Environmental Issues Class 12 Biology Revision Notes
Class 12 Biology students should refer to the following concepts and notes for Environmental Issues in standard 12. These exam notes for Grade 12 Biology will be very useful for upcoming class tests and examinations and help you to score good marks
Environmental Issues Notes Class 12 Biology
Pollution: Any undesirable change in physical, chemical or biological characteristics of air, land, water or soil which harms the human beings.
Pollutants: Agents that bring about pollution eg. smoke, dust, pollen, chemical pollutants, wastes rom hospitals, E-wastes etc.
Biodegradable and non -biodegradable pollutants
Ways of removing particulate matter
1. Electrostatic Precipitator
Electrical device to remove 99% particulate matter.Electrode wires produce a corona that releases electrons. Negatively charged dust particles get attached with electrons & are collected in plates.
Used to remove gases from industrial exhaust by spraying water or lime. Gases get dissolved in water while lime reacts to form precipitation of substances.
3. Proper maintenance of Automobiles
Reference Fig 16.1 NCERT
Advantage of CNG over diesel
• CNG burns most efficiently.
• Cheaper cannot be siphoned.
• Cannot be adulterated.
Problems in use of CNG
• Difficulty in laying down pipelines. Non-assurance of uninterrupted supply
Steps taken in Delhi to reduce pollution.
• Phasing out old vehicles.
• Use of unleaded petrol.
• Use of low sulphur Petrol and Diesel.
• Use of catalytic converters in vehicles Application of stringent pollution level norms for vehicles.
• It is undesirable high level of sound.
Harmful effects of noise pollution
• Psychological and Physiological disorders
• Damage of eardrums and hearing ability
• Cause sleeplessness, increased heartbeat altered breathing pattern, stress etc.
Steps to be taken to control noise pollution
• Use of sound absorbent materials or by muffling noise in industries
• Demarcation of horn free zones around hospitals and schools.
• Permissible sound levels of crackers,
• Timings after which Loudspeakers cannot be played
Deterioration in water quality due to physical, chemical or biological factor.
Sources of water pollution
a) Domestic sewage: Includes waste water from residential & public sewage system & contains suspended solids(sand,silt & clay), colloids(faecal matter, microbes, paper & cloth fibres) , dissolved materials(Nitrates, Ammonium phosphate, sodium and calcium salts) & biodegradable organic wastes.
b) Industrial wastes Includes heavy metals released along with waste water eg., Mercury , DDT which increases toxicity level of water affecting living bodies and results in biomagnification.
Biological Oxygen Demand (BOD) indicates the amount of dissolved oxygen utilised by the microorganisms for oxidising the organic matter present in the water body. Greater the organics, greater would be the pollution and lesser the dissolved oxygen.
Effects of BOD
• It is free floating (Planktonic) Algae.
• Imparts a distinct colour to water bodies
• Cause deterioration of water quality and fish mortality.
• Some blooms are toxic to humans and Animals.
Water hyacinth (Eichornia crassipes)
World‘s most problematic aquatic weed
Called as ‘Bengal Terror‘ Grows faster than our ability to remove.
Increase in concentration of the toxicant at successive tropic levels
Bio magnification of DDT in Aquatic food chain
Water → Zooplankton → Small Fish → Large Fish → Fish eating Birds
0.0003 ppm 0.04 ppm 0.5 ppm 2 ppm 5 ppm
Defined as Natural ageing of lake by biological enrichment of its water. Life supportive water in young lakes encourage growth of aquatic life & simultaneously deposition of organic remains at the bottom . Eventually floating plants grow in raised water temperature resulting in blockade of surface water that accelerates ageing called as eutrophication.
Cultural or accelerated eutrophication
Acceleration of ageing process of a lake by effluents from industries and homes.
Integrated waste water treatment in arcata
It consist of two steps
a) Conventional sedimentation, filtering and chlorine treatment,
b) Passing this water through marshes for neutralization absorption and assimilation of pollutants.
c) Upkeep of this project by FOAM (Friends of Arcata Marsh).
