NCERT Class 12 Biology Biology: Chapter 8 — MICROBES IN HUMAN WELFARE
Chapter 8 of the NCERT Class 12 Biology textbook, 'Microbes in Human Welfare,' introduces the crucial role of microorganisms in various aspects of human life. It highlights that microbes, including protozoa, bacteria, fungi, viruses, viroids, and prions, are ubiquitous and found in diverse environments, from soil and water to extreme conditions like hot springs and thick snow. The chapter details their applications in household products, industrial processes, sewage treatment, biogas production, and their function as biocontrol agents and biofertilizers. Understanding these microscopic organisms is vital for appreciating their impact on ecosystems and their utility in sustainable human practices, forming a key part of the CBSE curriculum.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 12 |
| Subject | Biology |
| Book | Biology |
| Chapter | Chapter 8 — MICROBES IN HUMAN WELFARE |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 2 minutes |
| Word count | 289 |
Learning outcomes
- Identify the diverse habitats and types of microbes.
- Understand the role of microbes in household and industrial products.
- Explain the application of microbes in sewage treatment and biogas production.
- Recognize microbes as biocontrol agents and biofertilizers.
Vocabulary
| Word | Meaning |
|---|---|
| Microbes | Microscopic organisms such as bacteria, fungi, viruses, etc. |
| Protozoa | Single-celled eukaryotic microorganisms. |
| Bacteria | Single-celled prokaryotic microorganisms. |
| Fungi | A kingdom of eukaryotic organisms that includes yeasts, molds, and mushrooms. |
| Viruses | Infectious agents that replicate only inside the living cells of other organisms. |
| Viroids | Infectious RNA particles smaller than viruses. |
| Prions | Proteinaceous infectious agents that cause neurodegenerative diseases. |
| Nutritive media | A substance providing nourishment for the growth of microorganisms. |
| Colonies | Visible masses of microorganisms growing on a solid medium. |
The complete chapter text is read in the official NCERT PDF viewer below (streamed from ncert.nic.in). This page provides NCERT Help study material — summary, vocabulary, practice questions, and FAQs — not a full reproduction of the textbook.
Read chapter online
This PDF is loaded from the official NCERT website (ncert.nic.in). Use the page buttons below to read — download is disabled on NCERT Help.
Read page by page below. PDF is streamed from the official NCERT website — no download button on this page.
Practice questions
- Where are microbes found? Answer: Microbes are found everywhere – in soil, water, air, inside our bodies, and in extreme environments like hot springs and under snow.
- Name the different types of microbes mentioned in the chapter. Answer: The types of microbes mentioned are protozoa, bacteria, fungi, viruses, viroids, and prions.
- What are prions? Answer: Prions are proteinaceous infectious agents.
- What is used to grow microbes in laboratories? Answer: Microbes are grown on nutritive media to form colonies.
Practice MCQs
Q1. Which of the following is NOT a type of microbe mentioned in the text?
Explanation: The text lists protozoa, bacteria, fungi, viruses, viroids, and prions as microbes. Algae are not explicitly mentioned in this introductory section.
Q2. Microbes can survive in extreme environments such as:
Explanation: The chapter states that microbes are present even in sites where no other life-form could possibly exist, including deep soil, under snow, in acidic environments, and in thermal vents.
Q3. What are proteinaceous infectious agents called?
Explanation: The text defines prions as 'proteinacious infectious agents'.
Q4. Microbes like bacteria and fungi can be grown on:
Explanation: The chapter mentions that bacteria and fungi can be grown on nutritive media to form colonies.
Q5. Which Kingdom among living organisms contains micro-organisms?
Explanation: While not explicitly detailed in this excerpt, the question refers to Class XI knowledge, implying that Monera (bacteria), Protista (protozoa), and Fungi all contain microorganisms.
Frequently asked questions
What are the main categories of microbes discussed in Chapter 8?
The chapter discusses protozoa, bacteria, fungi, viruses, viroids, and prions.
Can microbes survive in extreme conditions?
Yes, microbes can survive in extreme conditions such as high temperatures (like in geysers), deep soil, thick snow, and highly acidic environments.
What is the significance of microbes in human welfare?
Microbes play significant roles in household products, industrial production, sewage treatment, biogas generation, and as biocontrol agents and biofertilizers.
What are viroids and prions?
Viroids are infectious RNA particles, while prions are proteinaceous infectious agents.
How are microbes studied in laboratories?
Microbes are grown on nutritive media to form colonies, which are then used for studies.
What is the role of microbes in industrial products?
Microbes are used in the industrial production of various products, which will be detailed further in the chapter.
Related resources
Important topics
Topics covered
NCERT Class 12 Biology — Biology — Chapter 8 — MICROBES IN HUMAN WELFARE. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.