BIOLOGY multiple-choice questions on microorganisms along with their answers and brief explanations:

1. Which of the following is a characteristic feature of prokaryotic cells?

• A) Membrane-bound organelles

• B) Nucleus

• C) Circular DNA

• D) Multicellular structure
Answer: C) Circular DNA
Explanation: Prokaryotic cells, such as bacteria, typically have a single circular DNA molecule that is not enclosed within a nucleus.

2. What is the primary role of decomposer microorganisms in an ecosystem?

• A) Photosynthesis

• B) Nitrogen fixation

• C) Decomposition of organic matter

• D) Pathogen resistance
Answer: C) Decomposition of organic matter
Explanation: Decomposers, including certain bacteria and fungi, break down dead organic matter, recycling nutrients back into the ecosystem.

3. Which type of microorganism is primarily responsible for the fermentation process in bread-making?

• A) Bacteria

• B) Viruses

• C) Yeast

• D) Protozoa
Answer: C) Yeast
Explanation: Yeast, particularly Saccharomyces cerevisiae, ferments sugars in dough, producing carbon dioxide that causes the bread to rise.

4. Which of the following diseases is caused by a virus?

• A) Tuberculosis

• B) Malaria

• C) Influenza

• D) Ringworm
Answer: C) Influenza
Explanation: Influenza is caused by the influenza virus, while tuberculosis is caused by bacteria, malaria by protozoa, and ringworm by fungi.

5. What structure protects bacterial cells from environmental stress and provides shape?

• A) Cell membrane

• B) Cytoplasm

• C) Peptidoglycan cell wall

• D) Ribosomes
Answer: C) Peptidoglycan cell wall
Explanation: The peptidoglycan cell wall provides structural support and protection to bacterial cells, maintaining their shape.

6. Which of the following microorganisms can be used in biotechnology for gene cloning?

• A) Viruses

• B) Fungi

• C) Bacteria

• D) All of the above
Answer: D) All of the above
Explanation: All these microorganisms can be utilized in various biotechnological applications, including gene cloning, depending on the method and desired outcome.

7. What is the main method of transmission for the bacteria that causes cholera?

• A) Airborne droplets

• B) Contaminated water

• C) Direct contact

• D) Insect bites
Answer: B) Contaminated water
Explanation: Cholera is primarily transmitted through drinking water contaminated with the bacterium Vibrio cholerae.

8. Which of the following microorganisms is known for its role in nitrogen fixation?

• A) Escherichia coli

• B) Rhizobium

• C) Streptococcus

• D) Clostridium
Answer: B) Rhizobium
Explanation: Rhizobium is a genus of bacteria that form symbiotic relationships with leguminous plants, converting atmospheric nitrogen into a form usable by plants.

9. Which type of microorganism can reproduce both sexually and asexually?

• A) Bacteria

• B) Viruses

• C) Fungi

• D) Archaea
Answer: C) Fungi
Explanation: Fungi can reproduce both sexually (through spore formation) and asexually (through budding or fragmentation).

10. What is the primary function of antibiotics?

• A) To kill viruses

• B) To inhibit bacterial growth

• C) To enhance immune response

• D) To promote viral replication
Answer: B) To inhibit bacterial growth
Explanation: Antibiotics are designed to target and inhibit the growth of bacteria, making them effective against bacterial infections but ineffective against viruses.

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