Microorganisms Friend and Foe MCQs Class 8
CBSE Class 8 Science
SECTION 2: MICROORGANISMS – FRIEND AND FOE
Topic: Microorganisms Friend and Foe MCQs Class 8
Based on NCERT | CBSE Board Examinations
These Multiple Choice Questions (MCQs) are designed strictly as per the NCERT syllabus, making them ideal for CBSE Class 8 Science examination preparation.
1. Microorganisms can be seen only with the help of a:
Answer: B. Microscope
Explanation: Microorganisms are extremely tiny living organisms invisible to the naked eye. A microscope magnifies them so they can be observed and studied.
Explanation: Microorganisms are extremely tiny living organisms invisible to the naked eye. A microscope magnifies them so they can be observed and studied.
2. Which of the following is NOT a microorganism?
Answer: D. Earthworm
Explanation: Earthworms are visible multicellular organisms, whereas bacteria, viruses, and some algae are microscopic.
Explanation: Earthworms are visible multicellular organisms, whereas bacteria, viruses, and some algae are microscopic.
3. Microorganisms that prepare their own food are:
Answer: C. Algae
Explanation: Algae contain chlorophyll and perform photosynthesis, enabling them to make their own food.
Explanation: Algae contain chlorophyll and perform photosynthesis, enabling them to make their own food.
4. Which microorganism is used in making curd?
Answer: A. Lactobacillus
Explanation: Lactobacillus bacteria convert milk sugar into lactic acid, turning milk into curd.
Explanation: Lactobacillus bacteria convert milk sugar into lactic acid, turning milk into curd.
5. Yeast is used in the production of:
Answer: A. Alcohol
Explanation: Yeast ferments sugars to produce alcohol and carbon dioxide, used in brewing and baking.
Explanation: Yeast ferments sugars to produce alcohol and carbon dioxide, used in brewing and baking.
6. The process of conversion of sugar into alcohol is called:
Answer: B. Fermentation
Explanation: Fermentation is a biochemical process carried out by yeast in the absence of oxygen.
Explanation: Fermentation is a biochemical process carried out by yeast in the absence of oxygen.
7. Rhizobium bacteria live in:
Answer: B. Root nodules of legumes
Explanation: Rhizobium fixes atmospheric nitrogen into usable forms, enriching soil fertility.
Explanation: Rhizobium fixes atmospheric nitrogen into usable forms, enriching soil fertility.
8. Which of the following is an antibiotic?
Answer: A. Penicillin
Explanation: Penicillin, discovered by Alexander Fleming, kills or stops the growth of bacteria.
Explanation: Penicillin, discovered by Alexander Fleming, kills or stops the growth of bacteria.
9. Disease‑causing microorganisms are called:
Answer: B. Pathogens
Explanation: Pathogens are microbes that cause diseases in humans, animals, and plants.
Explanation: Pathogens are microbes that cause diseases in humans, animals, and plants.
10. Cholera is caused by:
Answer: B. Bacteria
Explanation: Cholera is caused by Vibrio cholerae and spreads through contaminated water.
Explanation: Cholera is caused by Vibrio cholerae and spreads through contaminated water.
11. Tuberculosis affects the:
Answer: B. Lungs
Explanation: TB bacteria primarily damage lung tissues.
Explanation: TB bacteria primarily damage lung tissues.
12. The carrier of malaria parasite is:
Answer: B
Explanation: Female Anopheles transmits Plasmodium protozoa.
Explanation: Female Anopheles transmits Plasmodium protozoa.
13. Food preservation by heating milk is:
Answer: B
Explanation: Pasteurization kills harmful microbes.
Explanation: Pasteurization kills harmful microbes.
14. Common salt preserves food by:
Answer: B
Explanation: Salt draws out water, preventing microbial growth.
Explanation: Salt draws out water, preventing microbial growth.
15. Viruses reproduce only inside:
Answer: C
Explanation: Viruses need host machinery to multiply.
Explanation: Viruses need host machinery to multiply.
16. Nitrogen fixation converts nitrogen into:
Answer: B
Explanation: Fixed nitrogen becomes usable by plants.
Explanation: Fixed nitrogen becomes usable by plants.
17. Which food item is made using bacteria?
Answer: B
Explanation: Lactobacillus converts milk to curd.
Explanation: Lactobacillus converts milk to curd.
18. Microorganisms that decompose waste are:
Answer: B
Explanation: They recycle nutrients back to soil.
Explanation: They recycle nutrients back to soil.
19. Foot and mouth disease affects:
Answer: C
Explanation: It is a viral disease in livestock.
Explanation: It is a viral disease in livestock.
20. Vaccines protect us by:
Answer: B
Explanation: Vaccines prepare immune system to fight pathogens.
Explanation: Vaccines prepare immune system to fight pathogens.
