All Free Biology MCQs with Answers

2691. The unifying character of all bacteria:

• A. Peptidoglycan
• B. Conjugation
• C. Haploid
• D. Capsule

Explanation: The correct answer, based on the options provided, is C) Haploid. All bacteria have a single set of chromosomes, which makes them haploid organisms. This characteristic is universal among bacteria.

2692. When cocci form a Iong chain of cells then the arrangement is called:

• A. Diplococci
• B. Sarcina
• C. Streptoococci
• D. Staphylococci

Explanation: So, when cocci form a long chain of cells, the arrangement is called "Streptococci."

2693. Which of the following is commonly present in aII bacteria.

• A. Nucleoid
• B. Pili
• C. Plasmid
• D. Cell wall

Explanation: The nucleoid is a region within bacterial cells where the genetic material (DNA) is located. Unlike the nucleus in eukaryotic cells, the nucleoid is not surrounded by a membrane. It contains the bacterial chromosome, which is a single, circular DNA molecule that carries essential genetic information.

2694. The type of glycocalyx that is loosely attached to the bacterial cell is called:

• A. Cell wall
• B. Capsule
• C. SIime
• D. Cell membrane

Explanation: The correct answer is C) Slime, as it is the type of glycocalyx that is loosely attached to the bacterial cell.

2695. The particles which don't have nucleic acid as their hereditary material:

• A. Virions
• B. Prions
• C. Viroids
• D. Non-enveloped viruses

Explanation: The correct answer is B) Prions, as they are particles that don't have nucleic acid as their hereditary material.

2696. Pathogenicity of bacteriophage is due to its:

• A. Envelope
• B. Tail
• C. Nucleic acid
• D. Capsid

Explanation: The correct answer is C) Nucleic acid. The pathogenicity of bacteriophages is primarily due to their nucleic acid, which carries the genetic information necessary for their replication and infection of bacterial cells.

2697. Antibiotics are mostly obtained from:

• A. Bacteria
• B. Angiosperms
• C. Viruses
• D. Fungi

Explanation: The correct answer is A) Bacteria, as many antibiotics are obtained from bacteria themselves.

2698. The uniqueness of bacterial photosynthesis is because it can occur:

• A. Without CO2
• B. Without chlorophyll a
• C. Without pigment
• D. Without light

Explanation: The correct answer is B) Without chlorophyll a, as bacterial photosynthesis can occur using different photosynthetic pigments, such as bacteriochlorophylls, which differ from chlorophyll a found in plants and cyanobacteria.

2699. Gram-positive bacteria differ from Gram-negative bacteria in the structure of their:

• A. Nucleoid
• B. Cell wall
• C. Cytoplasm
• D. Ribosomes

Explanation: The correct answer is B) Cell wall, as Gram-positive bacteria have a different cell wall structure (thick peptidoglycan layer) compared to Gram-negative bacteria (thin peptidoglycan layer surrounded by an outer membrane).

2700. Bacteria that need oxygen but can also live in the absence of oxygen are:

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

Explanation: The correct answer is D) Facultative anaerobes, as they can grow in the presence or absence of oxygen.