Welcome to the NCERT Solutions for Class 12 Biology Chapter 16 – Environmental Issues! This chapter provides a comprehensive understanding of various environmental issues and challenges faced by our planet. The NCERT Solutions provided here have been created by subject matter experts in the field of Biology and are based on the latest syllabus and guidelines provided by the National Council of Educational Research and Training (NCERT).
This chapter covers a range of topics related to environmental issues such as air pollution, water pollution, global warming, climate change, and deforestation. It provides an in-depth understanding of the causes, consequences, and possible solutions to these environmental challenges.
The NCERT Solutions provided here offer a detailed explanation of the concepts covered in the chapter, along with step-by-step solutions to the questions provided in the NCERT textbook for Class 12 Biology. These solutions have been designed to help students develop a strong foundation in the subject and prepare for their exams more effectively.
In addition to the solutions, this guide also includes useful tips and tricks, sample papers, and important notes to help students prepare thoroughly for their exams. With these resources at their disposal, students can gain a deeper understanding of the subject and achieve better grades in their exams.
We hope that this guide proves to be a valuable resource for students and helps them understand and appreciate the importance of protecting our environment.
NCERT SOLUTIONS FOR CLASS 12 BIOLOGY Chapter 16 Environmental Issues – Exercises
Answer the following Questions.
Question1. What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.
The various constituents of domestic sewage are:
- dissolved salts such as nitrates, phosphates, etc., from detergents.
- toxic metal ions from paints, varnishes, etc.
- biodegradable organic matter from kitchen and toilet.
- pathogenic microorganisms in the faecal matter.
- The effects of sewage discharge on a river:
When organic wastes from the sewage enter the water bodies, it serves as a food source for micro-organisms such as algae and bacteria. As a result, the population of these micro-organisms in the water body increases. Here, they utilize most of the dissolved oxygen for their metabolism. This results in an increase in the levels of Biological oxygen demand (BOD) in river water and results in the death of aquatic organisms. Also, the nutrients in the water lead to the growth of planktonic algal, causing algal bloom. This causes deterioration of water quality and fish mortality.
Question2. List all the wastes that you generate, at home, school or during your Trips to other places, could you very easily reduce? Which would be Difficult or rather impossible to reduce?
Wastes generated at home include plastic bags, paper napkin, toiletries, kitchen wastes (such as peelings of vegetables and fruits, tea leaves), domestic sewage, glass, etc.
Wastes generated at schools include waste paper, plastics, vegetable and fruit peels, food wrappings, sewage etc.
Wastes generated at trips or picnics include plastic, paper, vegetable and fruit peels, disposable cups, plates, spoons etc.
Yes, wastes can be easily reduced by the judicious use of the above materials. Wastage of paper can be minimized by writing on both sides of the paper and by using recycled paper. Plastic and glass waste can also be reduced by recycling and re-using. Also, substituting plastics bags with biodegradable jute bags can reduce wastes generated at home, school, or during trips. Domestic sewage can be reduced by optimizing the use of water while bathing, cooking, and other household activities.
Non- biodegradable wastes such as plastic, metal, broken glass, etc are difficult to decompose because micro-organisms do not have the ability to decompose them.
Question3. Discuss the causes and effects of global warming. What measures need to be taken to control global warming?
Long term rise in temperature of the Earth’s surface is called global warming.
Increase in the atmospheric levels of gases (CO2, CH4, NO2, etc.) due to extensive burning of fossil fuels. Accumulation of these gases in higher concentration does not allow the Earth’s heat to escape in the outer atmosphere, thus leading to increase in its surface temperature.
Effects of global warming: Global warming is defined as an increase in the average temperature of the Earth’s surface. It has been observed that in the past three decades, the average temperature of the Earth has increased by 0.6º C. As a result, the natural water cycle has been disturbed resulting in changes in the pattern of rainfall. It also changes the amount of rain water. Also, it results in the melting of Polar ice caps and mountain glaciers, which has caused a rise in the sea level, leading to the inundation of coastal regions.
