Notes-Part-2-Class-12-Biology-Chapter-15-Biodiversity, Conservation and Environmental Issues-Maharashtra Board

Biodiversity, Conservation and Environmental Issues

Maharashtra Board-Class-12th-Biology-Chapter-15


Topics to be Learn : Part-1

  • Introduction
  • Levels of biodiversity
  • Patterns of biodiversity
  • Biodiversity current scenario
  • Loss of biodiversity
  • Conservation and biodiversity
  • Biological Diversity Act 2002

Topics to be Learn : Part-2

  • Environmental  issues
  • Greenhouse effect and global warming
  • Ozone depletion
  • Deforestation
  • Mission Harit Maharashtra

Environmental issues :

To protect and improve the quality of our environment, Indian Government has passed the Environment Protection Act in 1986.

Reasons for rampant loss of natural resources :

Exponential growth of human population

  • Industrial development
  • Uncontrolled exploitation of nature
  • Utilization and production of synthetic materials '
  • Construction activities
  • Resultant pollution

Types of pollution :

Air pollution, Noise pollution, Water pollution, Radioactive pollution, Soil pollution are different types of pollution.

Pollutant : Substance that causes pollution is called a pollutant.

Air pollution :

  • Unfavourable alteration in air quality causing damage to the respiratory system is called air pollution.
  • Duration of exposure, concentration of pollutant and type of organism decide the severity of damage caused by air pollution.
  • In plants, yield of crops are affected. Premature death of plants is another effect of air pollution.
  • Major cause of air pollution is automobile traffic.

Types of air pollutants : Two main types -> Particulate and Gaseous pollutants.

Particulate air pollutants.

  • Particulate air pollutants are either solids or liquids.
  • Particles having larger diameter of 10 um settle in the soil but finer particles with 1 pm or less remain suspended in the air.
  • Central Pollution Control Board (CPCB) has declared that, particulate matter of size
  • 2.5 um or less in diameter (PM 2.5) are responsible for causing the greatest harm to humans. These fine particulates can be inhaled deep into the lungs and are responsible for irritation, inflammation and damage to lungs.
  • In addition to this, it causes breathing and respiratory disorders and premature deaths.
  • Examples of particulate pollutants are : Smoke, smog, pesticides, heavy metals, dust and radioactive elements.

Gaseous pollutants :

Gaseous pollutants : CO, CO2, SO2, NO, NO2, etc.

Carbon dioxide :

  • It is a greenhouse gas. It is produced in excess due to human activities such as burning of fossil fuels. It is also rising due to increasing deforestation.
  • The natural cycle of Carbon dioxide is disturbed due to human interference.
  • Otherwise, the process of photosynthesis can balance CO2 : O2 ratio of the air.
  • Aeroplane traffic such as a jet plane also emits lots of CO2.

Carbon monoxide (CO) :CO is produced due to incomplete combustion of fuels. It is a toxic gas. Vehicular exhausts produce lot of CO.

Nitrogen di oxide (NO2) and nitrogen monoxide (NO):

  • These are released by automobiles and chemical industries as waste gases. NO2 when combines with water vapours forms nitric acid.
  • It causes irritation to eyes and lungs. At high concentration, it causes injury to lungs, liver and kidneys.

Control measures for air pollution : For controlling emissions of gases and particulate pollutants which are released through vehicles and industries following devices are used :

(i) Electrostatic precipitator :

This is an important equipment which is used to remove particulate matter like soot and dust present in industrial exhaust. It is capable of removing almost 99% particulate matter present in exhaust of a thermal power plant.

Working :

Working :

  • In Electrostatic precipitator, high voltage is applied which produces electric discharge.
  • This discharge causes ionisation of air in the smokestack.
  • As a result, the free electrons are formed.
  • These electrons in the ionised air attach to the gaseous or dust particles moving up the stack.
  • Negatively charged particles move towards the positive electrode and settle down there.
  • They are then removed by vibrations of the electrodes and collected in the reservoir.


(ii) Exhaust gas scrubbers :

  • Exhaust gas scrubbers are used to clean air by removing both dust and gases.
  • The exhaust is passed through dry or wet packing material. When it is done, gases like SO2 are removed. For this purpose, the exhaust is passed through a spray of water or lime.

