Environmental Issues Class 12 Notes CBSE Biology Chapter 16 (Free PDF Download) (Not present in the current syllabus)

Section–A (1 Mark Questions)

1. When did the Air Prevention and Control of Pollution Act come into force?

Ans. Indian government attempted to combat air pollution and brought the air prevention and control of pollution act in 1981.

2. What is biomagnification? 

Ans. The concentration of DDT increases with every increase in the trophic level in the food pyramid. This s known as biomagnification.

3. Which method is the most suitable for the disposal of nuclear waste?

Ans. Storage of nuclear waste should be done in suitably shielded containers and buried within rocks deep below the Earth's surface (500 m deep)

4. Why is lead-free petrol or diesel recommended to reduce pollutants emitted by automobiles?

Ans. Automobiles fitted with catalytic converters are used to prevent air pollution. It is recommended not to use leaded petrol or diesel as lead inactivates the catalyst of the converter.

5. What is Joint Forest Management Concept?

Ans. The joint forest management concept was introduced in the 1980s, as an attempt to clear conflicts and bring out better-coordinated forest conservation, between the government and the small local groups residing near the area. 

Section–B (2 Mark Questions)

6. What is the difference between good and bad ozone?

Ans. The stratosphere extends up to a height of 50 km from the Earth's surface. 

• It is characterized by the presence of a thick ozone layer which is formed by the effect of ultraviolet radiations on oxygen. This layer is referred to as good ozone. 

• Ozone, in small amounts, is present in the troposphere, which is known to cause harm to plants and animals, hence called bad ozone. 

7. What is the importance of green house effect? Name few of the gree house gases.

Ans. The greenhouse gases methane, carbon dioxide, etc. are responsible for the greenhouse effect. The greenhouse effect is a naturally occurring phenomenon that is responsible for the heating of the Earth’s surface and the atmosphere.

8. What do you mean by accelerated eutrophication?

Ans. Cultural or accelerated eutrophication is nutrient enrichment of water bodies due to human activities like the passage of sewage, industrial effluents, and runoff from fertilized fields rich in nitrates and phosphates. 

9. Why Bharat stage IV emission norms have been applied?

Ans. Bharat stage IV emission norms have been in place since April 2010, for 4 wheelers in 13 megacities of India by the Government of India to regulate the emission of air pollutants from internal combustion engine equipment of motor vehicles. 

10. How BOD is used as a measure of water pollution?  

Ans. Biochemical oxygen demand is the amount of oxygen required for the oxidation of organic matter by microorganisms present in water. Hence, BOD is directly proportional to the amount of biodegradable organic matter in water or water pollution.

PDF Summary - Class 12 Biology Environmental Issues Notes (Chapter 16)

Any undesirable change that occurs in physical, chemical, or biological characteristics of air, land, water, or soil is known as pollution. The agents that are responsible for such undesirable changes are called pollutants. The  Government of India has passed the Environment (Protection) Act, 1986 to protect and improve the quality of our environment by controlling environmental pollution.  

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Sources of Pollution 

There are different sources of pollution. They are mentioned below in fig.2. 

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Air Pollution and Its Control 

Air pollution is harmful to both plants and animals. Air pollution affects the growth and yield of crops. They affect the respiratory system of humans. Particulate and gaseous air pollutants are released from thermal power plants, smelters, and other industries. These pollutants are very harmful, they should be filtered out before they should be released into the environment. For the removal of particulate matter, the most widely used method is an electrostatic precipitator. If the particulate matter has been inhaled it will cause breathing and respiratory symptoms, inflammations, irritations, and also premature deaths.  

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Electrostatic Precipitator

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Another major cause of atmospheric pollution in metro cities is the excessive use of automobiles.  In automobiles to prevent the emission of poisonous gases from them, catalytic converters, having expensive metals namely platinum-palladium and rhodium as the catalysts are fitted into automobiles. The use of unleaded petrol or diesel can reduce toxic emissions. The Air (Prevention and Control of Pollution) Act came into force in 1981 In India in the year 1981 the Air act came into force for prevention and control of pollution too. In the year 1987, the Air act was amended to include noise as an air pollutant.

