Protozoa I

1. The
Protozoans

2. Common Protozoa of Man

3. Introduction
• The distinction between
plant- like & animal-
like organisms is not
always easily made,
particularly among
unicellular life forms.
This difficulty reflects
what is surely a distant
but very real
evolutionary
relationship between
plants & animals.
• Protozoans are clearly

4. • Protozoan classification has
long been uncertain,
however, nucleotide
sequence data in particular
are changing the scenarios
of protozoan
interrelationships at a rapid
rate.
• Controversy abounds at the
most fundamental levels
of organization. Of
particular interest,
hundreds of unicellular
species lack mitochondria.
Whether these species

5. General Characteris tics
• It is difficult to
generalize about
protozoans; they
absolutely defy tidy
categorization.
• Structural
Description of A
Protozoa:
The entire
protozoan body is
bounded by a

6. • The cytoplasm bounded
by the p l a s ma l e mma
resembles that of
animal cells, except
that it is often
differentiated into a
clear, gelatinous outer
region, the e c t o p l a s m, &
an inner, more fluid
region, the e nd o p l a s m.
• Contractile vacuoles
are organelles involved
in expelling water from

7. Phylum
Ciliophora

8. Defining Characteris tics
• Body externally
ciliated in at least
some life cycle stages.
• Individual cilia are
connected below the
body surface through a
complex cord of fibers
(the infraciliature).
• Ciliates show the
highest degree of
subcellular
specialization
encountered among

9. • First among the
features of this
phylum is the
presence of the
external ciliation in
at least some stage
of the life cycle.
• The ultrastructure
of cilia is
remarkably uniform
throughout the

10. S tructure & F unction of Cilia
• Each cilium is
cylindrical & arises
from a b a sa l b o dy
(kinetosome). Within
the cilium are a
number of long rods
called mic r o t ub ul e s ,
composed of a
protein known as
t ub ul in.
• A cross section

11. • One pair of microtubule
is located centrally
within the cilium. These
two microtubules form
the central shaft the
cilium, and they are
often surrounded by a
membrane constituting a
c e nt r a l s he a t h.
• The entire microtubular
complex, consisting of
the nine doublet
microtubules & the

12. Pattern of Ciliation
• Individual cilia, seen
external to the cell
body, are associated w/
each other through a
complex inf r a c il ia t ur e
below the body surface.
• A striated fibril, called
a k ine t o d e s mo s , extends
from each kinetosome
(basal body) in the
direction of an adjacent
cilium of the same row.
• Thus, running along the

13. • In some species, groups
of cilia are
functionally associated
in such a way to form
discrete organelles.
One such organelle is
the so-called und ul a t ing
me mb r a ne , a flattened
sheet of cilia that
moves as a single unit.
• A second commonly
encountered ciliary
organelle is termed a

14. Other Morpholog ical F eatures
• One other
morphological
feature particularly
characteristic of
ciliates is the
covering of the body
by an often complex
series of membranes,
forming a p e l l ic l e .
• The inner membranes,
lying beneath the

15. • Trichocysts are
characteristically
associated with the
ciliate pellicle.
• Some species also
maintain a permanent
opening to the
outside (a cytproct;
procto = G: the anus)
for expelling
undigested wastes.

17. Reproductive Characteris tics
• In addition to the
presence of cilia & an
infraciliature, a second
unique characteristic of
all ciliates is the
possession by each
individual of two types
of nuclei; that is, the
nuclei of every ciliate
are d imo r p hic (of two
kinds).
• The ciliates are thus
he t e r o k a r y o t ic , while

22. Ciliate Lifes tyles
• About 65% of ciliate
species are free-living,
& most of these are
motile. Some other
species form temporary
attachments to living
or nonliving substrates
for feeding purposes,
while others are
permanently attached &
many may form colonies.
• Although all ciliates
have a distinct pellicle,