(iii) Catalytic converters :

The harmful gases like CO and nitrogen oxides which are present in the automobile exhausts are removed by catalytic converters. Thereby, harmful effects of air pollution are reduced.

Working :

Working :

  • In block 1 : Nitrogen oxides are present in the exhaust gases. They enter into reduction block of catalyst. The oxides of nitrogen react forming nitrogen and oxygen.
  • In block 2 : The exhaust gases enter the next block called oxidation block of the catalyst. Here, hydrocarbons and the newly formed oxygen react to form carbon dioxide.
  • In block 3 : The exhaust gases enter into last block from here the least harmful gases are released out.


Controlling Vehicular Air Pollution : A case study of Delhi :

Controlling Vehicular Air Pollution : A case study of Delhi

In the year 1990, Delhi ranked fourth among 41 most polluted cities of the world.

In response to PIL (Public Interest Litigation), Supreme court of India sent orders to Delhi government to take appropriate actions.

Following measures were taken by Delhi Government :

  • By 2002, all the city buses of Delhi were converted to CNG buses which now do not run on diesel.
  • The new fuel policy was introduced and the norms were set to reduce sulphur and aromatic content of petrol and diesel.
  • Upgradation of engines was done.
  • Bharat stage emission standards (BS) were set which were equivalent to Euro norms.
  • Bharat Stage II (BS II) to BS VI norms were given from 2001 to 2017.
  • Administration took certain measures like closing educational institutions, suspending of construction or demolition work, undertaking vacuum cleaning of roads, etc.
  • The polluting industries were penalized and Badarpur thermal power plant was temporarily closed down.


Noise pollution :

Noise pollution :

  • Noise is considered as an air pollutant which causes psychological and physiological changes in human beings.
  • Sound level can damage the ear drum causing permanent hearing loss. Other problems that noise causes are sleeplessness, increased heartbeat, altered breathing, psychological stress, interference in learning etc.

Sources of noise pollution : Machines, transportation, construction sites and industry.

Ways to reduce noise pollution :

  • Noise reduction in our industries can be accomplished through the use of sound absorbent materials or by muffling the noise.
  • To reduce decibel levels, laws prohibiting the use of horns in schools and hospitals must be strictly enforced.
  • The Indian government has rules and regulations regarding firecrackers and loudspeakers. The Supreme Court of India has prohibited the use of loudspeakers at public gatherings after 10 p.m.


Water pollution :

  • Most of the water pollution is manmade.
  • Smelling water having many pathogens, heavy metals and oils is called polluted water.
  • When water is impure, it cannot be used for human consumption.
  • Small amount about 0.1% impurities in water also makes the water polluted.
  • Water Prevention and Control of Pollution Act 1974 to safeguard the water resources.
  • Domestic sewage and Industrial effluents cause water pollution.

Domestic sewage and Industrial Effluents:

  • In domestic sewage, there are dissolved salts such as nitrates, phosphates, other nutrients and toxic metal ions as well as organic compounds.
  • Sewage also contains biodegradable organic matter and harmful bacterial and virus.
  • Organic matter can be decomposed by bacteria and other microorganisms. But such water is not potable.
  • Industrial effluents also contain harmful heavy metals and other solids.
  • Solids can be easily removed from water but the dissolved salts cannot be separated.
  • BOD or biochemical oxygen demand is a measure to estimate biodegradable organic matter present in the polluted water. It is defined as the amount of dissolved oxygen required by microorganisms for decomposing the organic matter present in water which is expressed in milligram of oxygen per litre (mg/L) of water.

Algal bloom : Excessive growth of free floating planktonic blue green algae causes algal bloom. It releases toxins in the water causing death of inhabitant fish.

Water hyacinth (Eichhornia crassipes) : Commonly called ‘Terror of Bengal‘ is an invasive species which grows excessively in water bodies and cause nuisance.

Natural eutrophication : Ageing of lake over a very long period due to nutrient enrichment of water is called natural eutrophication.

Cultural or accelerated eutrophication: Pollutants passing in the water body due to human activities cause cultural eutrophication in which there is accelerated aging process for the water body.

