Microorganisms: Friend and Foe Class 8 Extra Questions and Answers

These AP 8th Class Biology Important Questions and 2nd Lesson Microorganisms: Friend and Foe Class 8 Extra Questions will help students prepare well for the exams.

Class 8 Science Microorganisms: Friend and Foe Extra Questions

Microorganisms: Friend and Foe Class 8 Important Questions

Question 1.
What are microorganisms ?
Answer:
Some organisms can be seen only with the help of a microscope. Such organisms are called ‘microorganisims’.

Question 2.
Where can we find microorganisms ?
Answer:
Microorganisms can found in air, water, soil and all living organisms.

Question 3.
Write the names of some groups of microorganisms.
Answer:
Bacteria, fungi, protozoa, algae are some of the groups of microorganisms.

Question 4.
Write the names of diseases which are caused by bacteria.
Answer:
Diseases like typhoid, tuberculosis (T.B.) and septicemia (blood poisoning) are caused by bacteria.

Question 5.
Mention the diseases caused by protozoans.
Answer:
Malaria, Amoebiasis, Kala Azar, Sleeping sickness are some of the diseases caused by protozoans.

Question 6.
What are the uses of yeast ?
Answer:

1. Yeast cells are frequently used in the fermentation process of sugars.
2. Yeast is used in the preparation of cakes and buns in bakeries.

Question 7.
Which one is better to take antibiotics or vaccines ?
Answer:
Vaccines are better than antibiotics when the disease is prevented by vaccine.
Ex : Tuberculosis, Tetanus, etc.

Question 8.
What questions do you ask on role of mosquitoes and houseflies in spreading the diseases like Malaria and Swine flu ?
Answer:

1. How can we be safe, without affected by malaria and typhoid ?
2. Which organisms spread diseases like malaria and typhoid ?

Question 9.
Name the vaccine that prevents T.B.
Answer:
B.C.G (Bacillus Calmette – Guerin)

Question 10.
What is the mode of transmission of Dengue disease ?
Answer:
Aedes Mosquitoes spread Dengue disease.

Question 11.
Why is the idly or dosa batter prepared one day before ?
Answer:
We should prepare idly or dosa batter one day before to occur fermentation in it. Carbondioxide gas fill the batter increasing its volume and makes it spongy.

Question 12.
What is the name of the nitrogen fixing bacteria present in root nodules of legume plants ?
Answer:
Rhizobium.

Question 13.
What are communicable diseases ? Give examples.
Answer:
The diseases which spread from infected people to healthy ones through water, food and physical contact are called communicable diseases . Ex: Cholera, Typhoid, Chicken pox.

Question 14.
Name the viral diseases that can be prevented by controlling mosquito population.
Answer:
Chikun gunya, Dengue, Japanese encephalitis.

Question 15.
What should you do to control mosquito population ?
Answer:
Stagnant waters are the breeding grounds for mosquitoes. So, we should not allow water to stagnate in our surroundings.

Question 16.
What are preservatives ?
Answer:
The chemicals that are used to check the growth of microorganisms are called preservatives.
Ex : salt, sugar, vinegar and edible oils.

Question 17.
What are pathogens ?
Answer:
Disease causing micro organisms are called pathogens.

Question 18.
What is Pasteurisation ?
Answer:
The process in which milk is heated to about 70°C for 15 to 30 seconds and then suddenly cooled is called pasteurisation.

Question 19.
Which microbe is responsible for curding of milk ?
Answer:
Lactobacillus

Question 20.
What is fermentation ?
Answer:
The process of conversion of sugars into alcohol by yeast is called fermentation.

Question 21.
Give examples for antibiotics.
Answer:
Tetracycline, Streptomycin, Erythromycin etc.

Question 22.
Who discovered fermentation ?
Answer:
Louis Pasteur discovered fermentation in 1857.

