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Unit:
Protozoa
1
Introduction
PROTOZOA
Unit Contents
1 Introduction
2 Diversity
3 Classification
Traditionally the animal kingdom has
been divided into two subkingdoms;
Protozoa* and Metazoa*
...
Their principal importance is
as consumers of bacteria
( PROKARYOTES )
...
Protozoa are also important as
parasites and symbionts* of
multicellular animals
...
However, it is
impossible to draw a line between
unicellular animals (consumers), plants
(producers) and fungi (decomposers)
and it is customary to speak of the
Protista* as a separate kingdom of
unicellular eukaryotes that embraces
both heterotrophic protozoa and
autotrophic algae
...
Over 60,000 species have been
described although you can be sure this is only
a fraction of the total number of protist life
forms
...
Complexity in protists has
evolved through specialisation of different
parts of the cell - organelles and the
cytoskeleton* in particular
...
9 Evolution &
the Fossil
Record
Protozoa may occur singly or in colonies (e
...
Volvox
); may swim freely or be in contact
with a substratum or be sedentary; may be
housed in a shell (lorica) (e
...
foraminferans
, clothed in scales or other adhering matter, or
be naked; they may or may not be pigmented
...
g
...
g
...
11 Key
features (2)
10 Key
features
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Unit: Protozoa 3 Classification
Unit Contents
1 Introduction
Protozoan classification
2 Diversity
Four major groups of protozoa are recognised
and often given the status of phylum*
...
3
Classification
4 Flagellates
5 Amoebae
The groups are:
6 Sporozoans
flagellates (or Mastigophora)
amoebae (or Sarcodina)
sporozoans (or Sporozoa, Apicomplexa) and
ciliates (or Ciliophora)
...
We now know from
molecular data (especially RIBOSOMAL
RNA gene sequencing), that the different
groups of flagellates and amoebae are not
closely related and that there may be much
greater genetic distance between two groups of
flagellates than between flowering plants and
vertebrates
...
e
...
It is at present premature to try to
construct a phylogenetic classification of
protists, and for purposes of identification the
above traditional classification is a starting
point
...
5 Amoebae
Some flagellates have a characteristic
arrangement of the flagella,
6 Sporozoans
DINOFLAGELLATES for example
...
the Fossil
This makes them difficult to classify and until Record
recently flagellates were divided into plant-like
10 Key
Phytomastigophora* and Zoomastigophora*
...
g
...
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Unit: Protozoa 5 Amoebae
Unit Contents
1 Introduction
Amoebae
2 Diversity
Amoebae move
by means of flowing
cytoplasm* , usually with the production of
pseudopodia*
...
3
Classification
Note that some amoebae live in shells from
which the pseudopodia are extruded
...
RHIZOPODA have unsupported
pseudopodia (lobopodia
, filopodia
reticulopodia
)
...
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or
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7 Ciliates
8 Consortia &
Serial
Endosymbiosis
9 Evolution &
the Fossil
Record
10 Key
features
11 Key
features (2)
Unit: Protozoa 6 Sporozoans
Unit Contents
1 Introduction
Sporozoans
2 Diversity
These protozoa have no locomotory extensions
3
of the body and all species are parasitic
...
5 Amoebae
Most sporozoans are intracellular parasites or at
least part of their life-cycle takes place inside a 6 Sporozoans
host cell
...
8 Consortia &
Sporozoans reproduce by multiple fission* and Serial
Endosymbiosis
because they do not form true spores but all
possess an apical complex the name
9 Evolution &
Apicomplexa is often preferred
...
Record
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10 Key
features
11 Key
features (2)
Unit: Protozoa 7 Ciliates
Unit Contents
1 Introduction
Ciliates
2 Diversity
Ciliates form an extremely large group
3
distinguished by the possesion of CILIA , two Classification
different types of NUCLEUS and transverse
4 Flagellates
fission* of the organism when it divides (c
...
flagellates and amoebae)
...
All cilia beat with their effective stroke in the
same direction and the waves of ciliary bending
give the appearance of a wheat field blown by
gusts of wind
...
7 Ciliates
8 Consortia &
Serial
Endosymbiosis
9 Evolution &
Other similar examples of metachronal
the Fossil
rhythym* in animals e
...
10 Key
features
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Page 11 Key
features (2)
Unit:
Protozoa
8 Consortia & Serial
Endosymbiosis
Consortia & Serial
Endosymbiosis
The evolutionary origin of mitochondria* and
chloroplasts* , from symbiotic bacteria is now
widely accepted
...
With the transfer of genes from the symbiont's
nucleus to that of the host, the relationship
becomes obligate and the symbiont becomes an
organelle - no longer capable of independent
existence
...
features
Examples of symbiotic consortia include
CILIATES
HETEROTROPHIC FREE-LIVING
PROTOZOA
MARINE PROTOZOA
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11 Key
features (2)
Unit:
Protozoa
9 Evolution & the
Fossil Record
Evolution & the Fossil
Record
Unit Contents
1 Introduction
2 Diversity
3
Classification
One of the first criticisms levelled against
4 Flagellates
Darwin's theory of evolution through natural
selection was that many simple organisms have
5 Amoebae
been observed to remain largely unchanged
over long periods of geological time
...
They
are often cited as simple organisms that have
not evolved
...
Foraminifera have remained unicells from their
first appearance, but they have EVOLVED
...
The large
living foraminifera appear to owe their size to
symbiotic relationships with intracellular
photosynthetic protists (unicellular algae or
dinoflagellates) once again illustrating the
importance of symbiosis in evolution
...
Most are motile and heterotrophic
...
Excess water is eliminated by means of a
contractile vacuole
...
7 Ciliates
Features of amoeba
Pseudopodia are the locomotor or
food-capturing organelles
...
Features of sporozoans
8 Consortia &
Serial
Endosymbiosis
9 Evolution &
the Fossil
Record
10 Key
features
Ringlike, tubular, and filamentous organelles 11 Key
features (2)
at the apical end of the body are a
distinguishing feature of these parasitic
protozoa
...
Two types of nuclei are present:
6 Sporozoans
macronucleus and micronucleus