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NCERT Exemplar Class 12 Biology Solutions Chapter 16 Environmental Issues
Updated on Apr 26, 2025 02:38 PM IST | #CBSE Class 12th
NCERT Exemplar Solutions for Class 12 Biology Chapter 16, Environmental Issues, is a necessary book for students who aim to achieve high marks in board exams as well as competitive exams. The chapter covers significant environmental problems such as pollution, global warming, deforestation, and how they impact ecological balance. The solutions provide in-depth information regarding these subjects in various question patterns, including multiple-choice questions (MCQs), short answers, and long answers. The NCERT Exemplar Solutions for Class 12 Biology chapter 16 breaks down complex ideas into simple steps, allowing students to understand the concept properly and gain confidence to score very well in exams.
This Story also Contains
- Detailed Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Multiple Choice Questions)
- Find Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Very Short Answer Type Questions)
- Access Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Short Answer Type Questions)
- Get Answers to the Class 12 Science NCERT Exemplar Chapter 16 Environmental Issues(Long Answer Type Questions)
- NCERT Exemplar Class 12 Biology Solutions Chapter 16 Environmental Issues- Main Topics
- Most Important Questions Class 12 Biology Chapter 16 Environmental Issues
- Approach to solve Questions of Class 12 Biology Chapter 16: Environmental Issues
- NCERT Exemplar Class 12 Biology Chapter Wise Links
The explanations address not only the theoretical concept but also emphasize practical solutions to address environmental issues such as waste management and pollution control. NCERT Solutions for Class 12 Science have been handpicked by experts in the subject matter so that the explanations are clear and precise. Through step-by-step explanations and answers, the students can increase their degree of understanding in environmental science, as well as improve their ability to think. NCERT Exemplar Solutions is especially good for last-minute revision because it presents a safe and accurate reference manual on plotting out the chapter's main concepts.
Detailed Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Multiple Choice Questions)
The detailed answers to the MCQ solutions are given below:
Question:1
Non-biodegradable pollutants are created by:
a. nature
b. excessive use of resources
c. humans
d. natural disasters
Answer:
The answer is option (c), humansExplanation: Human beings create and use various non-biodegradable substances and end up creating various kinds of pollution in the process.
Question:2
According to the Central Pollution Control Board, the diameter of particles that are responsible for causing great harm to human health is:
a. 2.5-micrometre
b. 5.0-micrometer
c. 10.0-micrometer
d. 7.5 micrometre
Answer:
The answer is option (a), 2.50 micrometersQuestion:3
The material generally used for soundproofing of rooms like a recordingstudio and auditorium is:
a. cotton
b. coir
c. wood
d. Styrofoam
Answer:
The answer is option (d) StyrofoamExplanation: (d) Styrofoam prevents reflection of sound waves instead, it absorbs them after their collision.
Question:4
Compressed Natural Gas (CNG) is:
a. propane
b. methane
c. ethane
d. butane
Answer:
The answer is option (b) methaneQuestion:5
World’s most problematic aquatic weed is:
a. Azolla
b. Wolffia
c. Eichhornia
d. Trapa
Answer:
The answer is option (c) EichhorniaExplanation: Eichhornia is commonly known as water hyacinth and has been the most notorious aquatic weed found all over the world.
Question:6
Which of the following exhibits biomagnification?
a. SO2
b. Mercury
c. DDT
d. Both b & c
Answer:
The answer is option (d) Both (b) & (c)Explanation: Biomagnification is well known reason and result of chemicals like: Mercury and DDT.
Question:7
The expanded form of DDT is:
a. dichloro diphenyl trichloroethane
b. dichloro diethyl trichloroethane
c. dichloro dipyridyl trichloroethane
d. dichloro diphenyl tetrachloroacetate
Answer:
The answer is option (a) dichloro diphenyl trichloroethaneExplanation: (a) dichloro diphenyl trichloroethane according to its structural formula.
Question:8
Which of the following material takes the longest time for biodegradation?
a. Cotton
b. Paper
c. Bone
d. Jute
Answer:
The answer is option (c) BoneExplanation: This is the reason why bones of humans and animals have been found from prehistoric period.
Question:9
Choose the incorrect statement.
a. The Montreal protocol is associated with the control of emission of ozone-depleting substances
b. Methane and carbon dioxide are greenhouse gases
c. Dobson units are used to measure the oxygen content of air
d. Use of incinerators is crucial to disposal of hospital wastes
Answer:
The answer is option (c) Dobson units are used to measure oxygen contentExplanation: Dobson is the unit used to measure the thickness of ozone in air column.