Question 23.
Who discovered the first antibiotic ? What was it ?
Answer:
The first antibiotic was discovered by Dr. Alexander Flemming in the year 1929. The first antibiotic was Pencillin.

Question 24.
Give two examples for plant diseases caused by microbes.
Answer:
Citrus canker, Rust of Wheat.

Question 25.
Who discovered anthrax causing bacteria ?
Answer:
Robert Koch (1876) discovered the bacterium, Bacillus anthracis which causes anthrax disease.

Question 26.
Name the foods that are preserved with the help of sugar.
Answer:
Jams, Jellies and squashes are preserved by sugar.

Question 27.
How does sugar prevents the bacterial growth ?
Answer:
Sugar reduces the moisture content which inhibits the growth of bacteria which spoil food.

Question 28.
Name the foods that are preserved by using common salt.
Answer:

1. Fish and meat are covered with dry salt to check the growth of bacteria.
2. We can also preserve amla, raw mangoes, tamarind etc. by using common salt.

Question 29.
Name the foods that can be preserved by using oil and vinegar.
Answer:
Pickles, vegetables, fruits, fish and meat are preserved by using oil and vinegar.

Microorganisms: Friend and Foe Extra Questions

Question 1.
Why the cooked food spoil soon but not uncooked food ? Give your reasons.
Answer:

1. Cooking of food items makes the proteins in the food materials coagulate.
2. It also degrades the protective surface of the food.
3. Thus the cooked foods can be easily inhabited by microoganisms.
4. So they can be spoiled in less time than the uncooked food.

Question 2.
What will happen if you add buttermilk to chilled milk ?
Answer:

1. Lacto bacillus bacteria is responsible for the formation of curd.
2. When we add buttermilk to luke warm milk it takes 2 or 3 hours time to form curd.
3. But if we add buttermilk to chilled milk it takes more time or curd would not form.
4. Curdling indicates that the increase in number of bacteria in milk.
5. In chilled condition the number of bacteria do not increase in number there by curd would not be formed.

Question 3.
How Microbiology helps in identifying diseases and their prevention ?
Answer:

1. Microbiology plays a very vital important role in identifying the cause of diseases by the discovery of several microorganisms.
2. Microbiology helps in the preparation of diseases caused by microorganisms by the discovery of their transmission methods.

Question 4.
How do you appreciate the role of decomposers in the earth ?
Answer:

1. Microorganisms are the decomposers of the earth.
2. They decompose the organic matter from plant parts and dead animals. They enrich the soil with organic matter again.
3. Thus, they maintain the soil fertility and eliminate the wastes from the earth.
4. I appreciate the role played by decomposers in scavenging the earth by decomposing the organic matter of dead bodies.

Question 5.
What is pasteurisation ? How is it useful ?
(OR)
What is Pasteurisation ? What is the use of it ?
Answer:

1. Pasteurization : The milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled. This process was discovered by Louis Pasteur and is called Pasteurisation.
2. Use : By doing so it prevents the growth of microbes.

Question 6.
What are ‘bio – fertilizers’ ? How are they useful ?
Answer:

1. Microorganisms like Bacteria, Fungi which decompose the fallen plant parts, dung and vegetable peelings into simple chemical compounds.
2. They form ‘useful manure’ to the plants since this manure is formed naturally from biological activity of microorganisms, they are called ‘bio – fertilizers’.
3. Farmers are benefited economically. They don’t need chemical fertilizers to increase the soil fertility. Hence, Bio – fertilizers are considered as “friends of farmers”.

Question 7.
How do vaccines works in our body ?
Answer:
When a vaccine is given which contains weak microorganisms our body learn to fight them by producing antibodies whenever danger comes. When the disease causing microorganisms enter in our body, the already present antibodies fight and eliminate them. And the disease is controlled. The weakened disease causing microorganisms which are injected into our bodies are called as vaccine.

