Free Biodiversity and Variety of Life MCQs with Answers

2281. Saprophytic bacteria are:

• A. Autotrophs
• B. Decomposers
• C. Parasites
• D. Photosynthetic

Explanation: Option B is correct.Saprophytic bacteria are decomposers. Decomposers are organisms that break down dead organic matter. Saprophytic bacteria play an important role in the environment by breaking down dead plants and animals, which releases nutrients back into the soil and air. Examples of saprophytic bacteria include: Bacillus subtilis, Clostridium tetani ,Escherichia coliAutotrophs are organisms that can make their own food from sunlight and carbon dioxide. Decomposers are not autotrophs because they cannot make their own food. Parasites are organisms that live on or inside another organism and get their nutrients from that organism. Saprophytic bacteria are not parasites because they do not live on or inside another organism. Photosynthetic organisms are organisms that use sunlight to convert carbon dioxide into oxygen and carbohydrates. Saprophytic bacteria are not photosynthetic because they do not use sunlight to make their own food.

2282. Salmonella typhi causing typhoid and Clostridium tetani causing tetanus are which type of bacteria?

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

Explanation: Option A is correct.Salmonella typhi and Clostridium tetani are both bacilli. Bacilli are rod-shaped bacteria. They are one of the three main shapes of bacteria, along with cocci (spherical bacteria) and spirilla (spiral bacteria). Bacilli are found in a wide variety of environments, including soil, water, and the human body. Some bacilli are beneficial, such as those that produce lactic acid in yogurt and cheese. Other bacilli are pathogens, which means that they can cause disease. Salmonella typhi and Clostridium tetani are both examples of pathogenic bacilli. Salmonella typhi causes typhoid, a serious disease that can be fatal if it is not treated. Typhoid is transmitted through contaminated food and water. It causes fever, headache, and diarrhea. Clostridium tetani causes tetanus, a disease that affects the nervous system. Tetanus is caused by a toxin that is produced by the bacteria. The toxin causes muscle spasms, which can be severe and life-threatening. Tetanus is transmitted through contact with contaminated soil or other objects. Both Salmonella typhi and Clostridium tetani can be prevented by vaccination. The typhoid vaccine is recommended for people who are traveling to areas where typhoid is common. The tetanus vaccine is recommended for everyone as part of the routine childhood immunization schedule.Spirilla:Spiral bacteria.Example; Campylobacter (food poisoning), Leptospira (leptospirosis), Treponema pallidum (syphilis) Cocci: Spherical bacteria.Examples; Streptococcus (strep throat), Staphylococcus (staph infection), Neisseria (meningitis, gonorrhea) Comma-shaped bacteria are a type of spirilla. Comma-shaped bacteria include: Vibrio cholerae (cholera), Vibrio parahaemolyticus (food poisoning), and Helicobacter pylori (stomach ulcers).

2283. Select a method which cause the oxidation of constituent of a bacterial cell wall

• A. Dry Heat
• B. Moist Heat
• C. Filtration
• D. Ultraviolet Radiation

Explanation: This is the correct answer. Dry heat is a method of sterilization that involves exposing microorganisms, including bacteria, to high temperatures in a dry environment. This process causes the oxidation of the constituents of the bacterial cell wall, leading to cell death.Therefore, dry heat is the method that primarily causes the oxidation of the constituents of a bacterial cell wall.

2284. The incubation period of Syphilis is:

• A. 1-2 weeks
• B. 2-3 weeks
• C. 3-4 weeks
• D. 7 days

Explanation: The incubation period of syphilis, which is the time between exposure to the bacteria (Treponema pallidum) and the appearance of symptoms, typically ranges from 2 to 3 weeks. However, it can vary from 10 to 90 days, with an average of around 21 days.

2285. Which component is present only in the cell wall of Gram-positive bacteria but NOT in Gram-negative bacteria?

• A. Teichoic acids
• B. Lipids
• C. Peptidoglycan
• D. Periplasmic space

Explanation: Teichoic acids are unique components found only in the cell walls of Gram-positive bacteria. They are acidic, phosphate-containing polysaccharides that play a crucial role in maintaining the structural integrity of the cell wall and providing a negative charge to the cell surface.Gram-positive bacteria have a thick peptidoglycan layer (20-80 nanometers) and a teichoic acid layer, whereas Gram-negative bacteria have a thinner peptidoglycan layer (2-3 nanometers) and an outer membrane containing lipopolysaccharides.

2286. The cells of the non virulent strain of Streptococcus pneumonia are:

• A. Capsulated and S-Type
• B. Non-capsulated and S-Type
• C. Capsulated and R-Type
• D. Non-capsulated and R-Type

Explanation: Streptococcus pneumoniae strains are classified into two main types based on their capsule:- S-type (Smooth-type): Capsulated, virulent strains with a smooth colony morphology.- R-type (Rough-type): Non-capsulated, non-virulent strains with a rough colony morphology.The capsule is a layer of polysaccharides surrounding the bacterial cell wall, which helps protect the bacteria from phagocytosis and is a key virulence factor. Non-virulent strains lack this capsule, making them more susceptible to host immune responses.

2287. An additional covering surrounds the cell wall of some bacteria that either prevents the bacteria from being phagocytosed by host cells or helps them to make biofilm.Which of the following term is used for this covering?

• A. Capsule
• B. Slime
• C. Glycocalyx
• D. Spore

Explanation: The capsule is an additional covering that surrounds the cell wall of some bacteria, providing protection against:- Phagocytosis (engulfment by host cells)- Desiccation (drying out)- Antibiotics and other antimicrobial agentsThe capsule is composed of polysaccharides (complex sugars) and can be found in both Gram-positive and Gram-negative bacteria.

2288. Which mode of genetic exchange between bacteria involves cell-to-cell contact between the bacterial cells?

• A. Transduction
• B. Transformation
• C. Conjugation
• D. Both a and b

Explanation: Conjugation is the process of genetic exchange between bacteria that involves direct cell-to-cell contact between the bacterial cells. It requires a specialized structure called a conjugation pilus, which allows the cells to attach and transfer DNA from one cell to another.

2289. Which of the following is a prokaryote?

• A. Protista
• B. E.coli
• C. Amoeba
• D. Fungi

Explanation: E. coli (Escherichia coli) is a type of bacteria, which is a prokaryote. Prokaryotes are single-celled organisms that lack a true nucleus and other membrane-bound organelles. They have a simple cell structure and are typically small in size.

2290. Endospore formation is _

• A. A reproductive process
• B. A vegetative process
• C. Can be reproductive or vegetative depending on the conditions
• D. Is related to invading host cells

Explanation: Endospore formation is a survival mechanism used by certain bacteria, such as Bacillus and Clostridium species, to withstand harsh environmental conditions like high temperatures, radiation, and chemicals. During endospore formation, the bacterial cell undergoes a series of changes to produce a highly resistant, dormant cell called an endospore.Endospore formation is a vegetative process because it:- Involves the transformation of a single cell into a highly resistant form- Is not directly involved in reproduction or the production of new cells- Helps the bacterium survive adverse conditions, allowing it to remain dormant until favorable conditions return