Controlling Vehicular Air Pollution: A Case Study of Delhi 

In its level of air pollution, Delhi the capital of India leads the country. Air pollution in Delhi became so severe that public interest litigation  (PIL) was filed in the Supreme Court of India. The supreme court had advised public vehicles to switch from diesel to compressed natural gas (CNG). Since CNG is cheap it burns efficiently and very little of it is left unburnt that is why it is preferred. Other methods were also used to reduce pollution in Delhi such as the use of unleaded petrol, phasing out of old vehicles, use of low Sulphur petrol, etc.

Water Pollution and Its Control 

With the increase in pollution in water, the government has passed the Water (Prevention and Control of Pollution) Act, 1974  to safeguard our water resources.

Domestic Swage and Industrial Effluents 

The presence of ${ 0.1 }$% impurities in domestic sewage makes it unfit for human use. Solids are easy to remove, but dissolved salts such as nitrates, phosphates, and other nutrients are difficult to remove. Domestic sewage primarily contains biodegradable organic matter which can be decomposed using microorganisms. Biological oxygen demand can be used to measure the amount of biodegradable organic matter in sewage water. The presence of high amounts of nutrients in waters also results in excessive growth of planktonic (free-floating) algae in the water bodies, this is referred to as algal bloom which gives a distinct color to the water bodies.  

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Biomagnification: The increase in the concentration of toxicants at successive trophic levels is known as biomagnification. It occurs because the toxicant itself cannot be digested by an organism and is, therefore, is passed on to the next trophic level on consumption. 

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Biomagnification of DDT 

Eutrophication is defined as the aging of the lakes due to nutrient enrichment. A young lake is cold and clear. From different sources like surface run-off, streams, etc the nutrients are introduced in it. This will increases the fertility of the lake and also promote the growth of aquatic organisms. Over time, the lake becomes shallower due to the deposition of silt and organic debris. Then the lake is taken over by the warm water plants and marsh plants. Slowly the lake is populated by floating plants and eventually, the lake is converted to land. 

The size of the lake and other factors such as the natural aging of a lake may span thousands of years depending on the climate of that area. Pollutants created from human activities like industrial and domestic effluents can radically speed up the aging process. This concept is known as Cultural or Accelerated Eutrophication. The rapid growth of algae is promoted by the pollutants like nitrates and phosphates. This will result in a decrease in the amount of dissolved oxygen available to other aquatic organisms. Thus,  due to increased water pollution, a lake can choke to death.

Sources of Water Pollution 

There are two sources of water pollution- 

• Point sources are those sources that arise from a single, identifiable source. For example, pipe or ditch. 

• Non-point sources are those sources that arise from diffuse contaminants from more than one point or source.  For example, nutrient run-off from the agricultural land.

Effects of water pollution 

• Death of aquatic animals may occur due to depletion of oxygen. 

• Imbalance of ecosystem. 

• Contaminated water causes various diseases. Some deadly diseases like cholera,  dysentery, diarrhea, tuberculosis, jaundice, etc are caused because of polluted water. Approximately 80 percent of diseases associated with stomachs The electronic water-repellant in India are caused by polluted water.

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A Case Study of Integrated Waste Water Treatment

Artificial and natural processes are used for wastewater treatment. It involves- 

• Conventional sedimentation followed by the process of filtration and chlorine treatment.  

• After the completion of the first step, the biologists formed a series of six connected marshes which were spread over 60 hectares of marshland.  In this marshland, suitable plants, algae, fungi, and bacteria were seeded. They neutralize, absorb and assimilate the pollutants. In this way, the water gets purified naturally as it flows through the marshes. 

Solid Wastes 

Waste from the offices, schools, stores, hospitals constitutes municipal solid wastes. The dumping of these wastes gives birth to flies and rats. Sanitary landfills consist of depressions or trench where waste is dumped. Waste is categorized as biodegradable, non-biodegradable, and recyclable.  The biodegradable wastes can be buried in soil and are allowed to get decompose into harmless by-products.  Non-biodegradable wastes cannot be naturally broken down. Their use therefore must be reduced. Recyclable wastes are substances that can be used to retrieve at least a few useful substances. Non-biodegradable wastes must be recycled as much as possible. Hospital wastes are hazardous. They must be properly incinerated to prevent contamination and the spread of that too dangerous pathogens and chemicals. 

The electronic waste must be recycled to obtain useful metals. in developing countries, This process is still done manually. This will cause a high risk of exposure of the workers towards the toxic substances.

