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DELHI PUBLIC SCHOOL, HYDERABAD

CH8: MICROBES IN HUMAN WELFARE
WORKSHEET
CLASS: XII SUBJECT: BIOLOGY
OBJECTIVE QUESTIONS
MULTIPLE CHOICE QUESTIONS (1MARK)
1. Microbes are used in the production of:
a) Yogurt b) Cheese
c) Bread d) All of the above
2. Lactic acid bacteria (LAB) are used to convert milk into:
a) Cheese only b) Yogurt only
c) Both yogurt and cheese d) Butter
3. The characteristic flavour of yogurt is due to:
a) Lactic acid only b) Lactic acid and other metabolic products of LAB
c) The milk used d) Added flavours
4. Which microorganism is primarily used in bread making?
a) Bacteria b) Yeast (Saccharomyces cerevisiae)
c) Virus d) Protozoa
5. The leavening action in bread making is due to the production of:
a) Lactic acid b) Carbon dioxide
c) Alcohol d) Enzymes
6. Fermented beverages like beer and wine are produced using:
a) Bacteria b) Yeast
c) Fungi (other than yeast) d) Protozoa
7. Which of the following is NOT a product of microbial fermentation?
a) Cheese b) Wine
c) Fruit juice d) Vinegar
8. Biogas is primarily composed of:
a) Oxygen and nitrogen b) Methane and carbon dioxide
c) Hydrogen and carbon monoxide d) Sulphur dioxide and nitrogen
oxides
9. Biogas is produced by the anaerobic activity of:
a) Bacteria b) Methanogens

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]

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c) Fungi d) Protozoa
10. Which of the following microbes are used as bio fertilizers?
a) Rhizobium b) Azotobacter
c) Azospirillum d) All of the above
11. Bio fertilizers enhance soil fertility by:
a) Increasing chemical fertilizer use b) Fixing atmospheric nitrogen
c) Reducing water availability d) Increasing soil erosion
12. Mycorrhiza is a symbiotic association between:
a) Bacteria and roots of higher plants b) Fungi and roots of higher plants
c) Algae and fungi d) Bacteria and fungi
13. Which of the following is an example of a microbial biocontrol agent?
a) Chemical pesticides b) Bacillus thuringiensis (Bt)
c) Chemical fertilizers d) Weedicides
14. Biocontrol agents help to:
a) Increase pest populations b) Control pests and diseases naturally
c) Harm beneficial insects d) Pollute the environment
15. Single Cell Protein (SCP) refers to:
a) Protein extracted from a single animal cell
b) Protein produced by microorganisms grown on a large scale
c) Protein found in a single plant cell
d) Protein synthesized chemically
16. Which of the following microorganisms can be used for SCP production?
a) Bacteria b) Algae
c) Fungi d) All of the above
17. Sewage treatment primarily utilizes microbes for:
a) Physical removal of pollutants b) Decomposition of organic waste
c) Chemical treatment of pollutants d) Filtration of water
18. The secondary treatment of sewage involves:
a) Physical removal of solids b) Biological oxidation of organic matter
c) Chemical treatment of pollutants d) Disinfection of water
19. Activated sludge is used in:
a) Primary sewage treatment b) Secondary sewage treatment
c) Tertiary sewage treatment d) Sludge digestion

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]

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20. Which of the following is a beneficial role of microbes in the human gut?
a) Causing diseases b) Aiding in digestion
c) Producing toxins d) Competing with nutrients
21. The diagram below shows a typical biogas plant. With few structure labelled as
A, B and C. Identify A, B and C.

a) A – Sludge, B – Methane, Oxygen, C – Dung, water

(b) A – Sludge, B – Methane, Carbon dioxide, C– Dung, water
(c) A – Sludge, B – Ethylin, Carbon dioxide, C – Dung, water
(d) A – Sludge, B – Methane, Carbon dioxide, C – Sewage

22. Identify the blank spaces marked A, B, C and D from the table given below.

(a) A–Trichoderma polyspora, B – Organ transplant patients, C – Yeast (fungus), D –

Lowering of blood
cholesterol.
(b) A–Lowering of blood cholesterol, B – Trichoderma polyspora, C – Organ transplant
patients, D – Yeast
(fungus).
(c) A – Yeast (fungus), B – Lowering of blood cholesterol, C – Trichoderma polyspora, D
– Organ transplant patients.
(d) A – Organ transplant patients, B – Yeast (fungus), C – Lowering of blood
cholesterol, D – Trichoderma
polyspora.
23. Match the items of column-I with column-II and choose correct answer.

