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Case Study Questions for Class 8 Science Chapter 2 Microorganisms-Friend and Foe

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Here we are providing case study questions for CBSE Class 8 science Chapter 2 Microorganisms-Friend and Foe.

Case Study Questions

Question 1:

Daksh lived in delhi and he loves to play football. But as of now his half yearly exams were going on so his mother didn’t allow him to go out and play. She promised Daksh that as soon as his exams are over he can go and play. Post exams he went out to play football with his friends in the park. Suddenly a mosquito bit him under his left knee. He came home and everything was normal that time. The next day his health started getting affected. His Parents rushed him to the doctor. The doctor prescribed some medicines and some medical tests. The next day parents went to the doctor with Daksh’s medical report. In that report the platelet counts were very low. The doctor diagnosed him with Dengue fever. Daksh was hospitalised for some time and followed a strict diet to recover as early as possible. And eventually some days passed and he recovered.

Q. 1. Organisms which cannot be seen by naked eye. (a) Plants (b) Animals (c) Microorganisms (d) None of these

Q. 2. The causative organisms of dengue is (a) Anopheles mosquito (b) Aedes aegypti mosquito (c) Dengue virus (d) None of these

Q. 3. How does dengue virus spread?

Q. 4. Write any three preventive measures for dengue fever.

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Cbse, ncert and icse solution online, class 8 science case study question, case study question class 8 science (cbse / ncert board).

Class 8 Science Case Study Question and Answer: CBSE / NCERT Board Class 8 Science Case Study Question prepared by expert Science Teacher. Students can learn Case Based Question / Paragraph Type Question for NCERT Class 8 Science.

There are total 18 chapter Crop Production and Management, Microorganisms: Friend and Foe

, Synthetic Fibres and Plastics, Materials: Metals and Non-Metals, Coal and Petroleum, Combustion and Flame, Conservation of Plants and Animals, Cell – Structure and Functions, Reproduction in Animals, Reaching the Age of Adolescence, Force and Pressure, Friction, Sound, Chemical Effects of Electric Current, Some Natural Phenomena, Light, Stars and the Solar System, Pollution of Air and Water

For any problem during learning any Case or any doubts please comment us. We are always ready to help You.

CBSE Class 8 Science Case Study Question

• Chapter 1 Crop Production and Management Case Study Question
• Chapter 2 Microorganisms: Friend and Foe Case Study Question
• Chapter 3 Synthetic Fibres and Plastics Case Study Question
• Chapter 4 Materials: Metals and Non-Metals Case Study Question
• Chapter 5 Coal and Petroleum Case Study Question
• Chapter 6 Combustion and Flame Case Study Question
• Chapter 7 Conservation of Plants and Animals Case Study Question
• Chapter 8 Cell – Structure and Functions Case Study Question
• Chapter 9 Reproduction in Animals Case Study Question
• Chapter 10 Reaching the Age of Adolescence Case Study Question
• Chapter 11 Force and Pressure Case Study Question
• Chapter 12 Friction Case Study Question
• Chapter 13 Sound Case Study Question
• Chapter 14 Chemical Effects of Electric Current Case Study Question
• Chapter 15 Some Natural Phenomena Case Study Question
• Chapter 16 Light Case Study Question
• Chapter 17 Stars and the Solar System Case Study Question
• Chapter 18 Pollution of Air and Water Case Study Question

What is Case Study Question?

Ans. At case Study there will one paragraph and on the basis of that concept some question will made. Students have to solve that question.

How many marks will have at case based question?

Most of time 5 questions will made from each case. There will 1 or 2 marks for each question.

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

Question Wise Class 8 Science Chapter 2 Solutions Class 8 Science Chapter 2 NCERT Answers Class 8 Science Chapter 2 in Hindi Medium Class 8 Science Chapter 2 Extra Questions Class 8 Science Chapter 2 MCQ Class 8 Science NCERT Book Download Class 8 Science Chapter 2 Exemplar Book Class 8 Science Chapter 2 Exemplar Answers Class 8 Science NCERT Solutions Class 8 all Subjects NCERT Solutions

NCERT Solutions for Class 8 Science Chapter 2 Microorganisms Friend and Foe in English and Hindi Medium to Study Online or Download in PDF file format updated for new academic session 2024-25 following the latest CBSE Syllabus. Visit to NCERT Solutions main page to get all Subjects. The solutions are based on new NCERT books published for 2024-25 exams.

Class 8 Science Chapter 2 NCERT Solutions

• Class 8 Science Chapter 2 Question Answers
• Class 8 Science Chapter 2 in Hindi Medium

Class 8 Science Chapter 2 Extra Questions

• Class 8 Science Chapter 2 MCQ
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NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe is given below. Video Format solution based on NCERT Solutions 2024-25 is also available. Download 8 Science App for offline use for new session.

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Important Terms on Class 8 Science Chapter 2

1. microorganisms.

This part of chapter 2 of Class 8 Science focuses a branch of microbiology which introduced the importance of microorganism in our ecosystem. We have seen several kinds of plants and animals . However, there are many living organisms around us which we cannot see with eyes alone. These are called microorganisms or microbes, such as bacteria, fungi, protozoa and some algae. For example, you might have observed that during rainy season moist bread gets to spoil and its surface gets covered with greyish-white patches.

2. Microorganisms and Diseases

Remember, water and soil are full of tiny organisms, but all of them not comes into microorganisms or microbe’s category. Do you know? Viruses are also microorganisms. They reproduce only inside the cells of the host organisms and cause serious disease like Polio, Chickenpox, Common cold. Diseases like Typhoid, Tuberculosis are bacterial diseases which are caused by protozoans.

3. Where do Microorganisms Live?

Microorganisms can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. They are also found in polluted air and water as well as in inside the bodies of animals, including humans. Remember, microorganisms like amoeba can live alone while fungi and bacteria may live in colonies.

4. Microorganisms and Us

In this part of the content discusses the role of microorganisms, if microorganisms are good or bad for us. Thus, this part of the chapter will help, to an extent, in clearing this matter. As you know, that microorganisms play an essential role in our lives. Some of them are beneficial in many ways, whereas some others are harmful and causes diseases. They are used for various friendly purposes as they are used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals, faeces etc.) are broken down into harmless and usable substance by bacteria, called manure. In agriculture, they are used to increase soil fertility by fixing nitrogen .

5. Microorganisms as a Friends

You may know that microorganisms are used for the preparation of curd, bread and cake. Curd contains several microorganisms. The bacterium Lactobacillus promotes the formation of curd. Similarly, yeast is also used in the baking industry for making slices of bread, pastries and cakes. Microorganisms are also used for the large-scale production of alcohol, wine and acetic acid. As yeast is used for the smell of alcohol as sugar converts into alcohol. The process of conversion of sugar into alcohol is called ‘fermentation’.

6. Microorganisms in Medicine

Whenever we fall ill, the doctor gives us some antibiotic tablets, capsule or injection. The sources of these medicines are microorganisms. Do you think why they are used? These medicines kill or stop the growth of the disease-causing microorganisms. Hence, such medicines are called ‘Antibiotics’. Antibiotics are even mixed with the feed of livestock and poultry to check microbial infection in animals. They are also used to control many plant diseases. When a disease-carrying microbe enters our body, the body produces ‘antibodies’ to fight the invader. In our childhood, we must have been given an injection for ‘Smallpox’ and ‘Polio’ to protect our-self against these diseases. Generally, these vaccines are made from microbes or microorganisms.

7. Microorganisms as Decomposer

As you learn before, some bacteria and blue-green algae are able to fix nitrogen from the atmosphere to enrich the soil with nitrogen and increase its fertility. You often see a large amount of dead organic matter in the form of decaying plants and dead animals on the ground. You find that they disappear after some time. This is because the microorganisms decompose dead organic waste of plants and animals, converting them into manure or nutrients. The other plants and animals again use these substances.

8. Harmful Microorganisms

This part of the Class 8 Science deals with some diseases which are caused by microorganisms. Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals, called ‘Pathogens’.

9. Disease – Causing Microorganisms in Humans

Microbial diseases that can spread from an infected person to a healthy person through the air, water, food or physical contact, called ‘Communicable Diseases’. When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air, and then through the air, the virus enters the body of a healthy person while breathing. There are some insects and animals which act as ‘carriers’ of diseases causing microbes. Such as houseflies, mosquitoes, cockroach etc. Remember, ‘Anopheles Mosquito’ which careers the parasite of malaria. ‘Female Aedes’ mosquito act as a carrier of the dengue virus.

10. Disease – Causing Microorganisms in Animals and Plants

Anthrax is a dangerous human and cattle disease caused by the bacterium. Several microorganisms are there which causes diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. These diseases reduce the yield of crops. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous, causing severe illness and even death.

11. Food Preservation

In this part of the content gives an idea about food preservation from microorganism or microbes. As you know, spoilt food emits a bad smell and has a bad taste and change colour. So, it is very important that we preserve food to prevent it from being spoilt. Salt and edible oils are common chemicals generally used to check the growth of microorganisms, called ‘Preservatives’. Common salt has been used to preserve meat and fish for ages. Jams, jellies and squashes are preserved by sugar. As you know, boiling kills many microorganisms. You must have noticed that your mother is boiling milk before it is stored or used. Now in a day, dry fruits and even vegetables are sold in sealed airtight packets to prevent the attack of microbes.