Case Study of Remedy for Plastic Waste 

In Bangalore, a plastic sack manufacturer named Ahmed Khan developed an answer to the ever-increasing plastic waste. The answer developed was Polyblend. Polyblend may be a fine powder made from recycled plastic waste. They are often mixed with bitumen and used for laying roads. This increases the water-repellant properties of bitumen and thus increases the lifetime of the road.

Agrochemicals and Their Effects

The use of fertilizers and pesticides has increased manifold for crop production. Excessive use of chemical fertilizers causes adverse effects on soil fertility and crop yield. They may cause soil, water, and also air pollution.

Case Study of Organic Farming:

The method of integrated organic farming is an eco-friendly and cyclical procedure that generates zero waste. In this method, the waste products from one process are cycled and used as nutrients for other processes. This allows the utmost utilization of resources and increases the efficiency of production. Crop waste also can be used as a natural fertilizer within the sort of compost.

Radioactive Wastes

Radiations emitted from nuclear waste are extremely harmful. It affects both plants and animals because it causes mutations. At high doses, nuclear radiation is lethal but at lower doses, it creates various disorders, the foremost frequent of all being cancer. Therefore, nuclear waste is a particularly potent pollutant and has got to be addressed with utmost caution.

Green-House Effect and Global Warming

Sun rays reach the earth and warm the earth’s atmosphere. The earth’s atmosphere traps the sun rays which increases the temperature of the earth. This is known as the greenhouse effect. Carbon dioxide, methane, acid, water vapor acts as greenhouse gases. An increase in the concentration of these gases traps more sunlight which raises the earth’s temperature. This is known as global warming. As the temperature is raised, it causes melting of glaciers, changes in the weather, oxygen depletion, climate change will affect food production and agriculture also.

Ozone Depletion in the Stratosphere 

Ozone is present in the stratosphere which protects the atmosphere from harmful ultraviolet radiation. Ultraviolet radiations are very harmful to live organisms. They are harmful to DNA and proteins present in living organisms.  To measure the thickness of the ozone layer in a column of air from the ground to the top of the atmosphere the unit used is known as the dobson unit. Oxygen when absorbs ultraviolet rays, breaks into oxygen atoms. Ozone is formed when oxygen atoms combine with oxygen.  

The major cause of ozone depletion is a group of chemicals called chlorofluorocarbon (CFCs) such as Freon. CFCs are used in refrigerators. These CFCs in the atmosphere absorbs ultraviolet rays and forms chlorine free radical.

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Due to chlorofluorocarbons which are widely used in refrigerators, the ozone layer gets depleted. Degradation of ozone causes ozone holes. The atmosphere completely absorbs the UV radiations that have wavelengths shorter than UV-B. UV-B rays are dangerous and damages living organisms. They cause skin cancers, inflammation of the cornea, cataracts, etc. An international treaty, known as the Montreal Protocol, was signed in Montreal  (Canada) in the year 1987 (effective in 1989) to control the emission of ozone-depleting substances. This was done after recognizing the deleterious effects of ozone depletion.

Degradation by Improper Resource Utilization and Maintenance: 

Soil Erosion and Desertification: Fertile topsoil takes centuries to form. Soil erosion takes place due to human activities like over-grazing, over-cultivation, deforestation, and poor irrigation practices. This leads to the loss of topsoil and the formation of arid land. This will eventually lead to desertification and is a major threat to soil integrity because of rapid urbanization. 

Waterlogging and Soil Salinity: Improper drainage of water leads to waterlogging of the soil. Accumulation of water also causes attraction and dissolution of water-soluble salts. These salts are then deposited on the soil surface as a thin crust or collected around the plant roots. An increase in the salinity of soil affects plant growth and also damages agriculture. The green revolution has played a major role in increased waterlogging and soil salinity.

Deforestation: The complete removal of forest and tree cover due to reckless felling of trees is called deforestation and it is caused due to human activities.

Causes of Deforestation: 

1. Conversion of forests to farmlands: Forests are cleared by cutting of trees and burning stumps. The land is used for cultivation and the ash is used as fertilizer. After the cultivation of crops, the land is left fallow to allow the soil nutrients to regenerate. Lands do not get enough time to recover and form forests because of the rapid increase in population. 

