SAMPLE QUESTION PAPER FOR CLASS 8TH MICRORGANISMS FRIEND OR FOE

 

Class 8 – Science

Chapter: Microorganisms – Friend or Foe

Question Paper

Time: 1 Hour
Maximum Marks: 30

Section A: Objective Questions (1 mark each)

(Attempt all questions)

  1. Which of the following is not a microorganism?
    a) Bacteria
    b) Algae
    c) Amoeba
    d) Mushroom

  2. Name a microorganism used in the production of alcohol.
    a) Rhizobium
    b) Yeast
    c) Lactobacillus
    d) Plasmodium

  3. Which microorganism causes malaria?
    a) Virus
    b) Bacteria
    c) Protozoa
    d) Algae

  4. Which disease is caused by a virus?
    a) Cholera
    b) Tuberculosis
    c) Typhoid
    d) Polio

  5. Microorganisms that fix nitrogen in the soil are called:
    a) Decomposers
    b) Pathogens
    c) Nitrogen-fixing bacteria
    d) Yeast

Section B: Very Short Answer (2 marks each)

(Answer in 30–40 words)

  1. Name two harmful and two useful microorganisms.

  2. What is the role of microorganisms in the nitrogen cycle?

  3. Define pathogens with examples.

Section C: Short Answer Questions (3 marks each)

(Answer in 50–60 words)

  1. How do microorganisms help in food production? Give examples.

  2. What precautions must be taken while storing food to prevent microbial growth?

  3. How are vaccines helpful in preventing diseases?

Section D: Long Answer Question (5 marks)

(Answer in 100–120 words)

  1. Write a detailed note on the harmful effects of microorganisms. Include examples from human health, food spoilage, and agriculture.

  2. Which of the following causes tuberculosis?
    a) Virus
    b) Protozoa
    c) Bacteria
    d) Fungi

  3. Penicillin is obtained from which microorganism?
    a) Yeast
    b) Algae
    c) Fungus
    d) Protozoa

  4. Which of the following microorganisms is used in the preparation of curd?
    a) Amoeba
    b) Lactobacillus
    c) Rhizobium
    d) Penicillium

  5. Which of the following is an edible fungus?
    a) Yeast
    b) Penicillium
    c) Mushroom
    d) Aspergillus

  6. The microorganism responsible for causing dengue is transmitted by:
    a) Housefly
    b) Female Anopheles mosquito
    c) Aedes mosquito
    d) Culex mosquito

    7. ✍️ Section B: Very Short Answer (2 marks each)

    1. Name any two viral diseases.

    2. What are protozoa? Give one example.

    3. Why should we not touch spoiled food?

    4. What are microorganisms?

    5. Give one difference between bacteria and fungi.

    ๐Ÿง  Section C: Short Answer Questions (3 marks each)

    1. What is the role of microorganisms in cleaning the environment?

    2. Mention three harmful effects of microorganisms on plants.

    3. How does salt help in food preservation?

    4. What precautions should be taken while taking antibiotics?

    5. Explain how bread becomes spongy when yeast is added.

    ๐Ÿ“ Section D: Long Answer Questions (5 marks each)

    1. Describe the various uses of microorganisms in the food industry.

    2. Write a short note on the discovery and use of antibiotics.

    3. Explain the process of making alcohol with the help of microorganisms.

    4. How can microorganisms be both friends and foes? Explain with examples.

    5. What are communicable diseases? How do they spread? Name any two.

    6. ANSWER KEY:

      ๐Ÿ“˜ Answer Key: Microorganisms – Friend or Foe

      ✅ Section A: Multiple Choice Questions (1 mark each)

      1. Which of the following is not a microorganism?

        • ๐ŸŸข Answer: Mushroom

      2. Yeast is used in the production of:

        • ๐ŸŸข Answer: Alcohol

      3. Which microorganism causes malaria?

        • ๐ŸŸข Answer: Protozoa

      4. Which of these is a nitrogen-fixing microorganism?

        • ๐ŸŸข Answer: Rhizobium

      5. A disease caused by virus is:

        • ๐ŸŸข Answer: Polio

      ✍️ Section B: Fill in the Blanks (1 mark each)

      1. _________ is used in the production of bread.