12. Nitrogen Cycle

We know that our atmosphere has 78% nitrogen gas. Light and Nitrogen are the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acid and vitamins. Nitrogen cannot be taken by plants and animals directly. Certain bacteria and blue-green algae fix the nitrogen from the atmosphere and convert into compounds of nitrogen in the soil. When plants and animals die, bacteria and fungi convert the nitrogenous waste into nitrogenous compounds. And again, used by plants. As a result, the percentage of nitrogen in the atmosphere remains constant.

13. Nitrogen Fixation

As you know, the involvement of rhizobium bacteria in the fixation of nitrogen for leguminous plants. Rhizobium lives in the root nodules of leguminous plants and converts nitrogen into a soluble form for them. But that bacteria cannot make their own food. In return, leguminous plants provide food and shelter to the rhizobium bacteria. In this way, you can see microorganisms have tons of benefits, and they can cause deadly diseases too. As they are crucial in maintaining a balance in our ecological system, which helps to survive all living organisms.

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

No, microorganisms cannot be seen by naked eye as they are very small and are called microbes. They can be seen with the help of microscope.

What are the major groups of microorganisms?

Microorganisms are classified into four major groups are bacteria, fungi, protozoa and some algae.

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

Bacteria such as rhizobium and certain blue-green algae present in the soil can fix atmospheric nitrogen and convert into usable nitrogenous compounds, which are used by plants for the synthesis of plant proteins and other compounds.

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

The medicines that kill or stop the growth of the disease – causing microorganisms are called antibiotics. For example: Streptomycin, tetracycline, etc. Following precautions must be taken while taking antibiotics: Antibiotics should be taken only on the advice of a qualified doctor. One must finish the course prescribed by the doctor. Antibiotics must be avoided when not needed or in wrong doses.

Class 8 Science Chapter 2 MCQ with Answers

1. Which of the following reproduces only inside a host cell? (a) Bacteria (b) Virus (c) Amoeba (d) Fungus. 2. Paheli dug two pits, A and B, in her garden. In pit A, she put a polythene bag packed with some agricultural waste. In pit B, she dumped the same kind of waste but without packing it in a polythene bag. She, then covered both the pits with soil. What did she observe after a month? (a) Waste in pit A degraded faster than that in pit B. (b) Waste in pit B degraded faster than that in pit A. (c) Waste in both pits degraded almost equally. (d) Waste in both pits did not degrade at all. 3. A disease in human beings caused by virus is _______. (a) typhoid (b) influenza (c) dysentry (d) cholera 4. The two micro-organisms which live in symbiotic association in lichens are (a) fungus and protozoa (b) alga and bacteria (c) bacteria and protozoa (d) alga and fungus 5. The disease caused by a protozoan and spread by an insect is _________. (a) dengue (b) malaria (c) polio (d) measles 6. The gas released during the preparation of bread is (a) oxygen (b) carbon dioxide (c) nitrogen (d) sulphur dioxide 7. Pathogenic micro-organisms present in host cells are killed by medicines called (a) pain killer (b) antibodies (c) antibiotics (d) vaccines 8. Unscramble the jumbled words underlined in the following statements. (a) Cells of our body produce santiidobe to fight pathogens. (b) curbossulite is an air-borne disease caused by a bacterium. (c) Xanrhat is a dangerous bacterial disease. (d) Yeasts are used in the wine industry because of their property of meronettinaf.

1 (b) 2 (b) 3 (b) 4 (d) 5 (b) 6 (b) 7 (c) 8 (a) antibodies (b) tuberculosis (c) Anthra (d) fermentation

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Microorganisms: Friend And Foe Class 8 Science Extra Questions and Answers

Microorganisms Friend and Foe Class 8 Science Chapter 2 Extra Questions and Answers are provided here. We prepared these extra questions based on the latest NCERT Class 8 Science Book. CBSE Class 8 Science Chapter 2 Microorganisms: Friend and Foe Extra Questions will help you to properly understand a particular concept of the chapter.

Class 8 Science Chapter 2 Microorganisms: Friend and Foe Extra Questions

Very short answer type questions.

Question 1: What causes malaria?

Answer: Malaria is caused by protozoa.

Question 2: Which mosquito act as carrier of dengue virus?

Answer: Aedes mosquito acts as carrier of dengue virus.

Question 3: Name any two diseases that can be prevented by vaccination.

Answer: Polio and smallpox

Question 4: Give two examples of algae.

Answer: Chlamydomonas and Spirogyra

Question 5: Give two examples of protozoa.

Answer: Amoeba and Paramecium

Question 6: How are cholera and typhoid caused?

Answer: Cholera and typhoid are caused by bacteria.

Question 7: Give few of examples of fungi.

Answer: Bread mould, Penicillium and Aspergillus

Question 8: Who discovered penicillin?

Answer: In 1929, Alexander Fleming discovered penicillin.

Question 9: Name any two diseases caused by bacteria.

Answer: Typhoid and tuberculosis (TB)

Question 10: What causes foot and mouth disease of cattle?

Answer: Foot and mouth disease of cattle is caused by a virus.

Question 11: Who discovered the vaccine for smallpox?

Answer: Edward Jenner discovered the vaccine for smallpox in 1798.

Question 12: Name any two diseases caused by protozoa.

Answer: Diseases like dysentery and malaria are caused by protozoans.

Question 13: Name some antibiotics.

Answer: Streptomycin, tetracycline and erythromycin

Question 14: How are meat and fish preserved?

Answer: Meat and fish are covered with dry salt to check the growth of bacteria.

Question 15: What is fermentation?

Answer: The process of conversion of sugar into alcohol is called fermentation.

Question 16: Why do we boil milk before storing?

Answer: We boil milk before storing because boiling kills many microorganisms.

  Question 17: Name one plant disease caused by bacteria and its mode of transmission.

Answer: Citrus canker is caused by bacteria and transmitted through air.

Question 18: Why are the antibiotics not effective against colds and the flu?

Answer: Antibiotics are not effective against cold and flu as these are caused by viruses.

Question 19: Name one plant disease caused by virus and its mode of transmission.

Answer: Yellow vein mosaic of bhindi (Okra) is caused by virus and transmitted through insect.

Question 20: How can we control plant diseases?

Answer: They can be controlled by the use of certain chemicals which kill the microbes.

Question 21: Name one plant disease caused by fungi and its mode of transmission.

Answer: Rust of wheat is caused by fungi and transmitted through air and seeds.

Question 22: What causes food poisoning?

Answer: Food poisoning could be due to the consumption of food spoilt by some microorganisms.

Question 26: How do we preserve pickles?

Answer: We add salt or acid preservatives to pickles to prevent the attack of microbes.

Question 27: What are preservatives?

Answer: Chemicals (Salts, edible oils etc.) used to check the growths of microorganisms are called preservatives.

Question 28: Why pasteurized milk can be consumed without boiling?

Answer: Pasteurized milk can be consumed without boiling as it is free from harmful microbes.

Short Answer Type Question

Question 1: Name some unicellular and multicellular organisms.

Answer: Unicellular organisms- bacteria, some algae and protozoa

Multicellular organisms- algae and fungi

Question 2: How can we prevent the spread of communicable diseases?

Answer: We prevent the spread of communicable diseases:

• By keeping handkerchief on the nose and mouth while sneezing.
• By keeping distance from infected persons.

Question 3: How are viruses different from other microorganisms?

Answer: Viruses are quite different from other microorganisms. They reproduce only inside the host organism; bacterium, plant or animal cell.

Question 4: How do microorganisms clean the environment?

Answer: Some microorganisms decompose the organic waste and dead plants and animals into simple substances and clean up the environment.

Question 5: How are jams and squashes preserved?

Answer: Sodium benzoate and sodium metabisulphite are used in the jams and squashes to check their spoilage.

Question 6: What are the major groups of microorganisms?

Answer: Microorganisms are classified into four major groups. These groups are bacteria, fungi, protozoa and some algae.

Question 7: What are microorganisms?

Answer: Microorganisms or microbes are the living organisms around us which cannot be seen with naked eye.

Question 8: What diseases are prevented through vaccination?

Answer: Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination.

Question 9: Why do we keep food in refrigerator?

Answer: We keep food in the refrigerator because low temperature inhibits the growth of microbes and keep the food fresh.

Question 10: Why dry fruits and even vegetables are sold in sealed air tight packets?

Answer: Dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.

Question 11: Why is it important to vaccinate small children?

Answer: It is important to vaccinate small children in order to protect them against several diseases.

Question 12: Who discovered the bacterium which causes anthrax disease?

Answer: Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax disease.

Question 13: How are cholera and typhoid transmitted?

Answer: Cholera is transmitted through water or food. Typhoid is transmitted through water.

Question 14: Write any two common cattle diseases and its cause.

Answer: Anthrax is a dangerous cattle disease caused by a bacterium.

Foot and mouth disease of cattle is caused by a virus.

Question 15: Name the microorganisms which can fix atmospheric nitrogen in the soil.

Answer: Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen.

Question 16: Why sugar is used as preservative?

Answer: Sugar is used as preservative in jams, jellies and squashes. Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.

Question 17: Which microorganism is used for commercial production of alcohol, wine and acetic acid (vinegar)?

