Describe briefly the four major groups of Protozoa.

(A-D) Protozoa are microscopic unicellular protists with a heterotrophic mode of nutrition. They may be holozoic,saprobic,or parasitic. They are divided into four major groups:
$(1)$ Amoeboid protozoa: These are unicellular,jelly-like organisms found in fresh water,sea water,or moist soil. They lack a periplast and may be naked or covered by a calcareous shell. They use temporary protoplasmic outgrowths called pseudopodia for movement and capturing prey. Examples include $Amoeba$ (free-living) and $Entamoeba$ (parasitic).
$(2)$ Flagellated protozoa: These are free-living or parasitic,non-photosynthetic organisms that possess flagella for locomotion and capturing prey. An example is $Trypanosoma$,which causes sleeping sickness in humans.
$(3)$ Ciliated protozoa: These are aquatic organisms characterized by the presence of numerous cilia on their entire body surface and two types of nuclei. Cilia beat in a coordinated manner to move food-laden water into a cavity called the gullet. Examples include $Paramoecium$ and $Vorticella$.
$(4)$ Sporozoans: These include diverse organisms,most of which are disease-causing endoparasites. They are uninucleate,covered by a pellicle,and lack locomotory organelles like cilia or flagella. $A$ well-known example is $Plasmodium$,which causes malaria.