Short Answer Questions (Part - 1) - Microorganisms : Friend And Foe Class 8 Notes | EduRev

Science Class 8

Created by: Dr Manju Sen

Class 8 : Short Answer Questions (Part - 1) - Microorganisms : Friend And Foe Class 8 Notes | EduRev

The document Short Answer Questions (Part - 1) - Microorganisms : Friend And Foe Class 8 Notes | EduRev is a part of the Class 8 Course Science Class 8.
All you need of Class 8 at this link: Class 8

Q 1: Write short notes on

(a) Bacteria
(b) Viruses

Ans: Bacteria: Bacteria are single celled microorganisms. They can survive under all types of environment, ranging from ice cold climate to hot springs and deserts to marshy lands. Bacteria can be seen under microscope which enlarges their image from a hundred to thousand times. They are of spiral shape or rod shape.
Viruses: Viruses are microscopic infectious agent that acts as non-living outside host cell and inside host cell becomes living and show reproduction. It can affect all kinds of an organism including animals, plants and bacteria. Common ailments like cold, coughs and influenza (flu) are caused by viruses; serious diseases like chicken pox and polio are also caused by viruses.


Q 2: Write short notes on

(a) Protozoa

(b) Algae

Ans: Protozoa: Protozoa are unicellular animals. Some are free-living, others are parasites. Several parasitic protozoans cause diseases in human beings, domestic animals and plants. For example, Plasmodium, a protozoan, causes malaria.
Algae: Algae are green substances floating on the surface of a pond, lake, river, stagnant water, moist soil, stones. They tend to grow on wet surfaces. Therefore, they can synthesize their own food. They are found in water or in very moist places. 


Q 3: What do you mean by friendly microbes?
Ans:
 Microorganisms are beneficial to us in various ways; they not only prepare curd, bread, cake, wine and medicines for us but also used to increase soil fertility by fixing atmospheric nitrogen. Thus we called them as friendly microbes.


Q 4: How curd is formed?
Ans:
 Milk is turned into curd by bacteria. Curd contains several micro-organism including Lactobacilli bacteria.It promotes the formation of curd from milk. When a little of pre-made curd is added to warm milk,then Lactobacilli bacteria present in curd multiply in milk and convert the lactose sugar into lactic acid. This lactic acid then converts milk into curd. 


Q 5: Why yeast is used in the baking industry for making bread, cakes and pastries?
Ans:
 Yeast reproduces rapidly and produces carbon dioxide during respiration. Bubbles of gas fill the dough (mixture of atta or maida and some sugar and water) and increase its volume. This is the basic of using yeast in baking industry.

Short Answer Questions (Part - 1) - Microorganisms : Friend And Foe Class 8 Notes | EduRev


Q 6: Define the process of fermentation and its application.
Ans:
 Fermentation is the process of food processing in which sugar is converted into alcohol by the action of microorganisms. This process is used to produce alcoholic beverages such as wine, beer, and cider. For this purpose yeast is grown on natural sugars present in grains like barley, wheat, rice, crushed fruit juices etc.


Q 7: How antibiotics are related to microorganisms?
Ans:
Antibiotics are medicines that kill or stop the growth of disease causing microorganisms and they are prepared from microorganisms. For e.g. Streptomycin, tetracycline and penicillin are some of the antibiotics prepared from microorganisms like fungi and bacteria.


Q 8: Why vaccines are important?

Ans: Vaccines produces antibodies in our body to fight against disease causing microbes entering our body. Diseases like cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination, polio drop given to children is also a vaccine.


Q 9: What is the main motto of pulse polio program?
Ans:
 The main motto of pulse polio program is to protect children from polio, by providing them with polio drops.


Q 10: Write short notes on medicinal use of microorganisms.
Ans:
 Antibiotics are medicines that kill or stop the growth of disease causing microorganisms and they are prepared from microorganisms. For e.g. streptomycin, tetracycline and penicillin are some of the antibiotics prepared from microorganisms like fungi and bacteria.


Q 11: Write short notes on increasing soil fertility by the action of microorganisms.
Ans:
 Some bacteria and blue green algae are able to fix atmospheric nitrogen into nitrates and nitrates are an important constituent to increase soil fertility. These microbes are generally called biological nitrogen fixers.


Q 12: How do microbes clean our environment?
Ans: 
Microbes decompose the dead organic wastes of plants and animals converting them into simple substances. These substances are again used by other plants and animals. Thus microbes degrade the harmful and smelly substances and clean up the environment.


Q 13: Why some microorganisms are considered as harmful?
Ans:
 Some microorganisms cause diseases in human beings, plants and animals, like some species of bacteria causes tuberculosis and typhoid, some species of virus causes common cold and influenza. Some microorganisms also cause spoilage of food, clothing and leather items. Thus we consider some microorganisms are harmful.


Q 14: List all possible ways by which pathogens can enter our body.
Ans: 
Diseases causing microorganisms can enter our body through the air we breathe, water we drink and the food we eat. They can also get transmitted by direct contact through an infected person or carried through an animal.


Q 15: Define communicable diseases with examples.
Ans:
There are some microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact. Such kind of diseases is called communicable disease.
For example: Cholera, Chicken pox, Tuberculosis.


Q 16: Why we should keep a handkerchief on the nose and mouth while sneezing?
Ans: 
When a person suffering from common cold sneezes, the fine droplets of moisture containing thousands of viruses are spread in the air, these viruses may enter the body of healthy person while breathing, thus we should keep handkerchief on the mouth and nose while sneezing so that viruses may not spread In the air and enter into a healthy person’s body to make him sick.


Q 17: How does housefly spread diseases?
Ans:
 Houseflies sit on the garbage and animal excreta where pathogens stick to their bodies and these pathogens get transferred to uncovered food when these flies sit on uncovered food items and the person consuming these food fall sick.


Q 18: What are the advantages of sealed air tight packing for storage of food items? 

Ans: Sealed air tight packets prevent the attack of microbes and protect the food items inside it from getting spoiled and toxic.


Q 19: Write short notes on diseases causing microorganisms in animals.
Ans:
There are some microorganisms that cause disease in animals also like anthrax is a very dangerous human and cattle disease caused by a bacterium. Foot and mouth disease of cattle is caused by a virus.


Q 20: Write short notes on diseases causing microorganisms in plants.

Ans: There are some microorganisms that cause disease in plants like wheat, sugarcane, rice, potatoes, oranges, and apples. Like citrus canker disease caused by bacteria in plant, rust of wheat disease in wheat plant caused by fungi. These diseases reduce the yield of crops and can be controlled by using certain chemicals that kill microbes.

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