Question:10
Among the following which one causes maximum indoor chemicalpollution?
a. burning coal
b. burning cooking gas
c. burning mosquito coil
d. room spray
Answer:
The answer is option (a) burning coalExplanation: Burning of coal produces lot of carbon dioxide because solid fuel does not burn as efficiently as liquid or gaseous fuels.
Question:11
The green scum seen in the freshwater bodies is:
a. blue-green algae
b. red algae
c. green algae
d. both (a) and (c)
Answer:
The answer is option (d) both (a) and (c)Question:12
The loudness of a sound that a person can withstand without discomfortis about
a. 150 dB.
b. 215 dB.
c. 30 dB.
d. 80 dB
Answer:
The answer is option (d) 80 dB.Question:13
The major source of noise pollution worldwide is due to:
a. office equipment
b. transport system
c. sugar, textile and paper industries
d. oil refineries and thermal power plants
Answer:
The answer is option (b) transport systemExplanation: With the advent of progressing trade, commerce, and industry the means and the usage of transport has also increased. Be any trade or industry, transport is the final step for its execution.
Question:14
Match the following and choose the correct option
| Column I | Column II |
| A. Environment Protection Act | i. 1974 |
| B. Air Prevention & Control of Pollution Act | ii. 1987 |
| C. Water Act | iii. 1986 |
| D. Amendment of Air Act to include noise as an air pollutant | iv. 1981 |
a. A-iii, B-iv, C-i, D-ii
b. A-i, B-iii, C-ii, D-iv
c. A-iv, B-i, C-ii, D-iii
d. A-iii, B-iv, C-ii, D-i
Answer:
The answer is option (a) (i)-(C), (ii)-(D), (iii)-(A), (iv)-(B)Explanation: (a) (i)-(C), (ii)-(D), (iii)-(A), (iv)-(B)
Question:15
Catalytic converters are fitted into automobiles to reduce the emission ofharmful gases. Catalytic converters change unburnt hydrocarbons into:
a. carbon dioxide and water
b. carbon monoxide
c. methane
d. carbon dioxide and methane
Answer:
The answer is option (a) carbon dioxide and waterExplanation: Carbon monoxide is a lethal gas even in low concentration and hence option ‘b’ is incorrect. Methane is hydrocarbon and hence options ‘c’ and ‘d’ are ruled out.
Question:16
Why is it necessary to remove sulphur from petroleum products?
a. To reduce the emission of sulphur dioxide in exhaust fumes
b. To increase the efficiency of automobiles engines
c. To use sulphur removed from petroleum for commercial purposes
d. To increase the life span of engine silencers
Answer:
The answer is option (a) To reduce the emission of sulphur dioxide in exhaust fumesQuestion:17
Which one of the following impurities is easiest to remove from wastewater?
a. Bacteria
b. Colloids
c. Dissolved solids
d. Suspended solids
Answer:
The answer is option (d) Suspended solidsExplanation: Suspended solids can be removed by sedimentation and decantation. Dissolved solids can be removed by evaporation of water which is an energy intensive process. Removal of colloids needs centrifugation. Removal of bacteria involves use of bactericidal agents.
Question:18
Which one of the following diseases is not caused due to contamination of water?
a. Hepatitis-B
b. Jaundice
c. Cholera
d. Typhoid
Answer:
The answer is option (a) Hepatitis-BExplanation: Hepatitis B is spread through body fluids; like blood, sperm, sputum, mucus, etc.
Question:19
Nuisance growth of aquatic plants and bloom-forming algae in natural waters are generally due to high concentrations of:
a. carbon
b. sulphur
c. calcium
d. phosphorus
Answer:
The answer is option (d) phosphorusQuestion:20
Algal blooms impart a distinct colour to water due to:
a. their pigments
b. excretion of coloured substances
c. formation of coloured chemicals in water facilitated by physiological degradation of algae.
d. absorption of light by an algal cell wall.
Answer:
The answer is option (a) their pigmentsExplanation: If green algae are prevalent, they impart green color to water. Red algae impart red color and brown algae impart brown color.