Answer: Yeast is used for commercial production of alcohol, wine and acetic acid (vinegar).

Question 18: Name some commonly known antibiotics which are made from fungi and bacteria.

Answer: Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.

Question 19: What are the harmful effects of microorganisms on plants?

Answer: Several microorganisms cause diseases in plants like wheat, rice, potato, sugarcane, orange, apple and others. The diseases reduce the yield of crops.

Question 20: Name some diseases caused by virus.

Answer: Common ailments like cold, influenza (flu) and most coughs are caused by viruses. Serious diseases like polio and chicken pox are also caused by viruses.

Question 21: How does food become poisonous?

Answer: Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death.

Question 22: How can we prevent the spread of hepatitis B?

Answer: Ways to prevent the spread of hepatitis B

• Drink boiled drinking water.
• Vaccination

Question 23: Name the bacterium found in the roots of pea plant. How is this bacterium useful?

Answer: Rhizobium lives in the root nodules of leguminous plants such as beans and peas. It is involved in the fixation of nitrogen in leguminous plants (pulses).

Question 24: Why should we keep our food covered?

Answer: Flies sit on uncovered food and they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick. So, it is advisable to always keep food covered.

Question 25: Why are viruses considered to be on the borderline between living organisms and non-living things?

Answer: Viruses are also microscopic. They, however, reproduce only inside the cells of the host organism, which may be a bacterium, plant or animal.

Question 26:   Write some common uses of yeast.

Answer: Common uses of yeast are:

• It is used in the baking industry for making breads, pastries and cakes.
• It is used for commercial production of alcohol and wine.

Long Answer Type Question

Question 1: How can food be preserved by adding oil and vinegar?

Answer: Use of oil and vinegar prevents spoilage of food because bacteria cannot live in such an environment. Vegetables, fruits, fish and meat are often preserved by this method.

Question 2:  How milk is turned into curd?

Answer: A little curd is added to warm milk to set curd. Curd contains several microorganisms. Of these, the bacterium Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd.

Question 3: How does common cold spread?

Answer: When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses are spread in the air. The virus may enter the body of a healthy person while breathing.

Question 4: Why is tuberculosis considered as infectious disease?

Answer: Tuberculosis is considered as infectious disease because bacteria that cause tuberculosis are spread from one person to another through tiny droplets released into the air via coughs and sneezes.

Question 5: What causes tuberculosis and how is it spread?

Answer: Tuberculosis is caused by bacteria that spread from person to person through microscopic droplets released into the air. This can happen when someone with tuberculosis coughs, speaks, sneezes or spits.

Question 6: What are biological nitrogen fixers?

Answer: Some bacteria and blue green algae are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers.

Question 7: How can cholera be prevented?

Answer: To prevent cholera we must:

• Maintain personal hygiene and good sanitary habits.
• Consume properly cooked food and boiled drinking water.
• Vaccination.

Question 8: What are pathogens?

Answer: Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens.

Question 9: How do pathogens enter our body?

Answer: 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 through an animal.

Question 10:  Why should we not let water collect anywhere in the neighbourhood?

Answer: All mosquitoes breed in water. Hence, one should not let water collect anywhere, in coolers, tyres, flower pot etc. By keeping the surroundings clean and dry we can prevent mosquitoes from breeding.

Question 11: What will happen if we take antibiotics when not needed?

Answer: If we take antibiotics when not needed or in wrong doses, it may make the drug less effective when we might need it in future.Also antibiotics taken unnecessarily may kill the beneficial bacteria in the body.

Question 12: What are carriers of disease-causing microbes? Give examples.

Answer: There are some insects and animals which act as carriers of disease-causing microbes. Housefly is one such carrier. Another example of a carrier is the female

Anopheles mosquito, which carries the parasite of malaria.

Question 13: What happens when yeast powder is added to sugar solution and kept for 4-5 hours?

Answer: When yeast powder is added to sugar solution and kept for 4-5 hours, fermentation takes place. Sugar has been converted into alcohol by yeast. This process of conversion of sugar into alcohol is known as fermentation.

  Question 14: Why is yeast used in baking industry?

Answer: Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the gas fill the dough and increase its volume. This is the basis of the use of yeast in the baking industry for making breads, pastries and cakes.

Question 15: How do houseflies spread disease?

Answer: Housefly is one such carrier. The flies sit on the garbage and animal excreta. Pathogens stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens. Whoever eats the contaminated food is likely to get sick.

Question 16: Write a short paragraph on the harms caused by microorganisms.

Answer: Microorganisms are harmful in many ways. Some of the microorganisms cause diseases in human beings, plants and animals. Such disease-causing microorganisms are called pathogens. Some microorganisms spoil food, clothing and leather.

Question 17: What is called pasteurization?

Answer: It is a process in which milk is heated to about 700C for 15 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 pasteurization.

Question 18: What are communicable diseases? Give examples.

Answer: 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.

Question 19: Can microorganisms be seen with the naked eye? If not, how can they be seen?

Answer: Microorganisms or microbes are so small in size that they cannot be seen with the unaided eye. Some of these, such as the fungus that grows on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope.

Question 20: Where do microorganisms live?

Answer: They can survive under 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 microorganisms grow on other organisms while others exist freely. Microorganisms like amoeba can live alone, while fungi and bacteria may live in colonies.

Question 21:  Why is curd an important ingredient in making rava idlis and bhaturas?

Answer: Curd is added while making idli and bhatura dough as curd contains Lactobacillus bacteria that undergoes anaerobic respiration and in this process it acts on sugar of the flour and releases carbon dioxide gas, this gas make the dough rise and when baked or fried gas escapes leaving the idli or bhatura soft and spongy.

Question 22:  How a vaccine works?

Answer: When a disease-carrying microbe 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.

Question 23:  Mention some important uses of fungi.

Answer: Uses of fungi are as follows:

• Some antibiotics are made from fungi.
• When plants and animals die fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again.
• Yeasts are single-celled fungi. It is used in baking industry for making breads, pastries and cakes and for commercial production of alcohol and wine.

Question 24: Write 10 lines on the usefulness of microorganisms in our lives.

Answer: Microorganisms play an important role in our lives. Some of them are beneficial in many ways.

• They are used in the preparation of curd, bread and cake.
• They are used for the large-scale production of alcohol, wine and acetic acid (vinegar).                        
• They are also used in cleaning up of the environment. For example, the organic wastes (vegetable peels, remains of animals etc.) are broken down into harmless and usable substances by bacteria.
• Bacteria are also used in the preparation of medicines.
• In agriculture they are used to increase soil fertility by fixing nitrogen.

Question 25:  What are antibiotics? What precautions must be taken while taking antibiotics?

Answer: Antibiotics are the medicines prepared from microorganisms to kill or stop the growth of the disease-causing microorganisms.

Precautions to be taken while taking antibiotics:

• Antibiotics should be taken only on the advice of a qualified doctor.
• Course of antibiotics should be completed as prescribed by the doctor.
• Antibiotics should be taken in the right amount and at the right time. If antibiotics are taken unnecessarily it may kill the beneficial bacteria in the body.
• Antibiotics are not effective against cold and flu as these are caused by viruses.

Question 26: Explain nitrogen cycle.

Answer: Our atmosphere has 78% nitrogen gas. The atmospheric nitrogen cannot be taken directly by plants and animals. Certain bacteria and blue green algae present in the soil fix nitrogen from the atmosphere and convert into compounds of nitrogen. Once nitrogen is converted into these usable compounds, it can be utilised by plants from the soil through their root system. Nitrogen is then used for the synthesis of plant proteins and other compounds. Animals feeding on plants get these proteins and other nitrogen compounds. When plants and animals die, bacteria and fungi present in the soil convert the nitrogenous wastes into nitrogenous compounds to be used by plants again. Certain other bacteria convert some part of them to nitrogen gas which goes back into the atmosphere. As a result, the percentage of nitrogen in the atmosphere remains more or less constant.

Question 27:  What are the different methods of food preservation?

Answer: Different methods of food preservation are:

• Chemical Method – Salts and edible oils are the common chemicals generally used to check the growth of microorganisms.
• Preservation by Common Salt – Common salt has been used to preserve meat and fish for ages. Salting is also used to preserve amla, raw mangoes, tamarind, etc.
• Preservation by Sugar – Jams, jellies and squashes are preserved by sugar.
• Preservation by Oil and Vinegar – Use of oil and vinegar prevents spoilage of pickles because bacteria cannot live in such an environment. Vegetables, fruits, fish and meat are often preserved by this method.
• Heat and Cold Treatments – This process kills many microorganisms. Milk is boiled before it is stored or used.
• Storage and Packing – Dry fruits and even vegetables are sold in sealed air tight packets to prevent the attack of microbes.

• 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.

Table of Contents

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 70 0 C 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.

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.

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Q11: What are the important keywords in class 8 science chapter 1 “Microorganisms: Friend and Foe”?

A11: Important keywords from class 8 science chapter 2 microorganisms: friend and foe are given below: Nitrogen fixation: Process of converting atmospheric free nitrogen into nitrogenous compounds. Antibodies: The proteins produced by the body which protect your body when harmful substances (antigens) enter your body. Food poisoning: The illness caused by eating contaminated food. Preservatives: A substance added to foodstuff to protect them from spoilage.

