Check the below Online Education NCERT MCQ Questions for Microorganisms: Friend and Foe Class 8 Extra Questions and Answers Science Chapter 2 Pdf free download. https://ncertmcq.com/extra-questions-for-class-8-science/
Online Education for Class 8 Science Chapter 2 Extra Questions and Answers Microorganisms: Friend and Foe
Class 8 Science Chapter 2 Extra Questions Question 1.
Write the agent that is responsible for the spread of following diseases :
Polio = …………………….
Tuberculosis = …………………….
Answer:
Polio = Viruses
Tuberculosis = Bacteria.
Class 8 Science Chapter 2 Extra Questions And Answers Question 2.
Write the name of bacteria which converts milk into curd.
Answer:
Lactobacillus.
Class 8 Science Ch 2 Extra Questions Question 3.
Name two diseases caused by protozoans.
Answer:
Diseases like dysentery and malaria are caused by protozoans.
Ncert Class 8 Science Chapter 2 Extra Questions Question 4.
Name two diseases caused by bacteria.
Answer:
Typhoid and tuberculosis (T.B.).
Ncert Solutions For Class 8 Science Chapter 2 Extra Questions 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.
Ch 2 Science Class 8 Extra Questions Question 6.
What are the commercial uses of yeast?
Answer:
Yeast is used for commercial production of alcohol and wine.
Extra Questions For Class 8 Science Chapter 2 Question 7.
Name the process of conversion of sugar into alcohol.
Answer:
Fermentation.
Chapter 2 Science Class 8 Extra Questions Question 8.
Who discovered the process of fermentation ?
Answer:
Louis Pasteur in 1857.
Class 8 Chapter 2 Extra Questions Question 9.
Who discovered Penicillin?
Answer:
Alexander Fleming discovered the antibiotic called Penicillin in 1929.
Microorganisms Class 8 Extra Questions Question 10.
Name some of the diseases that can be prevented by vaccination.
Answer:
Cholera, tuberculosis, smallpox, hepatitis, etc.
Class 8 Chapter 2 Science Extra Questions Question 11.
Who discovered the vaccine for smallpox?
Answer:
Edward Jenner discovered the vaccine for smallpox in 1798.
Science Class 8 Chapter 2 Extra Questions Question 12.
Can you name some diseases for which you have been given injections in your childhood to protect you from them?
Answer:
They are diphtheria, tuberculosis, chickenpox, cholera, etc.
Class 8th Science Chapter 2 Extra Questions 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.
Science Chapter 2 Class 8 Extra Questions Question 14.
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 multi cellular.
For Example :
Bacteria : Lactobacillus
Protozoa : Amoeba, Paramecium.
Class 8 Science Chapter 2 Extra Question Answer Question 15.
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.
Questions On Microorganisms Class 8 Question 16.
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 :
(i) Write the observation noted by her after two hours.
(ii) 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.
Class 8 Microorganisms Friend And Foe Extra Questions Question 17.
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 Answers Question 18.
(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 micro-organisms.
(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.
Extra Questions Of Chapter 2 Science Class 8 Question 19.
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 :
- Rhizobium: Rhizobium bacteria and blue-green algae present in the soil fix nitrogen from the atmosphere and convert into nitrogenous compounds.
- Lactobacillus: Lactobacillus bacteria is useful in making curd from milk.
- Decomposers: Bacteria play an important role in cleaning the environment by decomposing the dead organic matter.
Class 8 Science Chapter 2 Important Questions Question 20.
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 lightning fixes the nitrogen to nitrogenous compounds.
Question 21.
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 :
- Nitrogen is one of the essential constituents of all living organisms as part of proteins, chlorophyll, nucleic acids and vitamins.
- The atmospheric nitrogen cannot be taken directly by plants and animals.
- The nitrogen-fixing bacteria and algae present in the soil fix nitrogen from the atmosphere and convert into nitrite and nitrate forms.
- Once nitrogen is converted into these usable forms, it can be utilized by plants through their roots. This is called the process of ‘fixing5 of nitrogen. Fig. Nitrogen cycle
- 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.
- 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 cycle works.
Multiple Choice Questions (MCQs)
1. Rhizobium bacteria present in root nodules of leguminous crops help in
(a) crop-rotation
(b) transplantation
(c) transpiration
(d) nitrogen fixation.
Answer:
(d) nitrogen fixation.
2. The following is a communicable disease :
(a) Tetanus
(b) Common cold
(c) Rabies
Answer:
(b) Common cold.