Biology 12 Environmental Issues Chapter 15 – Exercise

Q 1. What are the various constituents of domestic sewage? Discuss the effects of sewage discharge on a river.

Ans 1. The domestic waste contains everything that down the drain into the sewer of the house. Suspended solids are soil particles (sand and silt), inorganic colloidal particles (e.g., clay) and organic colloidal matter (faecal matter, cloth, paper, fibers. Eatable waste etc.), dissolved solids (nitrate. Phosphates etc. and toxic metalions) and pathogens.

Pollutants make water unfit for domestic and industrial use.

Water is needed by all organisms for metabolic activities. Many organisms use water as a habitat as well. Sewage can pollute water in a huge amount. Pollutants also make water harmful to living organisms.

Water organisms can tolerate low concentration of poisonous pollutants. Higher concentrations render water biologically barren by destroying life. Highly polluted water supports only a few very hardy species. This include diatoms, bacteria, blue-green algae are Oscillatoria and Microsystis. The green algae are Senedesmus and Stieoclonium. Some large plants, such as Potamogeton Pectinatus and P. natans, and the Moss fontinalis antipyretica occurs in water not excessively polluted.

Q 2. List all the wastes that you generate at home, school or during your trip to other places; could you very easily reduce? Which would be difficult or rather impossible to reduce?

Ans 2. Waste generated at home: paper, cloth, plastic, cans, carton boxes, wood, sewage, kitchen waste etc.

Waste generated at school: paper, chalk, plastic envelopes etc.

Waste generated during trips: paper, disposable cups, plates, spoons, plastic envelopes, discarded food etc. Yes, waste can easily be reduced by us through judicious use of materials, by by changing our habits and like styles.

The waste belongs to two categories: Biodegradable and non-biodegradable. It is difficult or rather impossible to degrade non-biodegradable waste because microorganisms can’t decompose these.

Q 3. Discuess the causes and effects of global warming. What measures need to be taken to control global warming.

Ans 3. Green House Effect: A building made chiefly of glass for growing or sheltering the delicate or exotic plants is called green house. The air in greenhouse is warmer than the outside air though it revives less solar radiation. The occurrence of higher temperature inside a greenhouse than outside. Even though the interior receives less solar radiation, is known as the “Green House Effect”.

Reason of Green House Effect.

  • Glass walls of the green house,
  • CO2 Contents, and
  • Water vapour contents of the air in the green house.

Q 4. Match the items in column A and B.

Column A Column B
i.               Catalytic converter

ii.              Electrostatic precipitator

iii.            Earmuffs

iv.             Landfills

a.     Particulate matter

b.     Carbon monoxide and nitrogen oxides

c.     High noise level

d.     Solid wastes

Ans 4.

Column A Column B
i.      Catalytic converter

ii.              Electrostatic precipitator

iii.            Earmuffs

iv.             Landfills

      b. Carbon monoxide and nitrogen oxides

a. Particulate matter

c. High noise level

d. Solid wastes

Q 5. Write critical notes on the following:

  1. Eutrophication
  2. Biological magnification
  3. Groundwater depletion and ways for its replenishment

Ans 5.

  1. Eutrophication: Phosphorus and nitrates dissolved in water act as nutrients and accelerate the growth of plankton (free-floating algae), called an algal bloom that may form a mat on the water surface. This increased productivity is called Eutrophication.
  2. Biological magnification (Bio-magnification): above mentioned toxic substances and large number of pesticides are non-biodegradable. Therefore, concentration of the toxic materials increases at each trophic level of a food chain. This phenomenon is called bio-magnification, or biological concentration.
  3. Underground water is no more pure and safe, particularly in cities and industrial areas. The common sources of underground water pollution are sewage and industrial effluents spilled over the ground, fertilizers and pesticides
Q 6.  Why ozone hole forms over Antarctica? How will enhanced ultraviolet radiation effect on us?

Ans 6. Chorofluorocarbons, which released in the atmosphere by developed countries, slowly enters the stratosphere and the winds move them towards the poles. Environmental conditions prevailing in Antarctica during winter months (June to august) are conducive for the formation of ozone hole. In these month, there is no sunlight in Antarctica and extremely low temperature (-850C) facilitates the formation of ice clouds. During winter, natural circulation of wind (polar vortex) completely isolates Antarctic air from the rest of the world. The ice clouds provide the catalytic surface for the reaction of chlorine atoms and then ozone. But this degradation of ozone occurs with the return of solar radiations to Antarctica during spring (September and October).