2. Urbanization: Rapid urbanization has led to the indiscriminate clearing of forests for various purposes such as agriculture, housing, industrialization, etc. 

Reforestation: The process by which restoration of forest covers is done to a place where forests once existed but were cleared off. It can occur naturally with sufficient time. The process can be sped up by human intervention involving planting plants and trees. 

Case Study of Participation of People  in Conservation of Forests: 

Bishnoi/Amrita Devi Bishnoi: The Bishnoi community peacefully co-exists with nature. In 1731, a forest nearby their village was ordered to be cleared by the King of Jodhpur. Amrita Devi, her family, and around 200 members of her village died protecting the trees. In her honor, the Government of India instituted an award called the “Amrita Devi Bishnoi Wildlife  Protection Award”. This is awarded to individuals or communities who are showing extraordinary courage and dedication in protecting wildlife. 

Chipko Movement: Local women of the Garhwal region in 1974 protected the trees against felling by hugging them. 

Joint Forest Movement: It is an initiative by the Government of India in the 1980s. It aims towards the involvement of local communities and people in the sustainable development of forests. 

Class 12 Revision Notes Chapter 16 PDF

The best part about these Class 12 Notes Environmental Issues by Vedantu is that these are free of cost and are available for download in PDF format. If students wish, they can print the Chapter 16 Environmental Issues Notes, which come in very handy, especially before an examination. The Notes Class 12 Biology Chapter 16 help students brush up on their knowledge in case they feel unsure about any particular topic.

NCERT Class 12 Revision Notes Biology Chapter 16 Solutions

Our NCERT Solutions Chapter 16 Class 12 Biology Notes cover the important points that the students need to be thorough with when they attempt the questions from the Environmental Issues chapter in their exam. The important points included in the Class 12 Environmental Issues Chapter 16 include:

Environmental Issues - What are They?

Environmental issues are the harmful effects caused to the environment because of human activities. It causes degradation in the quality of air, water, and soil. These unfavourable events cause environmental issues that affect the natural state of the environment.

Environmental Pollution

Pollution is an undesirable change caused to the chemical, biological, and physical composition of air, soil, and water. The wastes that cause pollution are called pollutants. The various pollution types include air, water, noise, soil, and radioactive pollution.

Understanding Global Warming

Global warming is the gradual increase in the temperature of the Earth. It happens when there is an increase in the level of greenhouse gases in the atmosphere. The greenhouse gases present in the atmosphere prevent heat captured from the sun from escaping to the outer space. These gases are thus, responsible for keeping the Earth warm. With the rise in the level of greenhouse gases, the Earth’s temperature also rises. This is an environmental concern that can cause problems to nature and, eventually, to humans. Global warming is caused because of industrialization, deforestation, vehicle emission, and farming in factories.

Solid Waste

Solid waste comes from offices, homes, hospitals, and schools that are disposed of by the town municipality. These comprise solid wastes like plastics, paper, glass, leather, and many more such things. Solid waste is either dumped or burnt in the sanitary landfill.

Depletion of Natural Resources

When the natural resources get depleted, then this too causes environmental pollution. The consumption of fossil fuels leads to the emission of greenhouse gas. This again causes a change in the climate and leads to global warming.

Electronic Wastes

Electronic wastes are basically electronic goods like computers that are unrepaired. These are called e-wastes, which are either buried in the landfills, or they are incinerated. The e-wastes that are generated in the developed countries are sent to the developing nations to recover metals like iron, copper, gold, nickel, etc. Recycling is the only way to treat the e-wastes, but care should be taken to carry out recycling in an environmentally friendly way.

Agro - Chemicals

Inorganic pesticides and fertilizers have seen a massive increase in use because of the green revolution. This helps to enhance the production of crops. The insecticides and pesticides are toxic, and these target the organisms in the ecosystem of the soil. These get biomagnified in the terrestrial ecosystem that causes eutrophication in the ecosystem of aquatic life.

Deforestation

Another major environmental concern is deforestation. This happens because of the destruction of trees that are used to make buildings. Trees are also cut for obtaining raw materials. Deforestation causes global warming, soil erosion, and also leads to extinction in biodiversity.

Others

Loss in biodiversity, depletion of the ozone layer, effects on marine life and increase in the carbon footprint are other factors that cause environmental issues.