Chapter 10: Microbes in Human Welfare Class 12 Biology NCERT Solutions

Explore the role of microbes in industries, sewage treatment, and biogas production with Chapter 10 NCERT Solutions. Download free PDFs for easy study. Scroll below for all solved questions.

To Help You Excel: NCERT Solutions for Class 12 Biology Chapter 10 – Microbes in Human Welfare

Our expertly curated NCERT Solutions for Chapter 10 offer detailed and student-friendly answers to all Intext and Exercise questions. These solutions are ideal for CBSE board preparation, NEET revision, and gaining conceptual clarity through real-life examples, illustrations, and keyword-based notes.

What You Will Learn in Chapter 10 – Microbes in Human Welfare

This chapter highlights how various microorganisms are used in industrial processes, health care, agriculture, and environmental sustainability.

Key Topics Covered:

1. Microbes in Household Products
– Role of Lactobacillus in curd formation
– Fermentation of dough and alcoholic beverages
– Use of yeast and other microbes in food preparation

2. Microbes in Industrial Products
– Production of antibiotics (penicillin) and organic acids
– Industrial enzymes and bioactive molecules
– Use of fermenters for large-scale production

3. Microbes in Sewage Treatment
– Primary and secondary treatment processes
– Role of aerobic and anaerobic microbes
– Formation and significance of biogas

4. Microbes in Biogas Production
– Anaerobic digesters and methanogens
– Steps in biogas formation
– Uses of biogas as renewable energy

5. Microbes as Biocontrol Agents
– Natural pest control through microbes
– Examples like Bacillus thuringiensis (Bt)
– Benefits over chemical pesticides

6. Microbes as Biofertilisers
– Role of cyanobacteria, Rhizobium, and mycorrhiza
– Biological nitrogen fixation and soil fertility

Why Use Our NCERT Solutions for Chapter 10?

These solutions break down technical terms and processes into easy-to-grasp explanations. They include neat diagrams, comparisons, and flowcharts that make revision quick and effective for exams.

Highlights of Our Solutions:

– Accurate, stepwise answers to all textbook questions
– Simple language with clear scientific explanations
– Diagrams of fermenters, sewage treatment, and biogas plants
– Summary tables of microbes and their uses
– Useful for CBSE and NEET preparation

NCERT Solutions for Chapter 10 – Microbes in Human Welfare

Intext Questions:
– Concise explanations of curd, alcohol, and antibiotic production
– Flowcharts for sewage treatment steps
– Real-world applications of microbes in daily life

Exercise Questions (Q.1 to Q.13):
– In-depth answers on antibiotics, biogas, and biofertilisers
– Conceptual questions about aerobic/anaerobic digestion
– Applications of Bt crops, Rhizobium, and methanogens
– Labelled diagrams for sewage treatment plant and fermenter

Download Chapter 10 Solutions PDF – Microbes in Human Welfare

Get easy access to fully solved NCERT questions in a neat PDF format for offline learning and revision.

What’s Inside the PDF:

– Updated and organized solutions for quick reference
– Clean diagrams and illustrations for better understanding
– All-important definitions and applications covered

Recommended Preparation Tips:

– Learn the steps and microbes involved in sewage treatment and biogas production
– Revise industrial products like antibiotics and organic acids with examples
– Practice diagrams of fermenters, STPs, and biogas units
– Compare chemical vs biological pest control methods
– Memorize microbial species and their specific uses in agriculture and industry

Additional Study Resources:

– Class 12 Biology Notes – Chapter 10
– NCERT Exemplar Solutions – Microbes in Human Welfare
– Flashcards for microbial types and industrial uses
– MCQs for NEET and board-level practice
– Summary tables of microbes and their roles

Explore the Power of Microbes for a Sustainable Future

Microorganisms are more than just microscopic beings — they are vital contributors to human life and the planet. With our NCERT solutions, you’ll not only prepare well for exams but also appreciate how microbes make the world a better place. Build a strong foundation for future studies in biotechnology, microbiology, and environmental science.

NCERT Solutions for Class 12 Biology Chapter 10 – Microbes in Human Welfare

Question 1. Bacteria cannot be seen with the naked eyes, but these can be seen with the help of a microscope. If you have to carry a sample from your home to your biology laboratory to demonstrate the presence of microbes under a microscope, which sample would you carry and why?

Answer: A sample of soil or stagnant water should be carried. These are rich in microbial populations like bacteria, fungi, algae, and protozoa. Under a microscope, these microbes can be easily observed.