Question:21
Match the items in column I and column II and choose the correct option:
| Column I | Column II |
| A. UV | i. Biomagnification |
| B. Biodegradable Organic matter | ii. Eutrophication |
| C. DDT | iii. Snow blindness |
| D. Phosphates | iv. BOD |
a. A-ii, B-i, C-iv, D-iii
b. A-iii, B-ii, C-iv, D-i
c. A-iii, B-iv, C-i, D-ii
d. A-iii, B-i, C-iv, D-ii
Answer:
The answer is option (c) A (iii), B (iv), C (i), D (ii)Question:22
In the textbook, you came across ''Three Mile Island and Chernobyl disasters associated with accidental leakage of radioactive wastes''. In India we had Bhopal gas tragedy. It is associated with which of the following?
a. CO2
b. Methyl Isocyanate
c. CFC
d. Methyl Cyanate
Answer:
The answer is option (b) Methyl Iso-CyanateFind Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Very Short Answer Type Questions)
The detailed answers to the very short answer questions are given below:
Question:1
Answer:
The lead in the petrol deactivates the catalysts and causes the emission of unburnt hydrocarbons into the atmosphere, resulting in air pollution.Question:2
Answer:
The Air (Prevention and Control of Pollution) Act came into force in the year 1981 and was amended in 1987 to include noise as an air pollutant.Question:3
Name the city in our country where the entire public road transport runs on CNG.
Answer:
By the end of the year 2002, in New Delhi, the entire transport runs on CNG.Question:4
Answer:
Presence of suspended impurities; like sand and clay causes siltation in water tanks since the water supply is drawn to overhead tanks from sources like river, deep bore well etc.Question:5
What is cultural eutrophication?
Answer:
Cultural eutrophication is a form of water pollution. When eutrophication is accelerated due to human activities; it is called cultural eutrophication. For example, the addition of excessive fertilizers into lakes or effluents from industries results in cultural eutrophication.Question:6
List any two adverse effects of particulate matter on human health.
Answer:
Following are the two adverse effects of particular matter on human health:(a) Asthma
(b) Respiratory tract infection
Question:7
What is the raw material for polyblend?
Answer:
Polyblends are the natural man-made fibres which are made by a mixture of 2 or more polymers. The raw material for polyblend is polythene.
Question:8
Answer:
Addition of polyblend to bitumen while laying the roads enhances water repellant property of bitumen. Thus, it increases road life by a factor of three.Question:9
Mention any two examples of plants used as windbreakers in the agricultural fields.
Answer:
Hedge, Jamun, Imli, Neem, Babul, Eucalyptus are some of the plants that can be used as windbreakers in the agricultural fields.Question:10
Name an industry which can cause both air and thermal pollution and as well as eutrophication.
Answer:
Fertilizer industry can cause both air and thermal pollution as well as eutrophication.Question:11
Answer:
Excessive growth of free-floating algae on water bodies due to their nutrient enrichment is called an algae bloom.Question:12
What do you understand by biomagnification?
Answer:
When a particular substance is passed on through various trophic levels; its concentration of the toxic substances increases at every step. This phenomenon is called biomagnification.Question:13
What are the three major kinds of impurities in domestic wastewater?
Answer:
Following are the three major kinds of impurities in domestic wastewater.(a) Suspended impurities like sand and silt.
(b) Colloidal materials like bacteria, faeces, cloth etc.
(c) Dissolved materials like nutrients (nitrates, phosphates, sodium, calcium)
Question:14
Answer:
Restoring a previously existing forest is called reforestation. The intervention of human beings can help in the process.Question:15
What is the best solution for the treatment of electronic wastes?
Answer:
Recycling is an environmentally friendly manner is the best solution for the treatment of electronic wastes. They can recycle 95-98% by weight.Access Answers to the NCERT Exemplar for Class 12 Science Chapter 16 Environmental Issues(Short Answer Type Questions)
The detailed answers to the short answer questions are given below:
Question:1
Answer:
Yes, It is true that carpets and curtains/drapes placed on the floor or wall surfaces can reduce the noise level. These objects are made of fibres and fibres act as sound absorber by reducing the noise level.Question 2:
What is hybrid vehicle technology? Explain its advantages with a suitable example?
Answer:2
Hybrid vehicle technology involves allowing the vehicle to run on a dual-mode like the use of the gasoline-run engine and battery-powered engine in the same vehicle.Gasoline-operated motor charged the battery and battery drives the vehicle. Hybrid vehicle helps in significantly reducing the consumption of gasoline and thus helps in reducing air pollution.