Control measures for preventing global warming:
- Reducing the use of fossil fuels
- Use of bio-fuels
- Improving energy efficiency
- Use of renewable source of energy such as CNG etc.
- Reforestation: Planting of trees saplings.
- Recycling of materials
Question4. Match the items given in column A and B:
|Column A||Column B|
|(a)||Catalytic converter||(i)||Particulate matter|
|(b)||Electrostatic precipitator||(ii)||Carbon monoxide and nitrogen oxides|
|(c)||Earmuffs||(iii)||High noise level|
|Column A||Column B|
|(a)||Catalytic converter||(ii)||Carbon monoxide and nitrogen oxides|
|(b)||Electrostatic precipitator||(i)||Particulate matter|
|(c)||Earmuffs||(iii)||High noise level|
Question5. Write critical notes on the following:
(b) Biological magnification
(c) Groundwater depletion and ways for its replenishment
- Eutrophication:- It is the natural ageing process of a lake caused due to nutrient enrichment. It is brought down by the runoff of nutrients such as animal wastes, fertilizers, and sewage from land which leads to an increased fertility of the lake. As a result, it causes a tremendous increase in the primary productivity of the ecosystem. This leads to an increased growth of algae, resulting into algal blooms. Later, the decomposition of these algae depletes the supply of oxygen, leading to the death of other aquatic animal life.
- Biological magnification: – To protect the crops from the several diseases and pests, a large number of pesticides are used. These pesticides reach the soil and are absorbed by plants with water and minerals from the soil. Due to rain, these chemicals can also enter water sources and into the body of aquatic plants and animals. As a result, chemicals enter the food chain. Since these chemicals cannot be decomposed, they keep on accumulating at each trophic level. The maximum concentration is accumulated at the top carnivore’s level. This increase in the concentration of pollutants or harmful chemicals with an increase in the trophic level is called biological magnification. For example, high DDT concentrations were found in a pond. The producers (phytoplankton) were found to have 0.04 ppm concentration of DDT. Since many types of phytoplankton were eaten by zooplankton (consumers), the concentration of DDT in the bodies of zooplankton was found to be 0.23 ppm. Small fish that feed on zooplankton accumulate more DDT in their body. Thus, large fish (top carnivore) that feed on several small fish have the highest concentration of DDT.
- Ground water depletion and ways for its replenishment: – The level of ground water has decreased in the recent years. The source of water supply is rapidly diminishing each year because of an increase in the population and water pollution. To meet the demand of water, water is withdrawn from water bodies such as ponds, rivers etc. As a result, the source of ground water is depleting. This is because the amount of groundwater being drawn for human use is more than the amount replaced by rainfall. Lack of vegetation cover also results in very small amounts of water seeping through the ground. An increase in water pollution is another factor that has reduced the availability of ground water.
Measures for replenishing ground water:-
- Preventing over-exploitation of ground water
- Optimizing water use and reducing water demand
- Rain water harvesting
- Preventing deforestation and plantation of more trees
Question6. Why ozone hole forms over Antarctica? How will enhanced ultraviolet Radiations affect us?
The ozone hole is more prominent over the region of Antarctica. It is formed due to an increased concentration of chlorine in the atmosphere.Chlorine is mainly released from chlorofluorocarbons (CFC’s) widely used as refrigerants.
- When released in stratosphere, these substances drift towards poles and get accumulated on the ice clouds formed at high altitudes.
- Ice provides a surface on which breakdown of all the CFC compounds takes place to release chlorine atom.
- (These chlorine atoms breakdown ozone resulting in thinning of the ozone layer. Normally, the ozone layer plays a protective role by absorbing harmful UV radiations but reduction in its thickness allows UV rays to reach Earth’s surface
Effects of ultraviolet radiation on humans:
- Early ageing of skin.
