NCERT Solutions Class 8 Science Chapter 2

NCERT Solutions for Class 8 Science Chapter 2: Microorganism Friends and Foe

Class 8 is when students learn essential subjects and concepts that prepare them for the upcoming courses. Science can be a challenging but equally exciting subject for the students. In addition to providing knowledge, this subject opens many doors to learning opportunities and career options. Based on the above-mentioned, we can easily understand why class 8 is a very crucial class for every CBSE student who wishes to take science as their main stream subject. 

Chapter 2 Microorganisms: Friends and Foe offers a complete knowledge of microorganisms and their habitats. Here, the students will learn about microorganisms, the mode of their reproduction and their usage. . In addition, the chapter highlights some essential sub-topics such as harmful microorganisms, pathogens, soil microorganisms, and nitrogen fixation by bacteria. Finally, students will learn how some microbes can be used to make medications and alcohol commercially. 

Extramarks NCERT solutions for class 8 Science chapter 2 will help the students to find the best answers to all questions given in the chapter. The subject matter experts present the answers after careful analysis of the concepts. As a result, students will get the appropriate responses in an easy-to-understand language as well as easy to remember format. Further, the solutions offer various types of questions. It includes filling in the blanks, matching the following, true or false, descriptive type questions from class 8 Science chapter 2. 

Extramarks is the most trusted learning platform as it offers the best learning experience and curated NCERT solutions to the students. Our NCERT solutions cover all essential subtopics under the chapter microorganism Friends and Foe. Using our solutions, students will be able to understand the effect of microorganisms on our environment. 

For an enhanced learning experience, students can visit the Extramarks for the NCERT study materials and refer to the latest updated syllabus. In addition, students can get other primary and secondary class solutions, including NCERT solutions class 9, NCERT solutions class 10, and NCERT solutions class 11. 

Key Topics Covered in NCERT Solutions for Class 8 Science Chapter 2

Class 8 science chapter 2 Microorganisms- Friend and Foe educate the students about the role of microorganisms and their effects.Microorganisms can spoil the food by decomposing the food material, some of them spoil leather and clothes. In addition, they are responsible for food poisoning. Through this information, students grab comprehensive information on the key topics. 

The subtopics in NCERT solutions for class 8 Science chapter 2 includes:

Habitats of Microorganisms
Microorganisms and us
Harmful microorganisms
Food Preservation
Nitrogen fixation
Nitrogen cycle


Microorganisms are microscopic organisms, usually unicellular and cannot be seen with the naked eye.  They include bacteria, fungi, protozoa and some algae  However, some of them can be seen with the naked eye during the rainy season. 

Habitats of Microorganisms

Microorganisms can live in all types of environments, especially during rainy seasons. They can survive in ice-cold climates, hot springs and deserts and marshy islands. One can also discover microbes in polluted air and water. In some cases, they are found inside the bodies of animals. Microbes like amoeba can live alone, while fungi and bacteria may live in colonies. Students can learn about the adverse effect of microbes in Extramarks NCERT solutions for class 8 Science chapter 2. 

Microorganisms and us

Microorganisms have different roles, including bad and good. Some organisms are harmful and may cause diseases. While others are used for nitrogen fixation and cleaning up the environment. Organic waste such as vegetable peels, remains of animals, and faeces are broken down into harmless and usable substances by bacteria, called manure. 

Harmful microorganisms

Various microorganisms are viruses, and they reproduce only inside the cells of the host organisms. It may cause severe diseases like Polio, Chickenpox, and Common cold. In addition, diseases like typhoid and tuberculosis are bacterial diseases caused by protozoans. The microorganism can survive in all environments, from ice-cold climates to hot springs and deserts to marshy lands. Following are the types of harmful diseases discussed in NCERT solutions for class 8 Science chapter 2: 

  • Pathogens: It is an organism that can cause severe disease.  Bacteria, protozoa, and viruses can be pathogenic. 
  • Carrier: A person or organism infected with an infectious disease agent but displays no symptoms. It can spread the infection. 
  • Airborne disease: Some diseases can spread by air, and these diseases are known as airborne diseases. Influenza is one of the best examples of airborne disease. 
  • Waterborne disease: Waterborne disease spreads through water, and typhoid is one of the best examples of waterborne disease. 
  • Plant diseases: Plants can be attacked by bacteria or viruses, and specific pathogens can cause infections in plants. It includes rice, potato, wheat, sugarcane, orange, and apple. 