Ecological sanitation (Ecosan)
A sustainable system for handling human excreta without using water but with composting
method.Advantages of ecosan
a) Wastage of water is reduced
b) Practical and efficient
c) Hygienic and cheap
d) Excreta can be recycled and used as natural fertilizer
Syringes, discarded medicines, Used gloves, Post-operative materials etc.
Should be treated before disposing off.
• Unused or damaged computers, calculators, mobile phones etc.
• Developed countries have plants for recycling e-wastes for recycling of metals.
• In developing countries e-wastes are buried in landfills or incinerated.
• Chemicals used in agricultural fields, Fertilizers, pesticides, weedicides etc.
• They are toxic to even non target organisms.
• Excess fertilizers cause Eutrophication.
• They cause soil pollution
Advantages of organic farming
• Economical Wastes do not get accumulated but recycled
• Does not cause Eutrophication
• Emit radiations and damage biological organisms.
• Nuclear wastes are called potent pollutants, as they are lethal even in lower doses.
Disadvantages of nuclear plants
• Accidental leakages may happen
• Unsafe disposal of radioactive wastes
• Radiation emitted cause mutations in organisms
• Radiation causes genetic disorders
Atmospheric cover around earth does not allow substantial amount of long wave radiation emitted by earth to escape in space. Infrared radiation is absorbed by greenhouse gases in atmosphere which is further returned as downward flux of radiation for keeping earth warm.Thus,greenhouse gases control of escape of heat from earth surface to outer space.
Green House Gases:-Carbon dioxide, methane, Chlorofluorocarbon
(CFC),Perfluromethane(CF4), Nitrous oxide(N2O) etc.
Harmful effect is global warming, increase in sea level etc.
Triatomic molecule of oxygen. .
• Found in stratosphere of atmosphere.
• CFCs discharged from lower atmosphere move upward .
• UV rays act on these CFCs and release chlorine atoms.
• Chlorine degrades ozone and release molecular oxygen.
• This process is irreversible and thus ozone is depleted.
Reference Fig 16.8 NCERT
The removal of top fertile layer due to human activities
• Over cultivation
• Over grazing
• Improper irrigation practices
• The crops may droop
• Leads to salinity of the soil.
Slash and burn agriculture/jhum cultivation
• Farmers cut down the trees of the forest and burn the plant remains.
• Ash is used as fertilizer and land is used for farming or cattle grazing
• Later, Land is left uncultivated for several years for replenishment of minerals
Effects of deforestation
• Leads to global warming due to excess carbon-dioxide
• Loss of biodiversity
• Damage to hydrological cycle
• Leads to soil erosion
• Desertification of land
• Restoring forest that was existing earlier
• E.g. Observing Van-Mahotsavas
• It also occurs naturally
• Developing a forest in a new area where no such forest existed in that area.
A case study of people’s participation in forest conservation
A king of Jodhpur wanted to arrange wood for his new palace in 1731.
Few Bishnois hugged the trees and asked to cut them first rather than cutting trees.
365 persons lost their lives in this act
A small temple is now present there in remembrance of this act
Amrita Devi Bishnoi Wild Life Protection Award is instituted for individuals of rural areas who take keen interest in protecting wild life.
It was started by local women of Garhwal, They hugged the trees to protect them from the axes of contractors.
Joint forest management (jfm)
• Strategy Government of India in 1980
• Local communities worked with the government to save the forest.
• Communities get forest products for encouragement.
Very Short Answer type Questions
1. What is meant by algal blooms? What is its significance?
Ans. Excess growth of certain phytoplankton due to excess nutrients in water causes Deteriorates water quality, leads to fish mortality.
2. Define eutrophication.
Ans. Nutrient enrichment in water bodies leading to depletion of oxygen and loss of life supporting Environment.
3. What is bio magnification?
Ans. Increase in the concentration of certain toxic chemicals at successive trophic levels.
4. What is BOD?
Ans. Biological Oxygen Demand is the measure of organic matter in any water sample.
5. What is the effect of DDT in birds?
Ans. DDT disturbs calcium metabolism in birds, thinning of egg shell and premature breaking of Eggs lead to decline in bird population.
