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

NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe provide solutions to all questions given in NCERT Textbook. Our expertly crafted solutions provide detailed, step-by-step answers to all textbook questions, making it easier for students to grasp complex concepts. By using our solutions, students can enhance their understanding, improve their problem-solving skills, and boost their confidence in the subject.

Chapter	Microorganisms: Friend and Foe
Textbook	NCERT
Type of Material	NCERT Solutions
Class	8
Subject	Science
Useful for	Class 8 Studying Students
Session	2024-25
Solutions provided	Yes
Intext Questions	Solved
No. of Intext Questions	7
No. of Exercise Questions	9
Total Questions Solved	16
Important Link	NCERT Solutions for Class 8 Science

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

INTEXT QUESTIONS SOLUTIONS

Q. 1. Boojho wants to know why certain living organisms are called micro-organisms or microbes.
Ans. The micro-organisms are so small in size that they cannot be seen with the naked eye and some of these can be seen only by microscope. That is why these are called micro-organisms.

Page – 19

Q. 2. Paheli saw that her mother added a little curd to warm milk to set curd for the next day. She is wondering, why?
Ans. Curd contains several micro-organisms, mainly the bacterium Lactobacillus, which promote the formation of curd. They start growing in milk and convert milk into curd.

Page – 21

Q. 3. Paheli wants to know why children/infants are given vaccination.
Ans. By vaccination, disease carrying microbes enters our body, the body produces antibodies to fight the invader. The body also remembers how to fight the microbe if it enters again. So, if dead or weakened microbes are introduced in a healthy body, the body fights and kills them by producing suitable antibodies. The antibodies remain in the body and we are protected from the disease-
causing microbes. This is how a vaccine works.

Page – 23

Q. 4. How do you prevent the spread of communicable diseases?
Ans. We should keep a handkerchief on the nose while sneezing. It is better to keep distance from infected persons.

Q. 5. Paheli is wondering why teacher keeps telling them not to let water collect anywhere in the neighbourhood.
Ans. All mosquitoes breed in water. Hence by keeping the surroundings clean and dry, we can prevent mosquitoes from breeding. One should not let water collect anywhere viz., in coolers, tyres, flower-pot, etc.

Page – 25

Q. 6. Paheli wonders how food can become poisonous.
Ans. Food poisoning could be due to the consumption of food spoilt by some micro-organisms. Micro-organisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death.

Page – 26

Q. 7. Boojho wants to know what is pasteurisation.
Ans. The milk is heated to 70⁰C for 15 seconds 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. It is called Pasteurisation.

EXERCISE QUESTIONS SOLUTIONS

Q. 1. Fill in the blanks.
(a) Micro-organisms 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 _________.

[NCERT Ex. Q.1, Page 29]

Ans. (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

[NCERT Ex. Q.2, Page 29]

Ans. (a) (ii) Alcohol is produced by the action of yeast.
(b) (ii) Streptomycin is an antibiotic effective against tuberculosis.
(c) (i) Female Anopheles mosquito is the carrier of malaria.
(d) (ii) The most common carrier of communicable diseases is Housefly.
(e) (iii) Idli dough rises due to growth of yeast cells.
(f) (iii) Fermentation.

Q. 3. Match the organisms in column I with their action in column II.

Column I	Column II
(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

Ans. (i) (e), (ii) (a), (iii) (b), (iv) (c), (v) (d), (vi) (f)

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

[NCERT Ex. Q.4, Page 29]

Ans. Micro-organisms cannot be seen with the naked eyes. They can be seen with the help of a micro-scope.

Q. 5. What are the major groups of micro-organisms?

[NCERT Ex. Q.5, Page 30]

Ans. Micro-organisms are divided into five major groups which are as follows:
(i) Bacteria: These are single celled organisms which are harmful, as they cause disease and some of them may be useful in vaccines.
(ii) Fungi: These are non-green plants which consume their food from the dead organic matter.
(iii) Protozoan: These are unicellular animals which cause diseases like malaria and dysentery.
(iv) Algae: These are photo-autotrophic organisms that may be unicellular or multicellular. They play an important role in medicines, agriculture, industry and as food.
(v) Viruses are also considered to be micro-organisms but are actually the connecting links between non-living and living organisms.

