Notes(2) : Microorganisms - Friend & Foe Class 8 Notes | EduRev

Class 8 : Notes(2) : Microorganisms - Friend & Foe Class 8 Notes | EduRev

 Page 1


            BAL BHARATI PUBLIC SCHOOL, PITAMPURA                   
                                  
                                     CLASS 8 CORE ASSIGNMENT 
   MICRO-ORGANISMS: FRIENDS AND FOE 
 
Q1. What are micro-organisms? 
A. The organisms which can not be observed by naked eyes. 
 
Q2. Write a short note on viruses. 
A. Viruses are micro organisms that reproduce only inside the cells of the host 
organism. They cause various diseases like cold, influenza, polio, AIDS, etc. 
 
Q3. Write a note on presence of various microbes in nature. 
A. Microbes can survive under all types of environment, ranging from ice cold to hot 
springs and every kind of moisture level. They are also found inside the bodies of 
various animals including humans. 
 
Q4. How are micro-organisms beneficial to mankind? 
A. 1. They help in cleaning up of the environment by degrading organic matter. 
2. They are used to increase soil fertility by fixing nitrogen 
3. Lactobacillus promoted the formation of curd. 
4. Bacteria are also involved in the making of cheese, pickles, etc. 
5. Yeast is used in the baking industry for making breads, pastries and cakes. It is 
also used in alcohol industry. 
6. Number of antibiotics are derived from various bacteria. 
7. Some bacteria and blue green algae are nitrogen fixers and help in increasing 
soil fertility. 
 
Q5. Why are chidren given vaccines? 
A. When a disease carrying micro-organism enters our body, the body produces 
antibodies to fight the invader. So, if dead and weakened micro-organisms are 
introduced in a healthy body, the body fights and kills them by producing 
antibodies. 
 
Q6. How do micro-organisms help in cleaning up of the environment? 
A. The micro-organisms help in converting complex organic substances into simpler 
molecules. These organic substances are the wastes produced by plant and 
animals and their dead remains. The so produced simpler molecules enter their 
respective nutrient cycles. 
 
Q7. Write a note on harmful micro-organisms. 
Page 2


            BAL BHARATI PUBLIC SCHOOL, PITAMPURA                   
                                  
                                     CLASS 8 CORE ASSIGNMENT 
   MICRO-ORGANISMS: FRIENDS AND FOE 
 
Q1. What are micro-organisms? 
A. The organisms which can not be observed by naked eyes. 
 
Q2. Write a short note on viruses. 
A. Viruses are micro organisms that reproduce only inside the cells of the host 
organism. They cause various diseases like cold, influenza, polio, AIDS, etc. 
 
Q3. Write a note on presence of various microbes in nature. 
A. Microbes can survive under all types of environment, ranging from ice cold to hot 
springs and every kind of moisture level. They are also found inside the bodies of 
various animals including humans. 
 
Q4. How are micro-organisms beneficial to mankind? 
A. 1. They help in cleaning up of the environment by degrading organic matter. 
2. They are used to increase soil fertility by fixing nitrogen 
3. Lactobacillus promoted the formation of curd. 
4. Bacteria are also involved in the making of cheese, pickles, etc. 
5. Yeast is used in the baking industry for making breads, pastries and cakes. It is 
also used in alcohol industry. 
6. Number of antibiotics are derived from various bacteria. 
7. Some bacteria and blue green algae are nitrogen fixers and help in increasing 
soil fertility. 
 
Q5. Why are chidren given vaccines? 
A. When a disease carrying micro-organism enters our body, the body produces 
antibodies to fight the invader. So, if dead and weakened micro-organisms are 
introduced in a healthy body, the body fights and kills them by producing 
antibodies. 
 
Q6. How do micro-organisms help in cleaning up of the environment? 
A. The micro-organisms help in converting complex organic substances into simpler 
molecules. These organic substances are the wastes produced by plant and 
animals and their dead remains. The so produced simpler molecules enter their 
respective nutrient cycles. 
 
Q7. Write a note on harmful micro-organisms. 
A. Certain micro organisms are diease causing. They are known as pathogens. Some 
micro organisms grow on food items and contaminate them by their toxic 
secretions. Thia leads to food poisoning. 
 
Q8. What are the various methods of food preservation/ 
A. Chemical method- sodium benzoate and sodium metabisulphite are common 
preservatives. They are used in the jams and squashes to check their spoilage. 
  Preservation by common salt- used to preserve meat, fish, amla, raw mangoes, 
tamarind, etc. 
   Preservation by sugar- jams, jellies and squashes are preserved by sugar. 
   Preservation by oil and vinegar- this prevents spoilage of pickles as bacteria 
cannot survive in such environment. 
    