6. What do you understand by ‗Ecosan‘?
Ans. Ecosanare the toilets which use compositing method for ecological sanitation.
7. Why are nuclear wastes called potent pollutants?
Ans.Are lethal even at lower doses and cause damaging disorders.
8. What is Jhum cultivation?
Ans Farmers cut down the tress, burn, use cattle for grazing and then allow the land to recover.
9. Mention two problems that have arisen due to green revolution.
Ans. Water logging and soil salinity.
10. What is snow blindness?
Ans. Inflammation of cornea caused by a high dose of UV-B radiation.
11. Which is the world‘s most problematic weed, also known as ―terror of Bengal”?
Ans. Eichornia crassipes(Water hyacinth).
12. What is the effect of DDT in birds?
Ans. Disturbs Calcium metabolism Thinning of egg shells and premature breakage of eggs, Decline of bird population.
Short Answer type Questions
Question. Mention the harm caused by fine particulate matter to human beings?
Ans. (i) Cause respiratory problems
(ii) Irritation of eyes
(iii) Inflammation of lungs
(iv) Premature death.
Question. Differentiate between biodegradable and non-biodegradable wastes
|Biodegradable wastes||Non-Biodegradable wastes|
|Can be broken down into harmless simple Compounds by the action of decomposers.||Cannot be broken down by microbes and get accumulated in the biosphere|
|Can be used as manure||Enter the food chain|
|Cause little pollution||Cause bio magnifications|
Question. Describe Chipko Movement.
Ans. It was launched in Garwhal, Himalayas by Shri Sunder LalBahuguna in 1974.
Local women showed enormous bravery in protecting the trees from the axes of the contractors by hugging them.
Question. What are the advantages of Organic farming?
Ans. Economical procedure as recycling takes place.
Waste not accumulated but recycled Efficiency and utilization of resources increased
Does not lead to eutrophication.
Question. Write an account on Ecological sanitation (Ecosan).
Ans. A sustainable system for handling human excreta, using dry composting toilets. Practical,
Hygienic, efficient and cost-effective solution to human waste disposal Human excreta can be Recycled into manure Used in Kerala and Sri Lanka.
Question. How do radioactive wastes cause damage to living organism?
Ans. Cause mutations in living organisms at a very high rate. Lethal in high doses Causes cancer and other disorders.Reduces the vegetation cover.
Question. What is ecological sanitation? What are its advantages?
Ans. It is sustainable system for handling human excreta without using water but by composting method.
Hygienic, practical and efficient, Conserves water can be recycled and, Acts as a natural fertilizer.
Question. Mention harmful effects of noise pollution on human health.
Ans. Stress Altered breathing pattern
Increased heart beating and blood pressure
Sleeplessness and headache
Question. What measures should be taken to reduce global warming?
Ans. Reduce use of fossil fuel
Efficient use of energy.
Reduce human population Control greenhouse gases.
Question. How can we reduce automobile pollution?
Ans. Un-Leaded Petrol- Reduces lead pollution in air.
Low Sulphur Diesel- Reduces sulphur pollution in air
Four stroke engines to reduce emission of unburnt hydrocarbons.
Tube-Ups to increase air-fuel ratio and help in better combustion.
Catalytic Converters to reduce pollution.
CNG to reduce pollution and conserve fossil fuels.
Question. Mention the adverse effects agrochemicals.
Ans. They are toxic to non-target organisms. They cause soil pollution Excess fertilizers cause eutrophication.
Question. Write a short note on ozone depletion.
Ans. Ozone found in stratosphere. CFCs discharged from lower atmosphere move upward. In stratosphere UV rays act on these CFCs release chlorine atoms. Chlorine degrades ozone and release molecular oxygen (O3O2). In this reaction chlorine acts, as catalyst and loss ozone is irreversible.
Question. Mention the Supreme Court directions to the Government to reduce pollution.
Ans. Switch over to CNG in public transport system
Enforcement of Euro II norms for vehicles.
Compulsory periodic check-up of pollution.
Use of unleaded petrol Low sulphur petrol and diesel
Catalytic converters in vehicles
Phasing out of old vehicles.
