Tick the correct answer. The process of conversion of sugar into alcohol is called:
- ANitrogen fixation.
- BMoulding.
- ✓Fermentation.
- DInfection.
Answer: C.
View full solution →Question types
Microorganisms: Friend and Foe question types
346 questions across 12 question groups — pick any mix to generate a Science paper with step-by-step answer keys.
346
Questions
12
Question groups
5
Question types
01
M.C.Q. [I MARKS]
209 Q→02Give the definition [1 M]
27 Q→03differences [2marks]
3 Q→04as requested in detail. [5 marks ]
10 Q→05Fill in the blanks: [1 M]
15 Q→06questions in short. [2 marks ]
10 Q→07scientific reasons[2 marks ]
11 Q→08true or false. [1 M]
13 Q→09questions in short. [3 marks ]
10 Q→10questions in details [4 marks ]
14 Q→11questions in on sentence. [1 M]
20 Q→12case /data -based (4 Marks)
4 Q→Sample Questions
Microorganisms: Friend and Foe questions
One sample from each question group in this chapter. Select any group above to see the full set with answer keys.
Tick the correct answer. The bread or idli dough rises because of:
- AHeat.
- BGrinding.
- ✓Growth of yeast cells.
- DKneading.
Answer: C.
View full solution →Tick the correct answer. The most common carrier of communicable diseases is:
- AAnt.
- ✓Housefly.
- CDragonfly.
- DSpider.
Answer: B.
View full solution →Tick the correct answer. Carrier of malaria$-$causing protozoan is:
- ✓Female Anopheles mosquito.
- BCockroach.
- CHousefly.
- DButterfly.
Answer: A.
View full solution →Tick the correct answer. The following is an antibiotic:
- ASodium bicarbonate.
- ✓Streptomycin.
- CAlcohol.
- DYeast.
Answer: B.
View full solution →Yeast
Virus
Vaccine
Rhizobium
Protozoa
Viruses and Bacteria
Fungi and Algae
Yeast and Mould
Write a short paragraph on the harmful effects of microorganisms.
Write 10 lines on the usefulness of microorganisms in our lives.
Match the organisms in Column $I$ with their action in Column $II.$
View full solution →| Column I | Column II | ||
|
$(i)$
|
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
|
|
What are the major groups of microorganisms?
Observe the set up given in Fig and answer the following questions.
$a.$ 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?
We use a $...........$ to see the microorganisms.
View full solution →The process of formation of curd from milk is known as the $...........$ of milk.
View full solution →$...........$ are the microorganisms that help in the process of decomposition.
View full solution →The first antibiotic discovered was $..........$
View full solution →Flu, cough and cold are caused by $..........$
View full solution →Name the microorganisms which can fix atmospheric nitrogen in the soil.
Can microorganisms be seen with the naked eye? If not, how can they be seen?
Write one important characteristic of virus.
How should we prevent spread of communicable diseases?
What will happen if spoilt food is consumed?
Why do idli and dosa maker add some yeast or old batter of pervious day to the newly-made batter and keep it for one day?
Ria thought of making curd. For this, she took lukewarm milk, mixed some curd into it and stir well. She kept the mixture in fridge. Next day she observed that curd was not set. Can you tell why the curd did not set?
Why oil is added while making pickle?
It is always suggested that not to eat anything from street hawkers. Why?
Food should always be covered.
Oxygen alone constitutes $78\%$ of air.
View full solution →Salt is used as a food preservative.
Jellies, jams and squashes are preserved by adding vinegar to them.
A fungi is used in the production of alcohol.
Amoebic dysentery is caused by algae.
Give reasons for the following: Raw vegetables and fruits are kept in refrigerators whereas jams and pickles can be kept outside.
Give reasons for the following: Farmers prefer to grow beans and peas in nitrogen deficient soils.
Give reasons for the following: Mosquitoes can be controlled by preventing stagnation of water though they do not live in water. Why?
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?
How can we prevent the following diseases? Typhoid.
What are antibiotics? What precautions must be taken while taking antibiotics?
Match the names of scientists given in Column $A$ with the discovery made by them given in Column $B.$
View full solution →|
|
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
|
Complete the following cycle given as Fig by filling the blanks $(a), (b), (c) (d)$
View full solution →Match the microorganisms given in the Column $A$ to the group to which they belong in Column $B.$
View full solution →|
|
Column $A$
|
|
Column $B$
|
|
$(a)$
|
Lactobacillus
|
$(i)$
|
Algae
|
|
$(b)$
|
Aspergillus
|
$(ii)$
|
Protozoa
|
|
$(c)$
|
Spirogyra
|
$(iii)$
|
Fungi
|
|
$(d)$
|
Paramecium
|
$(iv)$
|
Bacteria
|
Observe the Fig and answer the questions that follows:
$a.$ 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.
View full solution →$a.$ 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.
Suggest a suitable word for the following statements. Agent which spreads pathogens from one place to another.
Name the bacterium which causes anthrax disease.
Suggest a suitable word for the following statements. Chemicals which kill or stop the growth of pathogens.
Name two diseases that are caused by virus.
Polio drops are not given to children suffering from diarrhoea. Why?
The picture shows the nitrogen cycle.
$9.$ How do plants take up nitrogen$?$
$A.$ She should repeat the same experiment.
$B.$ She should leave the test tube undisturbed for six hours.
