Class 8 Science Chapter 2 Microorganisms: Friend and Foe Solutions | ASSEB Assam | English Medium

Class 8 Science Chapter 2 – Microorganisms: Friend and Foe – All Textual Solutions | ASSEB Assam (English Medium)

Class 8 Science Chapter 2 – Microorganisms: Friend and Foe Complete Textual Questions and Answers (ASSEB / SEBA Assam – English Medium)

Chapter 2 of the Class 8 Science curriculum, ‘Microorganisms: Friend and Foe’, is a fascinating and crucial chapter for students. These complete textual question-answer solutions (Class 8 Science Chapter 2 Textual Solutions) have been meticulously prepared based on the latest guidelines of the new ASSEB (Assam State School Education Board) syllabus and the National Education Policy (NEP). This comprehensive compilation includes textbook-based Very Short Answers (VSA), Short Questions, Long Answers, explanations, and key scientific definitions. Ospin Academy provides these solutions in a simple, accurate, and completely exam-oriented format.

The chapter ‘Microorganisms: Friend and Foe’ provides an in-depth understanding of the microscopic world, categorizing microbes into bacteria, fungi, protozoa, and some algae, alongside viruses. It explores the beneficial roles of microorganisms in making curd and bread, commercial uses, medicinal production (antibiotics and vaccines), and environmental cleaning. Conversely, it details harmful microorganisms causing diseases in humans, plants, and animals, as well as methods of food preservation. It is essential for students to thoroughly grasp these core concepts. Our textual solutions not only cover all the standard textbook exercises but also include important additional exam-oriented questions to ensure robust preparation.

What you will learn and get from these textual solutions:

• Clear explanations of major groups of microorganisms, fermentation, antibiotics, vaccines, and the nitrogen cycle.
• Accurate, point-wise answers for 1-mark objective questions (VSA) and 2-3 mark short textual questions.
• Standard and easy-to-understand explanations for 4-5 mark long descriptive questions, such as common human diseases caused by microbes and food preservation techniques.
• Complete coverage of end-of-chapter exercises, fill-in-the-blanks, matching questions, and scientific definitions.
• Extra important questions aligned with the new syllabus structure alongside standard MCQ solutions.

Exclusive features of Ospin Academy’s solutions:

• Fully textbook-based answers formulated strictly according to the latest ASSEB new syllabus guidelines.
• 100% accurate, high-quality notes written in simple English language for effortless memorization and understanding.
• Concise summaries and targeted answers specifically designed for quick revision before examinations.
• A curated selection of highly probable extra questions to give students a competitive edge.

Committed to the academic excellence of students, Ospin Academy offers these high-quality textual solutions. Start your preparation today to master the concepts of Science and achieve top scores in your upcoming examinations.

Class 8 Science

Chapter – 2                                       Ospin Academy

Micro Organisms: Friends and Foe

TEXTBOOK EXERCISES

Q. 1. Fill in the blanks.

(a) Microorganisms can be seen with the help of a __________.

Ans. microscope.

(b) Blue green algae fix _________ directly from air to enhance fertility of soil.

Ans. atmospheric nitrogen.

(c) Alcohol is produced with the help of _________.

Ans. yeast.

(d) Cholera is caused by _________.

Ans. bacteria.

Q. 2. Tick the correct answer:

(i) Yeast is used in the production of:

(a) sugar.

(b) alcohol.

(c) hydrochloric acid.

(d) oxygen.

Ans. (b) alcohol.

(ii) The following is an antibiotic:

(a) Sodium bicarbonate.

(b) Streptomycin.

(c) Alcohol.

(d) Yeast.

Ans. (b) Streptomycin.

(iii) Carrier of malaria-causing protozoan is:

(a) female Anopheles mosquito.

(b) cockroach.

(c) dragonfly.

(d) butterfly.

Ans. (a) female Anopheles mosquito.

(iv) The most common carrier of communicable disease is:

(a) ant.

(b) housefly.

(c) dragonfly.

(d) spider.

Ans. (b) housefly.

(v) The bread or idli dough rises because of:

(a) heat.

(b) grinding.

(c) growth of yeast cells.

(d) kneading.

Ans. (c) growth of yeast cells.

(vi) The process of conversion of sugar into alcohol is called:

(a) nitrogen fixation.

(b) moulding.

(c) fermentation.

(d) infection.

Ans. (c) fermentation.

Q. 3. Match the organisms in Column I with their action 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) Causes 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) Causes Malaria.
(vi) A virus	(f) Causing AIDS

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

Ans. No, microorganisms cannot be seen with the naked eye because they are too small. We can only see them under microscope.

Q. 5. What are the major groups of Microorganisms?

Ans. Microorganisms can mainly be divided into five groups:

(i) Bacteria.

(ii) fungi.

(iii) protozoa.

(iv) algae.

(v) virus.

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

Ans. Bacteria like Rhizobium, Azotobacter, Blue green algae like Anabaena and Nostoc can fix atmospheric nitrogen in soil.

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

Ans. Microorganisms are very useful to us.

They help us in the following ways:

(i) Microorganisms help us in food sector. They are used for curdling of milk, preparation of bread, cake, etc.

(ii) Microorganisms are used to produce alcohol at large scale.

(iii) They are also used to produce wine.

(iv) Yeast is used to prepare vinegar.

(v) They are also used as preservatives for food items.

(vi) Used to make different medicines especially the antibiotics.

(vii) Microorganisms are used to prepare vaccines for various diseases.

(viii) Useful for agriculture sector, as they enhance the fertility of soil by fixing the biological nitrogen.

(ix) They work as natural cleansers as they decompose the dead bodies of plants and animals.

(x) Microorganisms prepare manures by decomposing dead bodies of plants and animals.

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

Ans. Harmful effects of Microorganisms: Microorganisms can prove very harmful to us, as they cause a number of human and animal diseases. Diseases in humans like common cold, tuberculosis, measles, chicken pox, Polio, Cholera, Typhoid, Hepatitis B, Malaria, etc., are caused by microorganisms. Some serious disease slike Anthrax is also caused in animals by the microbes. Microbes grow on food products and render them unfit for consumption. Consumption of such food causes food poisoning. Microbes also spoil clothings and leather products. Microbes also cause diseases of plants like blights in potatoes, sugarcanes, oranges etc. They also reduce the yield.

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

Ans. Medicines taken to kill or stop the growth of harmful or disease causing microbes in human body are called antibiotics. Antibiotics are very useful as only antibiotics can save us from many microbial infections and diseases. Antibiotics are made from fungi and bacteria. Alexander Fleming discovered the first antibiotic called Penicillin in 1929. Now-a-days a number of antibiotics are used to cure a variety of human and animal diseases. Streptomycin, Tetracycline, Erythromycin etc., are some commonly used antibiotics.

Antibiotics should only be taken when advised by a qualified physician. Antibiotics should only be taken when needed otherwise, they become less effective for future use.