Food Preservation

It is essential to preserve food from microorganisms or microbes. Spoiled food emits a foul smell and has a sour taste, and sometimes it changes colour. Therefore, it is essential to preserve food to prevent it from being spoiled. Consequently, it is beneficial to use salt and edible oils to check the growth of microorganisms. It is known as preservatives. People use common salt to preserve meat and fish for a long time. 

Food preservation is one of the vital parts of the food industry. In conservation, certain chemicals inhibit the growth of bacteria, and it increases the life of the cooked food. Further, the protection can also be carried out at home. There are many ways to preserve food elaborated in NCERT solutions for class 8 Science chapter 2: 

  • Chemical methods: It is used in the food industry where sodium meta-bisulphate is a commonly used chemical preservative.
  • Common salt: Sodium chloride, also called the common salt, is used as a preservative at home and in vegetable pickles. It removes water and kills bacteria. 
  • Sugar: It is also used to preserve jams, jellies and squashes. The growth of microbes is restricted by sugar, which reduces the moisture content. 
  • Oil and Vinegar: Bacteria have no growth against oil and vinegar. Thus, many food preparations like pickles are preserved by adding vinegar. 

Nitrogen fixation

For the fixation of nitrogen, rhizobium bacteria is highly used. The rhizobium lives in the root nodules of leguminous plants and converts nitrogen into a soluble form for them. The bacteria cannot make their food. Instead, the leguminous plants offer food and shelter to the rhizobium bacteria. 

Microorganisms have tons of benefits but they can cause diseases to plants and animals. However, it helps in maintaining a balance in our ecological system. 

Nitrogen cycle

The nitrogen cycle is a biogeochemical cycle where the nitrogen is converted into various chemical forms. Light and nitrogen are essential constituents for all living organisms. In addition, it is part of proteins, chlorophyll, nucleic acid, and vitamins. Here, nitrogen cannot be taken by plants and animals. Instead, certain bacteria and blue-green algae fix the nitrogen from the atmosphere. It converts into compounds of nitrogen in the soil. 

Besides, when plants and animals die, bacteria and fungi convert the nitrogenous waste into compounds. In addition, it is used by plants, and the percentage of nitrogen in the atmosphere remains constant. Students can refer to NCERT solutions for class 8 Science chapter 2 and understand the nitrogen cycle formation. 

NCERT Solutions for Class 8 Science Chapter 2: Exercise & Answer Solutions

Science is one of the challenging subjects, and it can be difficult for many students to understand the key concepts. Therefore, NCERT solutions for class 8 Science chapter 2 offers a comprehensive solution set to help students understand the concept more clearly. NCERT solutions for class 8 Science chapter 2 help clarify the students’ doubts. Seven exercises given in these solutions elaborate on the critical concepts of microorganisms. Further, it includes short answers, long answers, and multiple-type answers. In addition, the students will also witness fill in the blanks, match the pair and true or false type of questions & answers. 

The solutions are accurate and prepared by a team of specialists with the latest CBSE guidelines. Chapter 2 Microorganism- Friends and Foe Class 8 educates students about the role and uses of microorganisms. Here, the students can learn the classes of microorganisms like bacteria, fungi, protozoans, and viruses. 

