Hello Readers! Welcome to the first blog post in Class 8 Science. Microorganisms Friend and Foe are Chapter 1 taken from the JKBOSE Class 8th Science textbook. In this blog post, we will discuss complete Microorganisms Friend and Foe Class 8 Questions. Before we move on to that here is a brief overview of the chapter. The following topics are discussed in detail in this chapter:
Microorganisms Friend and Foe Class 8 Questions
Overview of the Chapter
- WHAT IS A MICROORGANISM?
- WHERE DOES MICROORGANISM LIVE?
- MICROORGANISMS AND MAN (FRIENDLY MICROORGANISMS).
- HARMFUL MICROORGANISMS.
- FOOD PRESERVATION.
- NITROGEN FIXATION.
- NITROGEN CYCLE.
WHAT IS A MICROORGANISM? Those organisms which cannot be seen with the naked or unaided eyes are called microorganisms or microbes. We use a microscope or magnifying glass to see them. There are four main groups of microorganisms. These are bacteria, protozoa, fungi and algae. In addition to these, there is one special group of organisms called a virus.
WHERE DO MICROORGANISM LIVE: Microorganisms are found in all types of habitats. They are found in air water and soil. Microorganisms are found in almost all kinds of environments like hot springs, ice-cold water, saline water, desert soil, marshy land etc. They are also present inside the body of human beings as well as other animals.
MICROORGANISMS AND MAN (FRIENDLY MICROORGANISMS): Microorganisms are used for various purposes by human beings. Some of the beneficial uses of microorganisms are as follows:
- Making curd, bread and cake.
- Commercial production of alcohol, wine and acetic acid.
- Preparation of medicines called antibiotics.
- Increase the fertility of the soil by fixing atmospheric nitrogen.
- Decompose dead decaying plants and animals and help in recycling materials in nature.
HARMFUL MICROORGANISMS: Microorganisms are harmful in many ways. Some microorganisms cause diseases in human beings, some in plants and some cause diseases in animals. The disease-causing microorganisms are termed pathogens. The diseases caused by microorganisms in human beings are typhoid, tuberculosis, tetanus, polio, cholera, chickenpox, smallpox, AIDS etc. The diseases caused by pathogens in animals are anthrax, foot and mouth diseases, swine flu, bird flu etc. The diseases caused by microorganisms in plants are citrus canker, late blight of potato, black rot of cabbage, white rust of wheat etc.
FOOD PRESERVATION: The process by which food materials are prevented from spoilage by using chemical and physical methods is called food preservation. Some methods of food preservation are:
- Drying and dehydration.
- Using Preservatives.
- Preservation by common salt.
- Preservation by sugar.
- Preservation by oil and vinegar.
- Hot and Cold treatments.
- Pasteurisation.
- Vacuum drying.
- Proper storage and packing.
NITROGEN FIXATION: The process of conversion of atmospheric nitrogen into useful compounds of nitrogen which can be used by plants is called nitrogen fixation. Nitrogen can be fixed by lightning and certain nitrogen-fixing bacteria like Rhizobium, Azotobacter, Anabaena, and Nostoc.
NITROGEN CYCLE: The cycling of nitrogen through living things (plants and animals) and non-living environments (air, water and soil) is called the nitrogen cycle.
That’s all about a brief overview of this chapter. Now let’s move on to the solution section of the chapter.
Chapter 1 Microorganisms Friend and Foe Question Answers
Exercises
- Fill in the Blanks.
- Microorganisms can be seen with the help of a microscope or hand lens.
- Blue-green algae fix atmospheric nitrogen directly from the air to enhance the fertility of the soil.
- Alcohol is produced with the help of
- Cholera is caused by Bacteria.
- Tick the correct answer:
(a) Yeast is used in the production of
(i) Sugar
(ii) Alcohol
(iii) Hydrochloric acid
(iv) Oxygen
Ans. ii) Alcohol.
(b) The following is an antibiotic.
(i) Sodium bicarbonate
(ii) Streptomycin
(iii) Alcohol
(iv) Yeast
Ans. ii) Streptomycin.
(c) The carrier of malaria-causing protozoan is
(i) Female Anopheles mosquito
(ii) Cockroach
(iii) Housefly
(iv) Butterfly
Ans. i) Female Anopheles mosquito.
