All Free Biology MCQs with Answers

2701. A nitrogen-fixing organism that can be symbiotic is:

• A. Dinoflagellates
• B. Liverworts
• C. Rhizobium
• D. Moss

Explanation: The correct answer is C) Rhizobium, as it is a nitrogen-fixing organism that forms symbiotic relationships with certain leguminous plants.

2702. Mouth, lips, and skin are affected due to the infection of:

• A. Pox virus
• B. Herpes Virus
• C. Paramyxovirus
• D. Adenovirus

Explanation: The correct answer is B) Herpes Virus, as herpes viruses can cause infections that lead to cold sores or fever blisters on or around the mouth and lips.

2703. Tumor causing virus:

• A. DNA enveloped
• B. DNA non-enveloped
• C. RNA enveloped
• D. RNA non-enveloped

Explanation: The correct answer is C) RNA enveloped, as some RNA enveloped viruses, particularly retroviruses like HTLV-1, are known to cause tumors in animals and humans.

2704. Which of the following are the smallest bacteria?

• A. E. coli
• B. Mycoplasma
• C. Spirochete
• D. Streptococci

Explanation: The correct answer is B) Mycoplasma, as they are among the smallest known bacteria due to the absence of a cell wall, which contributes to their smaller size compared to other bacteria.

2705. Plasma membrane and everything in it is called:

• A. Leucoplast
• B. Phragmoplast
• C. Protoplast
• D. Cytoplasm

Explanation: The correct answer is C) Protoplast, as it refers to the living part of the cell, including the plasma membrane and everything in it.

2706. Hepatitis A and E are transrnitted by contact with _ from infected individuals.

• A. Scrum
• B. Blood
• C. Faeces
• D. Saliva

Explanation: The correct answer is C) Faeces, as Hepatitis A and E are primarily transmitted through contact with fecal matter from infected individuals.

2707. Viruses can infect and parasitize _.

• A. Mammals
• B. Humans
• C. Bacteria
• D. All of these

Explanation: The correct answer is D) All of these, as viruses can infect and parasitize mammals, humans, bacteria, and various other hosts.

2708. Which one is not a living character of the virus?

• A. Mutation
• B. Genome
• C. Replication
• D. Crystallization

Explanation: The correct answer is D) Crystallization, as it is not a living characteristic of the virus

2709. Stanley crystallized:

• A. HIV
• B. TMV
• C. HBV
• D. T2

Explanation: Based on the information provided in the options, the correct answer is B) TMV, as Wendell Stanley is associated with crystallizing the tobacco mosaic virus.

2710. Phage attaches to bacterial cell surface by its:

• A. Sheath
• B. Core
• C. Head
• D. Tail

Explanation: The correct answer is D) Tail, as the tail of the bacteriophage is responsible for attaching to the bacterial cell surface.