Q2Short answer
Microorganisms : Friend and Foe
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b
Chapter 2
Class 8 Science · 27 questions · 27 with answers
Questions
Q3Multiple choice
Pathogenic micro-organisms present in host cells are killed by medicines called
- (a)pain killer
- (b)antibodies
- (c)antibiotics
- (d)vaccines
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(c) antibiotics
Q4Multiple choice
The two micro-organisms which live in symbiotic association in lichens are
- (a)fungus and protozoa
- (b)alga and bacteria
- (c)bacteria and protozoa
- (d)alga and fungus
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(d) alga and fungus
Q5Multiple choice
The gas released during the preparation of bread is
- (a)oxygen
- (b)carbon dioxide
- (c)nitrogen
- (d)sulphur dioxide
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(b) carbon dioxide
Q6Multiple choice
The disease caused by a protozoan and spread by an insect is _________.
- (a)dengue
- (b)malaria
- (c)polio
- (d)measles
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(b) malaria
Q7Multiple choice
Paheli dug two pits, A and B, in her garden. In pit A, she put a polyhtene bag packed with some agricultural waste. In pit B, she dumped the same kind of waste but without packing it in a polythene bag. She, then covered both the pits with soil. What did she observe after a month?
- (a)Waste in pit A degraded faster than that in pit B.
- (b)Waste in pit B degraded faster than that in pit A.
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(b) Waste in pit B degraded faster than that in pit A.
Q8Multiple choice
E XEMPLAR PROBLEMS (c) Waste in both pits degraded almost equally. (d) Waste in both pits did not degrade at all.
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Q9Multiple choice
Suggest a suitable word for each of the following statements.
- (a)Chemicals added to food to prevent growth of microorganisms.
- (b)Nitrogen-fixing microorganism present in the root nodules of legumes.
- (c)Agent which spreads pathogens from one place to another.
- (d)Chemicals which kill or stop the growth of pathogens.
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(a) Chemicals added to food to prevent growth of microorganisms.
(c) Agent which spreads pathogens from one place to another.
(b) Nitrogen-fixing microorganism present in the root nodules of legumes.
(d) Chemicals which kill or stop the growth of pathogens.
Q10Multiple choice
Match the names of scientists given in Column A with the discovery made by them given in Column B. Column A Column B (a) Louis Pasteur
- (i)Penicillin (b) Robert Koch
- (ii)anthrax bacterium (c) Edward Jenner
- (iii)Fermentation (d) Alexander Fleming
- (iv)small pox vaccine (v) Typhoid
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(i) Penicillin (b) Robert Koch
(iii) Fermentation (d) Alexander Fleming
(ii) anthrax bacterium (c) Edward Jenner
(iv) small pox vaccine (v) Typhoid
Q11Very short answer
Name one commercial use of yeast.
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Baking bread/manufacture of alcoholic drinks
Q12Very short answer
Name the process in yeast that converts sugars into alcohol.
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Fermentation
Q13Very short answer
In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?
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Nitrogen
Q14Very short answer
Why should we avoid standing close to a tuberculosis patient while he/she is coughing? M ICROORGANISMS : FRIENDS AND FO E 9
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Tuberculosis is an air-borne disease which easily spreads when the infected person coughs.
Q15Very short answer
Polio drops are not given to children suffering from diarrhoea. Why?
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If the child is suffering from diarrhoea, the orally given vaccine may be excreted out because of frequent motions.
Q16Very short answer
Paheli watched her grandmother making mango pickle. After she bottled the pickle, her grand mother poured oil on top of the pickle before closing the lid. Paheli wanted to know why oil was poured? Can you help her understand why?