Biological magnification or biomagnification : Accumulation of certain pollutant in the tissues of organisms and their increasing concentrations along the food chain is called biomagnification. E.g. DDT and mercury show biomagnification.

Thermal pollution : Thermal pollution of water is caused due to rise in temperature of water.

  • The main source of thermal pollution are the thermal and nuclear power plants. The power plants use water as coolant and release hot water.
  • As many organisms are sensitive to temperature, sudden rise in temperature leads to loss of flora and fauna.

Measures to reduce sewage water :

Measures to reduce sewage water:

In order to conserve water and prevent creation of sewage, ecosan is a sustainable system for handling human excreta using dry composting toilets. This is a practical, efficient and cost-effective solution for human waste disposal.

Ecosan ;

  • Ecological sanitation (Ecosan) is a sanitation provision that safely reuses excreta in agriculture as a manure.
  • By Ecosan the need for chemical fertilizers is reduced. Ecosan toilet is a closed system without water and it is an alternative to leach pit toilets.
  • They are useful in places of water scarcity or places with risk of ground water contamination.
  • The principle of recovery and recycling of nutrients from excreta to create a valuable resource for agriculture is used here in Ecosan.
  • The pit of an ecosan toilet fills up after some time, then it is closed and sealed for about 8-9 months. In this time the faeces gets completely composted to organic manure. ‘
  • It is a practical, efficient and cost-effective solution for human waste disposal.
  • There are working Ecosan toilets in many areas of Gujarat, Kerala, Tamil Nadu and Sri Lanka.

Reverse osmosis : Sewage water is reused after performing reverse osmosis. It solves the problem of water scarcity and treatment of sewage water.

Rainwater harvesting : By harvesting rainwater, scarcity of water can be solved. For new constructions now it is mandatory to have provision for RWH.


Solid Waste Management :

Solid waste is everything that goes to trash. It includes wastes from home, offices, stores, schools, hospitals etc.

Municipal wastes : Wastes from homes, offices, stores, schools, hospitals, etc. together are called Municipal wastes. Municipality collects and disposes the same. It may contain paper, food wastes, plastics, glass, metals, rubber, leather, textile, etc.

One of the ways to dispose the solid waste is to burn them. Volume of the waste is reduced by burning but burning creates air pollution.

Sanitary landfills : Dumping the trash in open can attract rats and flies causing open dumps as the breeding ground for these pests. Therefore, sanitary landfills are created.

  • At sanitaly landfill sites, the wastes are compacted and buried in trenches. Everyday newer trash is added to landfills.
  • However, this method is not a fool proof solution for the waste management as in large metro cities amount of trash is increasing day by day and hence such landfills are falling short. There is also seepage of dangerous chemicals from the sanitary landfills which results into the pollution of underground water reserves.
  • Therefore, every human being should be sensitized towards the environmental issues.
  • Common man should have ecological conscience to reduce the non-biodegradable trash.

The solid wastes are categorized into three types :

(1) Bio-degradable

(2) Recyclable

(3) Non-biodegradable.

  • The generated garbage should be sorted prior to disposal. The matter that could be reused or recycled should not be thrown into trash but to be given to kabadiwallahs and rag-pickers.
  • The biodegradable materials undergo natural breakdown. Therefore they can be buried deep down in the ground in pits.
  • The non-biodegradable material should be reduced at source to curb the garbage generation. Packaging material, plastics, polybags, etc. which are used to a greater extent in modern times cause environmental pollution. Use of eco-friendly packaging and reduction in plastic has been advocated by the State Governments.

Biomedical wastes : Hazardous wastes generated by hospitals contain disinfectants, harmful chemicals and disease-causing pathogenic microorganisms. Therefore such wastes should be carefully handled, treated and then disposed. For disposal of harmful biomedical wastes the incinerators are used.

Electronic wastes (e-wastes) :

  • e-wastes are any material of electronic origin, such as irreparable computers, mobile phones, CDs, floppies, batteries etc.
  • e-wastes are managed by burying them in landfills or they are incinerated.
  • e-wastes generated in the developed world are exported to developing countries for further recycling and disposal.
  • In China, India and Pakistan, metals like copper, iron, silicon, nickel and gold are recovered from e-wastes during recycling process.
  • Developed countries, have facilities for recycling of e-wastes. But it involves manual participation and this exposes the workers to toxic substances present in e-wastes. For treating e-wastes, recycling is the only control measure. But it has to be done in an eco-friendly manner.

