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Practice Class 8 Science MCQ Questions with Answers based on the latest NCERT syllabus. Learn about microorganisms, yeast, antibiotics, fermentation, bacterial diseases, and malaria with detailed solutions, exam tips, and concept-based explanations for CBSE and State Board students.
Do You Know
Chapter Information
Subject: Science
Class: 8
Chapter: Microorganisms: Friend and Foe
Question Type: Multiple Choice Questions (MCQs)
Difficulty Level: Easy to Moderate
Based On: Latest NCERT Syllabus
Introduction
Microorganisms are tiny living organisms that play an important role in nature and human life. Some are useful in producing food, medicines, and beverages, while others can cause diseases. Understanding their uses, harmful effects, and methods of disease prevention is an essential part of Class 8 Science and helps students connect scientific concepts with real-life applications.
What You Will Learn
✔ Useful microorganisms
✔ Role of yeast in alcohol production
✔ Antibiotics and their importance
✔ Fermentation process
✔ Diseases caused by bacteria
✔ Transmission of malaria
Why This Topic Is Important?
Microorganisms influence agriculture, medicine, food production, and human health. Questions from this chapter are frequently asked in CBSE, State Board, Olympiad, and scholarship examinations. A clear understanding of these concepts also helps students develop awareness about disease prevention and the beneficial role of microbes.
Exam Relevance
These questions are useful for:
✔ CBSE Exams
✔ State Board Exams
✔ School Tests
✔ Unit Tests
✔ Half-Yearly Exams
✔ Annual Exams
✔ Olympiads
✔ Scholarship Examinations
Q1. Which microorganism is used in the production of alcohol?
A) Yeast
B) Amoeba
C) Lactobacillus
D) Penicillium
Answer
Yeast
Concept Behind This Question
Yeast is a useful microorganism that converts sugar into alcohol through fermentation.
Step-by-Step Solution
Yeast is a single-celled fungus widely used in food and beverage industries. During fermentation, it breaks down sugar in the absence of oxygen and produces alcohol along with carbon dioxide.
Amoeba is a protozoan, Lactobacillus is mainly used in curd formation, and Penicillium is known for producing antibiotics.
Therefore, the correct answer is: Yeast.
Exam Tip
Remember:
Yeast → Fermentation → Alcohol Production
Q2. Which of the following is an antibiotic?
A) Streptomycin
B) Sodium bicarbonate
C) Alcohol
D) Yeast
Answer
Streptomycin
Concept Behind This Question
Antibiotics are medicines that help destroy or stop the growth of harmful bacteria.
Step-by-Step Solution
Streptomycin is a well-known antibiotic used to treat certain bacterial infections.
Sodium bicarbonate is a chemical compound, alcohol is a disinfectant rather than an antibiotic, and yeast is a microorganism.
Therefore, the correct answer is: Streptomycin.
Exam Tip
Antibiotics are effective against bacterial infections but are not effective against viral diseases.
Q3. The process of conversion of sugar into alcohol is called?
A) Fermentation
B) Infection
C) Moulding
D) Nitrogen fixation
Answer
Fermentation
Concept Behind This Question
Fermentation is a biological process carried out by yeast.
Step-by-Step Solution
During fermentation, yeast converts sugar into alcohol and carbon dioxide under suitable conditions. This process is widely used in industries for preparing beverages and certain food products.
Therefore, the correct answer is: Fermentation.
Exam Tip
Remember the relationship:
Sugar + Yeast → Alcohol + Carbon Dioxide
Q4. Which disease is caused by bacteria?
A) Chicken pox
B) Influenza
C) Polio
D) Tuberculosis (TB)
Answer
Tuberculosis (TB)
Concept Behind This Question
Different microorganisms cause different diseases.
Step-by-Step Solution
Tuberculosis (TB) is caused by the bacterium Mycobacterium tuberculosis.
The other diseases listed are caused by viruses:
- Chicken pox
- Influenza
- Polio
Therefore, the correct answer is: Tuberculosis (TB).
Exam Tip
Remember:
TB → Bacteria
Polio, Influenza, Chicken pox → Viruses
Q5. Carrier of malaria-causing protozoan is?
