[8] Protozoa Flashcards
The protozoans are single-celled eukaryotic organisms belonging to
the
Kingdom Protista.
Each cell is a complete self-contained unit provided with organelles
that carry out functions such as
as nutrition, locomotion, respiration,
excretion, and attachment.
occupy moist habitats and niches, and
are heterotrophic. They feed on bacteria, particulate nutrients, or
even other smaller protozoa.
Protozoans lack cell walls,
Most are ? in size, with the pathogenic species usually
smaller than the commensals. Many protozoans have well-defined
cell shapes except the amoebas, whose shape constantly changes.
microscopic
All protozoans possess one or more nuclei, with some having a (2)
macronucleus and a micronucleus.
While the macronucleus controls metabolic and developmental functions, the micronucleus is necessary for reproduction. Some protozoa have a flexible covering called ? which serves as osmotic shield.
pellicle
The ? of many protozoa consists of a hyaline ectoplasm,
which is associated with their locomotory apparatus, the
peristome or mouth, contractile vacuoles, and cyst wall.
cell
Hence, this part of the cell mainly functions for locomotion
and sensation, ingestion of food, excretion, and protection,
respectively. Within the ectoplasm lies the typical
cytoplasm, called ?
endoplasm.
which is granular in appearance, is where the
food vacuoles, macronucleus, micronucleus, and centrosome are located. The food vacuoles and centrosome function for
nutrition and cell division, respectively.
endoplasm.
There are two stages of developmentin the protozoa:
The trophic or trophozoite stage and The cystic or cyst stage.
During the trophozoite stage, the organism is motile,
actively feeding and reproducing. However, it is also
very susceptible to drying.
The trophic or trophozoite stage
On the contrary, the cyst, is the resting stage.
The cystic or cyst stage.
During this time, the organism is nonmotile and very
resistant to chemicals and drying due to the presence
of a cyst wall.
The cystic or cyst stage.
occurs
when there is:
a. deficiency or over abundance of food supply,
b. Excess catabolic products in the environment,
c. Marked pH changes,
d. Desiccation of the medium,
e. Depletion or excess oxygen,
f. Overpopulation.
Encystation (trophozoite turning into a cyst)
a process wherein a single organism divides into
two equal organisms, is the most common form of reproduction
in protozoa.
Binary fission,
Similar to binary fission, ? also involves mitotic division of
the organism except that one of the newly formed cells is
smaller than the other.
budding
several rounds of nuclear
replication occur without cytokinesis. This multinucleated cell
will then form multiple progeny simultaneously.
In multiple fission or segmentation,
it can involve the production
and fusion of gametes in processes similar to higher organisms.
sexual reproduction