        • ๐ŸŸข Answer: Yeast

      2. Microorganisms that cause diseases are called _________.

        • ๐ŸŸข Answer: Pathogens

      3. _________ discovered the process of fermentation.

        • ๐ŸŸข Answer: Louis Pasteur

      4. _________ bacteria live in root nodules of leguminous plants.

        • ๐ŸŸข Answer: Rhizobium

      5. Malaria is spread by the bite of _________ mosquito.

      • ๐ŸŸข Answer: Female Anopheles

      ๐Ÿง  Section C: Very Short Answer Questions (2 marks each)

      1. Two useful and two harmful microorganisms:

      • ✅ Useful: Lactobacillus, Rhizobium

      • ❌ Harmful: Plasmodium, Salmonella

      1. What is fermentation?

      • ๐Ÿ”น The conversion of sugar into alcohol and carbon dioxide by yeast.

      1. What are antibiotics? Example?

      • ๐Ÿ”น Medicines that kill or stop bacterial growth.

      • ๐Ÿ”น Example: Penicillin

      1. What is food preservation? Give two methods.

      • ๐Ÿ”น Preventing spoilage by stopping microbial growth.

      • ๐Ÿ”น Methods: Refrigeration, Salting

      1. What is a vaccine?

      • ๐Ÿ”น A substance containing dead/weakened microbes to build immunity.

      ๐Ÿ“ Section D: Short Answer Questions (3 marks each)

      1. Three ways microorganisms are useful:

      • ✅ In making curd and bread

      • ✅ In making medicines (antibiotics)

      • ✅ In fixing nitrogen in soil

      1. How do microorganisms spoil food?

      • ❌ Grow on food

      • ❌ Produce toxins

      • ❌ Cause bad smell, taste, and spoilage

      1. Major groups of microorganisms:

      • ๐Ÿ”น Bacteria

      • ๐Ÿ”น Fungi

      • ๐Ÿ”น Protozoa

      • ๐Ÿ”น Algae

      • ๐Ÿ”น Viruses

      1. How do vaccines work?

      • ๐Ÿ”น Stimulate immune system to produce antibodies

      1. Why avoid stagnant water?

      • ❌ Mosquitoes breed there

      • ❌ Spread diseases like malaria, dengue

      ๐Ÿ“– Section E: Long Answer Questions (5 marks each)

      1. Harmful effects of microorganisms:

      • ❌ Cause diseases (cholera, TB)

      • ❌ Spoil food

      • ❌ Damage crops

      • ❌ Produce toxins

      • ❌ Cause epidemics

      1. Nitrogen cycle & role of microorganisms:

      • ๐Ÿ” Rhizobium fixes nitrogen

      • ๐Ÿ” Decomposers return nitrogen to soil

      • ๐Ÿ” Nitrifying bacteria make usable nitrates

      • ๐Ÿ” Denitrifying bacteria release nitrogen back into air

      1. Microorganisms in agriculture, medicine, industry:

      • ๐ŸŒฑ Agriculture: Rhizobium (nitrogen fixation)

      • ๐Ÿ’Š Medicine: Penicillium (antibiotic)

      • ๐Ÿญ Industry: Yeast for alcohol; bacteria for vinegar

      1. Friendly vs harmful microorganisms:

      • ๐Ÿ˜Š Friendly: Lactobacillus (curd), Penicillium (penicillin)

      • ๐Ÿ˜ท Harmful: Plasmodium (malaria), Salmonella (food poisoning)

      1. Precautions for storing food:

      • ✅ Use airtight containers

      • ✅ Refrigerate perishable food

      • ✅ Use salt/sugar as preservatives

      • ✅ Keep area clean and dry

      • ✅ Cook food properly

      • ANSWER KEY OF QUESTION PAPER 2

        Answer Key – Class 8 Science

        Chapter: Microorganisms – Friend or Foe

        ✅ Section A: Multiple Choice Questions (1 mark each)