Question 2. Give examples to prove that microbes release gases during metabolism.

Answer: Examples:

  • Dough used for making dosa and idli puffs up due to carbon dioxide release by fermenting microbes.
  • Swiss cheese develops large holes due to carbon dioxide produced by Propionibacterium shermanii.

Question 3. In which food would you find lactic acid bacteria? Mention some of their useful applications.

Answer: Lactic acid bacteria (LAB) are found in curd, cheese, and other fermented dairy products. They:

  • Convert lactose to lactic acid improving taste and texture.
  • Enhance vitamin B₁₂ content.
  • Suppress harmful gut bacteria.

Question 4. Name some traditional Indian foods made of wheat, rice, and Bengal gram (or their products) which involve the use of microbes.

Answer: Traditional Indian foods involving microbes:

  • Bread (wheat) – Yeast fermentation.
  • Idli, dosa (rice and black gram) – Fermented using Leuconostoc and Streptococcus species.
  • Dhokla, Bhatura – Fermented with lactic acid bacteria.

Question 5. In which way have microbes played a major role in controlling diseases caused by harmful bacteria?

Answer: Microbes produce antibiotics like:

  • Penicillin from Penicillium notatum.
  • Streptomycin and erythromycin to treat bacterial infections.

They also help in the production of vaccines against diseases like tuberculosis and diphtheria.

Question 6. Name any two species of fungi used in the production of antibiotics.

Answer:

  • Penicillium chrysogenum – Source of Penicillin.
  • Cephalosporium acremonium – Source of Cephalosporin.

Question 7. What is sewage? In which way can sewage be harmful to us?

Answer: Sewage is wastewater from homes and industries. It is harmful because it:

  • Reduces oxygen content in water, harming aquatic life.
  • Contaminates drinking water sources.
  • Spreads diseases through pathogenic microorganisms.

Question 8. What is the key difference between primary and secondary sewage treatment?

Answer:

Primary Treatment Secondary Treatment
Physical process – removal of large particles by sedimentation and filtration. Biological process – aerobic microbes decompose organic matter.

Question 9. Do you think microbes can also be used as a source of energy? If yes, how?

Answer: Yes, microbes are used in biogas plants where anaerobic bacteria digest organic waste to produce biogas, a renewable energy source. They also help in the production of Single-Cell Protein (SCP) as an alternative protein and energy source.

Question 10. Microbes can be used to decrease the use of chemical fertilizers and pesticides. Explain how this can be accomplished.

Answer: Microbes like Rhizobium fix atmospheric nitrogen, Azotobacter improves soil fertility, and Trichoderma acts as a biopesticide. Thus, biofertilizers and biopesticides reduce the need for chemical fertilizers and pesticides, promoting sustainable agriculture.

Question 11. Three water samples namely river water, untreated sewage water and secondary effluent discharged from a sewage treatment plant were subjected to BOD test. The samples were labelled A, B and C. BOD values were 20 mg/L, 8 mg/L and 400 mg/L respectively. Identify each sample.

Answer:

Sample BOD Value Identity
B 400 mg/L Untreated sewage water (most polluted)
C 20 mg/L Secondary effluent
A 8 mg/L River water (relatively clean)

Question 12. Find out the name of the microbes from which cyclosporin A and statins are obtained.

Answer:

  • Cyclosporin A – from Trichoderma polysporum.
  • Statins – from Monascus purpureus.

Question 13. Find out the role of microbes in the following and discuss it with your teacher.

(a) Single Cell Protein (SCP): Microbial biomass like Spirulina is used as a protein-rich food source, offering high nutrition and acting as an alternative to conventional animal and plant proteins.

(b) Soil: Microbes in soil decompose organic matter, recycle nutrients, fix nitrogen, and enhance soil structure and fertility, supporting sustainable agriculture.

Question 14. Arrange the following in decreasing order of their importance for human society: Biogas, Citric acid, Penicillin, and Curd.

Answer: Importance (most to least):

  1. Penicillin (life-saving antibiotic)
  2. Biogas (renewable energy)
  3. Curd (probiotic, nutritional food)
  4. Citric acid (industrial and food additive)

Question 15. How do biofertilizers enrich the fertility of the soil?

Answer: Biofertilizers enrich soil by:

  • Fixing atmospheric nitrogen (e.g., Rhizobium, Azospirillum).
  • Solubilizing phosphates (e.g., Phosphobacteria).
  • Decomposing organic matter.
  • Improving soil structure and fertility naturally.