Question

Which class of protozoa is totally parasitic?
A. Flagellata
B. Sporozoa
C. Rhizopoda
D. Ciliate

Answer 1

Hint: Protozoa are single-cell eukaryotes with nuclei. Many of them have mobility and heterotrophy within them. They have the characteristics same as animals. Such eukaryotes tend to rely on the debris or other microorganisms for their nutritive purpose.

Complete answer:
Phylum protozoa is divided according to locomotory organelles. They are divided into 4 groups: -Flagellata: The locomotion of these organisms are by flagella. These organisms include free living parasites, symbionts, and aquatic. The organism can be uninucleate or multinucleate. The body of flagellata is bounded by a firm pellicle. Examples of Flagellata include Trypanosoma, Leishmania etc. -Rhizopoda: The locomotory of these organisms are by the pseudopodia which are temporary protoplasmic outgrowth. Pseudopodia engulf the food particles very easily and their body is bounded by a shell. They are of different types- Lobopodia are blunt ,Filopodia are slender and unsupported, Axopodia with the axial support and Reticulopodia which are reticulate types. Examples of Rhizopoda include: Amoeba.
-Ciliate: These organisms locomote by the help of cilia during the life cycle. They contain regions for egestion and ingestion. The defense mechanism of ciliate is by the ejectable trichocyst. Examples of Ciliate include Opalinia.
-Sporozoa: These organisms have spore-like cells. They do not contain locomotory organelles. The body of sporozoa is bounded by elastic pellicle. Sporozoa are parasitic and cause disease. These are the pathogenic species which includes Plasmodium. The reproduction cycle is asexual or sexual in which daughter cells are produced by multiple nuclear fission. The sporozoa contains apical structures which produce the enzyme and allow the sporozoa to enter inside the host. With the help of ingesting cyst the host is infected, it divides and starts producing sporozoites cells which go into the host cell, the cell bursts and starts producing merozoites which infect the new host cell.

Hence, the correct answer is option (B).

Note: The Apical Complex is one of the large groups which contains sporozoan protists. The pathogenic and parasitic species which produce the disease are Plasmodium (P.falciparum, P. malariae), Toxoplasma gondii, and Pneumocysts carinii.