        1. Which of the following is not a microorganism?
          ➤ Answer: d) Mushroom

        2. Yeast is used in the production of:
          ➤ Answer: b) Alcohol

        3. Which microorganism causes malaria?
          ➤ Answer: b) Protozoa

        4. Which of these is a nitrogen-fixing microorganism?
          ➤ Answer: c) Rhizobium

        5. A disease caused by virus is:
          ➤ Answer: d) Polio

        ✍️ Section B: Fill in the Blanks (1 mark each)

        1. _________ is used in the production of bread.
          ➤ Answer: Yeast

        2. Microorganisms that cause diseases are called _________.
          ➤ Answer: Pathogens

        3. _________ discovered the process of fermentation.
          ➤ Answer: Louis Pasteur

        4. _________ bacteria live in the root nodules of leguminous plants.
          ➤ Answer: Rhizobium

        5. Malaria is spread by the bite of _________ mosquito.
          ➤ Answer: Female Anopheles

        ๐Ÿง  Section C: Very Short Answer Questions (2 marks each)

        1. Name two useful and two harmful microorganisms.
          ➤ Useful: Lactobacillus, Rhizobium
          ➤ Harmful: Plasmodium, Salmonella

        2. What is fermentation?
          ➤ The process by which microorganisms like yeast convert sugar into alcohol and carbon dioxide.

        3. What are antibiotics? Give an example.
          ➤ Antibiotics are medicines that kill or stop the growth of bacteria.
          ➤ Example: Penicillin

        4. What is food preservation? Name two methods.
          ➤ Preventing food spoilage by stopping microbial growth.
          ➤ Methods: Refrigeration, Salting

        5. What is a vaccine?
          ➤ A vaccine is a preparation of weakened or dead microbes used to develop immunity against a disease.

        ✍️ Section D: Short Answer Questions (3 marks each)

        1. Write three ways in which microorganisms are useful to us.
          ➤ In making curd and bread
          ➤ In producing antibiotics and vaccines
          ➤ In fixing nitrogen for plants

        2. How do microorganisms spoil food?
          ➤ By decomposing food, producing bad smell and toxins.

        3. What are the major groups of microorganisms?
          ➤ Bacteria, Fungi, Protozoa, Algae, Viruses

        4. How do vaccines work in our body?
          ➤ They stimulate the body to produce antibodies that protect against future infections.

        5. Why should we not let water stagnate around us?
          ➤ Stagnant water allows mosquitoes to breed, which spread diseases like malaria and dengue.

        ๐Ÿ“ Section E: Long Answer Questions (5 marks each)

        1. Explain the harmful effects of microorganisms on human health and food.
          ➤ Cause diseases (cholera, TB)
          ➤ Spoil food
          ➤ Release toxins
          ➤ Cause crop damage
          ➤ Can lead to food poisoning

        2. Describe the nitrogen cycle and the role of microorganisms in it.
          ➤ Rhizobium fixes nitrogen
          ➤ Decomposers release nitrogen from dead bodies
          ➤ Nitrifying bacteria convert ammonia to nitrates
          ➤ Denitrifying bacteria release nitrogen back into air

        3. Write a short note on the role of microorganisms in agriculture, medicine, and industry.
          ➤ Agriculture: Nitrogen fixation
          ➤ Medicine: Making antibiotics and vaccines
          ➤ Industry: Fermentation to make alcohol, vinegar

        4. Differentiate between friendly and harmful microorganisms with examples.
          ➤ Friendly: Lactobacillus (curd), Penicillium (antibiotic)
          ➤ Harmful: Plasmodium (malaria), Salmonella (food poisoning)

        5. What precautions should be taken while storing food to protect it from microorganisms?
          ➤ Store in airtight containers
          ➤ Refrigerate perishable items
          ➤ Use preservatives
          ➤ Keep the area dry and clean
          ➤ Cook and reheat food properly

        6. THANK YOU ALL OF YOU

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