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NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe will assist you in scoring more marks. This includes the textbook and their solutions for Microorganisms: Friend and Foe Chapter 2 of Class 8 Science, which is made in adherence to the updated syllabus 2023 released by CBSE.
Our solutions offer ample material to help students build a strong foundation and improve their understanding of the subject.
On this page, you will find all the NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe which includes detailed exercise-based solutions. These NCERT Solutions for Class 8 Science are downloadable and easy to access. Our Science experts have meticulously developed these solutions to support students in preparing for their Class 8 exams.
NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe
Microorganisms: Friend and Foe Class 8 Science NCERT Textbook Questions
Exercise Questions
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 ____________________.
Solution :
(a) Microorganisms can be seen with the help of microscope.
(b) Blue green algae fix nitrogen directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of Yeast.
(d) Cholera is caused by bacteria.
2. Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
Solution : (ii) Alcohol
(b) The following is an antibiotic
(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast
Solution : (ii) Streptomycin
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly
Solution : (i) Female Anopheles Mosquito
(d) The most common carrier of communicable diseases is
(i) ant (ii) housefly (iii) dragonfly (iv) spider
Solution : (ii) Housefly
(e) The bread or idli dough rises because of
(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading
Solution : (iii) Growth of yeast cells
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection
Solution : (iii) Fermentation
3. Match the organisms in Column A with their action in Column B
| A | 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 |
| A | B |
| (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 |
4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Solution :
No, microorganisms cannot be seen with the naked eye because they are very small in size. They can be seen with the help of a microscope.
5. What are the major groups of microorganisms?
Solution :
Microorganisms can be classified into four major groups which are as follows-
(a) Fungi
(b) Bacteria
(c) Protozoa
(d) Some Algae
6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Solution :
Bacteria such as Rhizobium and certain blue green algae can fix atmospheric nitrogen in the soil.
7. Write 10 lines on the usefulness of microorganisms in our lives.
Solution :
Microorganisms play a very important role in our lives. Some of their usefulness is listed below-
- Many antibiotics are produced by bacteria and fungi.
- A bacterium lactobacillus promotes the formation of curd.
- Microorganisms decompose dead organic waste of plants and animals converting them into simple substances, which can be used by other plants and animals. Therefore they enhance the plant growth.
- Microorganisms can be used to degrade the harmful and smelly substances and help to keep the environment clean.
- Microorganisms are used to increase the soil fertility by fixing the atmospheric nitrogen.
- Microorganisms are involved in the production of a lot food and beverages, including bread, cheese, yogurt and wine. They contribute to the fermentation process, which improves the taste, texture, and nutritional value of these products.
- They also play an important role in human digestive system.
- They are used in studying medicine and and biotechnology.
- Microbes are employed in the production of probiotics, which are beneficial bacteria that promote gut health and support the immune system.
- Microorganisms are also very helpful in producing vaccines against various diseases.
8. Write a short paragraph on the harmful effects of microorganisms.
Solution :
Microorganisms possess a lot of harmful effects. Some of the microorganisms which are called pathogens cause diseases in human beings, plants and animals. Pathogens enter our body through the air we breathe, the water we drink or the food we eat. They can also get transmitted by direct contact with an infected person or carried by an animal. Diseases like common cold, cholera can be easily transmitted from one person to another. Some microorganisms also spoil food, clothing and leather. Disease causing microbes also reduce the yield of crops.
9. What are antibiotics? What precautions must be taken while taking antibiotics?
Solution :
The medicines which kill or stop the growth of the disease-causing microbes are called antibiotics. It is important to take antibiotic only on the advice of a qualified doctor. One must finish the course prescribed by the doctor to make the drug more effective. Antibiotics must not be taken unnecessarily because it may kill beneficial bacteria also and the unnecessary or over doses may be very harmful.
Summary
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