NCERT SCIENCE BOOK CLASS 8 CHAPTER 2

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NCERT Grade 8 Science Chapter 2, Microorganisms: Friend and Foe deals with per CBSE Board guidelines from the latest NCERT book for Class 8 Science. If you are a student of class 8 who is using NCERT Textbook to study Science, then you must come across chapter 2 Microorganisms Friend and Foe. After you . The NCERT solutions for class 8 Science chapter 2 Microorganisms Friend and Foe is an important study material for the students of the 8th standard.


Ncert Science Book Class 8 Chapter 2

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NCERT Solutions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe Download NCERT Book Chapter 2; Download Exemplar Book Chapter 2. NCERT Textbook Solutions are considered extremely helpful when preparing for your CBSE Class 8 Science exams. TopperLearning study resources infuse. NCERT Solutions for Class 8 Science Chapter 2 Microorganisms Friend and Foe. Topics and Sub Topics in Class 8 Science Chapter 2 Microorganisms Friend.

Microorganisms are used for the large scale production of alcohol, wine and acetic acid vinegar. How do microorganisms clean the environment? Microorganisms degrade the harmful substances and clean the environment. How can we prevent a person from getting Hepatitis B? Name one disease caused by bacteria and one disease caused by virus in cattle. How can we control plant diseases? Plant diseases can be controlled by chemicals which kill the microbes. Why do we use oil and vinegar to preserve vegetables and fruits?

Use of oil and vinegar prevents spoilage of vegetables and fruits because bacteria cannot live in such an environment.

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Why do we keep milk in the refrigerator during summers? The low temperature in the refrigerator inhibits the growth of microbes. Why do we boil milk before storing? Boiling kills the microorganisms. How are dry fruits preserved? Dry fruits are preserved by keeping them sealed in airtight packets to prevent the attack of microbes.

Draw a well-labelled diagram of Paramecium. Draw a labelled diagram of Penicillium. Draw a labelled diagram of virus. Can you store pickles in iron containers? We can not store pickles in iron containers because the acid present in the pickles reacts with iron.

This can cause food poisoning, if consumed. What precautions must be taken while taking antibiotics? Antibiotics should be taken after consulting a doctor.

The complete dose of the antibiotics should be taken as prescribed. They should not be taken unnecessarly because they will kill the useful bacteria. Why are viruses considered to be on the borderline between living organisms and non-living things? Viruses cannot reproduce, respond to changes or use energy to grow.

Since viruses reproduce in the host cell, scientist regard viruses as a link between living and non-living. How are bacteria beneficial for us? Bacteria are useful to us as:. Write three types of bacteria on the basis of their shape.

Give one example of each. Three types of bacteria are:. Give reasons in support of your answer. How does a housefly transmit diseases?

A housefly gets attracted towards garbage and excreta. The harmful microorganisms present in excreta and garbage easily stick to its fine array of body hair and are thus, transferred to food stuffs whenever they sit on them and a result food gets poisoned. What will happen if you take antibiotics when not needed?

If you take antibiotics when not needed, you help bacteria in your body to develop resistance to them. Next time when you fall ill and need these antibiotics, they would be less effective. How does a vaccine act?

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The antibodies attack and destroy the weakened microbe as it enters the body. How is common cold spread?

When a person suffering from common cold sneezes, fine droplets of moisture carrying thousands of viruses causing common cold are spread in the air. The viruses may enter the body of a healthy person while breathing. How can you prevent the spread of communicable diseases? It is better to avoid contact with the infected person.

We should keep distance from infected persons. Give the methods of prevention of cholera. Cholera can be prevented by:. Microorganisms that grow on our food sometimes produce toxic substances. These make the food poisonous causing serious illness and even death. What will happen if yeast powder is put in sugar solution and kept for few hours? Name the process.

When yeast powder is put in sugar solution and kept for few hours, fermentation takes place. The sugar is converted into alcohol by yeast and this process is known as Fermentation. Describe the nitrogen cycle with the help of a neat and labelled diagram. Write 10 lines on the usefulness of microorganisms in our lives.

Microorganisms are useful in our lives in the following ways:. Write a short paragraph on the harms caused by microorganisms. How can we control the spread of malaria or dengue? All mosquitoes breed in water. Hence, by keeping the surroundings clean and dry, we can prevent mosquitoes from breeding. Therefore, it is a borderline between a living and a non- living thing.

Lactobacillus is a bacterium that sours milk and is used to makes curd from milk. Many fungi like Mushrooms and morels are edible which are rich Yeast is commonly employed in preparing food items like bread, cakes, idli, dosa, dhokla etc. Yeast is also used in breweries for making wines by the process of fermentation.

Introduction

Making medicines and vaccines: Bacteria and fungi are used to make medicines called antibiotics. The first antibiotic, penicillin was discovered by Alexander Flemming using the fungus penicillium. Some common antibiotics are streptomycin and terramycin. Microbes are used to make vaccines. Vaccines are weakened or dead germs introduced into the body.

Microorganisms : Friend and Foe NCERT Solutions - Class 8 Science

They offer protection against diseases like tuberculosis, polio etc. Bacteria and Yeast are used in making vitamin B complex tablets. The human hormonal called insulin can also be obtained from bacteria.

In Agriculture: Some bacteria like Rhizobium, blue green algae like Nostoc, live in the root nodules of plants such as gram, pea etc. These bacteria absorb the nitrogen of the atmosphere and convert it into nitrate which serves as natural fertilizers for plants, hence, enhancing soil fertility.

In cleaning the environment: Microbes help to keep our environment clean by decomposing dead matter. They decomposed substances are recycled as these get reused from the soil by plants. Some bacteria decompose sewage and other waste in water. Germs may enter the body of living organisms through air, contaminated food and water, from an infected person by direct or indirect contact or by a carrier.

Diseases that can spread from an infected person to a healthy individual through air, water or direct contact are called communicable diseases. Micro organisms also cause diseases in animals and plants. For examples- Anthrax is a disease caused by bacterium and affects human and cattle.

The lowest temperature at which a substance catches fire is called it ignition temperature. Types of combustion — rapid combustion and spontaneous combustion.

We should protect the endemic and endangered species. We should save trees, energy and water by reduce, recycle and reuse RRR. Just like bricks in building, the cells in the living organisms, are basic structural units.

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It is first observed by Robert Hooke in under a simple magnifying device. A human body has trillions thousand billion of cells of different shape and size. The smallest cell is 0. Mode of reproduction — Sexual reproduction — This type of reproduction beginning from the fusion of male and female gametes. Asexual reproduction — This type of reproduction in which only a single parent is involved. The human body undergoes several changes during adolescence. These changes mark the onset of puberty.

Increase in height, change in body shape, change in voice, development of sex organs, increase in activity of sweet and sebaceous glands, etc.

If the forces acting in opposite direction, the net force acting on the object is difference between the two forces. Force can change the state of motion or shape. Contact forces — Muscular forces and friction force. Non-contact forces — Magnetic force, electrostatic force and gravitational force.The chapter also deals different methods such as cooling, heating, pasteurisation and others to prevent food from microbial attack and preserve it for a long time.

Acetobacter aceti. A wrong dose of antibiotics makes the drug ineffective.

This might happen sometimes as we use javascript there. We really do hope that this resolve the issue. NCERT Book Chapter 5 Chapter 6: Combustion and Flame A chemical process in which a substance reacts with oxygen to give off heat is called combustion and the substance undergoes combustion is called combustible or fuel.

Some of the common examples are diatoms, chlamydomonas, and seaweed. Name three habitats of microorganisms.

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