Q12: What are some fundamental facts from Class 8 Science Chapter 2 Microorganisms: Friend and Foe?

A12: Fundamental facts – (i) Study of microorganisms is called Microbiology. (ii) Anton Von Leeuwenhoek is called Father of Microbiology

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

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Microorganisms: Friend and Foe Class 8 Notes: CBSE Science Chapter 2

• Revision Notes
• Chapter 2 Microorganisms: Friend And Foe

Class 8 Science Chapter 2 Notes PDF on Microorganisms: Friend and Foe Download for FREE

Class 8 Science Chapter 2 Microorganisms Friend and Foe Notes by Vednatu will explore the fascinating world of microorganisms, which are tiny living things that are all around us. This chapter is an essential part of the CBSE Class 8 Science Syllabus and provides a detailed look at how these microorganisms can be both helpful and harmful. 

You'll learn about the different types of microorganisms, such as bacteria, fungi, and viruses, and their roles in our lives. Some microorganisms help in processes like digestion and decomposition, while others can cause diseases. These notes will help you understand their importance, and how they impact our health and environment. Additionally, the Revision Notes for Class 8 Science are designed to make your learning experience smoother, allowing you to review the key topics quickly and efficiently.

Access Science Class 8 Chapter 2 Microorganisms: Friend and Foe

Microorganisms:, there are numerous organisms living around us that we may not be able to see. we can see some of them through a magnifying glass, like the fungus on bread. some others are so small that they cannot be seen without a microscope.  these organisms that cannot be seen by unaided eyes are termed microorganisms or microbes. the microorganisms can be broadly classified as: bacteria - they are a group of prokaryotic organisms (does not have membrane-bound nucleus or organelles) that constitute a major part of microorganisms. they can inhabit soil, water, and every other habit found on earth. they can be a few micrometers in length and can be of various shapes like spheres, rods, or spirals. example - escherichia coli, coliform bacteria, etc.  fungi - they are a group of eukaryotic organisms (have a membrane-bound nucleus and organelles) that are usually heterotrophic in nature. examples - penicillium, bread mould, mushroom, etc. protozoa - they are a group of unicellular eukaryotic organisms that may be parasitic or living independently and are heterotrophic (cannot prepare their own food) in nature. example - amoeba, paramecium, etc. algae - they are a group of photosynthetic eukaryotic organisms that are predominantly aquatic. example - spirogyra, chlamydomonas, etc. these groups of microorganisms may be harmful or useful in nature. the virus is also a microorganism, but they differ from the others in this group as they can reproduce only in the body of a host, be it animals, plants, or humans. example - aids, herpes, rubella, zika, etc., where do microorganisms live, the microorganism may be single-celled or unicellular as in bacteria, protozoa or they may be multicellular as in fungi, animals, etc.  they can survive in water, air and all kinds of environmental conditions like extreme cold climate to even the hot springs, deserts, and marshy lands. some of them even live inside the body of animals, and even humans.  some of them grow on their own whereas others thrive on the body of other animals. , microorganisms and us:, it is to be noted that these microorganisms play a vital role in our lives. some of them may be beneficial to us whereas some of them may have an adverse and harmful effect on us., friendly use of microorganisms:, microorganisms can be put to multiple uses, be it in the making of alcohol, bread, cake, or medicines or in agriculture or cleaning the environment.  making of curd and bread:   a bacterium, namely lactobacillus, multiplies in milk converting it into curd. the making of cheese, pickles, and various other food products also involve the use of bacteria.  the process of fermentation (conversion of sugar to alcohol) that is required in the rice batter for making idlis and dosa is again helped by bacteria and yeast.  when yeast is added to a dough, it reproduces rapidly releasing carbon dioxide which bubbles into the dough, making it rise. this property of yeast is used to make bread, cakes, etc. commercial use of microorganisms:   yeast is an ingredient that is widely used in the production of alcohol, wine, and vinegar. this is done by growing yeast on the natural sugar present in the fruit juices like grapes, grains like barley, wheat, rice, etc.  the sugars are converted to alcohol by fermentation. medicinal use of microorganisms:   the source of the widely used medicines, antibiotics(medicines that stop or kill the disease-causing agents) are again microorganisms.  these are manufactured by growing specific as a cure for various diseases.  some of the antibiotics are streptomycin, erythromycin, azithromycin, etc. vaccine:  a disease-causing microorganism called a pathogen produces antibodies against it when it enters our body. these antibodies are retained in our body and we are protected from that disease forever.  a vaccine is a biological substance that initiates the production of antibodies for a specific disease. thus a vaccination protects us from that specific disease.  children are generally vaccinated for many diseases like polio, tuberculosis, chickenpox, hepatitis, etc. smallpox has been eradicated this way. and currently, the covid vaccine is doing the same. increasing soil fertility:  there are some bacteria, like rhizobium that are present in the soil, generally in the roots of leguminous plants, that are capable of fixing the atmospheric nitrogen to enrich the soil with nitrogen which increases the fertility of the soil and the yield of the crop. cleaning the environment:  some of the microorganisms have the ability to decompose dead organic matter and convert them into simpler substances or manure that can be reused for animals or plants, making the environment clean. , harmful uses of microorganisms:.

They can be harmful in numerous ways to humans, plants, and animals and cause diseases. As stated, the disease-causing microorganisms are known by the name of pathogens.

Disease-Causing Microorganisms in Humans: 

The harmful pathogens enter the body of humans by means of air, water, or food. They can then spread to others by contact with the infected person or through an animal or insect.

The diseases that can spread from an infected person to a healthy person by means of air, water, or contact are termed communicable diseases. Examples - plague, chickenpox, tuberculosis, common cold, and the current Covid 19 infections.

These disease-bearing microorganisms are sometimes carried by insects and animals then they are termed as carriers of that disease. For example - the female anopheles mosquito is the carrier of Plasmodium that causes malaria.

The mode of transmission, type of microorganism, the disease caused by these microorganisms, and their prevention differ from each other as shown below:

The prevention of these diseases follows a general pattern of keeping the affected person and his belongings isolated, personal hygiene, proper sanitary practices, drinking boiled and clean water, controlling breeding sites of mosquitoes, consuming properly cooked food, and above vaccination against all these diseases on schedule.

Disease-Causing Microorganisms in Animals: 

Many of the microorganisms are a cause of certain diseases in animals too. A few of the diseases found in animals is as shown below:

Disease-Causing Microorganisms in Plants: 

Many microorganisms are responsible for diseases in plants of potato, rice, wheat, sugarcane, etc reducing the quality and quantity of the yield of the crops. These diseases can be controlled by the use of chemicals that destroys these organisms. Some of the diseases of plants are listed as below:

Food Poisoning:

When the microorganisms contaminate the food, they sometimes produce toxic substances which leads to the ill health of a person consuming it and has health problems like vomiting and needs to be taken to a hospital. This condition of consuming food contaminated with microorganisms is called food poisoning. 

Preservation of food:

As discussed above, contamination of the food by microorganisms leads to a change in the color and taste of the food. several methods can be followed to prevent this microorganism attack some of them are as follows: a. chemical method: generally salts and edible oils are used to control their growth and these are termed preservatives. example - salt in pickles, sodium benzoate in jams. b. common salt: this is a common practice where meat and fish or some fruits like raw mangoes, tamarind, etc are covered with salt to last them for longer periods. c. sugar: some food items like jams and jellies are preserved in sugar which reduces the moisture to inhibit the growth of microorganisms. d. oil and vinegar: this is also used commonly as the microorganisms cannot live in such conditions. this is widely used in making pickles. e. heat and cold treatments: it is a common practice to boil milk in order to store it. the method of heating milk to eliminate the microbes present in it is called pasteurization. similarly storing food at low temperatures also prevents the growth of these microbes., storage and packing.

Storage : Proper storage of food is crucial to keep it safe from harmful microorganisms. Food should be stored in clean, airtight containers and kept at the right temperature to prevent spoilage. For example, refrigeration slows down the growth of bacteria and moulds.

Packing : Good packing methods protect food from contamination. Using sealed packages prevents microorganisms from getting into the food. It also helps in preserving the food's freshness and extends its shelf life.

By following these practices, we can minimise the risk of foodborne illnesses and ensure that food stays safe and fresh.

Nitrogen Fixation:

Nitrogen fixation is a process where certain microorganisms help convert nitrogen from the air into a form that plants can use. In Class 8 Science Chapter 2, you’ll learn that plants need nitrogen to grow, but they can’t use nitrogen gas (N₂) in the air directly.

Certain bacteria, like those found in the roots of leguminous plants (e.g., peas, beans), can convert this nitrogen into nitrates and ammonia. These forms of nitrogen are then absorbed by plants through their roots and used to make important proteins and other compounds. This process is crucial for healthy plant growth and helps in maintaining soil fertility.

Nitrogen Cycle:

The nitrogen cycle can be defined as a biochemical process of circulating nitrogen in the atmosphere, through soil, organisms, and back to the atmosphere. 

The nitrogen present in the atmosphere cannot be consumed by plants or animals directly.

This nitrogen needs to be converted to nitrogenous compounds by some bacteria in the soil.

This converted form of nitrogen is used by the plants and when the animals feed on them they get that.