Long answer type questions
Question. a) Explain the functioning of electrostatic precipitator with the help of a diagram.
b) Mention the consequence if the electrostatic precipitator does not work in a power plant.
Ans. Used for removing particulate air pollutants.
Removes about 99 of the particulate pollutants from the exhaust of thermal power plants.
Electrode wires that are maintained at several thousand volts, which release electrons.
Electrons become attached to dust particles giving a net negative charge.
Collecting plates are grounded and attract the charged dust particles.
Velocity of air between the plates must be low enough to allow the dust particles to fall.
If electrostatic precipitator of a thermal plant stops working, all the particulate pollutants get released and pollute the air.
• Secondary air pollutants are produced from primary pollutants by photochemical oxidation.
eg.,Olefins, aldehydes, Peroxyacetyl Nitrate(PAN)
• Photochemical Smogs are formed by following reactions:
N2 + O2 → 2NO (From vehicle exhaust)
2NO + O2 → 2NO2
NO2 → NO + O
O +O2 → O3
NO +O3 → NO2 +O2
HC +NO + O2 → NO2 +PAN (Peroxyacetyl nitrate) (SMOG)
Ques. High value of BOD (Biochemical Oxygen Demand) indicates that
(a) water is less polluted
(b) consumption of organic matter in the water is higher by the microbes
(c) water is pure
(d) water is highly polluted.
Ques. Rachel Carson’s famous book “Silent Spring” is related to
(a) population explosion
(b) ecosystem management
(c) pesticide pollution
(d) noise pollution.
Ques. In an area where DDT had been used extensively, the population of birds declined significantly because
(a) birds stopped laying eggs
(b) earthworms in the area got eradicated
(c) cobras were feeding exclusively on birds
(d) many of the birds eggs laid, did not hatch.
Ques. Measuring Biochemical Oxygen Demand (BOD) is a method used for
(a) estimating the amount of organic matter in sewage water
(b) working out the efficiency of oil driven automobile engines
(c) measuring the activity of Saccharomyces cerevisiae in producing curd on a commercial scale
(d) working out the efficiency of RBCs about their capacity to carry oxygen.
Ques. Eutrophication is often seen in
(b) fresh water lakes
Ques. When domestic sewage mixes with river water
(a) small animals like rats will die after drinking river water
(b) the increased microbial activity releases micronutrients such as iron
(c) the increased microbial activity uses up dissolved oxygen
(d) the river water is still suitable for drinking as impurities are only about 0.1%.
Ques. Biochemical oxygen demand (BOD) in a river water
(a) has no relationship with concentration of oxygen in the water
(b) gives a measure of Salmonella in the water
(c) increases when sewage gets mixed with river water
(d) remains unchanged when algal bloom occurs.
Ques. DDT residues are rapidly passed through food chain causing biomagnification because DDT is
(a) moderately toxic
(b) non-toxic to aquatic animals
(c) water soluble
(d) lipo soluble.
Ques. A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this.
A. Lots of urea and phosphate fertilizer were used in the crops in the vicinity.
B. The area was sprayed with DDT by an aircraft.
C. The lake water turned green and stinky.
D. Phytoplankton populations in the lake declined initially there by greatly reducing photosynthesis.
Which two of the above were the main causes of fish mortality in the lake?
(a) A, C
(b) A, B
(c) B, C
(d) C, D
Ques. In which one of the following the BOD (Biochemical Oxygen Demand) of sewage (S), distillery effluent (DE), paper mill effluent (PE) and sugar mill effluent (SE) have been arranged in ascending order?
(a) SE < PE < S < DE
(b) PE < S < SE < DE
(c) S < DE < PE < SE
(d) SE < S < PE < DE
Ques. Which one of the following statements is correct?
(a) Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plants.
(b) Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and for plant nutrition in soil.
(c) At present it is not possible to grow maize without chemical fertilizers.
(d) Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies.
Ques. Which one of the following is not a bioindicator of water pollution?
(b) Stone flies
(c) Sewage fungus
Ques. Limit of BOD prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is
(a) < 30 ppm
(b) < 3.0 ppm
(c) < 10 ppm
(d) < 100 ppm.