Anti-plastic notifications: Government of Maharashtra has banned used of plastic by notification (23rd June 2018). This is a mission to make ‘Plastic Free Maharashtra’.

Greenhouse effect and Global warming:

Greenhouse effect : _

  • The greenhouse effect is a natural phenomenon that occurs on Earth.
  • The greenhouse effect raises the average temperature of the Earth's surface.
  • The earth's temperature would have been -18 °C if it hadn't been there. However, because of the greenhouse, it is now averaging 15 °C. This was referred to as a positive greenhouse effect.
  • However, in recent years, the excessive greenhouse effect has resulted in widespread global warming and climate change.
  • Infrared radiations are trapped due to atmospheric gases such as carbon dioxide, methane, etc. These gases absorb a major fraction of it and re-radiate the heat energy back to the earth’s surface. This exchange of heat goes in a cyclic manner.
  • Carbon dioxide and methane are main greenhouse gases; additionally, chloroflorocarbons (CFC), Nitrous oxide (N2O) and water vapours add to this effect.

Global warming :

Global warming :

  • Global warming is increased temperature of the earth. During past century, the temperature of the Earth has increased by 0.6 °C, most of it during last three decades.
  • This is mainly caused by greenhouse effect.
  • Global Warming depends upon the amount of CO2 and other greenhouse gases present in the atmosphere.
  • An increase in CO2 concentration increases earth‘s temperature by retaining more heat.
  • Carbon dioxide increases temperature by about 50%, CFCs increase it by 20% and methane increases it by 15% whereas other pollutants increase it by 10%. Atmospheric air pollution, industrialization and greenhouse effect cause global warming.
  • El Nino effects, melting of polar ice caps, Alps and Himalayas, and rising sea levels that cause coastal submergence are all caused by global warming.

Measures to reduce greenhouse effect and Global warming :

  • Reducing use of fossil fuel.
  • Efficient use of energy. Use of alternative energy sources like solar or wind energy.
  • Reducing deforestation.
  • Tree plantation and afforestation activities.
  • Reducing the rate of growth of human population.
  • International initiatives for reduction of greenhouse gases.


Know This :

El Nino effect is a climate cycle in pacific ocean with global impact on weather pattern. The cycle begins when warm water in the western tropical pacific ocean shifts eastwards along the equator towards the coast of America. Normally, this warm water pools near Indonesia and Philippines.

La Nina is a climatic pattern that describes the cooling of surface ocean waters along the tropical west coast of south America.

 Ozone depletion

  • In the upper stratosphere strata there is ozone layer. It is continuously formed by action of ultraviolet radiations on molecular oxygen.
  • Molecular oxygen also degrades back into ozone in the stratosphere. Ozone layer absorbs ultraviolet radiation from the sun and protects the flora and fauna from deleterious effects of radiation.
  • Living organisms are affected due to UV radiation because it causes damage to their
  • DNA and proteins by breaking the chemical bonds within DNA and proteins.
  • The unit for measuring thickness of ozone is Dobson unit (DU).
  • A balance between production and degradation of ozone in the stratosphere is lately disturbed due to excessive proportion of chlorofluorocarbons (CFCs) in the atmosphere.
  • Chlorofluorocarbons are used in refrigerators. When released they move upward and reach stratosphere. The ultraviolet rays in stratosphere, react with CFC and release Cl- atoms. Ozone is degraded by Cl-_atoms.
  • This later causes ozone depletion or formation of ozone hole as it is clearly seen over the Antarctic region.

Deleterious effects of Ozone depletion :

  • Aging of skin.
  • Damage to skin cells causing skin cancers.
  • Inflammation of cornea of human eye causing snow-blindness cataract.
  • Permanent damage to the cornea.
  • UV-B radiation cause damage to DNA and mutations.

