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CBSE Class 8  >  Class 8 Test  >  Science (Old NCERT)  >  Test: Microorganisms Friend & Foe- 1 - Class 8 MCQ

Microorganisms Friend & Foe- 1 - Class 8 Science Free MCQ Test with solutions


MCQ Practice Test & Solutions: Test: Microorganisms Friend & Foe- 1 (15 Questions)

You can prepare effectively for Class 8 Science Class 8 (Old NCERT) with this dedicated MCQ Practice Test (available with solutions) on the important topic of "Test: Microorganisms Friend & Foe- 1". These 15 questions have been designed by the experts with the latest curriculum of Class 8 2026, to help you master the concept.

Test Highlights:

  • - Format: Multiple Choice Questions (MCQ)
  • - Duration: 15 minutes
  • - Number of Questions: 15

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Test: Microorganisms Friend & Foe- 1 - Question 1
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Which microorganisms are responsible for fixing atmospheric nitrogen into the soil?

Detailed Solution: Question 1

  • Nitrogen-fixing bacteria are responsible for fixing atmospheric nitrogen into the soil.
  • This process enriches the soil with nitrogen, which is essential for plant growth.
  • These bacteria often reside in the root nodules of leguminous plants and contribute significantly to soil fertility.

Test: Microorganisms Friend & Foe- 1 - Question 2
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What role do certain microorganisms in the root nodules of leguminous plants play?

Detailed Solution: Question 2

Microorganisms residing in the root nodules of leguminous plants fix nitrogen from the air into the soil, enhancing soil fertility. This process is crucial for providing essential nutrients to plants.

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Test: Microorganisms Friend & Foe- 1 - Question 3
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Milk is heated to about 700C for 15 to 30 seconds and then suddenly chilled and stored, the process is known as:

Detailed Solution: Question 3

Pasteurization is a process in which milk is heated to about 70oC for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes. This process was discovered by Louis Pasteur and hence is called pasteurization.

Test: Microorganisms Friend & Foe- 1 - Question 4
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State whether the following statement is True or False:
Microorganisms are used in the preparation of curd, bread, and cake.

Detailed Solution: Question 4

Microorganisms like bacteria and yeast are used in making curd, bread, and cake. For example, the bacterium Lactobacillus helps in turning milk into curd by fermenting it. Similarly, yeast is used in making bread by fermenting the dough, causing it to rise due to carbon dioxide production. In some cakes, yeast is also used to produce carbon dioxide, giving the cake a spongy texture.

Test: Microorganisms Friend & Foe- 1 - Question 5
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While baking cakes, yeast reproduces rapidly and produces ___ gas.

Detailed Solution: Question 5

While baking cakes, yeast reproduces rapidly and produces carbon dioxide gas. This gas is responsible for the spongy texture of cake.

Test: Microorganisms Friend & Foe- 1 - Question 6
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What is the consequence of microorganisms growing on food?

Detailed Solution: Question 6

When microorganisms grow on food, they can cause food poisoning. These microorganisms may produce toxins or contaminate the food, leading to gastrointestinal illnesses.

Test: Microorganisms Friend & Foe- 1 - Question 7
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What role do bacteria play in the nitrogen cycle?

Detailed Solution: Question 7

Certain bacteria fix nitrogen from the atmosphere into the soil, making it available as a nutrient for plants. This process is essential for maintaining soil fertility and supporting plant growth.

Test: Microorganisms Friend & Foe- 1 - Question 8
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What is the main purpose of using common salt to preserve meat and fish?

Detailed Solution: Question 8

Common salt is used to preserve meat and fish to stop bacteria from growing on them. Bacteria can make food go bad and make us sick. So, by using salt, we can keep the meat and fish fresh for a longer time. It acts like a shield to protect our food from getting spoiled.

Test: Microorganisms Friend & Foe- 1 - Question 9
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Which microorganisms are known to cause serious diseases such as dysentery and malaria?

Detailed Solution: Question 9

Protozoans are responsible for causing serious diseases like dysentery and malaria. These single-celled organisms can infect the human body and lead to severe health issues.

Test: Microorganisms Friend & Foe- 1 - Question 10
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Food preservation by sugar reduces the _____ content to inhibit the growth of bacteria.

Detailed Solution: Question 10

  • Sugar acts as a preservative by drawing moisture out of food.
  • This process creates an environment that is less favorable for bacteria to grow.
  • When moisture is reduced, it inhibits the bacteria's ability to thrive and reproduce.
  • This is why sugary foods, like jams and jellies, can be stored for longer periods without spoiling.
  • Overall, reducing moisture content is key to effective food preservation with sugar.

Test: Microorganisms Friend & Foe- 1 - Question 11
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The bacterium present in curd is:

Detailed Solution: Question 11

- The bacterium responsible for curd formation is Lactobacillus.
- It is a type of lactic acid bacteria that ferments lactose, the sugar found in milk.
- This fermentation process produces lactic acid, which causes the milk to thicken and transform into curd.
- Lactobacillus thrives at temperatures between 30 to 40°C, making it ideal for curd production.
- Other options like Salmonella typhi and Vibrio cholera are harmful bacteria, while Penicillin is a fungus, not a bacterium.

Test: Microorganisms Friend & Foe- 1 - Question 12
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Antibiotics are medicines that kill or stop the growth of disease-causing ________.

Detailed Solution: Question 12

Antibiotics are medicines that kill or stop the growth of disease-causing bacteria. They are used to cure various diseases and infections. It is important to take antibiotics only when prescribed by a doctor and to complete the full course.

Test: Microorganisms Friend & Foe- 1 - Question 13
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______ is used for the production of alcohol and wine.

Detailed Solution: Question 13

Yeast is used for the production of alcohol and wine by the process of fermentation.

Test: Microorganisms Friend & Foe- 1 - Question 14
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Which of the following disease is spread due to bacteria?

Detailed Solution: Question 14

Tuberculosis: Tuberculosis is a bacterial infection caused by the bacterium Mycobacterium tuberculosis. It primarily affects the lungs but can also affect other parts of the body. 

    Test: Microorganisms Friend & Foe- 1 - Question 15
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    Vaccines are used to: 

    Detailed Solution: Question 15

    - Vaccines are used to prevent diseases.
    - Vaccines work by stimulating the immune system to recognize and fight specific pathogens, like viruses or bacteria.
    - They contain weakened or inactive parts of a particular organism that trigger an immune response.
    - This prepares the body to recognize and combat the pathogen if exposed in the future.
    - They do not cure diseases.
    - Curing implies treating an active disease, which is not the purpose of vaccines.
    - Vaccines do not cause diseases.
    - While mild symptoms may occur, they do not cause the disease they prevent.

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    About this Class 8 Practice Test

    This test contains 15 MCQs on Microorganisms Friend & Foe- 1 with detailed solutions for each question. It is part of the Science Class 8 (Old NCERT) course on EduRev, designed to align with the current Class 8 syllabus. Each solution explains not just the correct answer but also gives you an understanding of the topic — not just to attempt the question but also help you prepare for the exam with practice.

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