$C.$ She should repeat the experiment with test tubes containing more sugar solution.
$D.$ She should keep an extra set of test tubes with sugar solution but without the yeast.
$10.$ Plants and animals are continuously using nitrogen. Will there be a depletion of nitrogen in the environment due to this continuous use$?$ Explain your answer.
View full solution →$9.$ How do plants take up nitrogen$?$
$A.$ She should repeat the same experiment.
$B.$ She should leave the test tube undisturbed for six hours.
$C.$ She should repeat the experiment with test tubes containing more sugar solution.
$D.$ She should keep an extra set of test tubes with sugar solution but without the yeast.
$10.$ Plants and animals are continuously using nitrogen. Will there be a depletion of nitrogen in the environment due to this continuous use$?$ Explain your answer.
Manoj adds some yeast to two test tubes containing sugar solution.
One test tube is kept in ice and the other at room temperature.
The picture shows what happens after three hours.
$5.$ What is Manoj investigating$?$
$A.$ Does yeast grow in sugar solution only$?$
$B.$ Does yeast convert sugar into alcohol$?$
$C.$ Does temperature affect the growth of yeast$?$
$D.$ Which gas is produced as yeast grows in sugar solution$?$
$6.$ How can Manoj conirm if the gas produced in the test tube at room temperature was due to the yeast growing in it$?$
$A.$ She should repeat the same experiment.
$B.$ She should leave the test tube undisturbed for six hours.
$C.$ She should repeat the experiment with test tubes containing more sugar solution.
$D.$ She should keep an extra set of test tubes with sugar solution but without the yeast.
$7.$ What should Manoj keep the same in both the test tubes for a fair experiment$?$
Circle ‘Yes’ or ‘No’ for each row.
$8.$ What type of organism is yeast$?$
$A.$ Fungi
$B.$ Algae
$C.$ Bacteria
$D.$ Protozoa
View full solution →One test tube is kept in ice and the other at room temperature.
The picture shows what happens after three hours.
$5.$ What is Manoj investigating$?$
$A.$ Does yeast grow in sugar solution only$?$
$B.$ Does yeast convert sugar into alcohol$?$
$C.$ Does temperature affect the growth of yeast$?$
$D.$ Which gas is produced as yeast grows in sugar solution$?$
$6.$ How can Manoj conirm if the gas produced in the test tube at room temperature was due to the yeast growing in it$?$
$A.$ She should repeat the same experiment.
$B.$ She should leave the test tube undisturbed for six hours.
$C.$ She should repeat the experiment with test tubes containing more sugar solution.
$D.$ She should keep an extra set of test tubes with sugar solution but without the yeast.
$7.$ What should Manoj keep the same in both the test tubes for a fair experiment$?$
Circle ‘Yes’ or ‘No’ for each row.
| Should this be kept same for both the test tubes? | Yes or No |
| The concentration of sugar solution | Yes/No |
| The colour of the balloons | Yes/No |
| The amount of yeast added to each test tube | Yes/No |
$A.$ Fungi
$B.$ Algae
$C.$ Bacteria
$D.$ Protozoa
Suman wants to see how quickly carrots lose colour. Loss of colour shows rotting of carrot.
She observes carrot slices on a plate under three different conditions as shown below.
She notes how long the carrot slices on each plate take to change colour.
$3.$ What can Suman conclude from her activity$?$
$A.$ Carrots when kept under the sun do not rot easily.
$B.$ Carrots at room temperature lose colour more quickly.
$C.$ Carrots can be best preserved in hot and moist conditions.
$D.$ Carrots take more time to lose colour under cold conditions.
$4.$ Use the results of the activity to inish the graph below. The irst bar is drawn for you.
Put a label in the space provided for the axis on the left.
View full solution →She observes carrot slices on a plate under three different conditions as shown below.
She notes how long the carrot slices on each plate take to change colour.
| Under the sun | In a moist room at $25^\circ C$ | In the refrigerator | |
| Time carrot slices take to change colour | $2$ days | $5$ days | $8$ days |
$A.$ Carrots when kept under the sun do not rot easily.
$B.$ Carrots at room temperature lose colour more quickly.
$C.$ Carrots can be best preserved in hot and moist conditions.
$D.$ Carrots take more time to lose colour under cold conditions.
$4.$ Use the results of the activity to inish the graph below. The irst bar is drawn for you.
Put a label in the space provided for the axis on the left.
A trash can contains the following materials.
• Plastic straw
• Aluminium foil
• Tissue paper
• Glass bottles
• Chicken bones
$1.$ Select the materials from the list that can be decomposed by microbes?
$2.$ Rohit is suffering from stomach ache and is passing watery stool. What should Rohit do to prevent the spread of infection to other family members?
$A.$ He should eat properly cooked food.
$B.$ He should wear a mask all the time.
$C.$ He should maintain distance from other family members.
$D.$ He should wash his hands with soap after using the bathroom.
View full solution →• Plastic straw
• Aluminium foil
• Tissue paper
• Glass bottles
• Chicken bones
$1.$ Select the materials from the list that can be decomposed by microbes?
$2.$ Rohit is suffering from stomach ache and is passing watery stool. What should Rohit do to prevent the spread of infection to other family members?
$A.$ He should eat properly cooked food.
$B.$ He should wear a mask all the time.
$C.$ He should maintain distance from other family members.
$D.$ He should wash his hands with soap after using the bathroom.
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