Students can click on the links below for specific questions and solutions for NCERT solutions for class 8 Science chapter 2:

  • Chapter 2: Exercise 2.1 Solutions: 7 Questions

Extramarks also offer NCERT solutions for primary to secondary classes. The students can get click on the links below: 

  • NCERT Solutions Class 1
  • NCERT Solutions Class 2
  • NCERT Solutions Class 3
  • NCERT Solutions Class 4, 
  • NCERT Solutions Class 5
  • NCERT Solutions Class 6
  • NCERT Solutions Class 7
  • NCERT Solutions Class 8
  • NCERT Solutions Class 9
  • NCERT Solutions Class 10
  • NCERT Solutions Class 11
  • NCERT Solutions Class 12

NCERT Exemplar Class 8 Science

Science is a challenging subject; it requires a better understanding of the topics in the chapter. Therefore, students can enhance their learning by solving different types of questions. It helps them to develop a strong foundation on the sub-topics. The exemplar is designed with a different difficulty level, and students can get solutions for all the questions present in the exercise. It paves the way for the students of class 8 to understand the subject in a better way.

NCERT exemplar serves as the best study material for preparing for the science examination. The exemplar covers all the essential topics and concepts prescribed in the NCERT curriculum and CBSE class 8 Science syllabus. The issues and ideas are well explained in comprehensive language. It helps to build a strong foundation on all the concepts of microorganisms. As in the CBSE exam, they may have to answer various questions; the exemplar provides clarity on the same. Students can excel in the upcoming examination by answering the following kind of questions:

  • Long answer type of questions
  • Short answer type of questions
  • Different types of questions 
  • Multiple-choice questions

Our Extramarks NCERT solutions for class 8 Science chapter 2 provide questions from the chapter covering the topics of microorganisms. The students will learn about the role of microbes in nature and the different diseases associated with them. 

Key Features of NCERT Solutions for Class 8 Science Chapter 2

Extramarks has a team of science teachers who serve their knowledge in preparing the solutions for the subtopics covered in the chapter. However, it happens that students face difficulty understanding a few concepts. Therefore, they can refer to our NCERT solutions and clarify all their doubts by going through elaborated answers to the textbook questions. 

Following are the key features in NCERT solutions for class 8 Science chapter 2:

  • Students learn how to differentiate between nitrogen fixation and the nitrogen cycle. 
  • It is provided with detailed answers to all the exercises and consists of various questions such as filling in the blanks, matching the following and true or false.
  • NCERT solutions for class 8 Science chapter 2 are provided in a comprehensive language, hence,it helps students to grasp and retain the concepts quickly.
  • Our NCERT solution guide helps students to quickly revise the chapter before the exam.

Q.1 Fill in the blanks.
(a) Microorganisms can be seen with the help of a __________.
(b) Blue green algae fix _________ directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of ________.
(d) Cholera is caused by __________.


(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria

Q.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


(a) (ii) alcohol
(b) (ii) Streptomycin
(c) (i) female Anopheles mosquito
(d) (ii) housefly
(e) (iii) growth of yeast cells
(f) (iii) fermentation

Q.3 Match the organisms in Column A with their action in Column B.



(i) Bacteria (a) Fixing nitrogen
(ii) Rhizobium (b) Setting of curd
(iii) Lactobacillus (c) Baking of bread
(iv) Yeast (d) Causing malaria
(v) A protozoan (e) Causing cholera
(vi) A virus (f) Causing AIDS
(g) Producing antibodies





(i) Bacteria (e) Causing cholera
(ii) Rhizobium (a) Fixing nitrogen
(iii) Lactobacillus (b) Setting of curd
(iv) Yeast (c) Baking of bread
(v) A protozoan (d) Causing malaria
(vi) A virus (f) Causing AIDS

Q.4 Can microorganisms be seen with the naked eye? If not, how can they be seen?


No, microorganisms cannot be seen with the naked eye. They are too small to be seen with naked eye. They can be seen through magnifying lens and microscope. Microorganisms, such as protozoans, present in water can be seen under a microscope. Fungus, that grows on bread, can be seen with the help of a magnifying lens.

Q.5 What are the major groups of microorganisms?