The fungi and bacteria in the soil convert the nitrogen present in dead plants and animals to either gaseous or compounds that are reused by the plants.

Thus the balance of nitrogen is maintained in the atmosphere.

Questions for Practice

Very Short Answer Type Questions

Name the four major groups of microorganisms.

Are viruses microscopic?

Where do microorganisms live?

Define fermentation.

Who discovered the smallpox vaccine and when?

Short Answer Type Questions

What are antibiotics?

What are communicable disease?

Name microorganisms that cause disease in plants and animals.

Name a few common chemicals that are generally used to check the growth of the organisms.

What actions should be taken to prevent the communicable diseases?

Long Answer Type Questions

Explain the Nitrogen Cycle with a diagram.

What preventive measures should be taken if a person suffers from tuberculosis, cholera, hepatitis A, and Malaria?

Explain the process of fermentation.

5 Important Topics of Science Class 8 Chapter 2 Microorganisms: Friend and Foe

Importance of Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Revision notes help us quickly understand and remember key concepts before exams.

They save time by focusing on essential information and skipping unnecessary details.

These notes simplify complex topics, making them easier to understand and use.

They provide practical examples that show how theoretical knowledge is used in real-life situations.

Revision notes ensure thorough preparation by covering all important topics in a structured manner.

They increase confidence by clearly understanding what to expect in exams.

Accessible formats like PDFs allow for easy studying anytime and anywhere.

Tips for Learning the Class 8 Science Chapter 2 Microorganisms: Friend and Foe

Learn the different types of microorganisms (bacteria, fungi, viruses, and protozoa) and their characteristics. Recognising their types helps in understanding their roles.

Understand how microorganisms are beneficial, such as aiding digestion, decomposing organic matter, and being used in food production.

Understand how certain microorganisms can cause diseases and spoil food. Familiarise yourself with examples of harmful microorganisms and the diseases they cause.

Connect the information to real-life examples, like how yogurt is made using bacteria or how certain infections affect health.

In Chapter 2 Microorganisms: Friend and Foe Class 8 Notes will explore the dual nature of microorganisms. These tiny organisms play crucial roles in our lives—they can be beneficial by aiding digestion, decomposing waste, and helping in food production. However, they can also pose risks by causing diseases and spoiling food. Understanding these aspects helps us appreciate their importance and take necessary precautions to avoid harmful effects. Vedantu's notes offer a clear overview and detailed insights into how microorganisms impact our health and environment. By studying these notes, you'll gain a solid grasp of the chapter’s key concepts, which will be valuable for exams and everyday knowledge.

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FAQs on Microorganisms: Friend and Foe Class 8 Notes: CBSE Science Chapter 2

1. How are microorganisms used in Science Chapter Microorganisms: Friend and Foe Class 8 Notes?

As per Class 8th Science Chapter 2 notes, microbes are used to make food products, prepare new medicines, and different bioactive molecules at a very low cost.

2. What are pathogens in Science Chapter Microorganisms: Friend and Foe Class 8 Notes?

Pathogens are microorganisms that cause diseases in a host. They are generally parasites. Follow the notes of Science Class 8 Chapter 2 to find examples related to pathogens.

3. What are a carrier and a vector in class 8 science ch 2 notes?

A carrier is someone who is carrying pathogens and contaminating others. A vector is a carrier of diseases that contaminates a disease by biting a host. Study Chapter 2 Class 8 Science notes to find out more differences between a carrier and a vector.

4. What are Microorganisms according to Chapter 2 of Class 8 Science?

Microorganisms, often known as microbes, are living organisms that are invisible to the naked eye. They are only visible using a magnifying glass or a microscope. Depending on the kind, microbes can be unicellular or multicellular. Microorganisms, as indicated in Chapter 2 of Science Class 8, can be both hazardous and useful. They may be found anywhere. There are certain exceptions, such as fungus and algae, which humans can see without any special equipment when they infect food.

5. Where do Microorganisms live according to Chapter 2 of Class 8 Science?

Microorganisms may exist in a variety of conditions. Some, such as algae, can be found in water. The air contains bacteria and viruses, many of which cause sickness. Microbes such as archaea, fungus, protists, and others have been discovered within human and animal bodies on rare instances. Some bacteria, but not all, are tolerant to severe circumstances such as cold, heat, a lack of water, a high salt content, and a lack of oxygen in the environment.

6. Is a microorganism a friend or foe according to class 8 science chapter 2 notes?

Microorganisms can be both a friend and an adversary, according to Chapter 2 of Science Class 8. Several microorganisms are utilised in cooking, commercial and medical purposes, soil fertilisation, and other applications. On the other hand, some microorganisms are the cause of illness in people, plants, and animals. It should be noted that microorganisms are as much a part of our environment as other living beings and hence, they have an impact on nature in different ways.

7. In class 8 science chapter 2 notes what are the characteristics of Microorganisms?

Microorganisms are unicellular or multicellular organisms that cannot be seen by the naked eye. They are categorized into six major types as per their typical features: bacteria, protozoa, fungi, archaea, algae, and viruses. In the revision notes of Chapter 2 Class 8 Science provided by  Vedantu , you can learn to distinguish between different kinds of microorganisms based on their peculiarities. You will also get a detailed understanding of the various uses of different microbes in this particular chapter.

8. What is the Nitrogen Cycle according to Class 8 Microorganisms friend and foe Notes?

The nitrogen cycle is the conversion of nitrogen in the environment into chemical forms. Plants require nitrogen to flourish, but they cannot take it directly from the air. Bacteria and green algae are microorganisms that help break down nitrogen and refill the soil with it. These nitrogen molecules are then utilised by plants, and through plants, they reach other living organisms. It is a natural procedure that does not need any deduction.

9. Why are microorganisms important in Chapter 2 for Class 8 Science? 

They are important because they can be helpful, like in digestion and food production, or harmful, causing diseases and food spoilage.

10. What are some examples of beneficial microorganisms covered in Chapter 2 for Class 8 Science? 

Examples include bacteria used in making yogurt and cheese, and fungi used in baking bread.

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Case Study Based Questions: Force and Pressure | Science Class 8 PDF Download

Read the given passage below and answer the question:

In a game of volleyball, players often push the moving ball to their team mates to make a winning move. Sometimes the ball is returned to the other side of the court by pushing or smashing it. In cricket, a batsman plays his or her shot by applying a force on the ball with the bat.

Q1: What kind of force is applied by a batsman on a ball while hitting it? (a) Magnetic Force (b) Muscular Force (c) Frictional Force (d) Gravitation Force Ans: (b) Explanation: While hitting a ball, the force is caused by the action of muscles in the batsman’s body. The force resulting due to the action of muscles is known as the muscular force.

Q2: Force can be defined as: (a) Work done (b) Energy required to do work (c) Push or Pull (d) Push only Ans: (c) Sol: A push or a pull on an object is called a force.

Q3: In the given example of a volleyball game, what changes force brought about on the volleyball? (a) Change in direction of motion (b) Change in shape (c) Change in state of motion (d) Both Option (a) and (c) Ans: (d) Sol: When players hit the volleyball, its speed changes and also the direction of its motion changes.

Q4: How do you describe the state of motion? Ans: A change in either the speed of an object, or its direction of motion, or both, is described as a change in its state of motion. The state of rest is considered to be the state of zero speed. An object may be at rest or in motion; both are its states of motion.

Q5: Give two examples showing that force has brought about a change in the shape of an object. Ans: 1. Pressing a ball of dough by a rolling pin to make chapati. 2. Stretching a rubber band.

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NCERT Exemplar Class 8 Science Chapter 2 Micro organisms: Friend and Foe

June 20, 2022 by Bhagya

NCERT Exemplar Class 8 Science Chapter 2 Micro organisms: Friend and Foe are part of NCERT Exemplar Class 8 Science . Here we have given NCERT Exemplar Class 8 Science Chapter 2 Micro organisms: Friend and Foe.

Multiple Choice Questions Question. 1 Which of the following reproduces only inside a host cell? (a) Bacteria (b) Virus (c) Amoeba (d) Fungus Answer. (b) Virus is a micro organism, which is in an inactive or deal form outside the body of a host. It reproduces or replicates only when it enters a host and reaches its cells.

Question. 2 A disease in human beings caused by virus is (a) typhoid (b) influenza (c) dysentery (d) cholera Answer. (b) Influenza is an infectious disease caused by the influenza virus. It is also known as flu whose symptoms includes high fever, running nose, sore throat, headache, coughing and muscle pain etc. Typhoid, dysentry and cholera are bacterial infections.

Question. 3 Pathogenic micro organisms present in host cells are killed by medicines called (a) pain killer (b) antibodies (c) antibiotics (d) vaccines Answer. (c) Antibiotics are substances that may inhibit or kill the growth of different microbes. Micro organisms causing infection in host bodies are killed by consumption of these antibiotics.

Question. 4 The two micro organisms which live in symbiotic association in lichens are (a) fungus and protozoa (b) alga and bacteria (c) bacteria and protozoa (d) alga and fungus Answer. (d) Lichens is an association between a fungal and an algal species. It is mutually benefiting association where algae provides food to the tongue fungus return gets shelter from it.

Question. 5 The gas released during the preparation of bread is (a) oxygen (b) carbon dioxide (c) nitrogen (d) sulphur dioxide Answer. (b) Carbon dioxide (CO 2 ) is released during the preparation of bread. This is the process of fermentation in which yeast cells rapidly produces CO 2 , which causes risening of the dough used in preparation of bread.

