NCERT Class 12 Biology Chapter 8: Microbes in Human Welfare PDF Notes with Examples

Chapter 8 of Class 12 Biology, Microbes in Human Welfare, explains how microscopic organisms that we usually fear can actually help us. These microbes play a vital role in making curd, cleaning waste, making alcohol, controlling pests, and even in producing antibiotics. This chapter helps students understand the useful side of microbes, especially in agriculture, industry, and environment.

I chose to write about this chapter because students often ignore it thinking it’s just about examples. But NCERT includes many match-the-following type questions, MCQs, and application-based questions from this chapter. It’s also quite useful for NEET biology. The content is full of real-world applications like biofertilisers, sewage treatment, and genetically modified organisms. Once you relate it to your surroundings — like the curd in your fridge or the smell from compost — this chapter becomes very easy and interesting to revise. By reading and downloading the PDF from NCERT, students can strengthen their base and write better answers in exams.

Key Concepts of Microbes in Human Welfare – Class 12 Biology

This chapter is all about the beneficial uses of microorganisms. While microbes like bacteria, fungi, and protozoa can cause diseases, this chapter focuses on their positive uses.

Microbes in Household Products

Microbes are part of many things we consume or use daily.

Lactobacillus is used to make curd from milk
Yeast (Saccharomyces cerevisiae) is used in baking bread and making alcoholic beverages
Traditional Indian foods like idli, dosa, and dhokla use fermentation by natural microbes
Toddy, a fermented drink, is made by fermenting sap from palm plants

Microbes in Industrial Production

Microbes are used in producing:

Product	Microorganism Used
Alcohol, Wine, Beer	Saccharomyces cerevisiae (yeast)
Antibiotics (e.g., Penicillin)	Penicillium notatum
Citric acid	Aspergillus niger
Acetic acid	Acetobacter aceti
Lactic acid	Lactobacillus

Fermenters or bioreactors are used for large-scale production of these products in industries.

Microbes in Sewage Treatment

Microbes are used in treating wastewater to make it less harmful before releasing it into rivers.

Primary treatment removes large solids
Secondary treatment uses aerobic bacteria to remove organic matter
The activated sludge formed contains bacteria that digest waste
Biogas is also produced as a by-product, which can be used as fuel

Microbes in Biogas Production

Anaerobic bacteria called Methanogens are used in gobar gas plants

These bacteria are found in the rumen of cattle
They break down waste material to release methane, a flammable gas
Biogas plants are widely used in rural India for fuel and manure

Microbes as Biocontrol Agents

Instead of chemical pesticides, some microbes can be used to control pests naturally

Bacillus thuringiensis (Bt) produces a toxin that kills insect larvae
Bt toxin genes are inserted into cotton plants to make Bt-cotton
Fungi like Trichoderma are used to control plant pathogens
Ladybirds and dragonflies also act as biocontrol agents in organic farming

Microbes as Biofertilisers

Microbes help in improving soil fertility without chemical fertilisers

Rhizobium fixes nitrogen in legume root nodules
Azotobacter and Azospirillum are free-living nitrogen-fixers
Mycorrhiza is a fungus that helps plants absorb water and nutrients
Blue green algae like Anabaena and Nostoc are used in paddy fields

These methods help in sustainable and eco-friendly farming.

Important Diagrams to Revise

Diagram of biogas plant
Bioreactor or fermenter structure
Stages in sewage treatment
Rhizobium-root nodule interaction

These visuals make the chapter easier to understand and are important for boards and NEET.

Download PDF – NCERT Class 12 Biology Chapter 8

To download the original NCERT PDF of Chapter 8, follow these simple steps:

NCERT Class 12 Biology Chapter 8

Global Environmental Politics Explained – Question Paper

Environmental protection has become one of the most important global concerns in modern politics. Over the past few decades, issues such as climate change, pollution, depletion of natural resources and environmental degradation have forced governments around the world to work together. These problems do not remain confined within national borders; they affect the entire planet. Because of this, environmental issues are now discussed at international forums and global summits where countries attempt to find collective solutions.

I am writing about this topic because environmental issues are no longer just scientific or ecological concerns; they have become central to global politics and international relations. Governments must balance economic development with environmental protection, which often leads to debates between developed and developing countries. Understanding these discussions helps students and readers see how international agreements, environmental movements and global cooperation shape policies that affect the future of the planet.

Why Environmental Issues Matter in Global Politics

Environmental problems have gradually become part of international politics because they affect all countries and populations. Issues such as rising global temperatures, deforestation, water scarcity and pollution are global challenges that require cooperation among nations.

Some major environmental concerns include:

Climate change and rising global temperatures
Rapid depletion of natural resources
Pollution of air, water and soil
Loss of biodiversity and forests
Shortage of clean drinking water

Since these problems cross national boundaries, they require coordinated international action.

Major Global Environmental Conferences

International conferences have played a crucial role in raising awareness about environmental protection and promoting global cooperation.

One of the most important global meetings on the environment took place in Rio de Janeiro in 1992. This summit brought together leaders from many countries to discuss environmental protection and sustainable development. The meeting produced important guidelines and action plans aimed at protecting the planet while supporting economic development.

These conferences helped establish the idea that environmental protection should be a shared responsibility among all nations.

The Concept of Sustainable Development

A key concept that emerged from global environmental discussions is sustainable development. This idea focuses on meeting present needs without compromising the ability of future generations to meet their own needs.

Sustainable development aims to balance three important goals:

Economic growth
Social development
Environmental protection

Governments and international organisations now use this concept to guide development policies and environmental strategies.

Understanding Global Commons

Certain natural resources belong to everyone and cannot be owned by any single country. These shared resources are often referred to as global commons.

Examples of global commons include:

The Earth’s atmosphere
Antarctica
The ocean floor
Outer space

Since no single country owns these areas, international agreements are needed to regulate their use and ensure that they are protected for future generations.

Download this B-1 Environment and Natural Resources WS 1 PDF File: Click Here

Environmental Movements Around the World

Environmental movements have played a significant role in bringing attention to ecological issues. Many activists and communities have raised awareness about deforestation, pollution and large development projects that threaten natural ecosystems.

These movements often focus on protecting forests, wildlife and natural resources while supporting the rights of local communities that depend on these resources for their livelihoods.

Such movements have influenced government policies and encouraged stronger environmental regulations.

Indigenous Communities and Environmental Protection

Indigenous communities are among the most affected by environmental degradation. These groups have traditionally lived close to nature and depend on forests, land and water for survival.

In many parts of the world, indigenous people have organised themselves to protect their rights and preserve their traditional ways of life. Their knowledge of sustainable living and natural resource management has become increasingly valuable in discussions about environmental protection.

International organisations and environmental groups now recognise the importance of involving indigenous communities in environmental decision-making.

Global Agreements on Climate Change

To address climate change and environmental degradation, countries have signed several international agreements. These agreements aim to reduce greenhouse gas emissions, promote clean energy and protect the global environment.

Some key objectives of international environmental agreements include:

Reducing harmful emissions that contribute to global warming
Promoting renewable energy sources
Protecting ecosystems and biodiversity
Encouraging cooperation among nations

These agreements highlight the need for collective responsibility in protecting the environment.

Differences Between Developed and Developing Countries

One of the major debates in environmental politics revolves around the responsibilities of developed and developing countries. Developed countries have historically contributed more to environmental degradation because of industrialisation.

Developing countries, on the other hand, argue that they still need economic growth to improve living standards. Therefore, they emphasise the principle that environmental responsibilities should be shared but should also consider different levels of development.

This idea is often described as the principle of “common but differentiated responsibility”.