Protozoa are microscopic, unicellular eukaryotic organisms that can be free-living or parasitic. They have simple body structures without tissues or organs. Their protoplasm is organized into an outer ectoplasm and inner endoplasm, and they may contain one or more nuclei. Protozoa can reproduce asexually through fission, budding, or sporulation, or sexually through gamete formation or conjugation. They obtain nutrients through holozoic, holophytic, or parasitic means of nutrition and excrete waste through diffusion.

2. Minute, Microscopic & Eukaryotic organisms
Unicellular –without tissues and organs
Simple body organization – protoplasmic grade
They may either be free-living or parasitic. Some
are commensals in habit.

3. • Body is either naked or covered by a pellicle /
plasmalemma /theca /lorica.
• Protozoans are either solitary or colonial; in colonial
forms, the individuals are alike and independent.
• Asymmetrical / bilaterally/radial symmetrical.

4. • The protoplasm - outer ectoplasm and
inner endoplasm
• They may have one or more nuclei. Nucleus may
be monomorphic or dimorphic, vesicular (e.g. Enta
moeba) or massive (e.g. Amoeba)

5. Nutrition - holozoic / holophytic / parasitic.
In Euglena, the mode of nutrition is mixotrophic
(both holozoic and holophytic)
Digestion - intracellular.
Respiration - diffusion
Excretion - Diffusion- ammonotelic
Contractile vacuoles perform osmoregulation

6. • Reproduction - sexual or asexual method
• asexual - binary reproduction occurs by fission, multiple
fission, budding or sporulation
•
• sexual reproduction occurs by gamete
formation or conjugation.
• Encystment - unfavorable conditions and it also helps in
dispersal.