NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe

NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe, contains solutions to various questions in Exercise for Chapter 2.  At the end of the Solutions, all the keywords and Notes which are important to understand Science Chapter 2 Microorganisms: Friend and Foe Class 8, have been explained in a simple and easy to understand manner. We are providing NCERT Solutions for Class 8 all subjects which can be accessed by clicking here.

NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe – Video Explanation

Download NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe

NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe– Solutions to Question 1 and Question 2

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NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe– Solutions to Question 2 to Question 4

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NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe– Solutions to Question 5 to Question 7

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NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe– Solutions to Question 7 to Question 9

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NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe– Definition of the Keywords-Microorganisms, Virus, Antibiotics, Antibodies, Pathogens, Communicable diseases, Carriers, Preservatives and Pasteurization.

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NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe , Exercises includes – Fill in blank, Tick the correct, Match the following and Questions/ Answers  which helps you to understand the topic covered in Microorganisms: Friend and Foe Class 8, in a better manner to help you to score good marks in your examinations.

NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe – NCERT Exercises

Question 1:

Fill in the blanks:

(a) Microorganisms can be seen with the help of a __________.

(b) Blue green algae fix ___________ directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of _________.

(d) Cholera is caused by ________

Answer 1:

(a) Microorganisms can be seen with the help of a microscope.

(b) Blue green algae fix atmospheric nitrogen directly from air to enhance fertility of soil.

(c) Alcohol is produced with the help of yeast.

(d) Cholera is caused by bacteria.

Question 2:

Tick the correct answer.

(a) Yeast is used in the production of

(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen

(b)The following is an antibiotic

(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast

(c) Carrier of malaria-causing protozoan is

(i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly

(d) The most common carrier of communicable diseases is

(i) ant (ii) housefly (iii) dragonfly (iv) spider

(e) The bread or idli dough rises because of

(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading

(f) The process of conversion of sugar into alcohol is called

(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection

 Answer 2:

(a) (ii) alcohol

(b) (ii) Streptomycin

(c) (i) female Anopheles mosquito

(d) (ii) housefly

(e) (iii) growth of yeast cells

(f) (iii) fermentation




Question 3:

Match the organisms in Column A with their action in Column B.

mtc ques

 Answer :

mtc ans 2

Question 4:

Can microorganisms be seen with the naked eyes? If not, how can they be seen?

Answer 4:

No. A microorganism is too small to be seen with the unaided/naked eye.

They can be seen with the help of a microscope.

NCERT Solutions for Class 8 Science Chapter 2 – Microorganisms: Friend and Foe

Question 5:

What are the major groups of micro-organisms?

Answer 5:

There are four major groups of micro-organisms—

  1. Bacteria-These are microscopic single-celled organisms that live in a variety of environments. They may be spherical (Streptococcus bacteria), rod-shaped (Bacillus anthracis) or spiral (Spirillum) in structure.
  2. Fungi- It is a Eukaryotic organism that may exist as a single filamentous structure or may be multicellular.
  3. Protozoa- These are single-celled organisms that exist in diverse environments. These are also eukaryotic without any cell wall. For example- Amoeba or paramecium.
  4. Algae- These are eukaryotic aquatic organisms that have the ability to carry out photosynthesis. There are various types of algae, for example- green, yellow-green, red, brown, fire, golden-brown algae etc.
  5. Virus- These are microscopic infectious organisms that become active and replicate only when they are inside the host organism.

Question 6:

Name the microorganisms which can fix atmospheric nitrogen in the soil.

Answer 6:

Nitrogen-Fixing bacteria are the bacteria that can convert free nitrogen present in the atmosphere to fixed-nitrogen, in the form of inorganic compounds that can be used by plants.

Microorganisms that can fix nitrogen are –

Bacteria such as Azotobacter and archaea, Azolla -cyanobacteria, legume- rhizobia are crop-related nitrogen fixation bacteria present in the soil.




Question 7:

Write 10 lines on the usefulness of microorganisms in our lives.

Answer 7:

Ten lines on the usefulness of microorganisms in our lives are –

  1. Penicillium, a fungus is used in the production of antibiotics such as penicillin.
  2. Microorganisms are used in the making of wine by fermentation of sugar by yeasts.
  3. Microorganisms such as Rhizobium help in increasing the fertility of the soil by fixing nitrogen.
  4. Microorganisms are involved in the sewage disposal areas for decomposition, production of manures and reduction of pollution.
  5. They are used as preservatives for various food items which we consume in our daily lives.
  6. Bacterium Lactobacillus replicates in milk and is responsible for the formation of curd.
  7. They are used to produce vaccines for various diseases.
  8. Petroleum is also a product of microorganisms known as diatoms.
  9. Certain microorganisms are also used in the production of insecticides.
  10. An important vitamin, Vitamin B12 is also manufactured with the help of Fungi.

Question 8:

Write a short paragraph on the harms caused by microorganisms.

Answer 8:

Microorganisms are harmful in many ways.They are the source of various diseases. The disease-causing microorganisms are called pathogens. Pathogens can enter our body through various mediums such as air, water, food or even transmitting agents such as insects like housefly etc. These transmitting agents carry various harmful microbes and these enter our bodies causing diseases. Cholera, common cold, chicken pox and tuberculosis are examples of some communicable diseases. Typhoid is caused due to consumption of food contaminated by bacteria, Poliomyelitis is caused by virus and transmitted through air and water, ringworm is caused by fungus due to direct contact with an infected person etc.

Question 9:

What are antibiotics? What precautions must be taken while taking antibiotics?

Answer 9:

An antibiotic is a chemical compound that slows down or prevents the growth of disease-causing microorganisms. The precautions that must be taken while taking antibiotics are that antibiotics must not be taken when you do not need them otherwise it may lead to antibiotic resistance. Further, antibiotics must be taken at the appropriate time and in the right amount. The antibiotics must be taken under the supervision of a doctor and the course/dosage prescribed must be completed for effective results.

Topics Covered in Chapter 2 Microorganisms: Friend and Foe Class 8 Science :-

  • Microorganisms
  • Where do Microorganisms Live?
  • Microorganisms and Us
  • Harmful Microorganisms
  • Food Preservation
  • Nitrogen Fixation
  • Nitrogen cycle




Important Terms Relevant to understand NCERT Solutions for Class 8 Science Chapter 2-Microorganisms: Friend and Foe:-

Microorganisms: These are organisms that are so small that they are invisible to the unaided human eye and can be seen only with the help of a microscope. They are also known as microbes and include a wide range of organisms.

Virus: These are microscopic infectious agents that become active and replicate only when they are inside their host organisms.

Antibiotics: These are chemical substances that when consumed kill or inhibit the growth of disease-causing microorganisms. They are bacteria specific and generally do not cause any side-effects.

Antibodies: These are the protective proteins, also known as immunoglobulins, produced by the immune system of the body in response to the entry of a foreign substance or pathogen into the body. They help defend the body against harmful microbes by fighting them off.

Pathogens: These are the harmful disease-causing microorganisms which when enter the body cause various types of diseases.

Communicable diseases: These are the contagious diseases that can be transmitted directly or indirectly from an affected individual to a healthy individual through air, water, food or physical contact.

Carriers: These are the transmitting agents that carry and spread various microbes from one place to another.

Preservatives: These are the natural or artificial chemicals that slows down or prevents the spoilage of food by microbial action or any other undesirable chemical change.

Pasteurization: Discovered and named after Louis Pasteur. A process in which milk is heated at around 60-70 degree Celsius for around 30 seconds and then suddenly chilled and stored. This prevents the growth of microbes and hence contamination of milk.

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