Question

Refer to the given figure of Paramecium caudatum and select the option that correctly identifies A, B, C, and D.

I. A- Cell wall, B- Cilia Contractile, C- Vacuole, D- Cytostome
II. A- Pellicle, B- Cilia, C- Contractile vacuole, D- Cytostome
III. A- Pellicle, B- Cilia, C- Macronucleus, D- Cytostome
IV. A- Pellicle, B- Trichocysts, C- Micronucleus, D- Cytopharynx

Answer 1

Hint: Paramecium is a unicellular ciliate protist organism. It is generally found in freshwater systems. It has an outer stiff but elastic membrane called the pellicle. On the pellicle, it has cilia that are hair-like structures. Conjugation is mediated by the macronucleus in the paramecium body. The ingestion part of the Paramecium is called the cytostome.

Complete answer:
Paramecium is used as a test or model organisms in schools and various laboratories. It is a freshwater living organism that belongs to the kingdom protista. It is a ciliated unicellular organism. It is studied for various biological processes as it is easily available and easy to handle. They are readily cultivated and divided using conjugation. It is also called the “white rat” of the Ciliophora phylum.
Paramecium body size ranges from 50 to 330 micrometers in length. The Paramecium cells are typically ovoid and elongated in shape. The outer membrane of the Paramecium is stiff but elastic which protects the inner cell mass. It is responsible for providing definite shape to Paramecium. This layer is called the pellicle. In the figure, the pellicle is represented by A.
The pellicle is lined by thousands of tiny hair cells called cilia. It is represented by B in the figure. The cilia help in food entrapment and locomotion. The macronucleus is the largest organelle in the body of Paramecium. It is responsible for genetic reorganization during the conjugation. Conjugation is a type of sexual reproduction through which genetic material is exchanged between two paramecium cells using a conjugation tube. Macronucleus is represented by C in the figure. D in the figure represents the cell mouth or the cytostome. It is used for ingesting food material. This process is called phagocytosis. It is a groove-like structure.
Hence, the correct answer is option (III).

Note: Some of the Paramecium cells live in a mutualistic relationship with other organisms. Paramecium caudatum is around 0.33 mm in length. It usually divides through fission. This species of Paramecium have no regenerative effects.