Ques. Which one of the following is not used for disinfection of drinking water?
Ques. Common indicator organism of water pollution is
(a) Lemna pancicostata
(b) Eichhornia crassipes
(c) Escherichia coli
(d) Entamoeba histolytica.
Ques. Escherichia coli is used as an indicator organism to determine pollution of water with
(a) heavy metals
(b) faecal matter
(c) industrial effluents
(d) pollen of aquatic plants.
Ques. Which of the following is absent in polluted water?
(b) Water hyacinth
(c) Larva of stone fly
(d) Blue green algae
Ques. What is B.O.D.?
(a) The amount of O2 utilised by organisms in water.
(b) The amount of O2 utilised by microorganisms for decomposition.
(c) The total amount of O2 present in water.
(d) All of the above
Ques. The Minamata disease in Japan was caused through the pollution of water by
(b) methyl isocyanate
Ques. D.D.T. is
(a) not a pollutant
(b) an antibiotic
(c) a non-degradable pollutant
(d) a biodegradable pollutant.
Ques. Which of the following organism is likely to have more concentration of D.D.T. in its body?
(a) Top carnivores
(b) Primary producers
ACCELERATED EUTROPHICATION :- The acceleration of aging process of water by human‘s activities like effluents from the industries and homes.
AGRO-CHEMICALS :- The chemicals used in agriculture such as inorganic fertilizers, pesticides, herbicides, fungicides etc. are called agro-chemicals.
ALGAL BLOOM :- Presence of large amount of nutrients in water that cause excessive growth of free floating algae.
Biochemical Oxygen Demand (BOD) :- The amount of the oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria.
BIOMAGNIFICATION :- The increase in concentration of the toxicant at successive trophic levels.
DESERTIFICATION :- When large barren patches of land extend and meet over time, a desert is created.
EUTROPHICATION :-The natural aging of a lake by Biological Enrichment of its water.
• E-WASTE :- Irreparable computers and other electronic wastes
• GREEN HOUSE EFFECT :- The naturally occurring phenomenon that is responsible for heating of Earth‘s surface and atmosphere.
• INTEGRATED ORGANIC FARMING :-A Cyclical, zero waste procedure, where waste products from one process are cycled in as nutrients for other processes.
• MUNICIPAL SOLID WASTES :- The wastes from homes offices, stores, schools, hospital etc.
that are collected and disposed by municipality.
• NOISE :- The undesired high level of sound.
• POLLUTANTS :- Agents that bring about undesirable change in air, water land or soil are called pollutants.
• POLLUTION :- Any undesirable change in physical, chemical or biological characteristics of air, land, water or soil.
• POLYBLEND :- A fine powder of recycled modified plastic.
• REFORESTATION :- The process of restoring a forest that once existed but was removed at same point of time in the past.
• SANITARY LANDFILLS :- The process in which wastes are dumped in a depression or trench after compaction and covered with dirt everyday.
• SNOW-BLINDNESS CATARACT :- High dose of UV-B causes inflammation of cornea.
• SOIL EROSION :- Removal of fertile top soil due to human activities over – cultivation, deforestation etc.
• WATER LOGGING :-The stagnation of water in the field due to irrigation without proper drainage of water.
CBSE Class 12 Biology Environmental Issues Minds Map
Ques. The zone of atmosphere in which the ozone layer is present is called
(a) ionosphere (b) mesosphere
(c) stratosphere (d) troposphere.
Ques. Kyoto protocol was endorsed at
(a) CoP - 6 (b) CoP - 4
(c) CoP - 3 (d) CoP - 5.
Ques. The second commitment period for Kyoto Protocol was decided at
(a) Durban (b) Bali
(c) Doha (d) Cancun.
Ques. “Good ozone” is found in the
(a) mesosphere (b) troposphere
(c) stratosphere (d) ionosphere.
Ques. Global agreement in specific control strategies to reduce the release of ozone depleting substances, was adopted by
(a) Montreal Protocol (b) Kyoto Protocol
(c) Vienna Convention
(d) Rio de Janeiro Conference.
