisms that consume particles such as bacteria, yeast, and algae
2.Parasitic protozoa: They obtain nutrients from their hosts' bodily fluids.

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