NCERT Class 8 Science Chapter 2 - Microorganisms: Friend and Foe Extra Questions

Chapter 2 - Microorganisms: Friend and Foe Extra Questions

One Word Answer Questions
1. Unscramble the jumbled words underlined in the following statements
a) Curbossulite is an air-borne disease caused by a bacterium.
b) Xanrhat is a dangerous bacterial disease.
c) Yeasts are used in the wine industry because of their property of meronettinaf.
d) Cells of our body produce santiidobe to fight pathogens.
e) Aeeessrrwtip are added to food to prevent growth of microorganisms.
Answer:

a) Tuberculosis
b) Anthrax
c) Fermentation
d) Antibodies
e) Preservatives

2. Name the groups in which microorganisms are broadly classified.
Answer:
The groups in which microorganisms are broadly classified are
• Bacteria
• Fungi
• Protozoa
• Algae
• Virus

3. Write the name of a bacterium that helps in the formation of curd.
Answer:
Lactobacillus is the bacterium that helps in the formation of curd.

4. Write a use of yeast.
Answer:
The yeast is used to make alcohol, bread etc.

5. What are pathogens? Write another name of pathogens.
Answer:
The organisms which cause diseases in plants, animals, human beings are called pathogens. The another name for pathogens is germs or harmful microbes.

6. What does yeast produce during respiration?
Answer:
Carbon dioxide is the gas that the yeast produces during respiration.

7. Write the names of any two antibiotics.
Answer:
Streptomycin, Tetracycline

8. Name any two human diseases caused by viruses.
Answer:
The 2 human diseases caused by viruses are Measles, Chicken pox.

9. Name the first antibiotic discovered.
Answer:
Penicillin is the first antibiotic discovered.

10. Why is it difficult to prepare vaccine for diseases caused by viruses?
Answer:
One reason why making anti-viral medicines is harder than making antibacterial medicines is that viruses have few biochemical mechanisms of their own. They enter our cells and use our machinery for their life processes. This means that there are relatively few virus-specific targets to aim at. Hence it is difficult to make an antiviral medicines than anti-bacterial medicines.

11. Discuss in detail as to how micro-organisms help in:
a) making curd and cheese
b) making bread
c) making idli, dosa and dhokla
d) the manufacture of alcohol and beverages
Answer:

a) A bacteria called Lactobacillus is used in making curd which provides suitable acidic environment to form curd.

b) The fungus called yeast reproduces in flour dough and produces carbon dioxide during respiration which makes the dough soft and helps in making bread.

c) The fungus called yeast is added to the batter of idli or dosa. The yeast performs anaerobic fermentation. The fungus utilizes sugar and converts them ethanol and carbon dioxide. The gas (carbon dioxide) makes the dough soft & fluffy and causes the dough to rise.

d) The fungus (yeast) reproduces in sugar solution and converts it into alcohol. This process is called fermentation.

12. Why are some bacteria and fungi considered as natural purifiers?
Answer:
Some bacteria and fungi are considered as natural purifiers because they convert the plant wastes into manure by the action of microbes. These nutrients released in the process can be used by the plants again.

Very Short Answer Questions
13. What are microorganisms? Give four examples.
Answer:
Microorganisms are very small microorganisms that cannot be seen with naked or unaided eye. Example: Chlamydomonas, Spirogyra, Amoeba, Paramecium.

14. Define communicable diseases. Give some examples.
Answer:
Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases. Example: cholera, common cold, chicken pox and tuberculosis.

15. What do you mean by food spoilage?
Answer:
The process in which the food gets spoiled that is it not fit for human consumption is called food spoilage.

16. How are carriers harmful to us?
Answer:
Carriers carry many harmful pathogens. They transfer these pathogens to healthy flies as the flies sit on the garbage and animal excreta, which contains pathogens. When these flies sit on the food, the pathogens get stick to the food items. Whoever eats that contain contaminated food is likely to get ill. Hence, they’re harmful to us.