Question:3
Answer:
It is true that if the dissolved oxygen level drops to zero, the water will become septic. When this happens, many aquatic animals die because they do not get any dissolved oxygen to breathe. When sewage is discharged into a water body, microorganisms feed on organic impurities. In this process, they consume most of the oxygen present in water. This reduces the level of dissolved oxygen to negligible level.Question:4
Answer:
Carbon dioxide is one of the most common and potent greenhouse gas. It is produced by the burning of fossil fuels and other organic materials. Harmful effects of the increase in greenhouse gases include the melting of glaciers, respiratory problems in human beings, excessive temperature, etc. The excess level of carbon dioxide in the atmosphere results in global warming.Question:5
Answer:
Trees and shrubs are effective in reducing the noise level. Planting trees and shrubs near the boundary walls of buildings help in reducing noise level and act as dust catchers and air purifiers apart from adding aesthetic value to the surrounding. Such a decorated line of trees along the boundary or along the roadside is also called a sound barrier.Question:6
Answer:
It is an established fact that conservation efforts in the biodiversity-rich area always give better results. Hills have better biodiversity than plains because of less degree of human intervention. In addition, large forest cover for hills helps in reducing the chances of landslides and soil erosion. This is the reason the National Forest Commission of India has recommended a relatively larger forest cover for hills than for plains.Question:7
How can slash and burn agriculture become environment friendly?
Answer:
Slash and burn agriculture, also known as jhum cultivation, has been in use since ancient times by tribal people all over the world. Earlier, proper recovery time was allowed for forests to recover when a particular patch of land was left fallow. But due to increased population, this recovery period is often ignored. To make the slash and burn agriculture environment friendly, we need to give adequate recovery time and encourage the use of ashes obtained from burning the plants as fertilizers.Question:8
Answer:
Joint Forest Management Concept was introduced by the Government of India with the objective of involving and motivating the local community in forest management. In the past, it was observed that when the local people were excluded from forest management; they felt alienated. This was because they were robbed of their traditional rights on forests. This resulted in a clash of interests between the government and the local people, and the conservation efforts did not bear results. Involvement of local community produced better results in terms of conservation in a sustainable manner. Generation of employment was an added benefit from the program.Question:9
What do you understand by snow-blindness?
Answer:
Snow-blindness is also known as photokeratitis. It happens because of exposure of eyes to UV radiation and thus inflamed cornea. Burning sensation, pain, temporary loss of vision and increased tears are common symptoms of snow-blindness.Question:10
How has DDT caused a decline in the bird population?
Answer:
DDT is an organic compound and is a potent pesticide. The predator birds are at higher risk of having an extremely high level of DDT in their body. DDT is resistant to metabolism by living beings and hence tends to accumulate. The presence of DDT in a bird’s body leads to thinning of eggshells and their premature breaking. This explains the declining population of birds because of DDT.Question:11
Observe the figure A and B are given below and answer the following questions
i. The power generation by the above two methods is non-polluting True/False.
ii. List any two applications of solar energy
iii. What is a photovoltaic cell?
Answer:
(i) Yes, it is True that both the methods are non- polluting and environment friendly.(ii) Two applications of solar energy are using solar cells to produce electricity, using solar cooker for cooking food, using a solar heater for hot water.
(iii) A cell, which converts solar energy directly into electric energy by the photovoltaic effect, is known as photovoltaic cell.
Get Answers to the Class 12 Science NCERT Exemplar Chapter 16 Environmental Issues(Long Answer Type Questions)
The detailed answers to the long answer questions are given below:
Question:1
Answer:
Electronic waste is the residue of the electronic applications after usage. E-waste contains various metals, like copper, iron, nickel, gold, silver, etc. and plastic. Sources of E-waste: Computers, printers, scanners, webcam, mobile phones, music players, e-reader, etc.Problems associated with the disposal of e-waste:
- Dumping of e-waste will result in accumulation of plastic on land causing soil pollution and sometimes even air pollution.
- Extraction of metals; like iron or gold involves the incineration of plastic components which creates many polluting substances.
- Manual handling of e-waste can be harmful to workers since it contains many toxic metals.
- Most of the developed countries transport over half of their e-waste to the developing countries like India, China and Pakistan. Only the developed nations have facilities advanced enough to recycle e-waste in such huge capacities.
Question:2
Answer:
Organic farming is a method of farming that relies on various methods and inputs so that no synthetic input is used in the process. Green manure or bio-fertilizers are used instead of synthetic fertilizers. Bio-fertilizers include bacteria, fungi, and cyanobacteria. Pesticides and weedicides from natural sources are used, and those from synthetic sources are not used.Viability of Organic Farming in India:
- Organic farming can be highly beneficial in a labour surplus country; like India, because organic farming is highly labour intensive.
- Majority of Indian farmers still use cattle for farm operations. This means good availability of raw materials for making green manure is there.
- Indian farmers have traditional knowledge of many plants, which have pesticidal, and weedicide properties. This knowledge can be harnessed to get maximum output from organic farming.
