Free Biodiversity and Variety of Life MCQs with Answers

2071. If lipopolysaccharides did not appear in the wall of bacteria on staining then it will be known as _.

• A. Gram-negative
• B. Gram-positive
• C. Capsule
• D. Both Gram positive & negative

Explanation: The Gram stain procedure distinguishes between Gram positive and Gram negative groups by coloring these cells red or violet. Gram positive bacteria stain violet due to the presence of a thick layer of peptidoglycan in their cell walls, which retains the crystal violet these cells are stained with. Alternatively, Gram negative bacteria stain pink, which is attributed to a thinner peptidoglycan wall, which does not retain the crystal violet during the decoloring process. Gram-positive bacteria do not contain lipopolysaccharides, but carry surface teichoic acids, lipoteichoic acids and peptidoglycan instead. The outer membrane of Gram-negative bacteria contains lipopolysaccharides, proteins, and phospholipids. The bacterial capsule is a large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell.

2072. In cocci, three plane division results in the formation of sarcina which is a?

• A. Cube of 8 cocci
• B. Square of 4 cocci
• C. Irregular structure
• D. Triangular 6 cocci

Explanation: Sarcina is a genus of gram-positive cocci bacteria in the family Clostridiaceae. The genus takes its name from the Latin word "sarcina," meaning pack or bundle, after the cuboidal (2x2x2) cellular associations they form during division along three planes. Therefore option A is correct.

2073. Which of the following bacteria possesses a spherical shape?

• A. Bacillus anthracis
• B. Escherichia coli
• C. Spirillum minus
• D. Staphylococcus aureus

Explanation: Staphylococcus aureus (cocci) is a round shaped bacteria. Since it is spherical in shape therefore it is the right choice here.

2074. For respiratory metabolism, a bacterial cell membrane contains:

• A. Proteins
• B. Lipids
• C. Enzymes
• D. Chemicals

Explanation: Bacterial cells lack membrane-bound organelles such as mitochondria. Therefore, the enzymes needed for respiration are present in invaginations of the cell membrane, called 'Mesosomes'.

2075. Which of the following is not a sterilization method for the control of bacteria?

• A. Radiation
• B. Filtration
• C. High temperature
• D. Antiseptic

Explanation: Option A:Sterilization by ionizing radiation, primarily by cobalt 60 gamma rays or electron accelerators, is a low-temperature sterilization method that has been used for a number of medical products (e.g., tissue for transplantation, pharmaceuticals, medical devices).Option B:Filtration is the first and only sterilization method that eliminates bacteria by separating the microorganisms from the sterilized medium, but unlike other sterilization methods, it doesn't kill or stop the bacteria's ability to reproduce. The way it works is actually very simple.Option C:Pressure serves as a means to obtain the high temperatures necessary to quickly kill microorganisms. Specific temperatures must be obtained to ensure the microbicidal activity. The two common steam-sterilizing temperatures are 121°C (250°F) and 132°C (270°F).Option D:Antiseptics are germicides applied to living tissue and skin; disinfectants are antimicrobials applied only to inanimate objects. In general, antiseptics are used only on the skin and not for surface disinfection, and disinfectants are not used for skin antisepsis because they can injure skin and other tissues. While antiseptics can be effective at reducing the number of bacteria, they are not typically used for sterilization, which aims to eliminate all microorganisms. Hence the correct option is option D

2076. A type of bacterial cell that is completely surrounded by flagella is called:

• A. Diplococcus
• B. Tetrad
• C. Peritrichous
• D. Monotrichous

Explanation: Diplococcus and Tetrad are some of the shapes of bacteria and are not related to flagella. Monotrichous means 1 flagella. Hence the correct answer is Option C peritrichous.

2077. The sex pili is formed in which of the following processes?

• A. Sexual reproduction
• B. Binary fission
• C. Mitosis
• D. Conjugation

Explanation: The following diagram shows reproduction by conjugation and it can be seen that the recipient forms a pilus at the end.

2078. Under the microscope, the bacteria appear a bluish-purple color. Which class of bacteria are on the slide?

• A. Helix
• B. Around
• C. Rod
• D. Rigid helix

Explanation: c) Rod: The correct answer is option (c) "Rod." Rod-shaped bacteria are also known as bacilli. They have a cylindrical or rod-like shape. When stained using the Gram stain technique, some rod-shaped bacteria appear bluish-purple under the microscope. The color is a result of the Gram stain's interaction with the bacterial cell wall, which helps in the classification of bacteria based on their cell wall composition.

2079. Bacteria that can only survive in the presence of oxygen?

• A. Facultative anaerobes
• B. Obligate aerobes
• C. Obligate anaerobes
• D. Facultative aerobes

Explanation: Obligate aerobes are bacteria that need oxygen to grow and multiply but cannot do so in the absence of oxygen.

2080. Bacteria that live in intestine and produce vitamin K belong to?

• A. Vibrio
• B. Cocci
• C. Spirilla
• D. Bacilli

Explanation: Menaquinones are the naturally occurring form of vitamin K identified in bacteria. Bacilli in intestine produce vitamin K.