KSEEB Solutions For Class 8 Science Chapter 2 Micro organisms Friend And Foe

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KSEEB Solutions for Class 8 Science Chapter 2 Microorganisms Friend And Foe Points To Remember

Microorganisms: Living organisms that cannot be seen with the naked eye.
Types: Bacteria, Fungi, Protozoa, Algae, viruses.

Friendly microorganisms:
1. Making curd and bread
2. production of alcohol and wine
3. production of vaccines and antibiotics
4. increases soil fertility
5. cleaning of the environment.

Harmful microorganisms:
1. Diseases like cholera, TB, Typhoid, Measles, and Malaria are caused by micro-organisms in Humans.
2. Diseases like anthrax and foot and mouth disease are caused by bacteria and viruses in cattle.
3. Diseases like citrus canker, rust of wheat, and yellow vein mosaic of okra in plants.
3. Foods are spoilt by microorganisms.

Food preservation:
1. Chemical method
2. By sugar
3. Heat and cold treatments
4. By common salt
5. By oil and vinegar
6. Storage and packing

KSEEB Solutions For Class 8 Science Chapter 2 Micro Organisms Friend And Foe

Kseeb Solutions For Class 8 Science Chapter 2 Microorganisms Friend And Foe Pdf

Microorganisms Friend And Foe Ncert Textbook Exercises

Question 1. Fill in the blanks.
(1)Microorganisms can be seen with the help of a
(2) Blue-green algae fix directly from the air to enhance the fertility of the soil.
(3)Alcohol is produced with the help of
(4)Cholera is caused by
Answer:
(1) microscope
(2) nitrogen
(3) yeast
(4) bacteria

Question 2.Tick the correct answer:
1)Yeast is used in the production of
(1)sugar
(2) Alcohol
(3)hydrochloric acid
(4) oxygen

2)Which of the following is an antibiotic?
(1)Sodium bicarbonate
(2) Streptomycin
(3) Alcohol
(4) yeast

3)Carrier of malaria-causing protozoa is
(1)female Anopheles mosquito
(2)cockroach
(3)housefly
(4)butterfly

4)The most common carrier of communicable diseases is
(1)ant
(2) housefly
(3) dragonfly
(4) spider

5)The bread or idli dough rises because of
(1) heat
(2) housefly
(3) growth of yeast cells
(4) kneading

(6)The process of conversion of sugar into alcohol is called
(1) nitrogen fixation
(2) molding
(3) fermentation
(4) infection
Answer: 1) – (2); 2) – (2); 3) – (1); 4) – (2), (5) – (3); 6) – (3)

Karnataka Board Class 8 Science Chapter 2 Solutions

Question 3. Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer: Microorganisms cannot be seen by the naked eye because they are very small. They can be seen by using a microscope.

Question 4. What are the major groups of microorganisms?
Answer: Major groups of microorganisms is as follows:
1. Bacteria
2. Fungi
3. Protozoans
4. Algae
5. Viruses.

Question 5. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer: Rhizobium.

Question 6. Write 10 lines on the usefulness of microorganisms in our lives.
Answer: Uses of microorganisms are as follows :

  1. They are helpful in cleaning up the environment.
  2. Lactobacillus promotes the formation of curd.
  3. Bacteria are involved in the making of cheese
  4. Bacteria and yeast are helpful for the fermentation of rice idlis and dosa batter.
  5. Use of yeast in the baking industry for making bread, pastries, and cakes.
  6. Large-scale production of alcohol, wine, and vinegar.
  7. Microorganisms are helpful in producing vaccines against the disease.
  8. Antibiotics are produced from bacteria and fungi
  9. Some bacteria are able to fix nitrogen and increase soil fertility.
  10. Microorganisms decompose dead and decaying organic matter of plants and animals.

Question 7. Write a short paragraph on the harmful effects of microorganisms.
Answer: Microorganisms cause diseases in plants and animals,
Example: Cholera in humans is caused by bacteria called Vibrio cholera. In animals, the virus causes foot and mouth diseases. Microorganisms spoil the food by decomposing the food material. Some microorganisms spoil leather and clothes. Microorganisms are responsible for food poisoning.

KSEEB Class 8 Science Solutions For Microorganisms Friend And Foe 

Question 8. What are antibiotics? What precautions must be taken while taking antibiotics?
Answer:

Chemical agents that kill or stop the growth of disease-causing microorganisms are called antibiotic

Antibiotics should be taken only on the advice of a qualified doctor. Also, one must complete the course prescribed by the doctor.

Microorganisms Friend And Foe Activities

Question 1. Collect some moist soil from the field in a beaker and add water to it. After the soil particles have settled down, observe a drop of water from the beaker under a microscope. What do you see?
Answer: It is observed that some tiny organisms are moving around.

