Science In Everyday Life Solutions for Class 8 Science Chapter 2 Microorganisms are provided here with simple step-by-step explanations. These solutions for Microorganisms are extremely popular among Class 8 students for Science Microorganisms Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Science In Everyday Life Book of Class 8 Science Chapter 2 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Science In Everyday Life Solutions. All Science In Everyday Life Solutions for class Class 8 Science are prepared by experts and are 100% accurate.

Page No 39:

Question 1:

What is a microscope?

Answer:

The instrument which is used to see the objects which are too small to see with the naked eyes is called a microscope. The microscope has a lens attached to it which shows a bigger picture of the object placed under the lens.

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Question 2:

What are microorganisms? Name the five major groups into which microorganisms can be divided.

Answer:

Organisms which are not visible to the naked eye, and can be seen only through the microscope are called microorganisms. Microorganisms can be mainly classified into five major groups. They are:
(i) Bacteria
(ii) Protozoa
(iii) Fungi
(iv) Algae
(v) Virus.

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Question 3:

Name any four medicinal uses of microorganisms.

Answer:

Microorganisms serves various medicinal purposes which include
(i)  The production of antibiotics.
(ii) The production of vaccines.
(iii) The digestion of food in human beings and fight against disease causing microbes.
(iv) As a food supplement.

Page No 39:

Question 1:

Write one word for the following.

1. Organisms that are visible only with the help of a microscope ....................
2. Milk protein ....................
3. Bacteria present in milk ....................
4. A preparation of killed or weakened disease-causing microbes ....................
5. Process that involves heating a foodstuff to a high temperature and then cooling it rapidly ....................

Answer:

1. Microorganisms.
2. Casein.
3. Lactobacillus
4. Vaccine.
5. Pasteurization.

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Question 2:

Write two examples for each of the following.

1. Antibiotics .................... ....................
2. Communicable diseases .................... ....................
3. Diseases caused by bacteria .................... ....................
4. Diseases caused by protozoa .................... ....................
5. Diseases caused by fungus .................... ....................

Answer:

1. Penicillin and Streptomycin
2. Malaria and cholera
3. Typhoid and tuberculosis
4. Malaria and dysentery
5. Ringworm and apple scab

Page No 39:

Question 1:

Yeast and moulds are examples of
(a) fungi
(b) bacteria
(c) algae
(d) virus

Answer:

(a) Fungi
Yeasts and moulds are examples of fungi.

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Question 2:

Which of these microorganisms is used in the preparation of bread?
(a) Yeast
(b) Algae
(c) Bacteria
(d) Virus

Answer:

(a) Yeast
Yeast is used in the preparation of bread.

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Question 3:

Production of alcoholic beverages like beer and wine involves
(a) pasteurization
(b) fermentation
(c) tanning
(d) boiling

Answer:

(b) Fermentation

Production of alcoholic beverages like beer and wine involves fermentation.

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Question 4:

Food spoilage can be detected by
(a) foul odour
(b) surface discolouration
(c) sour taste
(d) all of these

Answer:

(d) all of these
Food spoilage can be detected by foul odour, surface discolouration and sour taste.

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Question 5:

Which of the following is a method of food preservation?
(a) Boiling
(b) Canning
(c) Dehydration
(d) All of these

Answer:

(d) all of these

Boiling, canning and dehydration are some of the methods of preserving the food.

Page No 39:

Question 1:

Match the following.

Column A  Column B
Lactobacillus Penicillin
Rhizobium Bread
Yeast Nitrogen fixation
Chlorella Curd
Antibiotic Rich source of proteins and other nutrients

Answer:

Column A Column B
Lactobacillus Curd
Rhizobium Nitrogen fixation
Yeast Bread
Chlorella Rich source of proteins and other nutrients
Antibiotic Penicillin



Page No 40:

Question 4:

How do microbes help in agriculture?

Answer:

Microbes such as Rhizobium and blue-green algae help in agriculture. Rhizobium which is present in the root nodules of the leguminous plants, helps in the nitrogen fixation which is later stored in the plant tissues as plant nutrients and thereby enhances the growth of crops. Apart from this, microbes help to increase the fertility of the soil through their activities.

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Question 5:

What are the two harmful effects of microorganisms?

Answer:

Harmful effects of microbes include:
(i) Spoiling the food through various microbial activities.
(ii) Causing diseases in living organisms.

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Question 6:

What are communicable diseases? Name any two communicable diseases of human beings, animals, and plants.

Answer:

Communicable diseases are the epidemic diseases that spread from infected living beings to the other healthy living beings. This occurs in human beings, animals and plants. Communicable diseases are caused by the microbes called pathogens. For example:
(i) Typhoid and Cholera are some communicable diseases caused in human beings due to microbes.
(ii) Rinderpest and foot and mouth disease are some communicable diseases caused in animals due to virus.
(iii) Rust of wheat and apple scab are some communicable diseases caused in plants due to fungus.

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Question 7:

List at least three things that help us detect that food is unfit for consumption.

Answer:

The activities of some microbes like fungus and bacteria causes the food to spoil. Eating the spoiled foods can cause an illness called food spoiling. Such food, which is unfit for consumption can be detected by its:
(i) foul odour
(ii) surface discolouration
(iii) sour taste.

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Question 8:

Name the main conditions required for the growth of microorganisms.