- Increased incidences of cancer of the skin.
- Cataract of the eyes.
- Inflammation of cornea of the eye (known as snow blindness).
- Weakened immune system.
Question7. Discuss the role of women and communities in protection and conservation of forests.
Women and communities have played a major role in environmental conservation movements.
- Case study of the bishnoi community: TheBishnoi community in Rajasthan strictly believes in the concept of living peacefully with nature. In 1731, the king of Jodhpur ordered his ministers to arrange wood for the construction of his new palace. For this purpose, the minister and the workers went to bishnoi village. There, a Bishnoi woman called Amrita Devi along with her daughter and hundreds of other Bishnois showed the courage to step forward and stop them from cutting trees. They embraced the trees and lost their lives at the hands of soldiers of the king. This resistance by the people of the village forced the king to give up the idea of cutting trees.
- Chipko movement: The Chipko movement was started in 1974 in the Garhwal region of the Himalayas. In this movement, the women from the village stopped the contractors from cutting forest trees by embracing them.
Question8. What measures, as an individual, you would take to reduce environmental pollution?
The following initiatives can be taken to prevent environmental pollution:
Measures for preventing Air pollution:
- Planting more trees
- Use of clean and renewable energy sources such as CNG and bio-fuels
- Reducing the use of fossil fuels
- Use of catalytic converters in automobiles
Measures for preventing water pollution:-
- Optimizing the use of water
- Using kitchen waste water in gardening and other household purposes
Measures for controlling Noise pollution:-
- Avoid burning crackers on Diwali
- Plantation of more trees
Measures for decreasing solid waste generation:-
- Segregation of waste
- Recycling and reuse of plastic and paper
- Composting of biodegradable kitchen waste
- Reducing the use of plastics
Question9. Discuss briefly the following:
(a) Radioactive wastes
(b) Defunct ships and e-wastes
(c) Municipal solid wastes
- Radioactive wastes: – Radioactive wastes are generated during the process of generating nuclear energy from radioactive materials. Nuclear waste is rich in radioactive materials that generate large quantities of ionizing radiations such as gamma rays. These rays cause mutation in organisms, which often results in skin cancer. At high dosage, these rays can be lethal. Safe disposal of radioactive wastes is a big challenge. It is recommended that nuclear wastes should be stored after pre-treatment in suitable shielded containers, which should then be buried in rocks.
- Defunct ships and e-wastes: – Defunct ships are dead ships that are no longer in use. Such ships are broken down for scrap metal in countries such as India and Pakistan. These ships are a source of various toxicants such as asbestos, lead, mercury etc. Thus, they contribute to solid wastes that are hazardous to health. E-wastes or electronic wastes generally include electronic goods such as computers etc. Such wastes are rich in metals such as copper, iron, silicon, gold etc. These metals are highly toxic and pose serious health hazards. People of developing countries are involved in the recycling process of these metals and therefore, get exposed to toxic substances present in these wastes.
- Municipal solid wastes: – Municipal solid wastes are generated from schools, offices, homes, and stores. It is generally rich in glass, metal, paper waste, food, rubber, leather, and textiles. The open dumps of municipal wastes serve as a breeding ground for flies, mosquitoes, and other disease-causing microbes. Hence, it is necessary to dispose municipal solid waste properly to prevent the spreading of diseases. Sanitary landfills and incineration are the methods for the safe disposal of solid wastes.
Question10. What initiatives were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?
Delhi has been categorized as the fourth most polluted city of the world in a list of 41 cities. Burning of fossil fuels has added to the pollution of air in Delhi.
Various steps have been taken to improve the quality of air in Delhi.
- Introduction of CNG (Compressed Natural Gas):By the orderof the supreme court of India, CNG-powered vehicles were introduced at the end of year 2006 to reduce the levels of pollution in Delhi. CNG is a clean fuel that produces very little unburnt particles.