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Oil prevents bacteria from attacking the pickle and spoiling it. SHORT ANSWER QUESTIONS
Q17Multiple choice
Match the microorganisms given in the Column A to the group to which they belong in Column B. Column A Column B (a) Lactobacillus
- (i)Algae (b) Aspergillus
- (ii)Protozoa (c) Spirogyra
- (iii)Fungi (d) Paramecium
- (iv)Bacteria
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(i) Algae (b) Aspergillus
(iv) Bacteria
(ii) Protozoa (c) Spirogyra
(iii) Fungi (d) Paramecium
Q18Fill in the blanks
Classify the following into friendly and harmful microorganisms. Yeast, malarial parasite, Lactobacillus, bread mould, Rhizobium, Bacillus anthracis Friendly Harmful ________ ________ ________ ________ ________ ________ ________ ________
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Friendly Harmful Yeast Malarial parasite Lactobacillus Bread mould Rhizobium Bacillus anthracis 114 E XEMPLAR PROBLEMS
Q19Short answer
While returning from the school, Boojho ate chaat from a street hawker. When he reached home, he felt ill and complained of stomach ache and fell ill. What could be the reason?
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The probable reason is that the chaat was contaminated by pathogenic microbes due to unhygienic conditions near the shop or the utensil used for serving could have contaminated.
Q20Short answer
What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?
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The ‘unused kneaded flour’, if left in warm conditions, gets infected by microbes which cause fermentation and spoils the flour. The pooris would remain in relatively good condition because they were deep fried in heated oil that kills microbes.
Q21Multiple choice
- (a)Name two diseases that are caused by virus.
- (b)Write one important characteristic of virus. 10 E XEMPLAR PROBLEMS
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(a) Name two diseases that are caused by virus.
(b) Write one important characteristic of virus. 10 E XEMPLAR PROBLEMS
Q22Multiple choice
Observe the Fig.2.1 and answer the questions that follows. Fig. 2.1
This question refers to a figure in the original PDF.
- (a)Write the name of the disease.
- (b)Name the causative agent of this disease?
- (c)How does the disease spread from one plant to another?
- (d)Name any two plant diseases and the microbes that cause them.
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(a) Write the name of the disease.
(b) Name the causative agent of this disease?
(c) How does the disease spread from one plant to another?
(d) Name any two plant diseases and the microbes that cause them.
Q23Long answer
How do vaccines work?
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Vaccines contain dead or weakened microbes of a particular disease. When a vaccine is introduced into a healthy body, the body fights and kills them by producing suitable antibodies. These antibodies remain in the body and protects it when the microbe enters the body again.
Q24Multiple choice
Observe the set up given in Fig. 2.2 and answer the following questions.
This question refers to a figure in the original PDF.
- (a)What happens to the sugar solution in A?
- (b)Which gas is released in A?
- (c)What changes will you observe in B when the released gas passes through it? Fig. 2.2 M ICROORGANISMS : FRIENDS AND FO E 11
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(a) What happens to the sugar solution in A?
(b) Which gas is released in A?
(c) What changes will you observe in B when the released gas passes through it? Fig. 2.2 M ICROORGANISMS : FRIENDS AND FO E 11
Q25Multiple choice
Observe the Fig.2.3 and answer the following questions. Fig. 2.3
This question refers to a figure in the original PDF.
- (a)Name the microorganism and the group to which it belongs.
- (b)Name the food item on which the organism grows.
- (c)Does it grow well in dry or in moist conditions?
- (d)Is it safe to eat infected bread?
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(a) Name the microorganism and the group to which it belongs.
(b) Name the food item on which the organism grows.
(c) Does it grow well in dry or in moist conditions?
(d) Is it safe to eat infected bread?
Q26Multiple choice
Give reasons for the following.
- (a)Fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling.
- (b)Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.
- (c)Farmers prefer to grow beans and peas in nitrogen deficient soils.
- (d)Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?
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(a) Fresh milk is boiled before consumption while processed milk stored in packets can be consumed without boiling.
(b) Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.
(c) Farmers prefer to grow beans and peas in nitrogen deficient soils.
(d) Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?
Q27Multiple choice
How can we prevent the following diseases?
- (a)Cholera
- (b)Typhoid
- (c)Hepatitis A 12 E XEMPLAR PROBLEMS
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(a) Cholera
(b) Typhoid
(c) Hepatitis A 12 E XEMPLAR PROBLEMS
Q28Multiple choice
Complete the following cycle given as Fig. 2.4 by filling the blanks
This question refers to a figure in the original PDF.
- (a),
- (b),
- (c)
- (d)Fig. 2.4
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(a) ,
(b) ,
(c)
(d) Fig. 2.4