Question. 6 The disease caused by a protozoan and spread by an insect is (a) dengue (b) malaria (c) polio (d) measles Answer. (b) Malaria is the disease which is caused by the spread of a protozoan, i.e. Plasmodium. It is spread in healthy individuals by the bite of a female Anopheles mosquito carrying this Plasmodium in their mouth (saliva).

Question. 7 Paheli dug two pits, A and B, in her garden. In pit A, she put a polythene bag packet with some agricultural waste. In pit B, she dumped the same kind of waste but without packing it in a polythene bag. She, then covered both the pits with soil. What did she observe after a month? (a) Waste in pit A degraded faster than that in pit B (b) Waste in pit 6 degraded faster than that in pit A (c) Waste in both pits degraded almost equally (d) Waste in both pits did not degrade at all Answer. (b) Waste in pit B degraded faster than that in pit A because packet B was kept open, so 02 could go in which helped the microbes in decomposing the waste materials easily.In packet A, since it was sealed, 02 could not enter and thus, microbial degradation did not occur.

Very Short Answer Type Questions Question. 8 Unscramble the jumbled words underlined in the following statements. (a) Cells of our body produce santiidobe to fight pathogens. (b) Curbossulite is an air-borne disease caused by a bacterium. (c) Xanrhat is a dangerous bacterial disease. (d) Yeasts are used in the wine industry because of their property of meronettinaf. Answer. (a) Antibodies are specific molecules produced against invading microbes. (b) Tuberculosis is an infectious air-borne disease caused by Mycobacterium tuberculosis. (c) Anthrax is an infectious disease of humans and animals caused by Bacillus anthracis. (d) Fermentation is a process occurring in yeast which converts sugar into gases (C02) and alcohols.

Question. 9 Suggest a suitable word for each of the following statements. (a) Chemicals added to food to prevent growth of micro organisms. (b) Nitrogen-fixing micro organism present in the root nodules of legumes. (c) Agent which spreads pathogens from one place to another. (d) Chemicals which kill or stop the growth of pathogens. Answer. (a) Preservatives are the chemicals added in food. They prevent microbial infection without altering the taste or appearance. (b) Rhizobium are the nitrogen fixing bacteria which fix the atmospheric nitrogen into that form (i.e. nitrates, nitraties) which is usable for plants. (c) Carrier/Vector are the modes of transmission of a disease. (d) Antibiotics are the antimicrobial agents for inhibiting or killing the growth of microbes.

Question. 11 Name one commercial use of yeast. Answer. Baking bread/manufacturing of alcoholic drinks is the commercial use of yeast.

Question. 12 Name the process in yeast that converts sugars into alcohol. Answer. Fermentation is the process by which yeast converts sugars into alcohol.

Question. 13 Preservatives are used in kitchen on daily basis. List a few of them. Preservatives prevent the spoilage of food lives for a long time from microbial infestation. Answer. Vinegar common salt and oil are common preservatives used in kitchen.

Question. 14 Why should we avoid standing dose to a tuberculosis patient while he/she is coughing? Answer. Tuberculosis is an air-borne disease, which is easily spreads when the infected person coughs. As coughing spreads germs in the air and these germs remain suspended in air until inhaled by person present in promixity of the patient who is suffering from the disease. That is why we should avoid standing close to a TB patient.

Question.  15 Polio drops are not given to children suffering from diarrhoea. Why? Answer. If the child is suffering from diarrhoea, the polio drops that is an oral vaccine for fighting against polio virus may be excreted out because of frequent motions. Thus, the child becomes susceptible to polio inaction as the vaccine becomes ineffective to fight against invading pathogen.

Question. 16 Paheli watched grandmother making mango pickle. After she bottled the pickle, her grandmother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why? Answer. The oil poured on the pickle forms a barrier between the pickle and air. This prevents the bacteria present in air from entering jar and attacking the pickle and spoiling it. Thus, increasing the shelf life of pickles.

Question. 19 While returning from the school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomachache and fell ill. What could be the reason? Answer. The reason could be that the chaat was contaminated by pathogenic micro organisms. The unhygienic conditions present near the shop becomes the breeding place for microbes, flies, etc. The pathogens can be transmitted to places by flies and other vectors, even the utensil used for serving could have been contaminated by the pathogenic micro organism. If such microbial contaminated food is consumed several disease like diarrhoea, dysentery, cholera, etc., may occur.

Question. 20 What will happen to ‘pooris’ and ‘unused kneaded flouri if they are left in the open for a day or two? Answer. The ‘unused kneaded flour’ if left in warm conditions, gets infected by microbes which causes fermentation and spoils the flavour, texture, etc., of the flour. The pooris would remains in relatively good condition because these were deep fried in heated oil that kills microbes.

Question. 21 (a) Name two diseases that are caused by virus. (b) Write one important characteristic of virus. Answer. (a) Influenza and chickenpox are two diseases caused by virus in humans. (b) Virus are dead when present in the environment. They can reproduce only inside the cells of an infected person (as host).

• Common rust Puccinia graminis (fungus) brown pustules which can be • elongated or ovule develops on both the leaf surfaces. On rupturing they release spores.
• Citrus canker Xanthomonas spp (bacteria) lesions on leaves, stems and fruits of citrus trees which fruit and leaves drops prematurely from trees.

Question. 23 How do vaccines work? Answer. Vaccines contain dead or weakened microbial strains of a particular disease. When a vaccine is introduced into a heathy body. It produces specific cells against the pathogen. These cells, are called antibodies and they becomes active when the pathogen attack our body. The body fights and kills them by producing specific set of reactions. These antibodies remain in the body for life long and protect against the microbe when microbe enters the body again. Vaccines can be given either orally (in the forms of drops) or injected in the body.

Question. 24 Observe the set-up given in figure and answer the following questions.

• What happens to the sugar solution in A?
• Which gas is released in A?
• What changes will you observe in B when the released gas passes through it?

• Yeast grow very rapidly on the sugar containing substrates. It multiplies and increases its number and in process converts the sugar into alcoholic products with the release of CO 2 gas. In flask A, fermentation is occurring due to the presence of yeast and its utilisation of sugar.
• Carbon dioxide is released in A during fermentation process.
• The gas released due to the fermentation of sugar in set up is CO 2 . When CO 2 is passed over lime water in set up S its color changes, i.e. the lime water turns milky.

• Name the microorganism and the group to which it belongs.
• Name the foodjtem on which the organism grows.
• Does it grow well in dry or in moist conditions?
• Is it safe to eat infected bread?
• The microorganism is Rhizopus, also known as the bread mould. It belongs to the microbial group of fungi.
• The Rhizopus grows well on moist and stale bread.
• This organism grows well in moist conditions. Dry conditions inhibit its growth.
• No, Intake of fungus infected bread can cause harm by producing poisonous chemicals or toxins which adversely effects the proper functioning of our body.

Question. 26 Give reasons for the following.

• Fresh milk is boiled before consumption while processed milk is stored in packets and can be consumed without boiling.
• Raw vegetables and fruits are kept in refrigerators, whereas jams and pickles can be kept outside.
• Farmers prefer to grow beans and peas in nitrogen deficient soils.
• Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?
• Fresh milk is boiled before consumption to kill the micro organisms that could be present in it. But packed milk is pasteurised and boiled at 70°C for 30 sec followed by sudden : chilling then stored. Thus, it can be consumed without boiling. Pasteurisation kill all micro organisms for making it free of any contamination.
• Raw vegetables and fruits get easily infected by micro organisms and get spoiled. They are kept in refrigerator at low temperature that inhibits growth of microbes. Jams and pickles contain sugar and salt as preservatives. These preservatives forms a protective layer and prevent spoilage of these products by inhibiting the growth of various micro organisms.
• Beans and peas are leguminous plants as they have Rhizobium, a bacteria in their root nodules. This bacteria can fix atmospheric nitrogen to enrich the soil with nitrogen and increase its fertility. Farmers grow leguminous plants in between the major crops, a practice called crop rotation to restore the used nutrients of the soil.
• Though mosquitoes, live on land, water is their breeding ground their larvae grow in water. Water stagnation is collecting of water in a small area, without any activity. Mosquitoes lay egg on such a surface. If water stagnation is prevented, their larvae cannot survive, thus reducing mosquito population.

Question. 27 How can we prevent the following diseases?

• Hepatitis-A
• Cholera An infectious disease caused by bacteria Vibrio cholerae. It occurs due to the consumption of contaminated or unhygienic food and water. It can be prevented by maintaining personal hygiene, good sanitation practice, consumption of clean drinking water, etc.
• Typhoid An acute illness caused by bacteria Salmonella typhi. It occurs by ingestion of typhoid bacterium through food, water, fomite, etc. Preventions includes consumption of hygiene and properly cooked meals, filtered or boiled water, etc.
• Hepatitis-A A disease caused by hepatitis. A virus. Symptoms of disease appears after 2 weeks of infection. Prevention includes proper vaccinasation drinking boiled water, wash hands before eating, etc.

• Lightning fixes nitrogen.
• Nitrogen fixing bacteria and blue-green algae fix atmospheric nitrogen.
• Nitrogenous waste from excretion and death.
• Bacteria turns compounds of nitrogen into gaseous nitrogen.