- Organic farming will also help in reducing soil pollution and groundwater pollution, especially in rural areas.
- It is cost-optimized and thus beneficial for the farmers.
Question:3
Answer:
Waterlogging and soil salinity are some of the problems that have come in the wake of the green revolution.Causes of waterlogging and soil salinity:
- Many canals were built to implement the Green Revolution. This made for easy availability of water for irrigation. Excess use of water during irrigation results in waterlogging. This draws salt to the soil surface and increases soil salinity.
- Also, excess use of fertilizers has led to the accumulation of many unused salts resulting in soil salinity.
(a) Increases soil salinity.
(b) Many crops cannot survive in water-logged conditions.
(c) Prolonged period of waterlogging will reduce the number of microorganism and creatures in the soil. This will reduce biodiversity in the soil.
(d) Decomposition of organic matter in stagnant water will release methane, which is a potent greenhouse gas.
Effects of Soil Salinity:
(a) Most of the plants cannot survive in saline soil leading to a reduction in the growth of crops. Root cells get shrunk due to saline water.
(b) Soil will become barren, causing extreme damage to agriculture.
(c) Desertification may take place.
Question:4
Answer:
A tree that can be used for multiple purposes like fruits, shade, timber, medicine, flowers, etc. is called a multipurpose tree. Two multipurpose trees are as follow:(a) Banana: Musa acuminate
(b) Coconut: Cocos nucifera
Uses of Banana:
- Fruits are used as food all over the world.
- Banana flowers are also used as food in many countries.
- Raw banana is used for making banana chips.
- Banana leaves are used as platter during a ceremonial feast in India.
- Banana leaves are also used as packing material.
- Fibre from the banana stem is used for making textiles.
- Banana stem is also used for making a makeshift raft.
- Fruits are used as food and as an additive in many culinary items.
- Coconut shell is used for making many useful items, like a ladle, toys, etc.
- Coconut leaf is used for making hand-fan, basket, mat, etc.
- Veins of coconut leaf are used for making a broom.
- Coconut fibre (coir) is used for making mattresses, carpets, ropes, etc.
- Coconut wood is used in construction and furniture.
- Coconut oil is used for various purposes all across the country.
Question:5
Answer:
Characteristic of a modern landfill site are as follows:(a) Methods to contain leachates such as lining clay or plastic liners: This helps in preventing the leachate from seeping into the underground aquifers. This prevents soil population and groundwater pollution.
(b) Compaction and covering of the waste to prevent it from being blown by the wind: Compaction helps in better space utilization because more waste can be accommodated in a smaller area. Covering prevents the spread of dust and harmful germs and is thus safer from a health perspective.
(c) Installation of a landfill gas extraction system to extract the gas for use in the generation of power: This enables a faster generation of methane, which can be used for power generation. In some countries, landfill sites have become important contributors to power generation.
Question:6
How does an electrostatic precipitator work?
Answer:
An electrostatic precipitator is a device which is used to extract the suspended dust particles from the gas.Working of an electrostatic precipitator is as follows:
- High voltage charge is used to collect particles on the charged plates. Electrode wires, maintained at high voltages, produce a corona that releases electrons.
- These electrons attach to dust particles and give them a net negative charge.
- Grounded collecting plates attract negatively charged dust particles. Thus, dust particles are removed from the air. A spray of water or lime is generated in the scrubber and exhaust is passed through this spray. Scrubber removes gases, like Sulphur dioxide from the air. Thus, polluting gases like Sulphur dioxide are removed from the air.
- Electrostatic precipitator can remove over 99% particulate matter present in the exhaust from a thermal power plant.
Question:7
Observe figure and answer the following questions. i. What ecological term is used to describe the DDT accumulation at different trophic levels?
i. What ecological term is used to describe the DDT accumulation at different trophic levels?
Answer:
(i) Biomagnification is the ecological term used to describe DDT accumulation at different trophic levels.(ii) An effect of DDT accumulation on birds includes the thinning of eggshells and their premature breaking as the metabolism of birds gets disturbed.
(iii) DDT accumulation leads to eutrophication, i.e. increased life in a water body.
(iv) DDT accumulation leads to eutrophication, which ultimately results in increased Biological Oxygen Demand.
(v) Minamata disease happens due to accumulation of mercury, Blackfoot due to arsenic and Itai- Itai due to cadmium.