Question 2. Take a few drops of water from a pond. Spread on a glass slide and observe through a microscope.
Answer: It is observed that some tiny organisms are moving around.
8th class science ch 2

Microorganisms Friend And Foe Class 8 Kseeb Solutions With Answers

Question 3. Take 1/2 kg flour (atta or maida), add some sugar, and mix with warm water. Add a small amount of yeast powder and knead to make a soft dough. What do you observe after two hours? Did you find the dough rising?
Answer: It is observed that the dough begins to rise up in volume. Yeast reproduces rapidly and releases Co2 during respiration. The stubble of this gas fills the dough and increases its volume.

Question 4. Take 500 ml. beaker filled up to 3/4 with water. Dissolve 2-3 teaspoons of sugar in it. Add half a spoon of yeast powder to the sugar solution. Keep it covered in a warm place for 4-5 hours. Now smell the solution. Can you get a smell?

Answer: It is observed that the solution smell like alcohol. This process of conversion of sugar into alcohol is known as fermentation.

Question 5. Take two pots and fill each pot half with soil. Mark them A and B. Put plant waste in pot A and things like polythene bags, empty glass bottles, and broken plastic toys in pot B. Put the pots aside. Observe them after 3-4 weeks.
Answer: It is observed that plant waste in pot A has been decomposed, whereas the polythene bags, empty glass bottles, and broken plastic toys in pot B did not undergo such changes.

Microorganisms Friend And Foe Additional Questions

Question 1. Riya’s grandmother always dries vegetables in the sun before pickling them. How does drying help vegetables?
Answer: Drying vegetables help to remove water, which is necessary for microbial growth. So drying helps in preserving them.

Question 2. On a pack of fruit juice, it is printed “IF THE PACKET IS PUFFED DO NOT BUY”. Give reasons.
Answer: Because packed juices may be contaminated by yeast which causes fermentation and makes them unfit for consumption.

Question 3. Name any two antibiotics.
Answer: Streptomycin and tetracycline.

Question 4. Name the scientist who discovered the vaccine for smallpox in 1798.
Answer: Edward Jenner

Question 5. What do you mean by communicable diseases?
Answer: The microbial diseases that can spread from an infected person to a healthy person by some agents like air, water, food, or physical contact are called communicable diseases.

Question 6. Write the name of a bacterium that helps in the formation of curd.
Answer: Lactobacillus

Question 7. Write the use of yeast.
Answer: Yeast is used in the production of alcohol, wine, beer, and other beverages.

Question 8. What are pathogens? Write another name for pathogens.
Answer: Disease-causing microorganisms are known as pathogens. They are also called germs.

Question 9. Define food preservation.
Answer: Food preservation is the method of preserving food from being spoiled by microbes.

Question 10. What is fermentation?
Answer: Fermentation is the process of conversion of food into alcohol.

Kseeb Class 8 Science Microorganisms Friend And Foe Exercise Solutions

Question 11. Define communicable diseases. Give some examples.
Answer: Communicable diseases are microbial diseases that can spread from an infected person to a healthy person through the air, water, or another physical contact; e.g., cholera, chicken pox, tuberculosis, common cold, etc.

Question 12. Give two examples of each of the following types of microorganisms:
(1)Algae
(2) Fungi
(3) Protozoa
Answer:
(1) Algae – Spirogyra, Chlamydomonas
(2)Fungi-Aspergillus, yeast
(3)Protozoa – Paramecium, Amoeba

Question 13.Unscramble the jumbled words underlined in the following statements
(1)Curbossulite is an air-borne disease caused by a bacterium.
(2)Xanrhat is a dangerous bacterial disease.
(3)Yeasts are used in the wine industry because of their property of meronettinaf.
(4)Cells of our body produce antidotes to fight pathogens.
(5)Aeeessrrwtip are added to food to prevent the growth of microorganisms.
Answer:
(1) Tuberculosis
(2)Anthrax
(3)Fermentation
(4)antibodies
(5)Preservatives

Multiple Choice Questions

Question 14. Which of the following reproduces only inside a host cell?
(1)Bacteria
(2) Virus
(3) Amoeba
(4) Fungus.
Answer:(2) Virus
Explanation: The virus is considered an intermediate between living and non-living. Outside a host-virus remains inactive. It can perform its life processes and reproduction only when it is inside a host cell.

Karnataka Board 8th Science Chapter 2 Important Questions And Answers

Question 15. A disease in human beings caused by a virus is
(1)Typhoid
(2) Influenza
(3) Dysentery
(4) Cholera
Answer: (2) Influenza
Explanation:

Typhoid is caused by the bacteria Salmonella typhoid.

Dysentry is caused by an amoeba which is a protozoan.

Cholera is caused by Vibrio cholera bacteria.