Microorganisms are classified into four major groups. The four major groups of microorganisms are:

  1. Bacteria
  2. Fungi
  3. Protozoa
  4. Algae

Q.6 Name the microorganisms which can fix atmospheric nitrogen in the soil.


The microorganisms that fix atmospheric nitrogen in the soil are Rhizobium and blue-green algae. These microorganisms are commonly called biological nitrogen fixers that fix atmospheric nitrogen to enrich soil with nitrogen and increase the fertility of soil.

Q.7 Write 10 lines on the usefulness of microorganisms in our lives.


Following are some functions of microorganisms that are important to us:

  1. At home, microorganism like yeast is used in the preparation of bread, cake, idli, dosa, etc.
  2. In baking industry, microorganism like yeast is used in making breads, pastries and cakes.
  3. A bacterium, Lactobacillus, helps in the setting of curd from milk.
  4. Microorganism like yeast is used in the production of alcohols and wine on large scale.
  5. In agriculture, microorganisms like Rhizobium and blue green algae help in the fixation of atmospheric nitrogen to enrich the fertility of soil.
  6. In medicine, microorganisms such as bacteria and fungi play an important role in the preparation of antibiotics.
  7. Microorganisms, such as certain bacteria, help in cleaning the environment by decomposing organic wastes into harmless and usable substances.
  8. They are also used in the preparation of vaccines to protect humans and other animals from various diseases.
  9. Certain microorganisms play an important role in the sewage treatment plant.
  10. Antibiotics prepared from microorganisms are also used to prevent microbial infection in the animals of livestock and poultry and to control various diseases in plants.

Q.8 Write a short paragraph on the harmful effects of microorganisms.


Microorganisms cause harm in many ways. Some of the harmful effects of microorganisms include causing diseases in humans, animals and plants and spoiling of food, clothes and leather. The disease causing microorganisms are called pathogens. Some bacterial microorganisms cause tuberculosis, typhoid, cholera, etc. in human beings. Diseases, like measles, chickenpox, polio, hepatitis, etc., are caused by viruses in human beings. In cattle, anthrax is caused by bacteria and foot and mouth disease is caused by fungi. In plants, disease like citrus canker, rust of wheat and yellow vein mosaic of bhindi are caused by bacteria, fungi and virus, respectively and reduces the yield of crops. Some microorganisms, like bacteria and fungi, spoil food by producing toxic substances. When these microorganisms are ingested by human beings along with the spoiled food, food poisoning is caused.

Q.9 What are antibiotics? What precautions must be taken while taking antibiotics?


Antibiotics are the medicines that are produced by the microorganisms to kill the disease causing microorganisms. The microorganisms that are used to prepare the antibiotics are bacteria and fungi.

The precautions that are to be taken while taking antibiotics are:

  1. It should be taken under a medical supervision.
  2. A complete course of antibiotics should be taken as prescribed by the physician.
  3. A right amount of antibiotics should be taken at right time as prescribed.
  4. Intake of wrong dose would make the antibiotic less effective.
  5. If not required, antibiotics should not be consumed as it may make body resistant, when it is needed in future and kill the beneficial bacteria present in the body.

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FAQs (Frequently Asked Questions)
1. What is in Chapter 2, Class 8 Science?

Class 8 Science chapter 2 Microorganisms deals with different microbes and their contribution to the environment. The students will learn about harmful microorganisms, food preservation and the nitrogen cycle.

2. What types of questions are provided in the NCERT solutions for class 8 Science chapter 2?

The students will witness different types of questions in NCERT solutions for class 8 Science chapter 2. A few such examples of different types of questions include the multiple-choice questions, fill in the blanks, and match the following. In addition, students often also get introduced to descriptive type questions.

3. How to benefit from NCERT solutions for class 8 Science chapter 2?

Students can access our NCERT solutions available on the website. The solutions are provided with straightforward explanations in comprehensive language. Therefore, they will be able to quickly clarify all their doubts in the chapter.