NCERT Exemplar Class 12 Solutions Subject Wise:
NCERT Exemplar Class 12 Biology Solutions Chapter 16 Environmental Issues- Main Topics
- Air Pollution and Its Control
- Water Pollution and Its Control
- Solid Wastes
- Agro-chemicals and their Effects
- Radioactive Wastes
- Greenhouse Effect and Global Warming
- Ozone Depletion in the Stratosphere
- Degradation by Improper Resource Utilisation and Maintenance
- Deforestation
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- NCERT Solution for Class 12 Physics
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- NCERT Solution for Class 12 Biology
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As per latest 2024 syllabus. Maths formulas, equations, & theorems of class 11 & 12th chapters
Most Important Questions Class 12 Biology Chapter 16 Environmental Issues
Environmental Issues is an important chapter that helps students understand how human activities impact nature and what measures can be taken to reduce this damage. Given below are the key questions listed below will increase your preparation and help you revise the main concepts effectively.
Question 1: The thickness of ozone in a column of air in the atmosphere is measured in terms of:
A. Dobson units
B. Decibels
C. Decameter
D. Kilobase
Answer:
Dobson units are a standard measure used to quantify the concentration of ozone in the Earth's atmosphere. One Dobson unit represents a layer of ozone that would be 0.01 millimeters thick if compressed to standard temperature and pressure (STP).
Hence, the correct answer is option 1, Dobson units.
Question 2: What is the process called in which nutrients, oxidants, or electron donors are released into the environment to stimulate naturally occurring microorganisms to degrade a contaminant?
Answer:
Biostimulation involves the addition of specific nutrients, electron donors, or oxidants to the environment to stimulate the activity of naturally occurring microorganisms to degrade contaminants. Hence, the process is known as biostimulation.
Question 3: What does the presence of Salmonella in tap water indicate contamination with?
Answer:
The presence of Salmonella in tap water can indeed be indicative of contamination with human excreta. Salmonella is a type of bacteria that commonly inhabits the intestines of humans and animals. It is typically transmitted through the faecal-oral route, meaning that contaminated faeces can contaminate water sources, leading to the presence of Salmonella in water.
Question 4: Which disease is caused by drinking water polluted with mercury?
Answer:
Minamata disease is a severe neurological disease caused due to mercury poisoning. It is caused due to the consumption of fish that were once living in mercury-poisoned water.
Symptoms of the disease include impaired balance due to nerve damage (ataxia), numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, and deterioration of hearing and speech.
Question 5: What are the components present in photochemical smog?
Answer:
Photochemical smog is the result of sunlight-inducing chemical reactions between the primary pollutants to form the secondary pollutants. This produces an effect of smoke and fog. The primary pollutants like volatile organic compounds, hydrocarbons, oxides of nitrogen, and oxides of sulfur react with water vapours and oxygen in the presence of sunlight to form ozone, peroxyacetyl nitrate, and nitrous oxides. These secondary pollutants persist in the environment and decrease visibility other than causing the deficiency of oxygen. Their presence induces severe respiratory illness in humans and animals and also affects the physiology of plants.
Must Read NCERT Notes subject-wise
- NCERT Notes for Class 12 Physics
- NCERT Notes for Class 12 Chemistry
- NCERT Notes for Class 12 Maths
- NCERT Notes for Class 12 Biology
Approach to solve Questions of Class 12 Biology Chapter 16: Environmental Issues
- Prepare short notes on different types of pollution, like air, water, soil, and noise pollution, along with their causes, effects, and control measures.
- Study pollutants like carbon monoxide, oxides of nitrogen and sulfur, CFCs, and greenhouse gases, by writing them in points.
- Understand the concept of how ozone is formed, destroyed, and the impact of global warming on organisms.
- Go through the topics like solid waste, e-waste, and methods like recycling, composting, and sewage treatment, as some questions might come from these topics.
- The practice of flowcharts, diagrams of environmental cycles, solving past years' questions, and exercises is required to gain confidence while answering in the exam.
Also, Check NCERT Books and NCERT Syllabus here
- NCERT Books Class 12 Biology
- NCERT Syllabus Class 12 Biology
- NCERT Books Class 12
- NCERT Syllabus Class 12
Environmental problems bring serious challenges to the sustainability of life on the planet Earth. The chapter highlights the need for prompt conservation, sustainable development, and environmentally friendly approaches to address such problems. Initiating measures such as waste disposal, re-afforestation, and the use of renewable energy sources can assist in restoring environmental harmony. Learning these problems and responsible steps are key to having a healthier world for the next generations.