Question 8.
Jeevan said that “If there are no microorganisms earth will remain with Wastes.” Will you agree this statement ? Why ?
Answer:
Yes, I will agree this statement. Because of :

1. Microorganisms present in the soil, air and water act upon wastes around us.
2. They decomposes them.
3. They are converted into simple substances.
4. Thus microorganisms help us in cleaning the environment.
5. So if there are no microorganisms earth will remain with wastes.

Question 9.
Pranavi is suffering from serious illness. Doctor prescribed antibiotics for five days. After three days of usage she stopped taking antibiotics. Is it right or not, discuss.
Answer:
No, it is not right. Doctor prescribed anitbiotics for five days. Because the doctor knows that the correct days of the recovering of her illness. After three days of usage she stopped taking antibiotics. But her illness is not completely recovered. It is breaking out after some time. So it is not right.

Question 10.
What are the precautions taken to eradicate malaria ?
Answer:

1. Malaria is caused by the pathogen plasmodium, is transmitted by female anopheles mosquito.
2. Methods used to prevent malaria include medications, mosquito elimination and the prevention of bites.
3. Using of indoor mosquito repellents, residual sprays, medicated mosquito nets and taking care not to store water.
4. Providing awareness how to control mosquito population.

Question 11.
One medical store owner is giving antibiotics to his customer who is suffering from ‘ fever without doctor’s prescription ? But the customer’s daughter Malathi is telling her father not to take antibiotics without doctor’s prescription. Whom do you support and why?
Answer:
We must use antibiotics prescribed by qualified doctor only. If you use antibiotics without consulting a qualified doctor it may harm us. Unnecessary use of antibiotics , affects blood cells which fight infections. Sometimes they may kill useful bacteria too in our intestine and this increases the resistance towards antibiotics.

Question 12.
Mention different questions to know about antibiotics.
Answer:

1. What are antibiotics?
2. In which year penicillin was announced as antibiotic?
3. Can antibiotics destroy the viruses?
4. Write different types of antibiotics.

Question 13.
Ask different questions about the significance of microbes.
Answer:

1. Name different nitrogen fixing microbes.
2. Can all microbes useful to mankind ?
3. What will hdppen if vaccines are not invented ?
4. Write about significance of microbes.

Question 14.
If we keep the dosa dough in Bacillus free chamber, what changes can you observe in the dosa dough after one day ?
Answer:

1. Fermentation of dosa dough will not take place.
2. The volume of the dosa dough will not increase and it will not turn into spongy texture.

Question 15.
Give examples for useful micro organisms.
Answer:

1. Lacto bacillus
2. Rhizobium
3. Pencillium
4. Yeast

Question 16.
Give examples for harmful micro organisms ?
Answer:

1. Plasmodium (Malaria)
2. HIV (AIDS)
3. Bacillus anthracis (Anthrax)
4. Dysentery (Entamoeba)

Question 17.
Write some slogans to create awareness among the public to protect from micro organisms.
Answer:

1. Use a toilet to achieve Swach Bharat.
2. Use mosquito nets – Prevent mosquito bites.
3. Keep your country clean by keeping your area clean.
4. Boil the drinking water before consumption.

Question 18.
What precautions do you suggest to avoid diseases ?
Answer:

1. We should consume boiled and purified water and healthy food daily.
2. Keep our surrounding neat and clean.
3. We should take vaccines to prevent different diseases.
4. We should practice personal hygiene and good sanitary habits.

Question 19.
List some common plant diseases caused by micro organisms.
Answer:

Plant disease	Micro organism	Mode of Transmission
1) Citrus Canker	Bacteria	Air
2) Rust of wheat	Fungus	Insects and seeds
3) Yellow vein mosaic of bhindi (okra)	Virus	Insect

Question 20.
Draw the diagram showing nitrogen fixing cyanobacteria.
Answer:

Question 21.
Draw a flow chart showing different stages in nitrogen cycle.
Answer:

Question 22.
Draw the diagram showing viruses.
Answer:

