BSEB Inter Exam Biology Short Long Type Important Question Environmental Issues Chapter

16. Environmental Issues

1. What do you mean by Global Warming ? Explain.

Ans.: When increase in earth temperature is considered worldwide, then it is called Global warming. There is possibility of increase in sea level and oncoming of flood due to increase in temperature beyond the limit range due to melting of polar ice caps. It is assumed that there will be increase in temperature between 1.5°C-4.5°C on 2050 yrs. It will result into submerging of various small islands and nearby town, cities of seas. It may cause deep concern.

2. What do you understand by Noise pollution ? Describe its various sources.

Ans. : Noise pollution is a physical form of pollution caused by unwanting sound that affects the receiver directly. It is loud disturbing sound dumped into ambient atmosphere without caring for the adverse effect it may have. Noise or pollutant sound has a value of 80 dB and above. Frequency of sound er is measured in Hertz. Range of human hearing is 50 Hz to 1500 Hz. unit of sound level is decibel. Moderate conversation so produces 60 dB sound, loud conversation 70 dB, scooter 80 SdB, jet Aeroplane 150 dB, etc.

Sources of Noise Pollution :

(i) Various industries such as printing presses, textile mills, etc.

(ii) Agricultural machines like tractors, tubewells, etc.

(iii) Transport vehicles like scooters, motor-cycles, car, buses, etc.

(iv) Crackers & loudspeakers used at festivals like marriages.

3. What do you mean by ozone layer? What is importance of ozone layer?

Ans.- Ozone layer : Ozone layer or shield is present in the stratosphere. It is also called ozonosphere. Ozonosphere lies at altitude of 23–25 km over equator and at slightly lower altitude elsewhere with 11-16km height over poles. Thickness of ozone is measured in Dobson units (D.U). The total thickness of ozone if condensed is 0.29 cm above equator and 0.40 cm above poles towards the end of winter. In stratosphere ozone is being formed and photodissociated it dissipates the energy of uv radiations. 

CFCL₃ + light → CFCl₂ + Cl

Because of it ozonosphere functions as shield against strong UV radiations.

Depletion in the concentration of ozone over a restricted area as over Antarctica is called ozone hole. ODS are substance which react with ozone present in the stratosphere and destroy the same. The major ODS are chlorofluorocarbons, nitrogen oxides, sulphur dioxide etc. CFC is used in refrigeration and is highly used. 

Cl + O₃ → ClO + O₂ 

CIO + O → C1 + O₂

Importance of ozone layer: Ozone layer act as shield against strong UV radiations from sun. It absorbs almost 90-95% of UV rays that is very harmful to organisms, on earth. So, ozone layer maintains the life on the earth. More UV radiations reach the earth over the tropics. The amount decreases towards the poles.

Ozonosphere is warm, and it prevent the escape of energy and heat from earth atmosphere.

4. What is Green House Effect? 

Ans.- CO₂ is completely limited to Troposphere So, its high concentration can act as serious pollutant, under normal conditions the whole of sunlight doesn’t reach the earth. About one fourth of incoming solar radiations are reflected back by clouds and gases. Only 50% of solar radiations reach the earth and heat it up. A small proportion is reflected from earth’s surface. The remaining are absorbed by atmospheric gases and reflected back to earth to keep it warm. The gases which are transparent to solar radiation but retaion and partially reflect back long wave heat radiations are called Green House Gases. These gases trap the solar radiation and warm the atmosphere. This effect is called Green House Effect. However recently the concentration of Green House Gases has started rising, resulting in enhanced Green House Effect that is increasing the mean global temperature. It is called Global Warming. The various Green House Gases are

-CO₂, CH₄, CFCs, N₂O etc.

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