NCERT Exemplar Class 12 Biology Chapter Wise Links
Below are the NCERT Exemplar Class 12 Biology
Frequently Asked Questions (FAQs)
1. Is this chapter important for exams than other chapters?
Every chapter is important for the exams. Only their weightage differs giving them more or less importance compared to each other.
2. Who has prepared the NCERT exemplar solutions for Class 12 Biology chapter 16?
The NCERT exemplar Class 12 Biology chapter 16 solutions are prepared by us. We, professionals, prepare the solutions after carefully examining and referring to many advanced books.
3. Can I download the solutions for this chapter?
Yes, you can easily download this chapter by using the link provided on the page to get an NCERT exemplar Class 12 Biology solutions chapter 16 pdf download.
4. How to make notes for this chapter?
The best way to prepare notes from any chapter is to read it carefully and note down the key points in your own words. Including diagrams or creating visual patterns can also help improve understanding and retention.
5. What are the major causes and effects of water pollution?
Causes: Water pollution is mainly caused by industrial waste, sewage discharge, agricultural runoff (pesticides and fertilizers), and plastic waste.
Effects: It leads to contaminated drinking water, marine life destruction, ecosystem imbalance, and the spread of waterborne diseases.
6. What is eutrophication, and how does it impact aquatic ecosystems?
Eutrophication is the excessive accumulation of nutrients, mainly nitrogen and phosphorus, in water bodies, leading to excessive algal growth.
Impact: It depletes oxygen levels, causing the death of aquatic organisms, disrupts ecosystems, and leads to the formation of dead zones, making water unfit for life.
7. How do solid wastes contribute to environmental issues?
Solid wastes are responsible for environmental problems as they contaminate land, water, and air. Mismanagement results in soil pollution, waterlogging of water bodies, and the emission of greenhouse gases from landfills. Non-biodegradable wastes such as plastic are detrimental to wildlife and oceanic ecosystems. Proper waste management through recycling and composting is necessary to mitigate its effects.
8. What are the best strategies for waste management and recycling?
Successful waste management and recycling measures involve minimizing waste at the source, separating biodegradable and non-biodegradable materials, and encouraging composting and recycling schemes. The use of environment-friendly packaging, reusing material, and waste-to-energy technologies reduces landfill waste. Government policies and public awareness are also vital to successful waste management.
9. How does global warming affect biodiversity and ecosystems?
Global warming disrupts biodiversity and ecosystems by causing habitat loss, shifting climate patterns, and increasing extreme weather events. Rising temperatures lead to species migration, coral bleaching, and the extinction of vulnerable species. It disturbs food chains, reduces biodiversity, and affects ecosystem stability. If unchecked, these changes can lead to irreversible ecological damage.
10. What is the role of greenhouse gases in climate change?
Greenhouse gases such as carbon dioxide, methane, and water vapor trap heat in the Earth's atmosphere, causing a warming effect referred to as the greenhouse effect. This results in global temperatures rising, altered weather patterns, glacier melting, and ecosystem disruptions. Greenhouse gas levels are increased by human activities such as the burning of fossil fuels and deforestation, exacerbating climate change. It is imperative that emissions be reduced and sustainable practices embraced to combat it.
11. How does deforestation impact the environment and biodiversity?
Deforestation leads to habitat loss, endangering wildlife and reducing biodiversity. It disrupts the balance of ecosystems, affecting soil fertility, increasing carbon dioxide levels, and contributing to climate change. The loss of trees also reduces oxygen production and disturbs the water cycle, leading to droughts and desertification. Overall, deforestation accelerates environmental degradation and threatens global ecological stability.
12. How do air quality standards help in reducing pollution?
Air quality standards help reduce pollution by setting legal limits on harmful pollutants like carbon monoxide, sulfur dioxide, and particulate matter. They regulate industrial emissions, vehicle exhaust, and waste burning to minimize air contamination. Monitoring and enforcing these standards ensure cleaner air, reducing health risks like respiratory diseases. Overall, they play a crucial role in protecting both the environment and public health.
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4 min ⋆ May 09, 2025 02:05 AM ISTQuestions related to CBSE Class 12th
Have a question related to CBSE Class 12th ?
Changing from the CBSE board to the Odisha CHSE in Class 12 is generally difficult and often not ideal due to differences in syllabi and examination structures. Most boards, including Odisha CHSE , do not recommend switching in the final year of schooling. It is crucial to consult both CBSE and Odisha CHSE authorities for specific policies, but making such a change earlier is advisable to prevent academic complications.
Manasvini Gupta 30 January,2025
Hello there! Thanks for reaching out to us at Careers360.