17. What do you mean by immunity?
Answer:
Immunity means the ability of a body to develop resistance against disease.

18. Give two examples of each of the following types of microorganisms:
a) Algae
b) Fungi
c) Protozoa
Answer:

a) Algae - Chlamydomonas, Spirogyra
b) Fungi - Bread mould, Penicillium
c) Protozoa - Amoeba, Paramecium

Short Answer Questions
19. Mention any three ways through which pathogens are transmitted.
Answer:
The three ways through which pathogens are transmitted are food, water, air, and physical contact.

20. It is always suggested that not to eat anything from street hawkers. Why?
Answer:
It is always suggested that not to eat anything from street hawkers. Most of the street hawkers sell food items in an open area which gets dirty and unhygienic due to flies and germs.

21. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer:
The medicines which kill or stop the growth of the disease causing microbes are called antibiotics.
Precautions taken while taking antibiotics are:
• We must take antibiotics only on the advice of a qualified doctor.
• We must complete the course prescribed by the doctor.
• If we take antibiotics when not needed or in wrong doses, it may make the drug less effective when we might need it in future.
• If we take antibiotics unnecessarily, it may kill the beneficial bacteria in the body.

22. How can we prevent the following disease?
a) cholera
b) typhoid
c) tuberculosis
Answer:

a) Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination.

b) Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination.

c) Keep the patient in complete isolation. Keep the personal belongings of the patient away from those of the others. Vaccination to be given at suitable age.

23. Mention any three preventive measures taken by you against the Covid-19 Virus.
Answer:
The three preventive measures should be taken by us against Covid-19 Virus are
• We must maintain social distancing.
• We must cover our mouth and nose with mask to prevent pathogens entering our mouth.
• We must wash our hands frequently.

Long Answer Questions
24. Seema got cough and cold badly. Her teacher asked her to take rest at home and use handkerchief while sneezing and coughing. She obeyed her teacher.
a) Why should we keep a handkerchief on nose and mouth while sneezing or coughing?
b) What are the modes of transfer of diseases from infected to healthy person?
c) Do you think Seema’s teacher decision was right? Why?
d) What value of Seema is shown here?
Answer:

a) We should keep our handkerchief on nose and mouth while sneezing and coughing because when we sneeze, we exhale some virus. These virus may transfer to the healthy person while breathing.

b) The modes of transfer of diseases from infected to healthy person are air, water, food and physical contact.

c) Yes, Seema’s teacher decision was right because cold and cough is a communicable disease and it spreads through air and there is a possibility of spreading to others.

d) Seema is an obedient girl. She follows her teacher’s guidance. She cares about others so she isolated and used handkerchief while sneezing and coughing.

25. On Rahul’s birthday, his mother prepared many dishes for him. After having their meal, they found that many food items were left over. Rahul’s mother kept these leftovers in a air-tight container and refrigerate them.
a) What is food preservation?
b) What will happen to the food if it is not refrigerated?
c) What is the role of refrigeration in food preservation method?
d) What value of Rahul’s mother is shown here?
Answer:

a) Food preservation is a process of preventing microbes from spoiling the food items.

b) The food will get spoiled as bacteria release some acids which makes the food poisonous to eat.

c) The process of refrigeration will slow down the growth of microbes which prevents spoilage of food items.

d) Rahul’s mother is intelligent, economical and has scientific aptitude to save food from spoilage.

26. Observe the figure, and answer the following questions.

a) Name the microorganism and the group to which it belongs.
b) Name the food item on which the organisms grows.
c) Does it grow well in dry or in moist conditions?
d) Is it safe to eat infected bread?
Answer:

a) The microorganism is bread mould. It belongs to fungus category.

b) It mainly grows on bread.

c) It grows well in moist conditions.

d) No, it is not safe to eat the infected bread because the fungus spoils the bread by releasing poisonous acids which makes the food harmful.

27. Observe the figure, and answer the questions that follow.
a) Write the name of the disease.
b) Name the causative agent of this disease.
c) How do the diseases spread from one plant to another?
d) Name any two plant diseases and the microbes that cause them.
Answer:

a) The name of the disease is Yellow vein mosaic of Bhindi (Okra).

b) The causative agent of this disease is Virus.

c) The diseases spread from one plant to other plants through insects.

d) The two plant diseases caused by microbes are
• Citrus Canker = Bacteria
• Rust of wheat = Fungi

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