(a) A – II; B – IV; C – III; D – I (b) A – III; B – IV; C – II; D – I

(c) A – IV; B – I; C – II; D – III (d) A – III; B – II; C – I; D – IV

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]

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24. Which one of the following is wrongly matched?

(a) Yeast – Ethanol (b) Streptomyces – Antibiotics
(c) Lactobacillus – Beer (d) Methanogens – Gobar gas
25. Read the following statement.
“A drug used for ———— (A) ———— patients is obtained from a species of the
organism ———— (B) — ———.” Identify A and B.

A B
(a) Heart Penicillium
(b) Organ- Penicillium
transplant
(c) Swine flu Monascus
(d) AIDS Pseudomonas

ASSERTION AND REASON TYPE

Instructions for each question: For each of the following questions, a statement of assertion
(A) is followed by a statement of reason (R). Choose the best answer from the options given
below:
 (a) Both A and R are true and R is the correct explanation of A
 (b) Both A and R are true but R is not the correct explanation of A
 (c) A is true but R is false
 (d) A is false but R is true
 (e) Both A and R are false
26:
 Assertion (A): Lactic acid bacteria (LAB) are used to make curd from milk.
 Reason (R): LAB produce lactic acid, which coagulates milk proteins and gives
curd its characteristic texture and flavor.
27:
 Assertion (A): Bread making utilizes yeast.
 Reason (R): Yeast produces carbon dioxide during fermentation, which causes
the dough to rise.
28:
 Assertion (A): Biogas is a renewable source of energy.
 Reason (R): Biogas is produced by the anaerobic breakdown of organic waste
by methanogenic bacteria.
29:
 Assertion (A): Biofertilizers enhance soil fertility.

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]

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 Reason (R): Biofertilizers are microorganisms that fix atmospheric nitrogen or

make other nutrients available to plants.
30:
 Assertion (A): Microbes are only harmful to humans.
 Reason (R): All microbes are pathogenic and cause diseases.
Answer: (e) Both the assertion and the reason are false. Many microbes are beneficial
and essential for human well-being, as seen in food production, medicine, and various
industrial processes. Only a small fraction of microbes are pathogenic.

CASE BASED QUESTIONS: 4MARKS

31. Ravi got selected as a principal speaker in an event that primarily caters to
spreading awareness about the benefits provided to us by various microorganisms.
He wanted to stress upon the usage of microbes in manufacturing of household
products. He wants to underline the various things we eat almost on a daily or weekly
basis that have microorganisms at the helm of their production process. Answer the
given questions to help him prepare himself for the probable Q-A session after his
speech.
(A) Jalebis are a staple Indian dessert. What role do microorganisms play in its
production? (B) List any two Indian food items other than curd based dishes which
are prepared with the help from beneficial microorganisms.
(C) Expand LAB. Ans. (B) (1) The batter
32. Shivam is considering organic farming as an option for his career. He has zeroed
upon a few biological practices. He is going through the magazines, research papers,
manuals and journals related to the practices adopted in maintaining an organic farm.
He listed some key questions based on the topic. Help him by finding appropriate
answers.
(A) Mention any two advantages of organic farming over conventional farming.
(B) There is a serious problem of butterfly caterpillar infestation in the area where
Shivam is planning to do organic farming. How can he solve this problem?
(C) Name any microbe which is used as biofertiliser.

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]

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SUBJECTIVE TYPE QUESTIONS

2 Mark Questions
1. What are microbes? Give two examples of useful microbes.
2. What are biofertilizers? Give two examples.
3. What are probiotics? How are they beneficial?
4. What is biogas? What are its main components?
5. What are single-cell proteins (SCP)?
3 Mark Questions
1. Explain the role of microbes in household food production, giving two
examples.
2. Describe the process of sewage treatment, highlighting the role of microbes.
3. Explain the use of microbes in the production of biogas.
4. How are microbes used in the production of antibiotics? Give an example.
5. Discuss the role of microbes as biocontrol agents.
5 Mark Questions
1. Describe the various ways in which microbes are used in the production of food
products, including dairy products, beverages, and other food items.
2. Explain the process of industrial production of alcohol, highlighting the role of
microbes.
3. Discuss the role of microbes in sewage treatment and waste management.
4. Describe the use of microbes as biofertilizers and biopesticides in sustainable
agriculture.
5. Explain the importance of microbes in various industrial processes, such as the
production of enzymes, organic acids, and other valuable products.

DELHI PUBLIC SCHOOL, HYDERABAD [CLASS: XII SUBJECT: BIOLOGY]