CBSE – 8th Standard Science

Chapter 2

Microorganisms: Friend and Foe

 

Qus 1. What are microorganisms or microbes?

Ans. There are other living organisms around us which we cannot see with eyes alone which are called microorganisms or microbes.

 

Qus 2. Name three uses of microorganisms?

Ans. Microorganisms are used for various purposes; they are used in the preparation of curd, bread and cake.

 

Qus 3. How bacteria can be used to increase soil fertility?

Ans. In agriculture bacteria is used to increase soil fertility by fixing nitrogen.

 

Qus 4. What do you mean by fermentation?

Ans. This process of conversion of sugar into alcohol is known as fermentation.

 

Qus 5. Who discovered the method of fermentation?

Ans. Louis Pasteur discovered fermentation in 1857.

 

Qus 6. What are antibiotics?

Ans. The source of some medicines are microorganisms, these medicines kill or stop the growth of the disease-causing microorganisms. Such medicines are called antibiotics.

 

Qus 7. Who discovered penicillin?

Ans. In 1929, Alexander Fleming discovered penicillin.

 

Qus 8. What is used for production of alcohol?

Ans. Yeast is used for commercial production of alcohol and wine.

 

Qus 9. Who discovered vaccine for small pox?

Ans. Edward Jenner discovered the vaccine for smallpox in 1798.

 

Qus 10. Name some diseases which can be prevented by vaccination?

Ans. Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.

 

Qus 11. What are pathogens?

Ans. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens.

 

Qus 12. What are communicable diseases?

Ans. Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases.

 

Qus 13. What are preservatives?

Ans. Salts and edible oils are the common chemicals generally used to check the growth of microorganisms. Therefore they are called preservatives.

 

Qus 14. Who discovered pasteurization?

Ans. Louis Pasteur discovered pasteurization.

 

 

Try these:-

What makes the dough rise while preparing idli, dosa, bhaturas and dhoklas ?

 How can be communicable diseases prevented ?

 What is botulism? Name the organism causing it.

What are symbiotic or commensal bacteria and what is their significance for humans?

 What is an antibiotic? Give any four examples of antibiotics.