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Practice Class 8 Science Chapter 2 Microorganisms: Friend and Foe MCQ Questions with Answers and Useful Details based on the NCERT syllabus. Revise food spoilage, preservation, disease prevention, nitrogen fixation, beneficial microorganisms, and harmful microorganisms.
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Chapter Information
Subject: Science
Class: 8
Chapter: Microorganisms: Friend and Foe
Question Type: Multiple Choice Questions (MCQs)
Practice Set: 14
Difficulty Level: Difficult
Based On: NCERT Syllabus
Introduction
Microorganisms are found everywhere around us and have both beneficial and harmful effects. They help in food preparation, medicine, agriculture, decomposition, and nutrient recycling. At the same time, some microorganisms cause diseases and spoil food.
The effects of microorganisms depend on their type and the conditions in which they live and grow. Proper hygiene, food preservation, vaccination, and safe agricultural practices can help reduce their harmful effects.
This Practice Set 14 brings together important conceptual points from the chapter, including beneficial microorganisms, food spoilage, disease transmission, nitrogen fixation, and preservation.
What You Will Learn
✔ Beneficial microorganisms
✔ Harmful microorganisms
✔ Food spoilage
✔ Food preservation
✔ Disease-causing microorganisms
✔ Nitrogen fixation
✔ Rhizobium
✔ Disease transmission
✔ Hygiene and prevention
✔ Applications of microorganisms
Why This Topic Is Important
Microorganisms affect almost every part of our lives. They can be useful in preparing food and medicines, maintaining soil fertility, and recycling nutrients. Some can also cause diseases in humans, animals, and plants.
Understanding both sides of microorganisms helps students develop a balanced scientific understanding instead of assuming that all microorganisms are either useful or harmful.
5 MCQs with Answers and Useful Details
Q1. Which microorganism is useful in the preparation of curd?
A) Lactobacillus
B) Plasmodium
C) Rhizobium
D) Yeast
Answer:
A) Lactobacillus
Useful Detail
Lactobacillus is a bacterium that helps convert milk into curd.
It converts lactose, the sugar present in milk, into lactic acid. The formation of lactic acid changes the texture and taste of milk and helps in curd formation.
This is an example of a useful application of bacteria in food production.
Correct Answer: A) Lactobacillus
Q2. Which method can help prevent microbial growth in food by removing moisture?
A) Drying
B) Adding water
C) Keeping food uncovered in a humid place
D) Increasing moisture
Answer:
A) Drying
Useful Detail
Drying is an important traditional method of food preservation.
Many microorganisms require available water for growth. Removing moisture from food makes conditions less favourable for the multiplication of microorganisms.
Examples include drying fruits, vegetables, grains, fish, and other foods.
Correct Answer: A) Drying
Q3. Which disease is transmitted by the bite of an infected female Anopheles mosquito?
A) Malaria
B) Tuberculosis
C) Cholera
D) Typhoid
Answer:
A) Malaria
Useful Detail
Malaria is caused by the protozoan Plasmodium.
The disease is transmitted through the bite of an infected female Anopheles mosquito, which acts as a vector.
This demonstrates that some disease-causing microorganisms are transmitted indirectly through specific carriers.
Correct Answer: A) Malaria
Q4. Which practice can help reduce the spread of many infectious diseases?
A) Maintaining proper hygiene and sanitation
B) Drinking contaminated water
C) Leaving food uncovered
D) Avoiding handwashing
Answer:
A) Maintaining proper hygiene and sanitation
Useful Detail
Proper hygiene and sanitation help reduce exposure to disease-causing microorganisms.
Regular handwashing, safe drinking water, proper disposal of waste, clean surroundings, and hygienic food handling can reduce the transmission of many infectious diseases.
Disease prevention often requires several protective measures rather than a single action.
Correct Answer: A) Maintaining proper hygiene and sanitation
Q5. Which statement correctly explains the importance of Rhizobium?
A) It causes malaria.
B) It helps in nitrogen fixation in association with leguminous plants.
C) It is used only for making bread.
D) It causes tuberculosis.
Answer:
B) It helps in nitrogen fixation in association with leguminous plants.
Useful Detail
Rhizobium is a nitrogen-fixing bacterium that lives in the root nodules of many leguminous plants.
It helps convert atmospheric nitrogen into forms that contribute to plant nutrition. In return, the bacteria receive food and shelter from the plant.
This association is an important example of the beneficial role of microorganisms in agriculture.
Correct Answer: B) It helps in nitrogen fixation in association with leguminous plants.
Important Formulas & Concepts
Science Chapter 2 does not contain mathematical formulas. Important scientific concepts are given below.
1. Lactobacillus
A bacterium that helps convert milk into curd by producing lactic acid.
2. Food Preservation
Methods used to prevent or delay food spoilage caused by microorganisms.
3. Drying
Removal of moisture from food to make conditions less favourable for microbial growth.
4. Malaria
A disease caused by the protozoan Plasmodium and transmitted by infected female Anopheles mosquitoes.
5. Vector
An organism that carries and transmits a disease-causing microorganism from one host to another.
6. Hygiene
Practices such as handwashing and clean food handling that help reduce the spread of infections.
7. Sanitation
Measures that maintain clean surroundings and safe disposal of waste and sewage.