Q9. What is pasteurization? 
A. This is a technique applied for milk to prevent growth of micro organisms. The 
milk is heated to about 70 degrees and then suddenly chilled and stored. 
 
Q10. Discuss symbiotic relationship of rhizobium with plants. 
A. The bacterium Rhizobium lives in the root nodules of leguminous plants like 
pulses, etc. It helps on fixing atmospheric nitrogen and increases soil fertility and 
the plant in return provides shelter to the bacterium. 
 
Q11. Discuss nitrogen cycle occurring in nature. 
A.  
Page 3


            BAL BHARATI PUBLIC SCHOOL, PITAMPURA                   
                                  
                                     CLASS 8 CORE ASSIGNMENT 
   MICRO-ORGANISMS: FRIENDS AND FOE 
 
Q1. What are micro-organisms? 
A. The organisms which can not be observed by naked eyes. 
 
Q2. Write a short note on viruses. 
A. Viruses are micro organisms that reproduce only inside the cells of the host 
organism. They cause various diseases like cold, influenza, polio, AIDS, etc. 
 
Q3. Write a note on presence of various microbes in nature. 
A. Microbes can survive under all types of environment, ranging from ice cold to hot 
springs and every kind of moisture level. They are also found inside the bodies of 
various animals including humans. 
 
Q4. How are micro-organisms beneficial to mankind? 
A. 1. They help in cleaning up of the environment by degrading organic matter. 
2. They are used to increase soil fertility by fixing nitrogen 
3. Lactobacillus promoted the formation of curd. 
4. Bacteria are also involved in the making of cheese, pickles, etc. 
5. Yeast is used in the baking industry for making breads, pastries and cakes. It is 
also used in alcohol industry. 
6. Number of antibiotics are derived from various bacteria. 
7. Some bacteria and blue green algae are nitrogen fixers and help in increasing 
soil fertility. 
 
Q5. Why are chidren given vaccines? 
A. When a disease carrying micro-organism enters our body, the body produces 
antibodies to fight the invader. So, if dead and weakened micro-organisms are 
introduced in a healthy body, the body fights and kills them by producing 
antibodies. 
 
Q6. How do micro-organisms help in cleaning up of the environment? 
A. The micro-organisms help in converting complex organic substances into simpler 
molecules. These organic substances are the wastes produced by plant and 
animals and their dead remains. The so produced simpler molecules enter their 
respective nutrient cycles. 
 
Q7. Write a note on harmful micro-organisms. 
A. Certain micro organisms are diease causing. They are known as pathogens. Some 
micro organisms grow on food items and contaminate them by their toxic 
secretions. Thia leads to food poisoning. 
 
Q8. What are the various methods of food preservation/ 
A. Chemical method- sodium benzoate and sodium metabisulphite are common 
preservatives. They are used in the jams and squashes to check their spoilage. 
  Preservation by common salt- used to preserve meat, fish, amla, raw mangoes, 
tamarind, etc. 
   Preservation by sugar- jams, jellies and squashes are preserved by sugar. 
   Preservation by oil and vinegar- this prevents spoilage of pickles as bacteria 
cannot survive in such environment. 
    
Q9. What is pasteurization? 
A. This is a technique applied for milk to prevent growth of micro organisms. The 
milk is heated to about 70 degrees and then suddenly chilled and stored. 
 
Q10. Discuss symbiotic relationship of rhizobium with plants. 
A. The bacterium Rhizobium lives in the root nodules of leguminous plants like 
pulses, etc. It helps on fixing atmospheric nitrogen and increases soil fertility and 
the plant in return provides shelter to the bacterium. 
 
Q11. Discuss nitrogen cycle occurring in nature. 
A.  
 
Read More
Offer running on EduRev: Apply code STAYHOME200 to get INR 200 off on our premium plan EduRev Infinity!

Complete Syllabus of Class 8

Content Category

Related Searches

ppt

,

Notes(2) : Microorganisms - Friend & Foe Class 8 Notes | EduRev

,

Important questions

,

shortcuts and tricks

,

Free

,

Exam

,

Viva Questions

,

MCQs

,

study material

,

Previous Year Questions with Solutions

,

Semester Notes

,

pdf

,

video lectures

,

past year papers

,

Summary

,

practice quizzes

,

mock tests for examination

,

Objective type Questions

,

Notes(2) : Microorganisms - Friend & Foe Class 8 Notes | EduRev

,

Extra Questions

,

Sample Paper

,

Notes(2) : Microorganisms - Friend & Foe Class 8 Notes | EduRev

;