Question 23.
Draw a neat lahelled diagram of Amoeba.
Answer:

Question 24.
Draw a neat diagram of chlamydomonas and label the parts.
Answer:

Question 25.
Draw a neat diagram showing algae. A.
Answer:

Question 26.
Draw a neat diagram showing protozoans.
Answer:

Question 27.
Draw a neat diagram that shows different types of Fungi.
Answer:

Question 28.
Draw a neat diagram that shows different kink of bacteria.
Answer:

Question 29.
What is the speciality of viruses in the world of micro organisms ?
Answer:

1. Viruses reproduce only inside the cells of the host organism which may be a bacterium, plant or animal.
2. So, they are considered as “the connecting links between living and non-living”.

Question 30.
Name the diseases caused by mosquitoes.
Answer:

1. Female Anopheles mosquito causes Malaria.
2. Female Aedes mosquito causes Dengue.
3. Culex mosquito causes Japanese Encephalitis (Brain fever).
4. Culex mosquito causes filaria.
5. Female Aedes mosquito causes chikungunya.
   The above diseases are caused by mosquitoes.

Question 31.
What is symbiosis ? Give one example.
Answer:
Mutually beneficial relationship between two organisms living together for food and shelter is called symbiosis.

Ex : Rhizobium bacteria lives in the root nodules of many leguminous plants such as beans and peas. The Rhizobium bacteria takes nitrogen from the atmosphere and fixes on the roots of plants. Plants give shelter to the bacteria. Thus both help each other.

Question 32.
Why is it advisable to always keep food covered ?
Answer:

1. It is advisable to keep food covered because the houseflies sit on the garbage and animal excreta.
2. The disease causing organisms (pathogens) stick to their bodies. When these flies sit on uncovered food they may transfer the pathogens.
3. Who soever eats the contaminated food likely to get sick. So it is advisable to avoid consuming uncovered items of food.

Question 33.
How did Alexander Flemming discovered penicillin ?
(OR)
Write the discovery of penicillin.
Answer:
In 1929 Alexander Flemming was working on a culture of disease causing bacteria. He found the spores of mould prevented the growth of bacteria and also killed many of these bacteria.

He identified the mould as penicillium notatum and the substance produced by this mould is Penicillium. It is named as Penicillin, which killed bacteria named as an Antibiotic by Flemming.

Question 34.
What are antibodies ? How are they useful ?
Answer:

1. When a disease carrying microbes enters our body, the body produces Antibodies to fight the invader.
2. The body also remembers how to fight the microbe if it enters again.
3. If dead or weakened microbes are introduced into the healthy body, it fights and kills the bacteria by producing suitable antibodies.

Question 35.
What is food poisoning ? Write some methods of food preservation.
Answer:
Food poisoning : It could be due to the consumption of food spoilt by some microorganisms causing vomitings, diarrhoea, etc.

Methods of food preservation :

1. Chemical methods.
2. Preservation by common salt.
3. Preservation by sugar.
4. Preservation by oil and vinegar.
5. Heat and cold treatment (Pasteurisation).
6. Storage and packing.

Question 36.
Rhizobium lives in the root nodules of leguminous plants such as beans and peas, with which it has a symbiotic relationship.
a) Which part of the leguminous plant Rhizobium lives ?
b) What is symbiosis ?
Answer:
a) Rhizobium bacteria lives in the root nodules of leguminous plants.

b) The mode of living of two organisms living together for food and shelter. Both organisms will be beneficial.
Such type of living of organisms is called Symbiosis.

Ex : Rhizobium bacteria lives in the root nodules of leguminous plants.
Rhizobium fix nitrogen in the soil from atmosphere, plants grow well supply food and shelter to the bacteria. Both organisms are beneficial.

Question 37.
What precautions must be taken while taking antibiotics?
Answer:

1. It is important to remember that antibiotics should be taken only on the advice of a qualified doctor and also must complete the course prescribed by the doctor.
2. If antibiotics are taken when not needed or in strong doses, it may make the drug less effective when we might need in future.
3. Also antibiotics take unncessarly may kill the beneficial bacteria in the body.

