Free Biodiversity and Variety of Life MCQs with Answers

2341. These are extremely thin, hair-like appendages of bacteria:

• A. Attachment
• B. Fimbriae
• C. Sex pili
• D. Flagella

Explanation: Flagella are extremely thin hair like appendages, whereas pili are non-helical, filamentous appendages. Pili are smaller than flagella and are not involved in motility. They act as sex pili to make a conjugation tube on one hand and act as organ of attachment on other hand. An attachment pilus is also called fimbria.

2342. When coccus divides in three planes, it will produce a:

• A. Sarcina
• B. Tetrad
• C. Streptococcus
• D. Staphylococcus

Explanation: When cocci divides in three plane it forms cube of 8 cocci or sarcina. Sarcina is a genus of bacteria characterized by their distinctive cuboidal, packet-like, or tetrad arrangement of cells. These bacteria are Gram-positive and usually occur in groups of four, eight, or more cells that remain attached and divide in multiple planes, forming a compact and regular arrangement. The name "Sarcina" is derived from the Latin word for "package" or "bundle."

2343. These bacteria very rarely have flagella:

• A. Cocci
• B. Bacilli
• C. Spirilli
• D. Repulsion

Explanation: Cocci bacteria, which are characterized by their spherical or ovoid shape, typically do not have flagella. Flagella are long, whip-like appendages that bacteria use for motility. Instead, cocci bacteria usually lack flagella and rely on other means of locomotion or remain non-motile. Their small, rounded shape is not conducive to the typical spiral or rod-shaped bacteria with flagella that use these structures for movement.

2344. Bacteria can also detect and move in response to chemical signals. This type of behavior is called:

• A. Chemotropism
• B. Chemotaxis
• C. Locomotion
• D. Repulsion

Explanation: Chemotaxis is the biological process by which cells, typically microorganisms such as bacteria, move in response to chemical gradients in their environment. It is a crucial mechanism for the navigation of cells toward attractants (positive chemotaxis) or away from repellents (negative chemotaxis).

2345. Thick, rigid spiral bacterium:

• A. Spirochaete
• B. Pseudomonas
• C. Spirillum
• D. Rhizobium

Explanation: Spirillum is a type of bacterium characterized by its spiral or helical shape. Spirilla are often elongated and have a rigid structure. Spirilla can be further classified based on their mobility and the presence of flagella. Some spirilla are motile and have flagella, which allow them to move through liquid environments. Others are non-motile and do not possess flagella.

2346. A bacillus bacterium with a single flagellum at one end is described as:

• A. Monotrichous
• B. Lophotrichous
• C. Amphitrichous
• D. Peritrichous

Explanation: "Monotrichous" is a term used to describe the arrangement of flagella on a bacterial cell. In a monotrichous arrangement, a bacterium has a single flagellum, a whip-like appendage used for motility, emerging from one end of the cell.

2347. These are hollow, non-helical, filamentous appendages:

• A. Flagella
• B. Pilli
• C. Trichomes
• D. Plasmids

Explanation: These are hollow, nonhelical, filamentous appendages. Pili are smaller than flagella and are not involved in motility. True pili are only present in gram-negative bacteria. They are made up of a special protein called pilin. They are primarily involved in a mating process between cells called the conjugation process. Some pili function as a means of attachment of bacteria to various surfaces.

2348. Following are the various names for nucleoid, EXCEPT:

• A. Nuclear body
• B. Chromatin body
• C. Nuclear region
• D. Nucleus

Explanation: The nucleus is a membrane-bound organelle found in eukaryotic cells. It is often referred to as the "control center" of the cell since it houses the cell's DNA and controls gene expression. The nucleus contains chromatin, nucleoli, and other structures involved in cellular processes. However, the term "nucleus" is not used to describe the DNA-containing region in prokaryotic cells. Instead, prokaryotes have a nucleoid, which is a distinct structure without a membrane that contains the genetic material. In summary, the correct option is D) Nucleus, because the nucleoid is a term specifically used in prokaryotic cells, while the other options refer to various structures or regions within the nucleus of eukaryotic cells.

2349. Some_ occasionally reach the length of 500 micrometer:

• A. Spirochetes
• B. Diplococci
• C. Streptococci
• D. Cocci

Explanation: Spirochetes are a group of bacteria that are characterized by their spiral shape. They are typically long and slender, and some species can indeed reach a length of 500 micrometers or even longer. Spirochetes are known for their unique way of moving by rotating their entire body, which allows them to navigate through various environments, including tissues and body fluids. Some well-known examples of spirochetes include Treponema pallidum, the bacteria that causes syphilis.

2350. The structure used for sexual contact between bacteria is/are:

• A. Flagella
• B. Plasmid
• C. Mesosome
• D. Pili

Explanation: Pili (singular: pilus) are hair-like appendages on the surface of bacteria. They are involved in various functions, including attachment to surfaces and bacterial motility. However, some bacteria also possess a specific type of pilus called a sex pilus or F pilus. Sex pilus is involved in a process called bacterial conjugation, which is a form of sexual contact between bacteria. During conjugation, a donor bacterium transfers a plasmid (often containing antibiotic resistance genes) to a recipient bacterium through the sex pilus. Therefore, the correct option for the structure used for sexual contact between bacteria is D) Pili.