NCERT Solutions for Class 8 Science Chapter 2 Microorganisms Friend and Foe
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NCERT Solutions for Class 8 Science Chapter 2 Microorganisms Friend and Foe
These Chapter 2 Class 8 Science NCERT Solutions are curated by the experts in a comprehensive which can be helpful in clearing your doubts instantly. It will make you understand the topics in most simple manner and grasp it easily to perform better. These NCERT Solutions for Science help you in improving the marks in the examinations and have edge over your classmates.
| Study Material for Class 8 Science Chapter 2 Microorganisms Friend and Foe |
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Page No: 29
Exercise
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
(a) Microorganisms can be seen with the help of a microscope.
(b) Blue green algae fix nitrogen directly from air to 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
► (ii) alcohol
(b) The following is an antibiotic
(i) Sodium bicarbonate
(ii) Streptomycin
(iii) Alcohol
(iv) Yeast
► (ii) Streptomycin
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly
► (i) female Anopheles mosquito
(d) The most common carrier of communicable diseases is
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider
► (ii) housefly
(e) The bread or idli dough rises because of
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading
► (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
► (iii) fermentation
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 | ||
Answer
Column
I
|
Column
II
|
||
(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?
Answer
Microorganisms are too small so they cannot be seen with naked eye. They can be seen with the help of a magnifying glass or microscope.
Page No: 30
5. What are the major groups of microorganisms?
Answer
There are five major groups of micro-organisms:
→ Bacteria - They are single celled disease-causing micro-organisms. They can be spiral or rod- shaped.
→ Fungi - They are mostly multicellular disease-causing microbes. Bread moulds are common examples of fungi.
→ Protozoa - They mainly include organisms such as Amoeba, Plasmodium,etc. They can be unicellular or multicellular.
→ Virus -Viruses are disease-causing microbes that reproduce only inside the host organism.
→ Algae - They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.
6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer
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.
Answer
Micro-organisms are too small to be seen through naked eyes. However, they are vital to plants and the environment.→ Lactobacillus is used to form curd from milk.
→ Rhizobium present in the roots of pulse plants fix nitrogen from air and supply nitrogen compounds to the pulse plants.
→ Micro-organisms are also used in winemaking, baking, pickling, and other food making processes.
→ Alcoholic fermentation by yeast is widely used in the preparation of wine and bread.
→ Microbes are used to reduce pollution. For example, decomposers such as bacteria and fungi break down dead bodies and excreta to form inorganic compounds, which can be absorbed by plants.
→ Microbes also play an important role in the preparation of medicines. Antibiotics are chemicals produced by micro-organisms to kill bacteria. Penicilin is an antibotic made from Penicilium.
→ Bacteria present in our intestine helps in proper digestion and release Vitmain B which is absorbed by intestine.
→ Many vaccines are prepared from micro-organisms. These vaccines are given to children to protect them from disease.
→ Certain microbes are also used in the biological treatment of sewage and industrial effluents.
→ Yeast is used in making idlis, bhaturas, bread, pastries and cakes.
8. Write a short paragraph on the harms caused by microorganisms.
Answer
9. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer
Antibiotics are medicines produced by certain micro-organisms to kill other disease-causing micro-organisms.
Precautions to be taken while using antibiotics:
→ Antibiotics should be taken under the supervision of a well qualified doctor.
→ Course (intake) of antibiotics should be completed as per the prescription given by the doctor.
→ Antibiotics should be taken in the right amount and at the right time. A wrong dose of antibiotics makes the drug ineffective. Also, excessive consumption of drugs may kill the useful bacteria present in our body.
Go Back To NCERT Solutions for Class 8 Science
Chapter 2 Microorganisms Friend and Foe Class 8 Science NCERT Solutions
Class 8 Science NCERT Solutions will be useful in gaining good marks in the examinations. These will help in improving application skills and clear your confusions. Syllabus is not only difficult but quite lengthy too thus NCERT Solutions will help you in covering those essential topics. It can be used to enrich knowledge and make lessons for learners more exciting.
Class 8 Science Chapter 2 Microorganisms Friend and Foe NCERT Questions and Answers - Topics
• Microorganisms
• Where do Microorganisms Live?
