1. Fill in the blanks :
2. Microorganisms can be seen with the help of a __________.
3. Blue green algae fix __________ directly from air to enhance fertility of soil.
4. Alcohol is produced with the help of __________.
5. Cholera is caused by __________.
6. i) microscope ii) nitrogen iii) yeast iv) bacteria
7. Tick the correct answer :
8. Yeast is used in the production of :
9. i) sugar ii) alcohol (P)
   iii) hydrochloric acid iv) oxygen
10. The following is an antibiotic :
11. i) Sodium bicarbonate ii) Streptomycin (P)

iii) Alcohol iv) Yeast

1. Carrier of malaria-causing protozoan is :
2. i) female Anopheles mosquito (P) ii) cockroach

iii) housefly iv) butterfly

1. The most common carrier of communicable diseases is :
2. i) ant ii) housefly (P)
   iii) dragonfly iv) spider
3. The bread or idli dough rises because of :
4. i) heat ii) grinding

iii) growth of yeast cells (P) iv) kneading

1. The process of conversion of sugar into alcohol is called :
2. i) nitrogen fixation ii) moulding
   iii) fermentation (P) iv) infection
3. Match the organisms in Column A with their action in Column B.

Column A Column B

1. i) Bacteria ( ) a) Fixing nitrogen
2. ii) Rhizobium ( ) b) Setting of curd

iii) Lactobacillus ( ) c) Baking of bread

1. iv) Yeast ( ) d) Causing malaria
2. v) A protozoan ( ) e) Causing cholera
3. vi) A virus ( ) f) Causing AIDS
4. g) Producing antibodies
5. i) e ii) a iii) b iv) c v) d vi) f
6. Can microorganisms be seen with the naked eye ? If not, how can they be seen ?
7. i) Microorganisms cannot be seen with the naked eye.
8. ii) They can be seen with the help of a magnifying glass or microscope.
9. What are the major groups of microorganisms ?
10. Microorganisms are classified into four major groups. They are –
11. i) Bacteria ii) Fungi iii) Protozoa v) Algae
12. Name the microorganisms which can fix atmospheric nitrogen in the soil.
13. Rhizobium, Anabaena, Nostoc, Azotobacter etc.
14. Write 10 lines on the usefulness of microorganisms in our lives.
15. i) Microorganisms play an important role in our lives.
16. ii) Microorganisms are used for various purposes such as bread making, preparation of curd, alcoholic beverages, vinegar etc.

iii) Some of the bacteria are used in the preparation of medicines.

1. iv) They play an important role in the decomposition of organic wastes and keeping the environment clean.
2. v) Some microorganisms increase the fertility of the soil by fixing nitrogen.
3. vi) Microorganisms are used for the production of vaccines.

vii) Certain microorganisms are used in the biological treatment of sewage.

viii) They are also used for the production of antibiotics.

 

8. Write a short paragraph on the harms caused by microorganisms.
9. i) Microorganisms cause diseases in animals. Eg : In cattle, the foot and mouth disease is caused by a virus.
10. ii) Several microbes cause diseases in plants. Eg : The productivity of wheat, orange, apple etc. is reduced due to microbial diseases in plants.

iii) Certain microbes, on entering into our body, produce toxic substances. This leads to diseases.

1. iv) Some microorganisms such as fungus spoil our food. For example, bread when left unused under moist conditions gets spoilt by fungus.
2. v) Some of the protozoans cause serious diseases like dysentery and malaria.
3. What are antibiotics? What precautions must be taken while taking antibiotics?
4. The medicines produced by certain microorganisms used to kill other disease-causing micro-organisms are called antibiotics. (or) The chemical substances that kill or stop the growth of microorganisms are called antibodies.

Eg : Streptomycin, tetracycline, penicillin etc.

Precautions to be taken while using antibiotics :

1. i) Antibiotics should be taken under the supervision of a well qualified doctor.
2. ii) Course (intake) of antibiotics should be completed as per the prescription given by the doctor.

iii) Antibiotics should be taken in the right amount and at the right time.