Q. 6. Name the micro-organisms which can fix atmospheric nitrogen in the soil.

[NCERT Ex. Q.6, Page 30]

Ans. Bacteria, like Rhizobium and blue green algae can fix atmospheric nitrogen in the soil.

Q. 7. Write 10 lines on the usefulness of micro-organisms in our lives.

[NCERT Ex. Q.7, Page 30]

Ans. Uses of micro-organisms:
(i) Micro-organisms are used in making of curd and bread.
(ii) Bacteria are also involved in the making of cheese, pickles and many other food items.
(iii) Acetobacter aceti bacteria is used for production of acetic acid from alcohol.
(iv) Yeast is used for commercial production of alcohol and wine.
(v) The antibiotics manufactured by growing specific micro-organisms are used to cure a variety of diseases.
(vi) Micro-organisms fix the nitrogen of atmosphere into soil giving rise to fertility of soil.
(vii) Micro-organisms decompose waste into simple materials and clean-up the atmosphere.
(viii) Micro-organisms decompose the dead organic varieties of plants and animals.
(ix) Vaccines are made by dead or weakened microbes.
(x) Certain microbes are also used in the biological treatment of sewage and industrial effluents.

Q. 8. Write a short paragraph on the diseases caused by micro-organisms.

[NCERT Ex. Q.8, Page 30]

Ans. Micro-organisms are also very harmful to us. They cause a number of diseases in humans as well as in other animals. Common cold, tuberculosis, measles, chicken pox, polio, cholera, typhoid, hepatitis-B, malaria are some common human diseases caused by microorganisms. Anthrax is a serious disease in animals caused by microbes. They also make food items unfit for use by food poisoning. They also spoil clothes and leather products. They also cause diseases in plants like blights in potatoes, sugarcanes, oranges, etc. They also reduce the crop production.

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

[NCERT Ex. Q.9, Page 30]

Ans. Antibiotics are tablets, capsules or injections which are used to kill or stop the growth of pathogens, i.e., disease causing microbes. Penicillin, tetracycline are the examples of antibiotics.
Precautions:
(i) It should be taken in proper dose only on the advice of qualified doctors.
(ii) Complete course prescribed by the doctor.
(iii) It should not be taken without any reason, or requirement.
(iv) Antibiotics taken unnecessarily may kill the beneficial bacteria in the body.

Learning Outcomes

Chapter 2 of Class 8 Science, “Microorganisms: Friend and Foe,” introduces students to the microorganisms and its types, friendly microorganisms, and various methods of preserving food. By the end of this chapter, students will have a clear understanding of how microorganisms are helpful, how they can preserve food.

•  Knowing types of micro-organisms.
•  Learning about various friendly micro-organisms.
•  Knowing how micro-organisms are helpful.
•  Discussing medicinal uses of micro-organisms.
•  Discussing harmful micro-organisms and the diseases they cause.
•  Knowing various methods of preserving food.
•  Learning the nitrogen cycle in nature.

Also access

• NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe
• NCERT Solutions for Class 8 Science Chapter 1 Crop Production and Management

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Topics covered in NCERT Class 8 Science Chapter 1

1.1	Agricultural Practices
1.2	Basic Principle of Crop Production
1.3	Preparation of Soil
1.4	Sowing

By referring to NCERT Solutions for Class 8 Science Chapter 2, students can quickly clarify difficult concepts. These solutions also ensure that students learn the correct answers to the exercise questions in their Class 8 Science NCERT textbook.

Stay connected to discover more about NCERT Solutions and get valuable preparation tips.

Important Links for Microorganisms: Friend and Foe

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