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4. Protozoa (singular : Protozoan) : They are (d) Nutrition : Protozoans are either
unicellular. They may be aerobic or anaerobic. parasitic or saprozoic. Euglena is an
The word protozoa means = “protos”, i.e. exception, it is autotrophic.

primitive and “zoans” i.e. animals. (e) Reproduction : Protozoans reproduce
(a) Habitat : Protozoa are found in water by :
and soil. They can be parasitic as in (i) Binary Fission
human intestine and animal rumen or
they can be free floating. Free floating Amoeba divides

forms of protozoa are called after it has grown
to a certain size.
zooplanktons.
The pseudopodia
(b) Size and shape : Protozoa are the are pulled in and
eukaryotic organisms. Size of protozoa the nucleus divides.
ranges between 10 to 52 micrometre
The cell body begins
Since protozoa lack the cell wall they can to divide when the
nucleus has split.
take up a number of shapes. Examples
of protozoa include Amoeba, Euglena, The daughters of
amoeba
Trypanosoma, Leishmania etc. are formed.

(c) Structure : Protozoa are eukaryotes, as
already mentioned, so they possess a Binary fission in amoeba
structure typical of eukaryotes.
(ii) Spore Formation
Protozoan cell is bound by a cell
membrane and their nucleus is
enclosed by a nuclear membrane. Cell

organelles like vacuoles, etc are present
in cell cytoplasm. Protozoans move with
the help of cilia, flagella or pseudopodia.

Spore formation

(iii) Budding

Bud begins Nucleus Bud now Budding produces
to form on copies becomes a chains of cells
parent cell and divides. separate
The bud daughter
receives cell
a copy
Basic structure of Protozoa
Budding in amoeba

There are 60,000 miles of blood vessels in the human body.

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