Answer:

Microbes cannot survive at a very high or low temperatures. In certain conditions they grow and multiply. The conditions required for the growth of microbes are,
(i) a moderately warm temperature
(ii) moisture
(iii) air

Page No 40:

Question 1:

What is a specimen? How does a coverslip help in making a slide? Write the basic steps for using a microscope.

Answer:

Specimen is a term which is commonly used for the objects which are viewed under a microscope. Placing the coverslip over the slide containing the specimen makes the specimen sample more thinner for detailed viewing and also prevents the objective lens of the microscope coming into contact with the specimen sample.
The basic steps which should be followed while using a microscope are:

(i) Ensure that the mirror is clean by cleaning it with soft, clean cloth.
(ii) The slide containing the specimen should be placed on the stage.
(iii) The focus of the eyepiece and the objective lens is adjusted till a very clear and accurate image is obtained.
(iv) Examine the slide through the eyepiece for further observations.

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Question 2:

Describe some commercial uses of microorganisms in detail.

Answer:

Microorganisms are also used for various commercial purposes like:

(i) Preparation of cheese and curds: A bacteria called Lactobacillus is used in making curds which provides suitable acidic environment to coagulate the casein (milk protein) forming curds. Apart from this, Streptococcus along with Lactobacillus is used in the production of cheese and paneer.
(ii) Preparation of alcoholic beverages: Alcoholic beverages are produced by a microbial action called fermentation which involves microscopic fungus called yeast.
(iii) Making bread: Yeasts are used in the preparation of breads, to give the right texture, which makes the bread porous and spongy.
(iv) Making toothpaste: Shells of diatoms and xanthum gum from Xanthomonas campestris are used in making toothpaste.
(v) Making vinegar, coffee and tobacco: Certain bacteria are used in making vinegar, coffee and tobacco.

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Question 3:

How can prepare curd at home?

Answer:

Preparation of curd from milk is quite an easy process. Warm some milk in a bowl and keep it aside. Add a teaspoonful of curd to the warm milk and stir well. Close the bowl with a lid and leave it overnight. The milk will be transformed into curd. This happens due to a bacterium present in the curd called Lactobacillus that converts the lactose sugar present in the milk to lactic acid that in turn provides a suitable acidic environment to coagulate the casein present in the milk, forming curd.

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Question 4:

Describe some medicinal uses of microorganisms with examples.

Answer:

Microorganisms serves various medicinal purposes which include:

(i)The production of antibiotics such as penicillin and Streptomycin with the help of certain bacteria and fungus, which is used to treat microbial diseases in animals and plants.
(ii) The production of vaccines which enhances the growth of antibodies in animal and human body, which fight against the infections and disease causing microbes.
(iii) Lactobacillus acidophilus, a bacteria present in human intestines, digests the food and fight against disease causing microbes.
(iv) Chlorella, a type of algae, which is rich in proteins and nutrients, is used as a food supplement.

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Question 5:

Describe how pathogens are transmitted from one person to another.

Answer:

The disease causing microbes are called pathogens. Pathogens often enter a human body by means of air, water and food. When the infectious person coughs or sneezes, the pathogens released into the air from the infectious person, enters the body of a healthy human causing diseases to him. Also, these pathogens are more often spread by the insects like female anopheles mosquito and housefly. When the same mosquito bites an infectious person and a healthy person, the pathogens are transmitted or when a housefly sitting on a garbage, sits on the food items, it transmits the pathogens through the food.

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Question 6:

Describe the mode of transmission, causative pathogen, and preventive measures of the following diseases:
(a) Malaria
(b) Cholera
(c) Typhoid
(d) Chickenpox
(e) Anthrax
(f) Foot and mouth disease
(g) Poliomyelitis
(h) Tuberculosis
(i) Ringworm

Answer:

 

Disease Mode of transmission Causative pathogen Preventive measures
(a) Malaria Occurs due to the bite of female anopheles mosquito  Protozoan Using mosquito nets and repellents, maintaining a  neat and clean environment .
(b) Cholera  Polluted water and contaminated food  Bacteria Maintaining a  neat and clean environment with proper sanitation, using boiled water for drinking, avoiding uncovered food .
(c) Typhoid  Contaminated food  Bacteria Maintaining a  neat and clean environment with proper sanitation
(d) Chickenpox  Air,  physical contact with the infected person  Virus  Vaccination.
(e) Anthrax  Grazing  Bacteria  Vaccination
(f) Foot and mouth disease  Air, contact with diseased animals  Virus  Vaccination
(g) Poliomyelitis  Air, water  Virus  Vaccination
(h) Tuberculosis  Air  Bacteria  Vaccination
(i) Ringworm  Direct contact with the infected person  Fungus  Avoiding sharing personal items like combs and towels with the infected person, maintaining good hygiene

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Question 7:

What is food preservation? Describe in detail any four common methods of food preservation.

Answer:

The preservation involves treating and storing the food using methods and techniques that could stop or slow down its spoilage which at the same time maintains its nutritional value, flavour and texture is called as food preservation. Following are some of the methods followed in food preservation:

(i) Boiling : The microbes present in food items can be killed by boiling. This method is often used for milk and water which kills the microbes present in them.
(ii) Dehydration : In this process, the water content present in the food items are removed, in the absence of which microbes cannot grow. Cereals and pulses are preserved in this method.
(iii) Canning : In this process the food items are stored in airtight cans to avoid spoiling. Fish, vegetables, jams and cooked food are preserved by this method.
(iv) Pasteurization : This method involves heating a foodstuff to a high temperature and then cooling it rapidly. Commercially available milk is generally preserved by pasteurization.



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