marjanblan-GOP07ZOjBEU-unsplash.jpg

16.  Environmental Issues 

  1. Pollution is the undesirable change brought about by chemical, particulate matter, or biological materials to air, water, or soil.

Air Pollution

  1. Air is a complex, dynamic natural entity, which is essential for supporting life on earth.

  2. Air pollutant is a substance that causes harm to the humans and other living organisms.

  3. Some of the common pollutants of air:

    1. Nitrogen dioxide

    2. Sulphur dioxide

    3. Carbon monoxide and carbon dioxide

    4. Volatile organic compounds

    5. Particulate matter

Control of Air Pollution

  1. Air pollution causes severe respiratory disorders in humans and other animals and also affects plants. It can be controlled by the following ways:

    1. Fitting smokestacks and smelters, with filters to separate pollutants from the harmless gases

    2. Particulate matter can be removed by using an electrostatic precipitator . It contains electrode wires maintained at several thousand volts, which produce electrons. These electrons cling on to dust particles and give them a net negative charge and are attracted by collecting plates, which are grounded. The velocityof air passing through the plates should be low enough to allow the dust to fall.

    3. A scrubber can be used to remove gases such as SO 2 wherein the exhaust passes through a spray of water or lime.

    4. Vehicular pollution can be reduced by using less polluting fuels such as CNG , which is more efficient and less costly as compared to petrol or diesel. In 2002, all the buses wereswitched to CNG in Delhi and this has indeed led to a fall inpollution levels in the city.

    5. Vehicles can be fitted with catalytic converters that havemetals such as platinum, palladium, and rhodium as catalysts.

    6. These catalysts carry out the following conversions:

      1. Unburnt hydrocarbons → CO 2 and H 2 O

      2. Carbon monoxide → Carbon dioxide

      3. Nitric oxide → Nitrogen gas

    7. Unleaded petrol must be used with catalytic converters as presence of lead

    8. in the petrol inactivates the catalyst.

Greenhouse Effect

  1. It is a natural phenomenon that keeps the earth’s atmosphere warm.

    1. Without this phenomenon, the temperature of the earth wouldbecome too cold for living beings to survive.

    2. The greenhouse gases (CO 2 , methane, etc.) absorb the heat ofsun and the earth and emit it back to the earth’s surface.

    3. Thus, these gases prevent a part of heat rays from escaping intoatmosphere.

    4. This cycle is repeated many times to maintain the earth’stemperature to an optimum 15ºC.

  2. The concentration of these gases has increased due to increasedindustrialisation, leading to the heating up of the earth’s surface(global warming).

  3. This has increased the overall temperature of the earth, resulting inchanges in the earth’s climate. During the last century, thetemperature of earth has increased by 0.6ºC.

  4. This increase in temperature is ultimately believed to cause themelting of polar ice caps, rise in the sea level, and submerging of the coastal areas.

  5. Greenhouse effect can be controlled by reducing the use of fossil fuels,which produce greenhouse gases on burning, afforestation, efficientenergy usage, etc.

Water Pollution

  1. Water is very essential for the maintenance of life on earth.

  2. Due to human activities, water bodies have become polluted all over

  3. the world.

  4. Some of the common pollutants and their sources are:

    1. Domestic sewage − It mainly contains organic matter, which isbiodegradable. Microorganisms involved in their degradationconsume a lot of oxygen and the BOD of the water bodyincreases leading to the death of fishes and other aquatic life.Sewage also contains many pathogenic microbes, which maycause the outbreak of many diseases such as typhoid, jaundice,etc.

    2. Industrial Effluents − Industrial effluents contain inorganictoxic substances, which may undergo biomagnification(increase in concentration of a toxin at successive trophiclevels). The toxin gets accumulated in the body of an organismand is passed on to the next level. For example, DDT and otherheavy metals such as mercury, cadmium, etc.

    3. Thermal wastewater discharge − Heated water flowing out ofthe thermal power plants increase the temperature of the waterbody. It eliminates the cold water species and promotes thewarm water species. In the long run, it causes damage to theindigenous biodiversity of the water body.