Montreal Protocol :

  • Montreal Protocol was signed agreement of an international treaty among different nations who had recognised the harmful effects of ozone depletion.
  • It was signed at Montreal (Canada) in 1987 to control emission of ozone depleting substances.
  • After signing of Montreal protocoland its subsequent execution in 1989, the ozone depletion has been reduced worldwide.

Deforestation :

  • Converting forested land into barren land is called deforestation.
  • Tropical forests are reduced by about 40% whereas temperate forests are lessened by 1% in the temperate region.
  • India is facing severe deforestation. There was 30% of forests in Indian land in early twentieth century. Now it has reduced to 19.4%.
  • It is recommended by National Forest Policy (1988) of India that the hilly area should have 67% while the plain area should have 33% forest cover.

Causes of deforestation :

  • Unplanned human activities.
  • Conversion of forest to agricultural land for growing food for ever-increasing human population.
  • Trees are cut for timber, firewood, for keeping cattle in farm and for other purposes.
  • For constructions of dams, road, railways, metros, residential complexes, etc.
  • For any kind of developmental activities due to Government Policies.
  • Slash and burn agriculture or Jhum cultivation in the north-eastern parts of India.
  • Severe deforestation is caused due to increasing human population and repeated cultivation that resulted into shortening of recovery phase.

Major Effect of deforestation :

  • Increased concentration of CO2 in the atmosphere.
  • Trees hold lot of carbon in their biomass which is lost with deforestation.
  • Loss of biodiversity due to habitat destruction.
  • Disturbances in hydrologic cycle.
  • Soil erosion and desertification in extreme cases.

Reforestation :

  • Restoring a forest that once existed is called reforestation.
  • There can be a natural reforestation or it can be due to human efforts by planting trees.
  • However, when it is due to human efforts the natural biodiversity may be lost.

Example of peoples participation in reforestation :

(1) Saalumara Thimmakka, an Indian environmentalist from state of Karnataka noted for her work in planting and tending to 385 banyan trees along a 4km stretch of highway between Hulikal and Kudur and planted nearly 8000 other trees.

Her work has been honoured with the National Citizens Award of India and Padma Shri Award in 2019.

(2) Moirangthem Loiya of Manipur worked for 17 years to restore Punshilok forest. He quit his job and took on the task of restoring the glory of 300 acres of forest land. He planted many trees, including bamboo, oak, ficus, teak, jackfruit, and magnolia. Today, the forest contains over 250 plant species, including 25 varieties of bamboo. It is now chosen as a home by a wide range of animals.

Case study of peoples participation in conservation of forests :

Case study of people’s participation in conservation of forests :

Following examples show people’s participation in the conservation of forests :

(1) In 1731, Amrita Devi had sacrificed her life to save trees along with other people of Bishnofs community. It was the example of sacrificing lives for the cause of saving trees and environment. Amrita Devi Bishnoi Wildlife Protection Award for individuals or communities from rural areas has been installed by the Government of India.

(2) Chipko Movement is people’s participation for the protection of trees. This happened in 1974 in Garhwal region of Himalayas. Chipko movement has now spread world-wide in which people hug the trees and save it from the axe of tree-cutters.

(3) Joint Forest Management (JFM) has been introduced by the Government of India in 1980s for working with the local communities for protection and management of the forests. It is an attempt to conserve forests in a sustainable matter.


Mission Harit Maharashtra :

  • In 2016, the Maharashtra government embarked on a four-year project to plant 50 crore trees.
  • Plantation targets were set for each district on a yearly basis.
  • The plantations are governed by the National Forest Policy (NFP).
  • A 24-hour toll-free helpline number 1926 has been established for information about plantation, protection, and mass awareness.
  • The Forest Department has also created a mobile application called 'MY Plants.' It keeps track of the plantation numbers, species, and location.
  • Number of Saplings were planted are, 2.87 crore saplings in 2016, 5.17 crore saplings in 2017, 15.17 crore saplings in 2018, 33 crore saplings in 2019.
  • Authorities are taking care of these plantations.
  • Also Japanese Miyawaki method of plantation is adapted by State Forest Department and Social Forestry Department.
  • Such plantations are in districts of Beed, Hingoli, Pune, Jalgaon, Aurangabad, etc.

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