Question 16. Pathogenic micro-organisms present in host cells are killed by medicines called
(1) Painkiller
(2) Antibodies
(3) Antibiotics
(4) Vaccines
Answer: (2) Antibiotics
Explanation:

Pain Killers give relief from pain.

Antibodies are produced by our immune system which acts and elicits a specific immune reaction.

Antibiotics that inhibit or kill certain bacteria.

Vaccines provide acquired immunity against a particular disease.

Question 17. The two micro-organisms which live in symbiotic association in lichens are
(1)Fungus and Protozoa
(2)Alga and Bacteria
(3)Bacteria and Protozoa
(4)Alga and Fungus
Answer: (4) Alga and Fungus

Question 18. The gas released during the preparation of bread is
(1)Oxygen
(2) Carbon dioxide
(3) Nitrogen
(4) Sulphur dioxide
Answer: (2) Carbon dioxide
Explanation: Carbon-di-oxide is released due to the fermentation process conducted by yeast. C02 causes the rising of the dough and makes the bread fluffy.

Kseeb 8th Standard Science Chapter 2 Notes And Solutions

Question 19. The disease caused by a protozoan and spread by an insect is.
(1) Dengue
(2) Malaria
(3)Polio
(4) Measles
Answer: (2) Malaria
Explanation: Malaria is caused by a protozoan named Plasmodium vivax which is transmitted by mosquitos. Other options are viral diseases hence they are wrong answers.

Question 20. Paheli dug two pits, A and B, in her garden. In pit A, she put a polythene bag packed with some agricultural waste. In pit B, she dumped the same kind of a waste but without packing it in a polythene bag. She then covered both pits with soil. What did she observe after a month?
(1)Waste in pit A degraded faster than that in pit B.
(2)Waste in pit B degraded faster than that in pit A.
(3) Waste in both pits degraded almost equally.
(4)Waste in both pits did not degrade at all.
Answer: (2) Waste in pit B degraded faster than that in pit A.
Explanation: Waste in pit B degrades faster than waste in pit A because Polythene in pit B is open and receives oxygen for composting whereas polythene in closed in pit A and organisms don’t receive oxygen to compost the waste material in the polythene bag.

Question 21. Suggest a suitable word for each of the following statements.
(1)Chemicals added to food to prevent the growth of microorganisms.
(2)Nitrogen-fixing microorganisms present in the root nodules of legumes.
(3)The agent spreads pathogens from one place to another.
(4)Chemicals that kill or stop the growth of pathogens.
Answer: 1. Preservatives
2. Rhizobium
3. Carrier/ vector
4. Antibiotics

Question 22. Name the process in yeast that converts sugars into alcohol.
Answer: Fermentation is the process in yeast that converts sugars into alcohol.

Question 23.In the soil, which nutrient is enriched by blue-green algae (cyanobacteria)?
Answer: Blue-green-algae enriches Nitrogen in the soil.

Question 24. Why should we avoid standing close to a tuberculosis patient while he/she is coughing?
Answer: Tuberculosis can spread through the air when the infected person coughs. Hence we avoid standing close to a tuberculosis patient while he/she is coughing.

Step-By-Step Solutions For Microorganisms Friend And Foe Class 8 Karnataka Board

Question 25. Polio drops are not given to children suffering from diarrhea. Why?
Answer: If the children are suffering from diarrhea oral polio drops will get excreted due to frequent motions. Hence children with diarrhea are not given polio drops.

Question 26. Paheli watched her grandmother making mango pickles. After she bottled the pickle, her grandmother 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?
Answer: Oils prevent the attack of bacteria which will help preserve the pickle for a long period of time.

Explanation Of Microorganisms Friend And Foe In KSEEB Science 

Question 27. Classify the following into friendly and harmful microorganisms.
Answer:
Friendly

Yeast

Lactobacillus

Rhizobium

Harmful Microorganisms

Malarial parasite

Bread mold

Bacillus anthracis

Question 28. While returning from 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?
Answer: 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 been contaminated.
The reason may be the contamination of food by pathogenic microbes. Contamination may be due to the unhygienic conditions near the shop or the utensil used to serve the chaat.

Kseeb Class 8 Science Chapter 2 Textbook Solutions

Question 29. What will happen to ‘pooris’ and ‘unused kneaded flour’ if they are left in the open for a day or two?
Answer: Pooris and unused kneaded flour get spoiled due to microbial activity. Food gets fermented when kept open and it will be spoiled.

Question 30. (1) Name two diseases that are caused by the virus.
(2)Write one important characteristic of the virus.
Answer:
1. Polio, HIV
2. A virus can reproduce only when it is inside the host cell.

Karnataka State Board Syllabus for Class 8 Textbooks Solutions

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