Protozoa are a diverse group of unicellular eukaryotic organisms that are heterotrophic and lack chlorophyll. They range in size from 1-150 micrometers and can be naked or covered by a pellicle. Locomotion is via pseudopodia, cilia, or none. Nutrition is holophytic, holozytic, saprophytic or parasitic. Reproduction can be sexual via conjugation or asexual via binary fission. Protozoa are classified into Sporozoa, Ciliophora, Rhizopoda, and Zoomastigophora. They can be beneficial by providing food, controlling insects, and purifying water, or harmful by poll

1. by,
K.ThangaMallika
I M.Sc., Microbiology

2. PROTOZOA
 Protozoa are a diverse group of unicellular eukaryotic
organisms.
 The word “protozoa” by coined by GEORG AUGUST
GOLDFUSS in 1818.
 They are heterotrophic organisms and they donot
have chlorophyll.
eg: Amoeba, paramecium, euglena.

4. CHARACTERISTICS
 A protozoan body consists of only mass of
protoplasm, so they are called acellular or non-cellular
animals.
 HABITAT - mostly aquatic, either free living or
parasitic.
 SIZE - most protozoans are in the size of 1 to 10
micrometer long, but Balantidium coli may measure
150 micrometer.

5.  BODY- body of protozoa is either naked or covered by a
pellicle.
 LOCOMOTION- locomotary organ are pseudopodia or cilia
or absent.
 NUTRITION - nutrition are holophytic (like plant) or
holozoic (like animal) or saprophytic or parasitic.
 DIGESTION - digestion is intracellular, occurs in food
vacoules.

6.  RESPIRATION - respiration occurs through the body
surface.
 OSMOREGULATION – contractile vacoules helps in
osmoregulation.
 In most protozoa, the cytoplasm is differentiated into
ectoplasm (the outer, transparent layer) and endoplasm
(the inner layer containing organelles).
 The structure of cytoplasm is mostly seen in species with
projecting pseudopodia, such as amoebas.

7.  REPRODUCTION - reproduction occurs by both sexual
and asexual reproduction.
 Asexual - usually by binary fission.
 Sexual - happens by Conjugation .
 NUCLEUS - Nucleus may be compact with diffuse
chromatin or vesicular with central or eccentric karyosome
(DNA) and peripheral chromatin (RNA).
 RESPIRATION – respiration is mostly anaerobic.

8. CLASSIFICATION OF PROTOZOA

9. SPOROZOA
 Commonly parasitic on
vertebrate animals.
 Locomotory organ and
contractile vacuoles are
absent.
 Body covered with pellicle.
 Exclusively endoparasites.
 Reproduction by means of
asexual and sexual.
 Examples: Plasmodium,
Monocystis.

10. CILIOPHORA
 Complex freshwater or
saltwater protozoan.
 It swims by the coordinated
beating of their cilia.
 Nuclei is of two types:
micronucleus and
macronucleus.
 Body is covered by pellicle.
 Examples: Paramecium,
Voricella.

11. RHIZOPODA
 These are amoeboid
organisms that produce false
pseudopodia.
 It preys on fungi , other
protists and small
invertebrates.
 Reporduction by means of
sexual and asexual.
 Mostly free living, some are
parasitic.
 Examples: Amoeba,
Entamoeba.

12. ZOOMASTIGOPHORA
 It is characterised by one or
more flagella.
 Free living or parasite.
 Body covered with cellulose,
chitin or silica.
 Sexual reproduction occurs
by longitudinal fission.
 Examples: Trypnosoma.

13. ECONOMIC IMPORTANCE OF
PROTOZOA
Protozoans are classified into two types based on
their activites.
 Harmful protozoa
 Beneficial protozoa

14. BENEFICIAL PROTOZOA
 Food - Protozoa provide food for insect larvae and
worms, which are taken by fishes and crabs and which
are eated by man.
 Insect control - Several protozoa control harmful
insects by persisting their bodies.
 Helpful in Sanitation - A large number of protozoa
living in polluted water feed upon organic matters and
thus purify it.

15.  Oil exploration - Petroleum is organic origin. The skeletal
deposit of Forminifera and Radiolaria are often found in
association with oil deposits. In this means, they help in
the exact location of oil.
 Scientific study - Many protozoa are used in biological and
medical researches.

16. HARMFUL PROTOZOA
 Pollution of water - Drinking water in natural condition is
made unpalatable by the reproduction of some free living
protozoa in it.
 Destruction of wooden articles - Some flagellater like
Trichonympha and Colonympha live in the gut of termites
and help in cellular digestion.
 Reduction in Fertility of soil - Protozoans feed on nitrogen
fixing bacteria thus reduce the fertility of soil.