Question

Describe briefly four major groups of Protozoa.

Answer 1

 Hint: Protozoans are unicellular eukaryotic organisms with heterotrophic nutrition classified under the kingdom Protista. They are classified based on their mode of locomotion into four major groups. The various modes of locomotion are flagella, cilia, pseudopodia, etc.

Complete Step by Step Answer: The four major groups of protozoans are:

Features	Amoeboid protozoans	Flagellated protozoans	Ciliated protozoans	Sporozoans
Habitat and habit	Freshwater, seawater, or moist soil mostly free-living, few parasites.	Free- living (aquatic) or parasitic.	Freshwater or marine, few parasites.	All Endoparasites.
Locomotory structure	Pseudopodia (False feet)	Flagella	Cilia	Absent
Special features	Silica shells in some forms.	Rare sexual reproduction with diverse types of association- commensal, symbiont, parasite.	Possess definite region of the ingestion (gullet) and egestion.	Infectious spore- like stage present in the life cycle.
Example and diseases	Amoeba (dysentery), Entamoeba.	Trypanosoma (Sleeping sickness)	Paramoecium	Plasmodium (Malaria)

Additional Information: The term “Protista” was coined by Ernst Haeckel. General characteristics of the Protists are: - Unicellular and eukaryotic. Some are colonial without much cellular differentiation. - Mode of nutrition maybe by pseudopodia, flagella or cilia, cilia being the fastest. - Reproduction is shown both by sexual and asexual means.
 Protists include: - Autotrophic/ Photosynthetic organisms: These are popularly known as Protists algae and constitute a major portion of phytoplankton. These are capable of synthesizing their food. For example, Dinoflagellates, Diatoms, and euglenoids.
- Consumer- Decomposer organisms: These are free- living, creeping over debris like fallen leaves and rotting wood. They lack chlorophyll and have a phagotrophic mode of nutrition. For Example, Cellular slime molds and acellular slime molds.
- Protozoans: For example, Zooflagellates, Sarcodines, Sporozoans, and ciliates.

Note: - All the unicellular eukaryotes, irrespective of their mode of nutrition, are included in the Kingdom Protista in Whittaker’s classification. - This kingdom is a link between the prokaryotic Kingdom Monera and the eukaryotic kingdom Fungi, Plantae, Animalia on the other hand. - They lack the tissue level of organization. - All the species that were unicellular prokaryotes were classified under Monera in previous classification schemes, while the unicellular eukaryotic species were classified in the Protista kingdom. Chlamydomonas, Chlorella (previously placed in algae inside plants and all with cell walls) and Paramecium and Amoeba (previously placed in the animal kingdom) were brought together by Kingdom Protista.