(d) The most common carrier of communicable diseases is
(i) Ant
(ii) Housefly
(iii) Dragonfly
(iv) Spider
Ans. ii) Housefly
(e) The bread or idli dough rises because of
(i) Heat
(ii) Grindling
(iii) Growth of yeast cells
(iv) Kneading
Ans. iii) Growth of yeast cells
(f) The process of conversion of sugar into alcohol is called:
(i) Nitrogen fixation
(ii) Moulding
(iii) Fermentation
(iv) Infection
Ans. iii) Fermentation.
- Match the organisms in Column I with their actions in Column II.
| Column I | Column II |
|---|---|
| i) Bacteria | a) Nitrogen Fixation |
| ii) Rhizobium | b) Setting of Curd |
| iii) Lactobacillus | c) Baking of Bread |
| iv) Yeast | d) Causing Malaria |
| v) A Protozoan | e) Causing Cholera |
| vi) A Virus | f) Causing AIDS |
| g) Producing Antibodies |
Ans.
| Column I | Column II |
|---|---|
| i) Bacteria | e) Causing Cholera |
| ii) Rhizobium | a) Nitrogen Fixation |
| iii) Lactobacillus | b) Setting of Curd |
| iv) Yeast | c) Baking of Bread |
| v) A Protozoan | d) Causing Malaria |
| vi) A Virus | f) Causing AIDS |
4. Can microorganisms be seen with the naked eye? If not, how they can be seen?
Ans. Microorganisms are extremely small to be seen with the naked eye. They can only be seen with help of a microscope or magnifying glass.
5. What are the major groups of microorganisms?
Ans. There are four major groups of microorganisms.
1. Bacteria
2. Fungi
3. Protozoa
4. Algae.
In addition to these, viruses are also considered a special group of microorganisms.
6. Name the microorganisms which can fix atmospheric nitrogen in the soil.
Ans. Microorganisms like Rhizobium. Blue-green algae, Nostoc Anabaena etc. fix atmospheric nitrogen in the soil.
7. Write 10 lines on the usefulness of microorganisms in our lives.
Ans. Following are the 10 lines on the usefulness of bacteria.
1. Microorganisms are used in the preparation of home-based items like curd, bread and cheese etc.
2. They are used in the commercial production of alcohol and wine.
3. They are also helpful in the preparation of vinegar.
4. They play important role in cleaning up the environment.
5. Microorganisms are also used in the preparation of antibiotics.
6. They are also used for the preparation of vaccines for various diseases.
7. Microorganisms are extremely useful in nitrogen fixation (Rhizobium).
8. They are also used in the tanning of leather.
9. They are also useful in the biological treatment of sewage and industrial effluents.
10. Microorganisms are useful in making cheese, pickles, idli, dosa and bhaturas etc.
8. Write a short paragraph on the harms caused by microorganisms.
Ans. Microorganisms are harmful to us in many ways. The growth of microorganisms spoils our clothes, shoes and food items and makes them unfit for our use. They are responsible for a variety of diseases in plants, animals and human beings. For example, diseases like cholera, chicken pox, tuberculosis, flu, Aids etc. in human beings are caused by microorganisms. Animal diseases like Anthrax and foot and mouth disease are caused by microbes. Several plant diseases like black rot of cabbage, white rust of mustard, and late blight of potatoes are also caused by microorganisms.
9. What are antibiotics? What precautions must be taken while taking antibiotics?
Ans. These are the medicines prepared from microorganisms used to kill or stop the growth of disease-causing microorganisms.
Following precautions should be kept in mind while taking antibiotics.
1. Antibiotics should be taken only on the prescription of a qualified doctor.
2. Antibiotics should not be used unnecessarily if not required.
3. You should avoid taking medicine to which you have previously had an allergic reaction.
4. You should use an antibiotic with care if you reduced liver or kidney function.
5. You should not use antibiotics against cold and flu as these are caused by viruses.
6. You must finish the course prescribed by the doctor.
7. Overuse of antibiotics should be avoided as it kills useful microbes inside our body and also makes a drug less effective if needed in future.
That’s all about Microorganisms Friend and Foe Class 8 Questions. Hope you found it useful. Do share your views about this post in the comment section below.
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