NCERT Solution For Class 8 Science, Chapter 2 – Microorganisms: Friend and Foe

NCERT Solutions is known as an extremely helpful resource for preparing for the exam. Takshila Learning provides its learners with access to a wealth of NCERT problems and their solutions. CBSE Class 8 Science NCERT Solutions are built by subject matter experts, so be sure to train learners for a good grade. The questions set out in the NCERT Books are prepared in compliance with the requirements of the CBSE.

NCERT Solution For Class 8 Science, Chapter 2 – Microorganisms: Friend and Foe provides us with all-inclusive information on all concepts. As students would have to learn the basics about the subject in class 8, this curriculum for class 8 is comprehensive study material, which explains the concepts in a great way.

Question 1.
Fill in the blanks.
(a) Microorganisms can be seen with the help of a _____
(b) Blue-green algae fix ______ directly from the air to enhance the fertility of the soil.
(c) Alcohol is produced with the help of _____
(d) Cholera is caused by ______

Answer:
(a) microscope
(b) nitrogen
(c) yeast
(d) bacteria

Question 2.

Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar
(ii) alcohol
(iii) hydrochloric acid
(iv) oxygen

Answer:
(ii) alcohol

(b) The following is an antibiotic:
(i) sodium bicarbonate
(ii) streptomycin
(iii) alcohol
(iv) yeast

Answer:
(ii) streptomycin

(c) Carrier of malaria-causing protozoan is:
(i) female Anopheles mosquito
(ii) cockroach
(iii) housefly
(iv) butterfly

Answer:
(i) female Anopheles mosquito

(d) The most common carrier of communicable diseases is
(i) ant
(ii) housefly
(iii) dragonfly
(iv) spider

Answer:
(ii) housefly

(e) The bread or idli dough rises because of:
(i) heat
(ii) grinding
(iii) growth of yeast cells
(iv) kneading

Answer:
(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

Answer:
(iii) fermentation

Question 3.
Match the organisms in column A with their action in column B.

Answer:
(i) (e)
(ii) (a)
(iii) (b)
(iv) (c)
(v) (d)
(vi) (f)

Question 4.
Can microorganisms be seen with the naked eye? If not, how can they be seen?

Answer:
The microorganisms cannot be seen with our naked eyes because they are very tiny in size. Some of these, such as fungus growing on bread, can be detected with a magnifying glass. Others cannot be recognized without the assistance of a microscope.

Question 5.
What are the major groups of microorganisms?

Answer:
Microorganisms are classified on the basis of their size, these groups are:

(a) Bacteria(b) Fungi(c) Protozoa(d) Some algae

Question 6.
Name the microorganisms which can fix atmospheric nitrogen in the soil.

Answer:
Rhizobium, Clostridium, Azotobacter.

Question 7.
Write 10 lines on the usefulness of microorganisms in our lives.

Answer:
Microorganisms are useful to us in many ways, 10 lines on the same are:

• Bacteria like Lactobacillus convert milk into curd.
• Bacteria are also involved in the making of cheese.
• Acetobacter acetic is used for producing acetic acid from alcohol.
• Yeast is used in the commercial production of alcohol, wine, and bakery products.
• Some specific microorganisms are helpful in the manufacturing of antibiotics.
• Microorganisms act as cleansing agents and decompose the waste products into manure.
• Dead or weakened microbes are used in the preparation of vaccines.
• Some bacteria fix atmospheric nitrogen and increase soil fertility.
• Algae, yeast, fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods that are suitable for human or animal consumption.
• Some microorganisms are taken as probiotics, that are believed to provide health benefits when consumed.

Question 8.
Write a short paragraph on the harms caused by microorganisms.

Answer:
Microorganisms are destructive to us in many ways. For example, microorganisms, named pathogens cause illness in humans, plants, and animals. Pathogens or germs enter a healthful body through air, water, infected food, and person by direct or indirect contact or by the carrier. Common diseases like cold, influenza (flu), cough, polio, chickenpox are caused by viruses. Foot and mouth diseases in cattle are also provoked by viruses. Typhoid, tuberculosis (TB) is caused by bacteria. Anthrax a hazardous human and cattle disorders are also caused by bacteria.

Illnesses like dysentery and malaria are caused by protozoa. Ringworm is caused by fungi and several microbes cause diseases in plants and thus lessens the yield. Citrus canker, a bacterial disease, impacts trees of citrus fruit and is spread by air. Bhendi yellow vein mosaic disease is caused by a virus and is dissipated by germs in ladyfingers. Rust of wheat is a fungal disease reaches people through the air. Microorganisms that grow on our sustenance sometimes produce deadly substances. These make the food unhealthy causing serious illness and even death. This foodborne disease is called food poisoning.

Question 9.
What are antibiotics? What precautions must be taken while taking antibiotics?

Answer:
Antibiotics are the drugs that kill or stop the expansion of the disease-causing microbes. They are generated by growing certain microorganisms. They are used to remedy a variety of diseases.

It is important to take antibiotics only on the guidance of an eligible doctor. One must complete the course prescribed by the doctor to make the medicine more effective and beneficial. Antibiotics must not be taken unnecessarily because it may kill beneficial and helpful bacteria also. Antibiotics are, however, not useful against cold and flu as they are caused by viruses.

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