Free Biodiversity and Variety of Life MCQs with Answers

2161. A slippery outer covering in some bacteria that protects them from phagocytosis by host cells is:

• A. Flagellum
• B. Cell wall
• C. Peptidoglycan
• D. Slime

Explanation: The slime layer is a slimy, gelatinous outer covering that surrounds some bacterial cells. It plays a crucial role in protecting bacteria from phagocytosis, which is a process. where specialized immune cells, such as macrophages and neutrophils, engulf and destroy invading microorganisms.

2162. During unfavourable conditions, certain bacteria produces:

• A. Ribosomes
• B. Plasmids
• C. Mitochondria
• D. Spores

Explanation: Spores are specialized structures produced by certain bacteria, fungi, and other organisms during unfavorable conditions. Bacterial spores are highly resistant environmental strasses like heat, radiation, and dessication. Spore formation is a survival strategy that allows bacteria to enter a dormant state, protecting their genetic material and essential components until more favorable conditions arise. When conditions improve, spores can germinate and grow into vegetative cells again.

2163. Following are the forms of mesosomes EXCEPT:

• A. Vesicles
• B. Tubules
• C. Lamellae
• D. Squares

Explanation: Squares are not a recognized form of mesosomes. Mesosomes typically exhibit vesicular, tubular, or lamellar shapes but squares are not a known form or structure associated with mesosomes.

2164. Important vectors in modern genetic engineering are _ :

• A. Plasmid
• B. Mesosome
• C. Nucleoid
• D. Ribosome

Explanation: Plasmids are important vectors in modern genetic engineering. A plasmid is a small, circular DNA molecule that can raplicate independently within a bacterial cell. Scientists often use plasmids to introduce foreign DNA bacterial cells for various purposes, such as producing recombinant proteins, studying gene function and creating genetically modified organisms. Plasmids can be engineered to carry specific genes of interest and then transferred into host cells, allowing for the expression of those genes.

2165. Pili are made of special protein called _:

• A. Pilin
• B. Tubulin
• C. Flagellin
• D. Myosin

Explanation: Pili, also known as fimbriae are thin, hair-like structures found on the surface of many bacteria. They are composed of a specialized protein called pilin. Pilin proteins are assembled into filamentous structures that extend from the bacterial surface. Pili have various functions. including facilitating bacterial attachment to surfaces (such as host tissues or other bacterial cells) and participating in processes like bacterial conjugation, which involves the transfer of genetic material between bacterial cells.

2166. Square of four cocci is_:

• A. Tetrad
• B. Sarcina
• C. Diplococcus
• D. Streptococci

Explanation: A tetrad refers to the arrangement of four cocci in pairs of two, forming two sets of pairs atright angles to each other. This arrangement gives the appearance of a square of four cocci. Tetrads are often observed in bacterial cell division where cocci remain attached after division. This arrangement is distinct from other pattems, making it the correct answer.

2167. Syphilis is caused by:

• A. Spirochete
• B. Nostoc
• C. Water blooms
• D. Cyanobacteria

Explanation: This option is comact because syphilis is caused by Treponema pallidum, a bacterium that belongs to the spirochete group. Spirochetes are distinguished by their spiral shape and Treponema pallidum is specifically known for causing syphilis.

2168. _ is an invagination of cell membrane which helps in cell division.

• A. Fimbriae
• B. Nucleoid
• C. Mesosome
• D. Endospore

Explanation: Mesosomes are invaginations or infoldings of the cell. membrane in certain bacterial cells. They were once thought to play a role in processes like DNA replication and cell division.

2169. Treatment by using attenuated culture of bacteria is called _.

• A. Chemotherapy
• B. Sterilization
• C. Antisepsis
• D. Vaccination

Explanation: An attenuated vaccine consists of live, whole bacterial celis viral particles that are treated in such a way that they have reduced virulence with in the host but retain their ability to provoke an immune response.

2170. CV-1 complex is formed during Gram staining in:

• A. Mycoplasmas
• B. Gram-negative bacteria
• C. Gram-positive bacteria
• D. Archaebacteria

Explanation: CV-1 complex is formed and retained during Gram staining in Gram-positive bacteria. Their thick peptidoglycan layer prevents the decolorizer. washing away the crystal violet-iodine complex keeping them stained purple.