• Microorganisms and Us
→ Friendly Microorganisms
→ Making of Curd and Bread
→ Commercial Use of Microorganisms
→ Medicinal Use of Microorganisms
→ Vaccine
→ Increasing Soil Fertility
→ Cleaning the Environment
• Harmful Microorganisms
→ Disease causing Microorganisms in Humans
→ Disease causing Microorganisms in Animals
→ Disease causing Microorganisms in Plants
→ Food Poisoning
• Food Preservation
→ Chemical Method
→ Preservation by Common Salt
→ Preservation by Sugar
→ Preservation by Oil and Vinegar
→ Heat and Cold Treatments
→ Storage and Packing
• Nitrogen Fixation
• Nitrogen cycle
Chapter 2 Microorganisms Friend and Foe NCERT Solutions for Class 8 Science - Notes
• Microorganisms are too small and are not visible to the unaided eye.
• Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae.
• Viruses are also microscopic but are different from other microorganisms. They reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal.
• Serious diseases like polio and chicken pox are also caused by viruses. Diseases like dysentery and malaria are caused by protozoans whereas typhoid and tuberculosis (TB) are bacterial diseases.
• Microorganisms live in all types of environment, ranging from ice cold climate to hot springs; and deserts to marshy lands. They are also found inside the bodies of animals including humans.
• Some of microorganisms are beneficial in many ways whereas some others are harmful and cause diseases.
• Friendly Microorganisms: Help in the production of alcohol, making curd, cake, bread, idli, making antibiotics and vaccine. In agriculture they are used to increase soil fertility by fixing nitrogen. These plays a great role in cleaning the environment.
• Disease-causing microorganisms are called pathogens. 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.
• Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.
• There are some insects and animals which act as carriers of disease-causing microbes. Housefly is one such carrier.
• Several microorganisms cause diseases in animals. For example, anthrax is a dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.
• Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others which reduce the yield of crops.
• Food poisoning could be due to the consumption of food spoilt by some microorganisms.
• Processing of food to prevent them from spoilage and to retain their nutritive value for long period is called food preservation. The common chemicals generally used to check the growth of microorganisms are called preservatives.
• Food can be preserved using methods like adding preservatives such as salt, sugar, oil and vinegar, pasteurisation.
• The process of converting atmospheric nitrogen into compound of nitrogen is called nitrogen fixation
• A continuous process by which nitrogen and its compounds are interconverted in the environment and in living organisms including nitrogen fixation and decomposition is called nitrogen cycle.
Chapter 2 Microorganisms Friend and Foe Class 8 Science Questions and Answers - MCQ Questions with answers
1. Which of these are not included in the prevention of measles?
a) Vaccination
b) Antibodies
c) Both a and b
d) None of the above
► b) Antibodies
2. Fungi are :
a) animal like organism
b) plant like organism
c) always saprophytes
d) always unicellular
► b) plant like organism
3. Microbes are present :
a) everywhere
b) soil, air, polluted water
c) water, soil
d) air, water
► a) everywhere
4. An infectious disease is
a) caused only by bacteria
b) spread from person to person
c) spread from animal to animal
d) caused only by viruses
► b) spread from person to person
5. The bacterium present in curd is:
a) Salmonella typhi
b) Lactobacillus
c) Penicillin
d) Vibrio cholera
► b) Lactobacillus
6. Rhizobium bacteria
a) Help in digestion
b) Cause diseases
c) Help in nitrogen fixation
d) All of the above
► c) Help in nitrogen fixation
7. Which is a fungal disease in human?
a) amoebiasis
b) tuberculosis
c) anthrax
d) Athlete’s foot
► d) Athlete’s foot
8. The microorganism which helps in fermentation is:
a) Rhizobium
b) Yeast
c) E.coli
d) Rhizopus
► b) Yeast
9. Vaccines are made up of
a) Chemicals
b) Weak microorganisms
c) Viruses
d) Drugs
► b) Weak microorganisms
10. Which of the following diseases is caused by bacteria?
a) Chicken pox
b) Tuberculosis
c) Dengue
d) Polio
► b) Tuberculosis
Through these Chapter 2 Class 8 Science NCERT questions and answers, students should not waste time and adopt a strategy that helps them operate and learn at maximum efficiency. It will set a good foundation for your future goals and improve your studying habits.