Question 38.
Explain how microorganisms are friendly to us.
Answer:
Microorganisms are friendly in our daily life :

1. Lactobacillus convert milk into curd.
2. Yeast is used in the preparation of bread, cakes and pastries.
3. Yeast is also used in the large scale production of alcohol and wine through fermentation.
4. Decomposing bacteria are useful in cleaning up the environment.
5. Some bacteria are used in the preparation of medicines.
6. In agriculture some bacteria are useful to increase the soil fertility.
7. Bacteria are used in making of cheese, pickles and many other food items.

Extra Questions of Microorganisms: Friend and Foe Class 8

Question 1.
How do microorganisms increase the soil fertility ?
Answer:

1. Some bacteria and blue-green algae are able to fix nitrogen from the atmosphere to enrich the soil with nitrogen and increase soil fertility.
2. A bacterium called Rhizobium lives in the root nodules of leguminous plants and fixes nitrogen symbiotically.
3. Some decomposing bacteria decompose the organic matter in soil and increase soil fertility.
4. Bacteria like Clostridium and Azatobactor fix, the atmospheric nitrogen and improve soil fertility.

Question 2.
Write a detailed note on food preservation.
Answer:
Food can be preserved safely by using different methods. They are :
1) Chemical method

• Salt and edible oils are used as chemicals to preserve pickles.
• Sodium benzoate and sodium metabisulphate are commonly used preservatives in preserving foods like jams and squashes to check their spoilage.

2) Preservation by common salt

• In this method, meat and fish are covered with dry salt to check the growth of bacteria.
• Salting is also used to preserve amla, raw mangoes and tamarind etc.,

3) Preservation by oil and vinegar ,

• Pickles, vegetables, fruits, fish and meat are often preserved by this method.
• Use of oil and vinegar prevents the growth of bacteria in food.

4) Pasteurisation :
In this method, milk is heated to about 70°C for 15 to 30 seconds and then suddenly chilled and stored. It prevents the growth of food spoiling microbes.

5) Heat and cold treatment:

• Boiling kills many micro organisms. So, store the milk after boiling.
• Keep the food (vegetables, fruits) in refrigerator. Low temperature inhibits the – growth of microbes.

6) Storage and packing :
Dry fruits and vegetables are sold in air tight packets to prevent the attack of microbes.

Question 3.
Write a detailed account on nitrogen cycle.
Answer:

1. In atmosphere, about 78% of nitrogen is present, but it can’t be used by plants and animals directly.
2. The nitrogen fixing bacteria and algae present in the soil fix the nitrogen from atmosphere and convert into nitrite and nitrate forms.
3. Plants absorb these nitrites and nitrates with the help of roots. Nitrogen is very essential to produce proteins and other nitrogenous compounds.
4. When plants and animals die. bacteria and fungi present in soil convert various nitrogenous compounds into nitrites and nitrates.
5. Some specialized bacteria convert these nitrites and nitrates from the soil into nitrogen gas.
6. This maintains, a constant balance in the percentage of nitrogen in the atmosphere.

Question 4.
If there are no microorganisms on the earth what will happen ?
Answer:

1. If micro organisms are not present on earth the earth will be full of dead organisms and plants.
2. The plants can not fix the atmospheric nitrogen in the soil.
3. We can not get fermented products.
4. The life becomes impossible on the earth.

Question 5.
Write some common human diseases caused by micro organisms, their mode of transmission and general preventive measures in a table.
Answer:

Human Disease	Causative Microorganism	Mode of Transmission	Preventive Measures (General)
Tuberculosis Measles Chicken Pox Polio	Bacteria Virus Virus Virus	Air Air Air / Contact Air / Water	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.
Cholera Typhoid	Bacteria Bacteria	Water / Food Water	Maintain personal hygiene and good sanitary habits. Consume properly cooked food and boiled drinking water. Vaccination.
Hepatitis A	Virus	Water	Drink boiled drinking water. Vaccination.
Malaria	Protozoa	Mosquito	Use mosquito net and repellents. Spray insecticides and control breeding of mosquitoes by not allowing water to collect in the surroundings.

