NCERT Solutions for Class 8 Science Chapter 2 is Microorganisms. Students will be able to gather knowledge on microorganisms after studying this solution .Their habitats, classes of microorganisms like bacteria, fungi, protozoans and viruses, mode of their reproduction, use of microorganisms, harmful microorganisms, pathogens, soil microorganisms, nitrogen fixation by bacteria. These answers will help you to achieve perfection on the concepts involved in chapter Microorganisms, Friend and Foe.
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NCERT Solutions for Class 8 Science Chapter 2 : Microorganisms
1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a ____________.
(b) Blue green algae fix __________ directly from air and enhance fertility
(c) Alcohol is produced with the help of __________.
(d) Cholera is caused by __________.
(a) Microorganisms can be seen with the help of a microscope.
(b) Blue green algae fix nitrogen directly from air and enhance fertility of soil.
(c) Alcohol is produced with the help of yeast.
(d) Cholera is caused by bacteria- Vibrio choler.
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.
(a) Option (ii) is the correct answer.
(b) Option (ii) is the correct answer.
(c) Option (i) is the correct answer.
(d) Option (ii) is the correct answer.
(e) Option (iii) is the correct answer.
(f) Option (iii) is the correct answer.
3. Match the organisms in Column A with their action in Column B.
(i) Bacteria (a) Fixing nitrogen
(ii) Rhizobium (b) Setting of curd
(iii) Lactobacillus (c) Baking of bread
(iv) Yeast (d) Causing malaria
(v) A protozoan (e) Causing cholera
(vi) A virus (f) Causing AIDS
(g) Producing antibodies
(i) Bacteria (e) Causing cholera
(ii) Rhizobium (a) Fixing nitrogen
(iii) Lactobacillus (b) Setting of curd
(iv) Yeast (c) Baking of bread
(v) A protozoan (d) Causing malaria
(vi) A virus (f) Causing AIDS
4. Can microorganisms be seen with the naked eye? If not, how can they
The microorganisms cannot be seen with our naked eyes because they are very small in size. Some of these, such as fungus growing on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope.
5. What are the major groups of microorganisms?
Microorganisms are classified into the following major groups:
6. Name the microorganisms which can fix atmospheric nitrogen in the
Rhizobium can fix atmospheric nitrogen in the soil.
7. Write 10 lines on the usefulness of microorganisms in our lives.
Microorganisms are useful to us in many ways. For example,
Bacteria like Lactobacillus convert milk into curd.
Bacteria are also involved in the making of cheese.
Acetobacter aceti is used for producing acetic acid from alcohol.
Some bacteria fix atmospheric nitrogen and increase soil fertility.
Yeast is used in the commercial production of alcohol, wine and bakery products.
Some specific microorganisms are helpful in manufacturing of antibiotics.
Microorganisms act as cleansing agents and decompose the waste products into manure.
Dead or weakened microbes are used in the preparation of vaccines.
Algae, yeast, fungi or bacteria may be used as an ingredient or a substitute for protein rich foods that are suitable for human or animal consumption.
Some microorganisms are taken as probiotics that are believed to provide health benefits when consumed.
8. Write a short paragraph on the harmful effects of microorganisms.
Microorganisms are harmful in many ways. Microorganisms called pathogens cause disease in humans, plants and animals. Pathogens or germs enter a healthy body through air, water, contaminated food and infected person by direct or indirect contact or by the carrier. Ailments like cold, influenza, cough, polio, chicken pox are caused by viruses. Foot and mouth diseases in the cattle are also caused by viruses. Typhoid, tuberculosis (TB) are caused by bacteria. Anthrax a dangerous human and cattle diseases is also caused by bacteria.
9. What are antibiotics? What precautions must be taken while taking
The medicines which kill or stop the growth of the disease-causing microbes are called antibiotics. They are manufactured by growing specific microorganisms.
Precautions that must be taken while taking antibiotics are:
Take antibiotic only on the advice of a qualified doctor.
Finish the course prescribed by the doctor to make the drug more effective.
Antibiotics must not be taken unnecessarily because it may kill beneficial bacteria also.