NCERT Exemplar Class 8 Science Solutions

• Chapter 1 Crop Production and Management
• Chapter 2 Microorganisms: Friend and Foe
• Chapter 3 Synthetic Fibres and Plastics
• Chapter 4 Materials : Metals and Non-Metals
• Chapter 5 Coal and Petroleum
• Chapter 6 Combustion and Flame
• Chapter 7 Conservation of Plants and Animals
• Chapter 8 Cell Structure and Functions
• Chapter 9 Reproduction in Animals
• Chapter 10 Reaching the Age of Adolescence
• Chapter 11 Force and Pressure
• Chapter 12 Friction
• Chapter 13 Sound
• Chapter 14 Chemical Effects of Electric Current
• Chapter 15 Some Natural Phenomena
• Chapter 16 Light
• Chapter 17 Stars and the Solar System
• Chapter 18 Pollution of Air and Water

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Ncert solutions for class 8 science.

NCERT is on the priority list of recommendation of the Central Board of Secondary Education (CBSE). Here, you will find all the chapter-wise NCERT Solutions for Class 8 Science. It will help you to understand the subject and perform well in exams.

In CBSE Class 8, Science is divided into 3 parts – Physics, Chemistry, and Biology

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Chemistry is one of those subjects which are equally important from academics as well practical point of view. NCERT is specially made to clear most of the topics of the syllabus of chemistry. NCERT solutions help the students to clear all the doubts regarding any chapter. Here, you will find all the solutions of NCERT questions.

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CBSE Class 8 Science NCERT Solutions Chapter-wise

• Chapter 1 – Crop Production and Management
• Chapter 2 – Microorganisms: Friend and Foe
• Chapter 3 – Synthetic Fibres and Plastics
• Chapter 4 – Materials: Metals and Non-metals
• Chapter 5 – Coal and Petroleum
• Chapter 6 – Combustion and Flame
• Chapter 7 – Conservation of Plants and Animals
• Chapter 8 – Cell – Structure And Functions
• Chapter 9 – Reproduction in Animals
• Chapter 10 – Reaching the Age of Adolescence
• Chapter 11 – Force and Pressure
• Chapter 12 – Friction
• Chapter 13 – Sound
• Chapter 14 – Chemical Effects of Electric Current
• Chapter 15 – Some Natural Phenomena
• Chapter 16 – Light
• Chapter 17 – Stars and Solar System
• Chapter 18 – Pollution of Air and Water

NCERT Solutions for Class 8 Chemistry Chapter-wise

Ncert solutions for class 8 science chapter 1 – crop production and management.

This chapter involves the study of yields and their respective administration. It also highlights various harvests, different climatic conditions, etc. Moreover, the type of nourishment is also stated in the chapter with respect to different crops. Gathering and capacity are also highlighted in this chapter.

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

There are various types of microorganisms present on this planet. They all have their own characteristics. After completing this chapter, the students will be able to answers questions like Where do microorganisms live?

NCERT Solutions for Class 8 Science Chapter 3 – Synthetic Fibres and Plastics

This chapter states the meaning of artificial synthetic fibers and plastics which are largely used in our daily life for many purposes. Moreover, it will explain the types of synthetic fibers and plastics along with characteristics of both. Moreover, the chapter puts the concept of the environment along with the application or usage of such materials.

NCERT Solutions for Class 8 Science Chapter 4 – Materials: Metals and Non-Metals

Materials include two major segments viz. Metals and Non-Metals. This chapter will unveil the world of metals and non-metals by explaining their properties and applications. After studying this chapter, the students will be able to classify the components into metals and non-metals considering their respective property along with the respective uses of metals and non-metals.

NCERT Solutions for Class 8 Science Chapter 5 – Coal and Petroleum

Coal and Petroleum are one of the largest used energy resources in any country. Though with the passage of time, their use is diminishing due to a movement towards conventional sources of energy. This chapter helps the students to know the Natural Gas as an asset and how it is being depleted due to high usage. Moreover, the students will be confronted with the term ‘Fossil Fuels’. Towards the end, it puts the topics of ill-effects of fossil fuels on the environment also.

NCERT Solutions for Class 8 Science Chapter 6 – Combustion and Flame

This chapter tries to explain the types of fuels being used in different work and places like at home, in vehicles, in factories, etc. Different sources of powers like Cow dung, coal, wood, charcoal, diesel, CNG, etc. are also highlighted. Use of flame becomes an important part of the discussion. Moreover, the students will come to know about the difference in the implications of burning different types of fuels. Detailed differentiation between the consuming of a flame and consuming of fuel is also stated in between the chapter.

NCERT Solutions for Class 8 Science Chapter 7 – Conservation of Plants and Animals

Conservation of Plant and Animals is a complex chapter to study. This chapter states the different human activities which are affecting the life of Plants and Animals along the various means to conserve them.

NCERT Solutions for Class 8 Science Chapter 8 – Cell: Structure and Functions

In general, cells are of two types – Plant Cell and Animal Cell. There are different characteristics of both of them making them different on various grounds. Moreover, the chapter talks about the discovery of the cell, its properties, and composition.

NCERT Solutions for Class 8 Science Chapter 9 – Reproduction in Animals

Continuation of any species completely depends on the process of reproduction. This chapter specifies how various animals reproduce. Various modes and procedures of reproduction are explained in detail in this chapter for a better understanding of the students.

NCERT Solutions for Class 8 Science Chapter 10 – Reaching the Age of Adolescence

Adolescence is the time period in any person’s life in which he/she undergoes various changes both physically and mentally. This chapter shows the changes in the various organs during this period and the role of hormones. Moreover, students will come to know about the conceptive organs of the body.

NCERT Solutions for Class 8 Science Chapter 11 – Force and Pressure

Force and pressure are the most important concept in physics form theoretical as well as practical means. After studying this chapter, the students will be able to understand the future complex problems.

NCERT Solutions for Class 8 Science Chapter 12 – Friction

Backing or the opposition power or force constitutes Friction. It has become an essential part of today’s education system. This chapter allows the students to know about the application of friction in everyday life. In this chapter, students will find many diagrams and images for a better understanding of the topic.

NCERT Solutions for Class 8 Science Chapter 13 – Sound

In the initial stage of the chapter, the chapter talks about the distinction between music and noise. Later, the chapter starts to focus on Noise Pollution showing its impact on the environment. Moreover, it highlights certain means to minimize the noise in the environment. A better understanding of the topic will help the students to gain much knowledge about this topic in the future.

NCERT Solutions for Class 8 Science Chapter 14 – Chemical Effects of Electric Current

This chapter tries to move forward with the concept of nature of element and its relation with the current flow. Moreover, it analyses the behavior of various materials with respect to current flow. It provides a detailed analysis of the passing of electricity through conductors and insulators.

NCERT Solutions for Class 8 Science Chapter 15 – Some Natural Phenomena

Moving a little away from general science topics, this chapter talks about the concept of lightning and earthquakes. It also discusses the related concepts like the magnitude of earthquake and lightning, the reasons behind both of them, etc.

NCERT Solutions for Class 8 Science Chapter 16 – Light

Everyone knows that the speed of light is the fastest. In this chapter, students will come to know about the various properties and application of light. Towards the end, the chapter also talks about the Braille system used by the visually-impaired people.

NCERT Solutions for Class 8 Science Chapter 17 – Stars and the Solar System

There are various celestial bodies in the solar system. This chapter helps the students to learn about various celestial bodies like the moon. Moreover, we would learn about the properties of such bodies.

NCERT Solutions for Class 8 Science Chapter 18 – Pollution of Air and Water

Anything that contaminates the purity of a substance, that particular element is known as ‘Pollutant’. In this chapter, the students would be able to know about the pollutants of air pollution and water pollution. The chapter ends with various suggestions to avoid such pollutants.

Solved Questions for You

Question 1: Explain why some fibres are called synthetic.

Answer: Some fibres are called synthetic because they are not made from natural fibres. Instead, they are made by chemical processing of petrochemicals. The synthetic fibres are made up of very large units called polymers. Some of the synthetic fibres are – nylon, rayon, acrylon.

Question 2: Define adolescence.

Answer: Adolescence is the biological processes drive many aspects of growth and development, with the onset of puberty marking the transition from childhood to adolescence. Puberty is the transitional period  between childhood and adulthood, during which growth of the body occurs, secondary sexual characters appears, fertility is achieved and profound physiological changes takes place. The normal range of onset is ages 8 to 14 in females and ages 9 to 15 in males.

Question 3: Explain how you can take care of your eyes.

Answer: Eyes are very sensitive organ of the human body and should be taken care of.

The following steps should be followed to take care of your eyes:

• Have a regular checkup with the eye specialist. If advised, use spectacles of proper power after an eye test.
• Do not rub your eyes. If there is irritation or dust particles enter your eyes, wash them with clean water.
• Regularly wash your eyes with clean water.
• Do not read a book too close or too far from the eye as it causes stress.
• Have a proper diet. Eat food items rich in vitamin A like raw carrots, broccoli and eggs.
• Avoid overexposure(example looking at sun) or underexposure(example reading in dark) of light to the eye.

Question 4: Explain how deforestation leads to reduced rainfall.

