Microorganisms Friend and Foe class 8 questions and answers: Science Class 8 chapter 2 question answer
| Textbook | Ncert |
| Class | Class 8 |
| Subject | Science |
| Chapter | Chapter 2 |
| Chapter Name | Microorganisms Friend and Foe ncert solutions |
| Category | Ncert Solutions |
| Medium | English |
Are you looking for Class 8 Science chapter 2 question answer? Now you can download ncert solutions for class 8 science chapter 2 pdf from here.
Question 1: Fill in the blanks.
(a) Microorganisms can be seen with the help of a _______.
(b) Blue green algae fix _______ directly from air and enhance fertility
of soil.
(c) Alcohol is produced with the help of _______.
(d) Cholera is caused by _______.
Answer 1: (a) Microscope
(b) Nitrogen
(c) Yeast
(d) Bacteria (Vibrio cholera)
Question 2: Tick the correct answer.
(a) Yeast is used in the production of
(i) sugar (ii) alcohol (iii) hydrochloric acid (iv) oxygen
(b) The following is an antibiotic
(i) Sodium bicarbonate (ii) Streptomycin (iii) Alcohol (iv) Yeast
(c) Carrier of malaria-causing protozoan is
(i) female Anopheles mosquito (ii) cockroach (iii) housefly (iv) butterfly
(d) The most common carrier of communicable diseases is
(i) ant (ii) housefly (iii) dragonfly (iv) spider
(e) The bread or idli dough rises because of
(i) heat (ii) grinding (iii) growth of yeast cells (iv) kneading
(f) The process of conversion of sugar into alcohol is called
(i) nitrogen fixation (ii) moulding (iii) fermentation (iv) infection
Answer 2:
- a) (ii) alcohol
- b) (ii) Streptomycin
- c) (i) female Anopheles mosquito
- d) (ii) housefly
- e) (iii) growth of yeast cells
- f) (iii) fermentation
Question 3: Match the organisms in Column A with their action in Column B.
| A | B |
| (i) Bacteria | (a) Fixing nitrogen |
| (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 |
Answer 3:
| A | B |
| (i) Bacteria | (e) Causing cholera |
| (ii) Rhizobium | (a) Fixing nitrogen |
| (iii) Lactobacillus | (b) Setting of curd |
| (iv) Yeast | (c) Baking of bread |
| (v) A protozoan | (d) Causing malaria |
| (vi) A virus | (f) Causing AIDS |
Question 4: Can microorganisms be seen with the naked eye? If not, how can they be seen?
Answer 4: The microorganisms cannot be seen with our naked eyes because they are very small in size. Some of these, such as fungus growing on bread, can be seen with a magnifying glass. Others cannot be seen without the help of a microscope.
Question 5: What are the major groups of microorganisms?
Answer 5: The major groups of microorganisms include:
- Bacteria
- Virus
- Fungi
- Algae
- Protozoa
Question 6: Name the microorganisms which can fix atmospheric nitrogen in the soil.
Answer 6: Bacteria: Rhizobium, Azotobacter, Clostridium, Frankia
Question 7: Write 10 lines on the usefulness of microorganisms in our lives.
Answer 7: Some of the usefulness of microorganisms in our lives is mentioned below.
- Food Production: Microorganisms like Lactobacillus help in making curd, cheese, and yogurt.
- Fermentation: Yeast (Saccharomyces cerevisiae) is used in baking and brewing industries.
- Medicine: Many antibiotics, like penicillin, are produced by fungi and bacteria.
- Nitrogen Fixation: Bacteria like Rhizobium help improve soil fertility by fixing nitrogen.
- Decomposition: Microorganisms break down organic waste and recycle nutrients in nature.
- Biogas Production: Anaerobic bacteria help produce biogas from organic waste.
- Genetic Engineering: Microbes are used in biotechnology to create vaccines and insulin.
- Water Treatment: Microorganisms help in sewage treatment by breaking down pollutants.
- Pest Control: Certain bacteria like Bacillus thuringiensis act as natural pesticides.
- Probiotics: Beneficial bacteria improve gut health and digestion in humans.
Question 8: Write a short paragraph on the harmful effects of microorganisms.
Answer 8: Microorganisms can harm us in some ways. For instance, pathogens are microbes that cause human, plant, and animal diseases. Viruses are the source of many common illnesses, such as chicken pox, polio, cough, and influenza. Bacteria cause tuberculosis, typhoid, and the deadly animal and human disease anthrax. Protozoa produce diseases, including malaria and dysentery. Furthermore, food deterioration and food poisoning are caused by microorganisms.
Question 9: What are antibiotics? What precautions must be taken while taking antibiotics?
Answer 9: Antibiotics are medicines that kill or inhibit the growth of bacteria. They are used to treat bacterial infections, such as pneumonia, tuberculosis, and strep throat. Examples include penicillin, amoxicillin, and erythromycin.
Precautions While Taking Antibiotics:
- Take antibiotics only when prescribed by a doctor.
- Complete the full course, even if you feel better.
- Do not skip doses or stop early to prevent antibiotic resistance.
- Avoid self-medication, as the wrong antibiotic can be ineffective or harmful.
- Do not use antibiotics for viral infections like colds or flu.
- Maintain proper dosage and timing as advised by the doctor.
- Inform your doctor about allergies or side effects.
- Avoid alcohol, as it may interfere with antibiotic effectiveness.
- Take antibiotics with food or water if recommended to prevent stomach upset.
- Store antibiotics properly and never share them with others.