Question 1. Fill in the blanks.
(a) Microorganisms can be seen with the help of a________________.
(b) Blue-green algae fix ______________ directly from air to enhance fertility.
(c) Alcohol is produced with the help of __________.
(d) Cholera is caused by ____________.
Solution :
(a) Microorganisms can be seen with the help of a microscope.
(b) Blue-green algae fix nitrogen directly from air to enhance fertility.
(c) Alcohol is produced with the help of yeast.
(d) Cholera is caused by bacteria.
Question 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 carbonate
(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.
Solution :
(a) —> (ii)
(b) —> (ii)
(c) —> (i)
(d) —> (ii)
(e) —> (iii)
(f) —> (iii)
Question 3. Match the organisms in Column A with their action in Column B.
| Column I | Column II |
| (a) Bacteria (b) Rhizobium (c) Lactobacillus (d) Yeast (e) A protozoan (f) A virus | (i) Fixing nitrogen (ii) Setting of curd (iii) Baking of bread (iv) Causing malaria (v) Causing cholera (vi) Causing AIDS |
Solution :
| Column I | Column II |
| (a) Bacteria (b) Rhizobium (c) Lactobacillus (d) Yeast (e) A protozoan (f) A virus | (i) Causing cholera (ii) Fixing nitrogen (iii) Setting of curd (iv) Baking of bread (v) Causing malaria (vi) Causing AIDS |
Question 4. Can microorganisms be seen with the naked eyes? If not, how can they be seen?
Solution : Micro-organisms are too small to be seen through naked eyes. They can be seen with the help of a magnifying glass or microscope.
For example, fungus that grows on bread is so small that it can be seen only with the help of a magnifying glass or microscope.
No, microorganisms cannot be seen with the naked eye. They can only be seen with the help of microscope.
Question 5. What are the major groups of microorganisms?
Solution : There are five major groups of micro-organisms:
→ Bacteria – They are single celled disease-causing micro-organisms. They can be spiral or rod- shaped.
→ Fungi – They are mostly multicellular disease-causing microbes. Bread moulds are common examples of fungi.
→ Protozoa – They mainly include organisms such as Amoeba, Plasmodium,etc. They can be unicellular or multicellular.
→ Virus -Viruses are disease-causing microbes that reproduce only inside the host organism.
→ Algae – They include multicellular, photosynthetic organisms such as Spirogyra, Chlamydomonas, etc.
Question 6. Name the microorganism which can fix atmospheric nitrogen in the soil.
Solution : Certain bacteria such as Rhizobium and blue green algae present in the soil fix atmospheric nitrogen and convert it into compounds of nitrogen.
Question 7. Write 10 lines on the usefulness of microorganisms in our lives.
Solution : Micro-organisms are too small to be seen through naked eyes. However, they are vital to plants and the environment.
1. Rhizobium present in the roots of pulse plants fix nitrogen from air and supply nitrogen compounds to the pulse plants.
2. Micro-organisms are also used in winemaking, baking, pickling, and other food making processes.
3. Alcoholic fermentation by yeast is widely used in the preparation of wine and bread.
4. Microbes are used to reduce pollution. For example, decomposers such as bacteria and fungi break down dead bodies and excreta to form inorganic compounds, which can be absorbed by plants.
5.Microbes also play an important role in the preparation of medicines. Antibiotics are chemicals produced by micro-organisms to kill bacteria. Penicilin is an antibotic made from Penicilium.
6. Bacteria present in our intestine helps in proper digestion and release Vitmain B which is absorbed by intestine.
7. Many vaccines are prepared from micro-organisms. These vaccines are given to children to protect them from disease.
8. Certain microbes are also used in the biological treatment of sewage and industrial effluents.
9.Yeast is used in making idlis, bhaturas, bread, pastries and cakes.
10.Lactobacillus is used to form curd from milk.
Question 8. Write a short paragraph on the harms caused by microorganisms.
Solution : The harm caused by microorganisms are as follows-
a. They cause many communicable diseases like cholera, common cold, tuberculosis etc.
b. Malaria is caused by a microorganism called plasmodium.
c. Several plants diseases are caused by bacteria and fungi.
d. Food poisoning is caused by microorganism.
e. They are responsible for spoiling of food.
Question 9. What are antibiotics? What precautions must be taken while taking antibiotics?
Solution : The medicines that kill or stop the growth of the disease-causing microorganism are called antibiotic. Streptomycin, tetracycline, erythromycin etc. are common antibiotics. They are manufactured by growing specific micro-organisms and are used to cure a variety of diseases.
Precautions to be taken while using antibiotics :
* Antibiotics should be taken under the supervision of a well qualified doctor.
* Course (intake) of antibiotics should be completed as per the prescription given by the doctor.
* Antibiotics should be taken in the right amount and at the right time. A wrong dose of antibiotics makes the drug ineffective. Also, excessive consumption of drugs may kill the useful bacteria present in our body.