    4. Eutrophication

      1. It is the ageing of a water body due to nutrient enrichment of itswater. It can be natural or artificial.

      2. The natural process takes thousands of years, but due to humanactivities, this process has got accelerated (accelerated/culturaleutrophication).

      3. Release of nutrient rich sewage and industrial effluents lead tointroduction of nutrients such as nitrogen and phosphorus andincrease in temperature and BOD of the water body, causingincreased biological activity, thereby leading to algal blooms.

      4. This results in the loss of indigenous flora and fauna.

      5. In some cases, large masses of floating plants (bog) develop,finally converting the water body into land.

Control of Water Pollution

  1. Raw sewage can be treated using biological and other means toremove the solid, suspended, and inorganic materials before it isreleased back into the environment.

  2. Nitrogenous fertilizers can be denitrified using microbes, which canconvert nitrate and nitrite into gaseous nitrogen by a process called denitrification.

  3. Integrated wastewater management as practiced in Arcata,California In this approach, the water is first treated by conventionalmeans such as filtration, sedimentation, and chlorine treatment,followed by bioremediation. (Marshes having appropriate plants,bacteria, fungi, and algae were seeded, which assimilate dangerouspollutants such as heavy metals)

Solid Waste

  1. Consists of all the unwanted undesired materials thrown into thedustbin

  2. It may be composed of biodegradable or nonbiodegradablewastes.

  3. Open dumps used for disposing solid waste serves as breeding groundfor rats and flies. Therefore, sanitary landfills are used as a substitutefor these.

  4. Biodegradable wastes can be either aerobically on anaerobicallybroken down using microbes. The nonbiodegradablewaste can berecycled, reused, or dumped in landfills.

  5. Hospital wastes also contain hazardous materials, which have to bedisposed properly. Hospital wastes are generally incinerated.

  6. Irreparable computers and other electronic goods make up ewastes,which are either dumped in land fills or are incinerated. Ewastecanbe recycled also to recover metals such as copper, iron, silicon, gold,etc.

  7. To use the plastic waste in an efficient way, polyblend , a fine powderof recycled modified plastic, has been developed. When polyblend ismixed with bitumen, it can be used to lay roads with greater waterrepellent capacity and greater life.

Agrochemicals and Radioactive Wastes

Agrochemicals

  1. The increased use of pesticides, fertilizers for increasing the producehas led to eutrophication and biomagnifications in water sources.

  2. In order to check this, the concept of organic farming is increasinglybecoming popular. In this technique, instead of using chemicalfertilizers and pesticides, natural materials and techniques such asorganic manure (cow dung manure), compost, biological pest control,and crop rotation are used. This leads to a balanced soil, which doesnot cause soil infertility, but causes the rejuvenation of the soil.

Radioactive Wastes

  1. Nuclear energy is a nonpollutingenergy except the threats posed byaccidental leakage and difficult disposal of radioactive waste.

  2. Radioactive substances cause severe damages such as mutations andcancer in lower doses and higher doses can be lethal.

  3. Radioactive wastes should be suitably pretreatedin shieldedcontainers buried under rock surfaces about 500 m under the earth’ssurface.

Improper Utilisation of Resources

  1. Natural resources can get degraded by their improper use.

    1. Soil erosion and desertification − Overcultivation,overgrazing, deforestation, and poor irrigation techniques lead tosoil erosion and desertification.

    2. Water logging and soil salinity Lackof proper drainageleads to water logging, which affects the crops and also leads toincrease in the salinity of the soil.

Ozone Depletion and Deforestation

Ozone Depletion

  1. The ozone layer is found in the upper part of the stratosphere.

  2. It protects the earth from the harmful UV rays of the Sun. High energyUV rays break the bonds within the molecules such as DNA andproteins.

  3. Ozone is formed by the action of UV rays on oxygen molecule and itsthickness is measured in Dobson units (DU) .

  4. The ozone layer is getting depleted by the action ofchlorofluorocarbons (CFCs) found in refrigerants and perfumes.

  5. The CFCs are acted upon by UV rays in the stratosphere, liberating theCl atoms, which act as catalysts to degrade ozone into molecularoxygen.