Ques. Montreal Protocol aims at
(a) biodiversity conservation
(b) control of water pollution
(c) control of CO2 emission
(d) reduction of ozone depleting substances.
Ques. Montreal protocol which calls for appropriate action to protect the ozone layer from human activities was passed in the year
(a) 1985 (b) 1986
(c) 1987 (d) 1988.
Ques. Identify the correctly matched pair.
(a) Basel convention – Biodiversity conservation
(b) Kyoto protocol – Climatic change
(c) Montreal protocol – Global warming
(d) Ramsar convention – Ground water pollution
Ques. In coming years, skin related disorders will be more common due to
(a) water pollution
(b) depletion of ozone layer
(c) pollutants in air
(d) use of detergents.
Ques. Formation of ozone hole is maximum over
(a) Europe (b) Africa
(c) India (d) Antarctica.
Ques. Which country has the greatest contribution for the hole formation in ozone layer?
(a) Russia (b) Japan
(c) USA (d) Germany
Ques. Prolonged liberal irrigation of agricultural fields is likely to create the problem of
(a) acidity (b) aridity
(c) salinity (d) metal toxicity.
Ques. Match the items given in column I with those in column II and select the correct option given below.
Column I Column II
A. Eutrophication (i) UV-B radiation
B. Sanitary landfill (ii) Deforestation
C. Snow blindness (iii) Nutrient enrichment
D. Jhum cultivation (iv) Waste disposal
A B C D
(a) (ii) (i) (iii) (iv)
(b) (i) (iii) (iv) (ii)
(c) (iii) (iv) (i) (ii)
(d) (i) (ii) (iv) (iii)
Ques. Joint Forest Management Concept was introduced in India during
(a) 1980s (b) 1990s
(c) 1960s (d) 1970s.
Ques. Which one of the following is a wrong statement?
(a) Most of the forests have been lost in tropical areas.
(b) Ozone in upper part of atmosphere is harmful to animals.
(c) Greenhouse effect is a natural phenomenon.
(d) Eutrophication is a natural phenomenon in freshwater bodies.
Ques. Chipko movement was launched for the protection of
(a) forests (b) livestock
(c) wetlands (d) grasslands.
Ques. If we uncover half of the forest covering the earth, what crisis will be produced at most and at first?
(a) Some species will be extinct.
(b) Population and ecological imbalance will rise up.
(c) Energy crisis will occur.
(d) Rest half forests will maintain this imbalance.
Ques. Which of the following is the main factor of desertification?
(a) Over-grazing (b) Tourism
(c) Irrigated agriculture (d) All of these
Ques. Deforestation will decrease
(a) soil erosion (b) land slides
(c) soil fertility (d) rainfall.
Ques. Soil conservation is
(a) conversion of sterile soil into fertile one
(b) aeration of soil (c) erosion of soil
(d) protection against loss.
Please refer to attached file for CBSE Class 12 Biology - Environmental Issues
|CBSE Class 12 Biology Parthenogenesis Notes|
|CBSE Class 12 Biology Reproduction In Organisms Notes|
|CBSE Class 12 Biology Microbes In Human Welfare Notes|
|CBSE Class 12 Biology Biotechnology Principles And Processes Notes|
|CBSE Class 12 Biology Biotechnology And Its Application Notes|
|CBSE Class 12 Biology Organisms And Populations Notes|
|CBSE Class 12 Biology Ecosystem Notes|
|CBSE Class 12 Biology Biodiversity And Conservation Notes|
|CBSE Class 12 Biology Environmental Issues Notes|
|CBSE Class 12 Biology Human Reproduction Minds Map|
|CBSE Class 12 Biology Human Reproduction Notes|
|CBSE Class 12 Biology Human Reproduction Study Guide|
|CBSE Class 12 Biology Reproductive Health Notes Set A|
|CBSE Class 12 Biology Reproductive Health Notes Set B|
|CBSE Class 12 Biology Reproductive Health Study Guide|
|CBSE Class 12 Biology Evolution Minds Map|
|CBSE Class 12 Biology Evolution Notes Set A|
|CBSE Class 12 Biology Evolution Notes Set B|
|CBSE Class 12 Biology Evolution Study Guide|