8. Rhizobium
A nitrogen-fixing bacterium associated with the roots of leguminous plants.
9. Beneficial Microorganisms
Microorganisms that provide useful products or services in food production, agriculture, medicine, and nature.
10. Harmful Microorganisms
Microorganisms that cause diseases or spoil food and other materials.
Related Practice Questions
Q1. How does Lactobacillus help in making curd?
Q2. Why does drying help preserve food?
Q3. Which organism causes malaria?
Q4. What is a vector?
Q5. Why is Rhizobium beneficial to leguminous plants?
Mini Quiz Challenge
Try answering these questions within 60 seconds.
Q1. Which bacterium helps make curd?
A) Lactobacillus
B) Plasmodium
C) Rhizobium
D) Salmonella
Q2. Which preservation method removes moisture?
A) Drying
B) Adding water
C) Washing
D) Soaking
Q3. Malaria is caused by:
A) Plasmodium
B) Yeast
C) Rhizobium
D) Lactobacillus
Q4. Which insect transmits malaria?
A) Female Anopheles mosquito
B) Housefly
C) Honeybee
D) Butterfly
Q5. Rhizobium is associated with:
A) Root nodules of leguminous plants
B) Human lungs
C) Milk only
D) Bread dough
Exam Tips
✔ Remember Lactobacillus → curd.
✔ Remember Plasmodium → malaria.
✔ Remember female Anopheles mosquito → malaria transmission.
✔ Learn that drying reduces available moisture.
✔ Understand the meaning of a vector.
✔ Remember Rhizobium → root nodules → nitrogen fixation.
✔ Revise hygiene and sanitation as disease-prevention measures.
✔ Distinguish useful microorganisms from harmful microorganisms.
✔ Learn examples of food preservation methods.
✔ Avoid memorising disease names without learning their causative organisms and transmission routes.
Quick Revision Notes
✔ Lactobacillus: Helps convert milk into curd.
✔ Lactic Acid: Produced during the conversion of milk sugar by Lactobacillus.
✔ Drying: Removes moisture and helps prevent microbial growth.
✔ Malaria: Caused by Plasmodium.
✔ Vector: Carrier that transmits a pathogen.
✔ Anopheles Mosquito: Female mosquito that transmits malaria.
✔ Hygiene: Helps reduce exposure to pathogens.
✔ Sanitation: Helps maintain clean and healthy surroundings.
✔ Rhizobium: Helps in nitrogen fixation.
✔ Microorganisms: Can be both beneficial and harmful.
Common Mistakes Students Make
❌ Thinking yeast is responsible for making curd.
❌ Confusing Plasmodium with a bacterium.
❌ Forgetting that malaria is transmitted by a mosquito vector.
❌ Thinking drying increases microbial growth.
❌ Confusing Rhizobium with Lactobacillus.
❌ Assuming all bacteria are harmful.
❌ Thinking hygiene alone can prevent every infectious disease.
❌ Forgetting the role of root nodules in nitrogen fixation.
Key Takeaways
✔ Lactobacillus is useful in curd formation.
✔ Drying helps preserve food by reducing moisture availability.
✔ Plasmodium causes malaria.
✔ Female Anopheles mosquitoes transmit malaria.
✔ Vectors help transmit disease-causing organisms.
✔ Hygiene and sanitation help prevent many infectious diseases.
✔ Rhizobium helps in nitrogen fixation.
✔ Microorganisms have both beneficial and harmful effects.
FAQs
Q. Which microorganism is used to make curd?
Answer:
Lactobacillus is a bacterium that helps convert milk into curd.
Q. How does drying preserve food?
Answer:
Drying removes moisture from food, making the conditions less favourable for the growth of many microorganisms.
Q. Which microorganism causes malaria?
Answer:
Malaria is caused by the protozoan Plasmodium.
Q. What is a vector?
Answer:
A vector is an organism that carries and transmits a disease-causing microorganism from one host to another.
Q. What is the role of Rhizobium?
Answer:
Rhizobium helps in nitrogen fixation and commonly lives in the root nodules of leguminous plants.
Conclusion
Class 8 Science Chapter 2 – Microorganisms: Friend and Foe provides a comprehensive revision of several important concepts from the chapter.
Students revised Lactobacillus, food preservation, drying, malaria, Plasmodium, vectors, hygiene, sanitation, Rhizobium, and nitrogen fixation.
These concepts help students understand how microorganisms can be both useful and harmful and how their activities affect food, health, agriculture, and the environment.
Related links
- Class 8 English Chapter 3 Wisdom Paves the Way part-1
- Class 8 Maths Chapter 5 – Number Play part-4
- Class 8 History Chapter 2 From Trade to Territory part-10
- Class 8 English Chapter 2 A Concrete Example part-10
- Class 8 Science Chapter 2 Microorganisms Friend and Foe part-12
- Class 8 Maths Chapter 5 – Number Play part-3
- Class 8 English Chapter 2 A Concrete Example part-9
- Class 8 History Chapter 2 From Trade to Territory part-9
- Class 8 Maths Chapter 5- Number Play part-2
- Class 8 Science Chapter 2 Microorganisms Friend and Foe part-11
- Class 8 History Chapter 2 From Trade to Territory part-8
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