Results in the thinning of ozone layer every year over most of Antarctica. This hole disappears in summer due to warming up of air and the mixing up of Antarctic air with that of the rest of the world.

Enhanced UV radiations on earth would an effect humans and other animals by causing.

Q 7. Discuss the role of women and communities in protection and conservation of forests.
Ans 7. In 1731, a Bishnoi omen Amrita Devi showed exemplary courage by hugging a tree to prevent its cutting. Her three daughters and hundreds of other Bishnoi followed her. They were killed by soldiers of king of jodhpur. This movement forced the kind to abandon cutting of trees. Later “chipko movement” was started by Sunder Lal Bahuguna and others to prevent cutting of trees.
Q 8. What measures, as an individual, you would take to reduce environmental pollution?
Ans 8. To reduce environmental pollution, I will change my habits and lige style so as to reduce the use of disposable materials. I will also use perfectly those items which can easily be recycled and also will minimize the use of fossil fuels.

Q 9. Discuss briefly the following:

  1. Radioactive wastes
  2. Defunct ships and e-wates
  3. Municipal solid wastes.


  1. Radioactive wastes is the physical pollution of air, water and soil with radioactive materials. Radioactivity is the property of certain elements (radium, thorium, uranium, etc.) to spontaneously emit protons (alpha particles), electrons (beta particles) and gamma rays (electromagnetic waves of very short wave length) by disintegration of their atomic nuclei. The elements that give off radiation as they disintegrate are said to be radioactive.
  2. defunct ships also contribute to solid wastes. Such ships are broken down for scrap metal in developing countries like India. These defunct ships are the source of toxicants like asbestos, polychlorinated biphenyls, tributyl tin, lead, mercury etc. the workers get expend to three chemicals and coastal area in the vicinity of ship-breaking yard gets polluted.

Computers and other electronic goods are irresponsible. These are known as electronic wastes or e-wastes.

  1. A variety of solid waste materials from domestic and commercial operations are scattered by man over the landscape or dumped outside the towns every day. These materials include peels of vegetables and fruits, ashes, leftovers of eatables, discarded paper, clothes, leather goods and cardboard boxes, unserviceable wooden articles, spoiled food items, empty bottles, cans and plastic containers, trash bads polypropylene sacks, ropes, net segments, carcasses and others.

Q 10. What initiative were taken for reducing vehicular air pollution in Delhi? Has air quality improved in Delhi?

Ans. Under the direction of supreme court of India, the state government of Delhi took following measure to improve the quality of air:

  1. switching over the entire fleet of public transport buses from diesel to CNG by the end of 2002.
  2. Phasing out of old vehicles,
  3. Use of unleaded petrol,
  4. Use of low Sulphar petrol and diesel,
  5. Use of catalytic converters in vehicles, and
  6. Application of euro II norms for vehicles.

Q 11. Discuss briefly the following:

  1. Greenhouse effect
  2. Catalytic converter
  3. Ultraviot-B

Ans 11.

  1. Green House Effect: A building made chiefly of glass for growing or sheltering the delicate or exotic plants is called green house. The air in greenhouse is warmer than the outside air though it revives less solar radiation. The occurrence of higher temperature inside a greenhouse than outside. Even though the interior receives less solar radiation, is known as the “Green House Effect”.
  2. catalytic converters are devices that are fitted into automobiles for reducing the emission of genes. These have expensive metal (platinum-palladium and rhodium) as catalysts. As the exhaust passes through the catalytic converters, unburnt hydrocarbons are converted into CO2 and H2O and carbon monoxide and nitric oxide are changed to CO2 and N2
  3. UV-B are short wavelength harmful radiations that penetrate through the ozone hole to strike the earth. On earth, these can affect human beings and other animals by causing.
  • Skin cancer,
  • Blindness and increased incidence of cataract in eyes, and
  • Malfunctioning of the immune system.

Leave a Reply

Your email address will not be published.