- Phasing out of old vehicles
- Use of unleaded petrol
- Use of low-sulphur petrol and diesel
- Use of catalytic converters
- Application of stringent pollution-level norms for vehicles
- Implementation of Bharat stage I, which is equivalent to euro II norms in vehicles of major Indian cities.
The introduction of CNG-powered vehicles has improved Delhi’s air quality, which has lead to a substantial fall in the level of CO2 and SO2. However, the problem of suspended particulate matter (SPM) and respiratory suspended particulate matter (RSPM) still persists.
Question11. Discuss briefly the following:
(a) Greenhouse gases
(b) Catalytic converter
(c) Ultraviolet B
- Greenhouse gases: – Thegreenhouse effect refers to an overall increase in the average temperature of the Earth due to the presence of greenhouse gases. Greenhouse gases mainly consist of carbon dioxide, methane, and water vapour. When solar radiations reach the Earth, some of these radiations are absorbed. These absorbed radiations are released back into the atmosphere. These radiations are trapped by the greenhouse gases present in the atmosphere.. This helps in keeping our planet warm and thus, helps in human survival. However, an increase in the amount of greenhouse gases can lead to an excessive increase in the Earth’s temperature, thereby causing global warming.
- Catalytic converter: – Catalytic converters are devices fitted in automobiles to reduce vehicular pollution. These devices contain expensive metals such as platinum, palladium, and rhodium that act as catalysts. As the vehicular discharge passes through the catalytic converter, the unburnt hydrocarbons present in it get converted into carbon dioxide and water. Carbon monoxide and nitric oxide released by catalytic converters are converted into carbon dioxide and nitrogen gas (respectively).
- Ultraviolet-B: – Ultraviolet-B is an electromagnetic radiation which has a shorter wavelength than visible light. It is a harmful radiation that comes from sunlight and penetrates through the ozone hole onto the Earth’s surface. It induces many health hazards in humans. UV −B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV −B cause corneal cataract in human beings.
Conclusions for NCERT SOLUTIONS FOR CLASS 12 BIOLOGY CHAPTER 16 ENVIRONMENTAL ISSUES
NCERT Solutions for Class 12 Biology Chapter 16 – Environmental Issues offer a comprehensive understanding of the various environmental challenges faced by our planet. The solutions provided in this guide have been prepared by experts in the field of Biology and are based on the latest syllabus and guidelines provided by the NCERT.
This chapter covers a range of topics related to environmental issues and provides an in-depth understanding of the causes, consequences, and possible solutions to these challenges. The solutions provided here are presented in a step-by-step manner to help students understand the concepts better and prepare for their exams more effectively.
In addition to the solutions, this guide also includes important notes, tips, and sample papers to help students prepare thoroughly for their exams. With these resources at their disposal, students can gain a deeper understanding of the subject and achieve better grades in their exams.
Q: What topics are covered in this chapter? A: This chapter covers a range of topics related to environmental issues such as air pollution, water pollution, global warming, climate change, and deforestation.
Q: Are the solutions provided in this guide accurate? A: Yes, the solutions provided in this guide have been prepared by subject matter experts and are based on the latest syllabus and guidelines provided by the NCERT. These solutions are accurate and reliable.
Q: Are these solutions helpful for exam preparation? A: Yes, these solutions are designed to help students prepare for their exams more effectively. The solutions are presented in a step-by-step manner to help students understand the concepts better.
Q: How can these solutions help in understanding environmental issues? A: These solutions provide a comprehensive understanding of the causes, consequences, and possible solutions to various environmental issues. By studying these solutions, students can develop a deeper understanding of these issues and the role they can play in protecting the environment.
Q: Are these solutions suitable for students of all skill levels? A: Yes, these solutions are suitable for students of all skill levels. The solutions are presented in a simple and easy-to-understand manner, making them accessible to students with different levels of knowledge and understanding.