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Chapter 2: The sub kingdom of Protozoa Introduction All living organisms are categorized into 5 main kingdoms: Bacteria and Archaea, which are prokaryotes (lacking a nucleus and cellular organelles), and the eukaryotes, which include Plantae (plants), Fungi (fungi), and Animalia (animals).However, today other classification including the kingdom of Protista in which several groups of eukaryotic organisms (Protozoa : animals like protists, Algae: plants like Protists and Fungi : fungi like Protists) is proposed.In earlier biological classifications Protozoa and metazoans are classified under the kingdoms of Animalia where unicellular protozoa were considered as simple animals.

Chapter 2: The sub kingdom of Protozoa
Introduction
All living organisms are categorized into 5 main kingdoms: Bacteria and Archaea, which are
prokaryotes (lacking a nucleus and cellular organelles), and the eukaryotes, which include
Plantae (plants), Fungi (fungi), and Animalia (animals). In earlier biological classifications
Protozoa and metazoans are classified under the kingdoms of Animalia where unicellular
protozoa were considered as simple animals. However, today other classification including
the kingdom of Protista in which several groups of eukaryotic organisms (Protozoa : animals
like protists, Algae: plants like Protists and Fungi : fungi like Protists) is proposed.
Definition and General Features of Protozoa
The term "protozoa" refers to primitive, microscopic, and motile organisms.
 Unicellular: Protozoa are single-celled organisms that carry out all necessary
functions for survival, such as nutrition, reproduction, and movement.
 Eukaryotic: These organisms have a defined nucleus surrounded by a nuclear
membrane, and they possess various cellular organelles.
 Heterotrophic: Protozoa do not contain chloroplasts (except for some Flagellates) and
rely on consuming other organisms for nutrition.
 Based on their method of movement, protozoa are classified into:
o Flagellates (Mastigophora): These have one or more flagella.
o Rhizopods: These move using pseudopodia (false feet).
o Sporozoa (Apicomplexa): These are obligatory parasitic protoz