Question

Describe briefly the four major groups of Protozoa.

Answer 1

Answer:

• Protozoans are unicellular, microscopic eukaryotes.
• All protozoans are heterotrophic.
• Some are free living, others infect higher animals and function as parasites.
• They reproducesmainly through binary fission however exceptions exist.
• They have a holozoic mode of nutrition. (Holozoic means food from the outside has to be ingested and internally broken down for the body to be able to utilise it.)
• There are four major groups of protozoans:
• Amoeboid protozoans: (example: Amoeba)
• They can be found in fresh water, moist soil and sea water.
• They move with the help of psuedopodia.
• They do not have a periplast (a type of membrane)
• They maybe free living or parasitic.

• Ciliated protozoans: (example: Paramecium)They are aquatic.
• Their bodies are covered by tiny hair like structures called cilia.
• They use their cilia for movement and for caputuring their prey.
• They have an outer cavity on their cell surface.

• Flagellated protozoans: (example: Trypanosoma)
• These protozoans are either free living or parasitic
• They possess a flagellum.
• They use the flagellum for locomotion.

• Sporozoans: (Example: Plasmodium)
• These protozoans have an infective spore-like stage.
• All of them are parasitic
• They have an elaborate life cycle involving more than one host.
• They do not possess any cilia or flagella.

JAI SHREE RAM

Answer 2

Answer:

Answer

Protozoans are microscopic unicellular eukaryotic organisms with heterotrophic mode of nutrition. Their nutrition may be holozoic, saprobic, or parasitic. These are divided into four major groups.

(1) Amoeboid protozoans or sarcodines

They are unicellular, jelly-like protozoa found in fresh or sea water and in moist soil. Their body lacks a periplast. Therefore, they may be naked or covered by a calcareous shell. They usually lack flagella and have temporary protoplasmic outgrowths called pseudopodia for locomotion. These pseudopodia or false feet help in movement and capturing prey. They include free living forms such as Amoeba or parasitic forms such as Entamoeba.

(2) Flagellated protozoans or zooflagellates

They are free living, non-photosynthetic flagellates without a cell wall. They possess flagella for locomotion and capturing prey. They include parasitic forms such as Trypanosoma, which causes sleeping sickness in human beings and free living forms such as Noctiluca.

(3) Ciliated protozoans or ciliates

They are aquatic individuals that form a large group of protozoa. Their characteristic features are the presence of numerous cilia on the entire body surface and the presence of two types of nuclei. All the cilia beat in the same direction to move the water laden food inside a cavity called gullet. They include organisms such as Paramaecium, Vorticella etc.

(4) Sporozoans

They include disease causing endoparasites and other pathogens. They are uninucleate and their body is covered by a pellicle. They do not possess cilia or flagella. They include the malaria causing parasite Plasmodium.