  6. The ozone depletion is particularly greater in Antarctica, resulting inthe formation of a large thinned ozone layer commonly known asozone hole .

  7. The UV rays of shorter wavelength cause skin cancers, mutations inthe cellular DNA, snowblindness,cataract, etc.

  8. To check this ozone depletion, Montreal Protocol was passed in 1987to control the use of substances that cause ozone depletion.

Deforestation

  1. It is the unlimited cutting of trees and conversion of forests intocultivable land.

  2. In the beginning of 20 th century, India had 30% of its area underforests, which was reduced to just 19.4% by the end of 20 th century.

  3. Deforestation is a result of a number of human activities such asincreased population and the demand for land.

  4. Trees are cut for timber, fuel, and also for Slash and burnagriculture , also called Jhum cultivation. In this, trees are cut andplant remains in the forest are burned since the ash acts as a fertilizer.

  5. Some of the major effects of deforestation are the increase incarbondioxidelevels, loss of habitat for wild animals, soil erosion, andconsequent desertification.

  6. Deforestation can be controlled by reforestation and afforestation.

  7. In 1980s, the concept of Joint Forest Management was introducedby the government of India. In this, support of local communities wastaken for conservation of forests and in return, the local people werefree to use the products obtained from the forests.

REVISION NOTES

 

CLASS 11 BIOLOGY

UNIT I – DIVERSITY IN THE LIVING WORLD

Chapter 1 – The Living World 

Chapter 2 – Biological Classification 

Chapter 3 – Plant Kingdom 

Chapter 4 – Animal Kingdom 

UNIT II – STRUCTURAL ORGANISATION IN PLANTS AND ANIMALS

Chapter 5 – Morphology of Flowering Plants 

Chapter 6 – Anatomy of Flowering Plants 

Chapter 7 – Structural Organisation in Animals 

UNIT III – CELL : STRUCTURE AND FUNCTIONS

 

Chapter 8 – Cell: The Unit of Life 

Chapter 9 – Bio-Molecules 

Chapter 10 – Cell Cycle and Cell Division 

UNIT IV – PLANT PHYSIOLOGY 

Chapter 11 – Transport in Plants 

Chapter 12 – Mineral Nutrition 

Chapter 13 – Photosynthesis in higher plants 

Chapter 14 – Respiration in Plants 

Chapter 15 – Plant Growth and Development 

UNIT V – HUMAN PHYSIOLOGY 

Chapter 16 – Digestion And Absorption 

Chapter 17 – Breathing and Exchange of Gases 

Chapter 18 – Body fluids and circulation 

Chapter 19 – Excretory Products and their Elimination 

Chapter 20 – Locomotion and Movement 

Chapter 21 – Neural Control and Coordination 

Chapter 22 – Chemical Coordination and Integration 

CLASS 12 BIOLOGY

Unit-VI Reproduction
  

Chapter 1 : Reproduction in Organisms 

Chapter 2 : Sexual Reproduction in Flowering Plants 

Chapter 3 : Human Reproduction 

Chapter 4 : Reproductive Health 

Unit-VII Genetics and Evolution

Chapter 5 : Principles of Inheritance and Variation 

Chapter 6 : Molecular Basis of Inheritance 

Chapter 7 : Evolution 

Unit-VIII Biology and Human Welfare

Chapter 8 : Human Health and Disease 

Chapter 9 : Strategies for Enhancement in Food Production 

Chapter 10 : Microbes in Human Welfare 

Unit-IX Biotechnology  

Chapter 11 : Biotechnology Principles and Processes 

Chapter 12 : Biotechnology and its Applications 

Unit-X Ecology and Environment 

Chapter 13 : Organisms and Populations 

Chapter 14 : Ecosystem 

Chapter 15 : Biodiversity and Conservation 

Chapter 16 : Environmental Issues 

  • LinkedIn
  • YouTube
  • Facebook
  • Twitter

RAVSUN

NEET/Board/Foundation

Contact Us