Answer:   Plants and water bodies are the sources of most of the moisture and water vapour that constitutes the clouds that bring rain (in continental regions). Forests act as large transpiration zones and contribute greatly to the atmospheric moisture. In their absence, the water of the soil just seeps down or flows away and thus they cannot contribute to rain.

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NCERT Solutions for Class 8

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• NCERT Solutions for Class 8 Chemistry Chapter 5 Free PDF Download
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• NCERT Solutions for Class 8 Physics Chapter 16 Free PDF Download
• NCERT Solutions for Class 8 Physics Chapter 13 Free PDF Download
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• CBSE Study Material
• CBSE Important Questions
• Important Questions For Class 8 Science

CBSE Important Questions for Class 8 Science

CBSE Important Questions for Class 8 Science help students face the exams confidently. As the exam nears, they should complete the syllabus and start with the revision. The CBSE Important Questions for Class 8 Science will help them revise the subject quickly. Here, we have compiled the important questions for all the chapters of the CBSE Class 8 Science subject. By solving them, students will understand the types of questions asked in the exam. All types of questions are provided for students’ practice from basic to high level. CBSE Class 8 Science is a fascinating subject and includes interesting topics, thus providing basic knowledge about light, current, force, human beings, etc. Solving these CBSE Class 8 Science Important Questions is the best way to revise the major concepts of the subject.

The subject experts created the questions based exclusively from the exam perspective. Students must start solving them at least 20 days before the annual exam. By doing so, they will be able to analyse their weak areas and work on them. Practising the CBSE Important Questions will improve their performance and overall score in CBSE Class 8 Science exam.

There is a total of 18 chapters in NCERT Class 8 Science book. In the table below, we have provided the Important Questions for CBSE Class 8 Science for all the chapters. We have also included all types of questions, i.e. very short, short and long answers. These questions will cover all the crucial topics and the CBSE Class 8 Science syllabus.

How to Practise the CBSE Class 8 Science Important Questions

• Practise the question of a particular chapter in one go.
• Refrain from looking for the answer while solving the questions.
• Allocate a time duration for solving the questions and try to finish it accordingly.
• After completing all the questions, do a self-evaluation.
• Go through those questions again that could not be solved.

We, at BYJU’S, also provide other study materials such as CBSE Class 8 Science sample papers , notes, exemplars, solutions, etc.

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• What is Democracy? Why Democracy? Class 9 Case Study Social Science Political Science Chapter 1

Last Updated on September 10, 2024 by XAM CONTENT

Hello students, we are providing case study questions for class 9 social science. Case study questions are the new question format that is introduced in CBSE board. The resources for case study questions are very less. So, to help students we have created chapterwise case study questions for class 9 social science. In this article, you will find case study for CBSE Class 9 Social Science Political Science Chapter 1 What is Democracy? Why Democracy? It is a part of Case Study Questions for CBSE Class 9 Social Science Series.

Table of Contents

Case Study Questions on What is Democracy? Why Democracy? Class 9

Read the following passage and answer the questions:

In Pakistan, General Pervez Musharraf led a military coup in October 1999. He overthrew a democratically elected government and declared himself the ‘Chief Executive’ of the country. Later, he changed his designation to President and in 2002 held a referendum in the country that granted him a five year extension. Pakistani media, human rights organisations and democracy activists said that the referendum was based on malpractices and fraud. In August, 2002 he issued a ‘Legal Framework Order’ that amended the Constitution of Pakistan. According to this

Order, the President can dismiss the national and provincial assemblies. The work of the civilian cabinet is supervised by a National Security Council which is dominated by military officers. After passing this law, elections were held to the national and provincial assemblies. So, Pakistan has had elections, elected representatives have some powers. But the final power rested with military officers and General Musharraf himself.

Q. 1. Who said that the referendum held in 2002 was based on malpractices and fraud?

Ans. Pakistani media, human rights organisations and democracy activists said that the referendum held in 2002 was based on malpractices and fraud.

Q. 2. What was the motive towards issuing a ‘Legal Framework Order’ in August 2002?

Ans. General Pervez Musharraf issued a ‘Legal Framework Order’ in August 2002 with the motive to ensure that he had the ultimate power to decide how he wanted Pakistan to be ruled.

Q. 3. What were the amendments made in the Constitution of Pakistan under Legal Framework Order?

Ans. The amendments made in the Constitution of Pakistan under Legal Framework Order were:

(i) The President can dismiss the national or provincial assemblies.

(ii) The work of the civilian’s cabinet is supervised by a National Security Council which is dominated by military officers.

• Electoral Politics Class 9 Case Study Social Science Political Science Chapter 3
• Constitutional Design Class 9 Case Study Social Science Political Science Chapter 2
• Food Security in India Class 9 Case Study Social Science Economics Chapter 4
• Poverty as a Challenge Class 9 Case Study Social Science Economics Chapter 3
• People as Resources Class 9 Case Study Social Science Economics Chapter 2
• Drainage Class 9 Case Study Social Science Geography Chapter 3
• Physical Features of India Class 9 Case Study Social Science Geography Chapter 2
• India – Size and Location Class 9 Case Study Social Science Geography Chapter 1
• Forest Society and Colonialism Class 9 Case Study Social Science History Chapter 4
• Nazism and the Rise of Hitler Class 9 Case Study Social Science History Chapter 3

Socialism in Europe and the Russian Revolution Class 9 Case Study Social Science History Chapter 2

The french revolution class 9 case study social science history chapter 1, topics from which case study questions may be asked.

Here is a list of topics from which case study questions may be asked.

• What is Democracy?
• Features of Democracy
• Why Democracy?
• Broader Meaning of Democracy

The word ‘Democracy’ is derived from two Greek words ‘Demos’ and ‘Kratia’. Demos means ‘The People’ and ‘Kratia’ means ‘The Power’. These two words together mean ‘authority of the people’.

Democracy is a form of government in which the ruling power is vested in the hands of elected representatives of the people.

Frequently Asked Questions (FAQs) on What is Democracy? Why Democracy? Class 9 Case Study

Q1: what are case study questions.

A1: Case study questions are a type of question that presents a detailed scenario or a real-life situation related to a specific topic. Students are required to analyze the situation, apply their knowledge, and provide answers or solutions based on the information given in the case study. These questions help students develop critical thinking and problem-solving skills.

Q2: How should I approach case study questions in exams?

A2: To approach case study questions effectively, follow these steps: Read the case study carefully: Understand the scenario and identify the key points. Analyze the information: Look for clues and relevant details that will help you answer the questions. Apply your knowledge: Use what you have learned in your course to interpret the case study and answer the questions. Structure your answers: Write clear and concise responses, making sure to address all parts of the question.

Q3: What are the benefits of practicing case study questions from your website?

A3: Practicing case study questions from our website offers several benefits: Enhanced understanding: Our case studies are designed to deepen your understanding of historical events and concepts. Exam preparation: Regular practice helps you become familiar with the format and types of questions you might encounter in exams. Critical thinking: Analyzing case studies improves your ability to think critically and make connections between different historical events and ideas. Confidence: Practicing with our materials can boost your confidence and improve your performance in exams.

Q4: What are the important keywords in this chapter “What is Democracy? Why Democracy?”?

A4: Important keywords for CBSE Class 9 What is Democracy? Why Democracy? are given below: Democracy: The word ‘Democracy’ is derived from two Greek words ‘Demos’ and ‘Kratia’. ‘Demos’ means ‘The People’ and ‘Kratia’ means ‘The Power’. Thus it means the rule of the people. Direct Democracy: This is the oldest and real form of democracy in which the people directly participate in managing the affairs of the State. Indirect Democracy: Indirect democracy is also known as representative democracy. In this democracy, people elect their representatives on the basis of universal adult franchise and through them they carry on their administration. Initiative: Refers to the power of the voters to get the laws passed in accordance with their wishes. Referendum: The method of referendum gives the final authority to the people to accept or reject the laws passed by the legislature. Plebiscite: A method in which people are asked to accept or reject a proposal.

Q5: In which country do the women not have the right to vote?

A5: Saudi Arabia.

Q6: How did the word ‘Democracy’ originate?

A6: The word ‘Democracy’ is derived from a Greek word ‘Demokratia’. In Greek ‘Demos’ means people and ‘Kratia’ means rule. So democracy is rule by the people. It is a form of government in which the rulers are elected by the people

Q7: What is Referendum?

A7: A direct vote in which the entire electorate is asked to either accept or reject a proposal.

Q8: What is the strength and weakness of democracy?

A8: We require a constant effort to save and strengthen democratic forms of decision making. What we can do as citizens is, we can make a difference to make our country more or less democratic. This is the strength and weakness of democracy.

Q9: Is democracy all about rulers and governments? Can we talk about a democratic classroom? Or a democratic family?

A9: Democracy is not only about the rulers and government. It is also about the people. The people elect their representatives for a fixed tenure. They have the choice to replace them in the next elections if representatives elected by them do not act accordingly. We can talk about a democratic classroom or a democratic family where we can express our views independently.

Q10: Are there any online resources or tools available for practicing “ What is Democracy? Why Democracy?” case study questions?

A10: We provide case study questions for CBSE Class 9 Social Science on our website. Students can visit the website and practice sufficient case study questions and prepare for their exams.

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