Microorganisms: Friend and Foe Class 8 Extra Questions and Answers Science Chapter 2 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.
Class 8 Science Chapter 2 Extra Questions and Answers Microorganisms: Friend and Foe
Extra Questions for Class 8 Science Chapter 2 Microorganisms: Friend and Foe with Answers
Microorganisms: Friend and Foe Class 8 Extra Questions Very Short Answer Type
Question 1.
Write the agent that is responsible for the spread of following diseases:
Polio =________
Tuberculosis = _________
Answer:
Polio = Viruses
Tuberculosis = Bacteria
Question 2.
Write the name of bacteria which converts milk into curd.
Answer:
Lactobacillus
Question 3.
Name two diseases caused by protozoans.
Answer:
Diseases like dysentery and malaria are caused by protozoans.
Question 4.
Name two diseases caused by bacteria.
Answer:
Typhoid and tuberculosis (T.B.).
Question 5.
Where are microbes found?
Answer:
- They are present everywhere because they can survive under all types of environments.
- They are also found inside human body.
Question 6.
What are the commercial uses of yeast?
Answer:
Yeast is used for commercial production of alcohol and wine.
Question 7.
Name the process of conversion of sugar into alcohol.
Answer:
Fermentation.
Question 8.
Who discovered the process of fermentation?
Answer:
Louis Pasteur in 1857.
Question 9.
Who discovered Penicillin?
Answer:
Alexander Fleming discovered the antibiotic called Penicillin in 1929.
Question 10.
Name some of the diseases that can be prevented by vaccination.
Answer:
Cholera, tuberculosis, smallpox, hepatitis, etc.
Question 11.
Who discovered the vaccine for smallpox?
Answer:
Edward Jenner discovered the vaccine for smallpox in 1798.
Question 12.
Can you name some diseases for which you have been given injection in your childhood to protect you from them?
Answer:
They are diphtheria, tuberculosis, chiekenpox, cholera, etc.
Question 13.
What is the most prominent role of microorganisms in pollution control?
Answer:
They degrade the harmful substances and thereby play prominent role in pollution control.
Microorganisms: Friend and Foe Class 8 Extra Questions Short Answer Type 1
Question 1.
Define microorganisms with two examples.
Answer:
A microorganism is a living thing that is too small that it can’t be seen with the naked eye. Microorganisms can be found in air, water and in the bodies of plants and animals. They may be unicellular or multicellular.
For Example:
Bacteria: Lactobacillus
Protozoa: Amoeba, Paramecium
Question 2.
How do microorganisms help to improve the fertility of soil?
Answer:
Rhizobium bacteria present in the nodules of the roots of leguminous plants helps in the replenishment of the soil with nitrogen. Rhizobium bacteria takes nitrogen from the atmosphere and fix it directly into nitrogenous compounds and increase the fertility of the soil.
Question 3.
Seema took 50 gm of flour (atta) and added some sugar and mixed it with warm water„and also added small amount of yeast powder into it:
Write the observation noted by her after two hours.
What is the function of yeast in this activity?
Answer:
(i) After two hours the flour (atta) is found to be raised a little bit.
(ii) Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of the carbon dioxide gas fill the flour mix and increase its volume. This is the basis of the use of yeast in the baking industry for making breads, pastries and cakes.
Question 4.
What is pseudopodia? Write down two examples.
Answer:
Pseudopodia: A pseudopodium is a temporary arm-like projection of the cell of a microorganism.
Examples :
Pseudopodia are used for motility.
Pseudopodia are used for ingestion.
Microorganisms: Friend and Foe Class 8 Extra Questions Short Answer Type 2
Question 1.
(a) What are antibiotics?
(b) Name any two antibiotics?
(c) How are antibiotics manufactured?
Answer:
(a) Antibiotics are the medicines which kill or stop the growth of the disease-causing microorganisms. The source of these medicines is microorganisms.
(b) Streptomycin, Tetracycline.
(c) The antibiotics are manufactured by growing specific microorganisms which checks the growth of some other bacteria or microorganisms. Antibiotics are used to cure a variety of diseases. They are also used to control many plant diseases.
Question 2.
How are bacteria beneficial to us? Explain by giving any three examples.
Answer:
Bacteria are very useful to human beings though some other bacteria are harmful too.
Following are some examples that are very useful to us :
(a) Rhizobium: Rhizobium bacteria and blue-green algae present in the soil fix nitrogen from the atmosphere and convert into nitrogenous compounds.
(b) Lactobacillus: Lactobacillus bacteria is useful in making curd from milk.
(c) Decomposers: Bacteria play an important role in cleaning the environment by decomposing the dead organic matter.
Question 3.
How can nitrogen be replenished in soil? Explain with an example.
Answer:
Nitrogen in the soil can be replenished by two different ways:
Rhizobium bacteria present in the nodules of the roots of leguminous plants helps in the replenishment of the soil with nitrogen. Rhizobium bacteria takes nitrogen from the atmosphere and fix it directly into nitrogenous compounds. These crops are like beans and peas which with which it has a symbiotic relationship Rhizobium.
Nitrogen sometimes gets fixed through the action of lightning in the clouds. High temperature generated in the lightening fixes the nitrogen to nitrogenous compounds.
Microorganisms: Friend and Foe Class 8 Extra Questions Long Answer Type
Question 1.
What is nitrogen cycle? Describe with the help of a diagram how nitrogen- cycle works.
Answer:
The process of consumption of nitrogen by living beings (animals and plants), taking it from the atmosphere and returning back to the atmosphere by various processes, is called nitrogen cycle.
Nitrogen-cycle:
(i) Nitrogen is one of the essential constituents pf all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins.
(ii) The atmospheric nitrogen cannot be taken directly by plants and animals.
(iii) The nitrogen-fixing bacteria and algae present in the soil fix nitrogen from the atmosphere and convert into nitrite and nitrate forms.
(iv) Once nitrogen is converted into these usable forms, it can be utilized by plants through their roots. This is called the process of ‘fixing of nitrogen.
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(v) Nitrogen is then used for the synthesis of amino acids, proteins, etc. in plants. Animals feeding on the plants thus get these nitrogen-containing compounds.
(vi) When plants and animals die, bacteria and fungi present in the soil convert the various compounds of nitrogen back to nitrates and nitrites. Certain specialized bacteria convert nitrates and nitrites into nitrogen gas which goes back into the atmosphere. As a result, the percentage of nitrogen in the atmosphere remains more or less constant. This is how nitrogen-works.
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