Ah, you're looking for CBSE quarterly question papers for mathematics, right? Those can be super helpful for exam prep.
Unfortunately, CBSE doesn't officially release quarterly papers - they mainly put out sample papers and previous years' board exam papers. But don't worry, there are still some good options to help you practice!
Have you checked out the CBSE sample papers on their official website? Those are usually pretty close to the actual exam format. You could also look into previous years' board exam papers - they're great for getting a feel for the types of questions that might come up.
If you're after more practice material, some textbook publishers release their own mock papers which can be useful too.
Let me know if you need any other tips for your math prep. Good luck with your studies!
Jefferson 25 September,2024
It's understandable to feel disheartened after facing a compartment exam, especially when you've invested significant effort. However, it's important to remember that setbacks are a part of life, and they can be opportunities for growth.
Possible steps:
-
Re-evaluate Your Study Strategies:
- Identify Weak Areas: Pinpoint the specific topics or concepts that caused difficulties.
- Seek Clarification: Reach out to teachers, tutors, or online resources for additional explanations.
- Practice Regularly: Consistent practice is key to mastering chemistry.
-
Consider Professional Help:
- Tutoring: A tutor can provide personalized guidance and support.
- Counseling: If you're feeling overwhelmed or unsure about your path, counseling can help.
-
Explore Alternative Options:
- Retake the Exam: If you're confident in your ability to improve, consider retaking the chemistry compartment exam.
- Change Course: If you're not interested in pursuing chemistry further, explore other academic options that align with your interests.
-
Focus on NEET 2025 Preparation:
- Stay Dedicated: Continue your NEET preparation with renewed determination.
- Utilize Resources: Make use of study materials, online courses, and mock tests.
-
Seek Support:
- Talk to Friends and Family: Sharing your feelings can provide comfort and encouragement.
- Join Study Groups: Collaborating with peers can create a supportive learning environment.
Remember: This is a temporary setback. With the right approach and perseverance, you can overcome this challenge and achieve your goals.
I hope this information helps you.
Kanishka kaushikii 17 September,2024
Hi,
Qualifications:
Age: As of the last registration date, you must be between the ages of 16 and 40.
Qualification: You must have graduated from an accredited board or at least passed the tenth grade. Higher qualifications are also accepted, such as a diploma, postgraduate degree, graduation, or 11th or 12th grade.
How to Apply:
Get the Medhavi app by visiting the Google Play Store.
Register: In the app, create an account.
Examine Notification: Examine the comprehensive notification on the scholarship examination.
Sign up to Take the Test: Finish the app's registration process.
Examine: The Medhavi app allows you to take the exam from the comfort of your home.
Get Results: In just two days, the results are made public.
Verification of Documents: Provide the required paperwork and bank account information for validation.
Get Scholarship: Following a successful verification process, the scholarship will be given. You need to have at least passed the 10th grade/matriculation scholarship amount will be transferred directly to your bank account.
Scholarship Details:
Type A: For candidates scoring 60% or above in the exam.
Type B: For candidates scoring between 50% and 60%.
Type C: For candidates scoring between 40% and 50%.
Cash Scholarship:
Scholarships can range from Rs. 2,000 to Rs. 18,000 per month, depending on the marks obtained and the type of scholarship exam (SAKSHAM, SWABHIMAN, SAMADHAN, etc.).
Since you already have a 12th grade qualification with 84%, you meet the qualification criteria and are eligible to apply for the Medhavi Scholarship exam. Make sure to prepare well for the exam to maximize your chances of receiving a higher scholarship.
Hope you find this useful!
Yuvan 30 August,2024
hello mahima,
If you have uploaded screenshot of your 12th board result taken from CBSE official website,there won,t be a problem with that.If the screenshot that you have uploaded is clear and legible. It should display your name, roll number, marks obtained, and any other relevant details in a readable forma.ALSO, the screenshot clearly show it is from the official CBSE results portal.
hope this helps.
Ashvadha 12 July,2024
Popular CBSE Class 12th Questions
A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is
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Option 2)
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Option 4)
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An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range
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Option 2)
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Option 4)
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A particle is projected at 600 to the horizontal with a kinetic energy . The kinetic energy at the highest point
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Option 2)
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Option 4)
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In the reaction,
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Option 2)
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How many moles of magnesium phosphate, will contain 0.25 mole of oxygen atoms?
| Option 1)
0.02 |
Option 2)
3.125 × 10-2 |
| Option 3)
1.25 × 10-2 |
Option 4)
2.5 × 10-2 |
Colleges After 12th
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