Question

The cell mouth in some protozoans is known as
a) Cytoproct
b) Cytostome
c) Peristome
d) Cytopharynx

Answer 1

To answer this question we must know few basic information about protozoans. Protozoa are unicellular, eukaryotic, heterotrophic organisms which are either free-living or parasites that lack a cell wall. There are many different cell organelles which can perform various tasks performed by different organs in higher animals like mouth, anus, intestinal tract, etc.

Complete answer:
Protozoans are heterotrophic and are considered to have holozoic nutrition. Holozoic nutrition is a type of heterotrophic nutrition which is characterized by the ingestion and internal processing of gaseous, liquids or solid food particles.
They ingest their food by the process of phagocytosis. Some of the protozoan groups have a specialised structure called cytostome for phagocytosis which is usually in the form of a microtubule supported funnel or groove.
Food is directed into the cytostome and is being sealed into the vacuoles. Only certain groups of protozoa have cytostomes.
The pseudopodia of amoeboid help in catching the prey. Thousands of cilia present in the ciliates drive the food-laden water into the gullet.
The ingested food comes to the food vacuole and gets acted upon by lysosomal enzymes. The digested food then gets distributed throughout the cell.
Hence, the cell mouth in some protozoans is called the Cytostome.
Therefore, the correct option is B which is answered 'Cytostome'.
Cytoproct is a structure through which waste is ejected in single celled eukaryotes.
Peristome is an anatomical tooth-like projection surrounding the mouth of a capsule in case of Mosses.
Cytopharynx is a tube-like passageway by which food passes through. It is found in protozoans.

Note:
Ciliophora or Ciliates have a fixed shape due to covering of pellicle and may have tentacles. Contractile vacuoles are present in them. Some species have an organ for defence which is called trichocysts. They move with the help of these cilia and the movement of cilia is the one which also helps in taking food inside the gullet.