Q1. Fill in the blanks:
(a) Microorganisms can be seen with the help of a microscope.
Microscope(b) Blue-green algae fix nitrogen directly from air to enhance the fertility of the soil.
(c) Alcohol is produced with the help of yeast.
(d) Cholera is caused by bacteria.
Q2. Tick the correct answer:
(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
Ans: (ii) alcohol
(b) The following is an antibiotic
(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast
Ans: (ii) Streptomycin
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly
Butterfly
Ans: (i) female Anopheles mosquito
(d) The most common carrier of communicable diseases is
(i) ant (ii) housefly (iii) dragonfly (iv) spider
Ans: (ii) housefly
(e) The bread or idli dough rises because of
(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading
Ans: (iii) growth of yeast cells
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) molding (iii) fermentation (iv) infection
Ans: (iii) fermentation
Q3. Match the organisms in Column I with their action in Column II.
Column A | 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 |
Ans:
Column A | Column B |
(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 |
Q4. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Ans: The microorganism can not be seen with naked eyes. Microorganisms are too small and are not visible to 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.
Q5. What are the major groups of microorganisms?
Ans: Microorganisms are classified into four major groups:
Q6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Ans: Bacteria like Rhizobium and blue-green algae are microorganisms which can fix atmospheric nitrogen in the soil thus increase soil fertility. These microbes are commonly called biological nitrogen fixers.
Blue-green algae
Q7. Write 10 lines on the usefulness of microorganisms in our lives.
Ans: Microorganisms are quite useful in our lives in many ways :
Q8. Write a short paragraph on the harms caused by microorganisms.
Ans: 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. Pathogens spread a number of Microbial diseases or communicable diseases like cholera, common cold, chickenpox and tuberculosis from an infected person to a healthy person through air, water, food or physical contact.
Some microorganisms spoil food, clothing and leather. Food poisoning is caused due to the consumption of food spoilt by some microorganisms.
Microorganisms
Q9. What are antibiotics? What precautions must be taken while taking antibiotics?
Ans: Antibiotic is a medicine that kills or stops the growth of disease-causing microorganisms in humans and animals. The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases. Antibiotics medicines like Streptomycin, tetracycline and erythromycin are commercially produced from bacteria and fungi.
Antibiotics
Precautions in taking Antibiotics:
(i) Antibiotics should be taken only on the advice of a qualified doctor. And one must finish the course prescribed by the doctor.
(ii) Antibiotics must be avoided when not needed or required.
(iii) Antibiotics taken unnecessarily may kill the beneficial bacteria in the body.
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