Question 6.
What are the differences between Antibiotic and Vaccine ?
Answer:

Antibiotic	Vaccine
1) An antibiotic is a medicine that inhibits (stop) or kills the growth of bacteria.	1) Vaccine improves the immunity to a particular disease.
2) Antibiotics cure the disease.	2) Vaccine prevent the disease.
3) Antibiotics are available in the form of tablets, capsules, syrups or drops, ointments or injections.	3) Vaccines are given orally or through injections.
4) Antibiotics are produced by growing specific microorganisms.	4) The weakened disease causing microorganisms are injected into our bodies.
5) It functions for short duration.	5) It functions long duration or lifelong.
6) Ex: Penicillin, tetracycline, streptomycin, erythromycin, etc.	6) Ex : Polio, smallpox, chickenpox, etc.

Question 7.
Make a list of scientists and their discoveries related microorganisms.
Answer:

Name of the scientist	Discovery
Robert Koch	Bacteria which cause cholera and tuberculosis.
Alexander Flemming	His best known discoveries are the enzyme lysozyme in 1923 antibiotic substance and penicillin from the fungus penicillium notatum.
Edvard Buchner	Fermentation process by extract of yeast cells.
Edward Jenner	Smallpox vaccine.
Louis Pasteur	Pasteurisation, vaccines for rabies and anthrax.

Question 8.
Write the names of some vaccines and their preventive diseases.
Answer:

Vaccine	Preventive disease	Age
BCG	TB	Birth, 10 years.
DPT	Diptheria Pertussis Tetanus	6 weeks, 10 weeks 14 weeks, 18 months.
Hepatitis-B	Hepatitis-B	Birth, 6 weeks, 14 weeks
OPV	Polio	Birth, 6 weeks, 10 weeks, 14 weeks, 5 years booster.
MMR	Measles. Mumps, Rubella	9 months, 15 months, booster dose.
PCV	Pneumonia	6 weeks. 10 weeks. 14 weeks 15 months, booster dose.
Typhoid	Typhoid	2 years, 5 years booster dose.
Varicells	Chickenpox	1 year.

Question 9.
Identify and name the pictures given below.


Answer:
a) Paramoecium.
b) Spindle shaped muscle cells,
c) Long branched Nerve Cell.
d) Virus,
e) A Hoe (Used for removing weeds).

Question 10.
You may have observed the below microorganism under the microscope while doing the experiment with spoilt bread.
Observe the figure and answer the following questions.

a) Name the microorganism given in the diagram.
b) To which group does the microorganism belong ?
c) Name the food item on which the microorganism grows.
d) Does it grow well in dry or inmoist conditions ?
e) Is it safe to eat infected bread ?
Answer:
a) The given diagram is Bread mould.
b) It belongs to fungi.
c) This microorganism grows on Bread.
d) No, it grows on moist bread.
e) No, it is not safe to eat infected bread. It causes diseases.

Question 11.
Study the diagram showing the Nitrogen cycle and answer the questions that follow.

a) In the portion of the diagram labelled P, what is meant by ‘fixing’ of nitrogen ?
b) Explain how leguminous plants such as beans are invovled in nitrogen fixation.
c) What is the importance of the process described in the portion of the diagram labelled Q ?
Answer:
a) Fixing of nitrogen : The process of conversion of atmospheric nitrogen into its usable forms is called fixing of nitrogen.
b) Nitrogen fixing bacteria live in root nodules of leguminous planks. So they are in-volved in nitrogen fixation.
c) This process helps to maintain the level of nitrogen in the atmospere.