A) Butterfly
B) Cockroach
C) Housefly
D) Female Anopheles mosquito
Answer
Female Anopheles mosquito
Concept Behind This Question
Malaria spreads through a specific mosquito that carries the malaria parasite.
Step-by-Step Solution
The protozoan responsible for malaria is transmitted from one person to another through the bite of an infected female Anopheles mosquito.
Maintaining cleanliness, preventing stagnant water, and using mosquito protection help reduce the spread of malaria.
Therefore, the correct answer is: Female Anopheles mosquito.
Exam Tip
Remember:
Disease → Malaria
Carrier → Female Anopheles Mosquito
Important Formulas & Concepts
1. Microorganisms
Main groups include:
- Bacteria
- Fungi
- Protozoa
- Algae
- Viruses
2. Fermentation
Fermentation is the process in which yeast converts sugar into alcohol and carbon dioxide.
Concept:
Sugar → Alcohol + Carbon Dioxide
3. Antibiotics
- Produced by certain microorganisms.
- Used to treat bacterial diseases.
- Should be taken only on medical advice.
4. Useful Microorganisms
- Yeast – Bread and alcohol production
- Lactobacillus – Curd formation
- Penicillium – Production of antibiotics
5. Bacterial Diseases
Examples include:
- Tuberculosis (TB)
- Cholera
- Typhoid
6. Malaria
- Caused by a protozoan (Plasmodium).
- Spread through the bite of an infected female Anopheles mosquito.
Related Practice Questions
- Which microorganism is used in bread making?
- Why should antibiotics not be used unnecessarily?
- What products are formed during fermentation?
- Name two diseases caused by bacteria.
- How can malaria be prevented?
Mini Quiz Challenge
True or False
- Yeast is used in alcohol production.
- Streptomycin is an antibiotic.
- Fermentation converts sugar into alcohol.
- Tuberculosis is caused by a virus.
- Female Anopheles mosquito spreads malaria.
Exam Tips
✔ Learn the useful applications of microorganisms.
✔ Remember the names of common antibiotics.
✔ Understand the difference between bacterial and viral diseases.
✔ Revise the process of fermentation.
✔ Memorize important disease-causing organisms and their carriers.
Quick Revision Notes
✔ Yeast produces alcohol through fermentation.
✔ Streptomycin is an antibiotic.
✔ Fermentation converts sugar into alcohol and carbon dioxide.
✔ Tuberculosis is caused by bacteria.
✔ Malaria is spread by the female Anopheles mosquito.
✔ Lactobacillus helps in curd formation.
Common Mistakes Students Make
❌ Confusing yeast with bacteria.
❌ Thinking alcohol is an antibiotic.
❌ Mixing up fermentation and infection.
❌ Assuming tuberculosis is caused by a virus.
❌ Believing that all mosquitoes spread malaria.
Key Takeaways
- Yeast plays an important role in alcohol production.
- Antibiotics help control bacterial infections.
- Fermentation is a useful biological process.
- Tuberculosis is a bacterial disease.
- Malaria is transmitted by the female Anopheles mosquito.
FAQs
1. Which microorganism is used to produce alcohol?
Yeast is used for alcohol production through fermentation.
2. What is an antibiotic?
An antibiotic is a medicine that helps kill or stop the growth of harmful bacteria.
3. What is fermentation?
Fermentation is the process in which yeast converts sugar into alcohol and carbon dioxide.
4. Which disease is caused by bacteria?
Tuberculosis (TB) is caused by bacteria.
5. Which mosquito spreads malaria?
The female Anopheles mosquito acts as the carrier of the malaria parasite.
Conclusion
This Class 8 Science MCQ Practice Set focuses on the important concepts of microorganisms, antibiotics, fermentation, bacterial diseases, and malaria. Regular practice of these concept-based questions helps students strengthen scientific understanding, improve analytical skills, and perform confidently in school examinations and competitive tests.
NCERT Reference
Book: NCERT Science Class 8
Relevant Chapter:
- Chapter 2 – Microorganisms: Friend and Foe
Based On: Latest NCERT Curriculum (CBSE)
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