Class 12 Biology Chapter 17 Environmental Issues

Class 12 Biology Chapter 17 Environmental Issues The answer to each chapter is provided in the list so that you can easily browse through different chapters Assam Board HS 2nd Year Biology Chapter 17 Environmental Issues Question Answer.

Class 12 Biology Chapter 17 Environmental Issues

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Also, you can read the SCERT book online in these sections Solutions by Expert Teachers as per SCERT (CBSE) Book guidelines. These solutions are part of SCERT All Subject Solutions. Here we have given Assam Board Class 12 Biology Chapter 17 Environmental Issues Solutions for All Subjects, You can practice these here.

Environmental Issues

Chapter – 17

ECOLOGY

Very Short Answer Type Questions

Q.1. ____is undesired high level of sound. 

Ans : Noise. 

Q.2. The amount of biodegradable organic matter in sewage can be measured by estimating _____

Ans : BOD (Biochemical Oxygen Demand) 

Q.3. The biological name of water hyacinth is _____

Ans : Eichornia crassipes. 

Q.4. Irreparable computers and other electronic goods constitute ____ wastes. 

Ans : Electronic. 

(B) . True or False (1 Marks Each) :

Q.1. Chipko movement was carried out in Western Ghat. 

Ans : False. 

Q.2. Euro II norms stipulate that sulphur be controlled at 350ppm in petrol.

Ans : False. 

Q.3. Air (Prevention and Control of Pollution) Act came into force in 1981. 

Ans : True. 

Q.4. Particulate size 2.5 microns-or more in diameter are responsible for causing greatest harm to human health.’ 

Ans : True.

(C) . Very Short Answer Question (1 Marks Each) : 

Q.1. What is pollution? 

Ans : Pollution can be defined as the undesirable change in chemical, physical or biological nature of air, water, soil etc. 

Q.2. Why environment (Protection) Act. 1986 enacted? 

Ans : Environment (Protection) Act, 1986 was enacted to protect and improve the quality of environment i.e. air, water, soil etc. 

Q.3. Why motor vehicles fitted with catalytic converter should use unleaded petrol? 

Ans : The motor vehicles filled with catalytic convertor should be use unleaded petrol because it can reduce the emission of pollutant to the environment. 

Q.4. What is noise? 

Ans : Noise can be defined as the unpleasant sound which can cause physiological, psychological and biochemical disorder in living body. Wrong sound in wrong place at wrong time can be called as noise. 

Q.5. Define algal bloom.

Ans : Due to the presence of excessive nutrients in water which causes over population of algae or algal bloom. 

Q.6. Define cultural eutrophication. 

Ans : The surface run off from field of inorganic fertilizers, pesticides, insecticides, manures bring heavy loads of pollutants into natural water bodies. Fertilizers include nitrates, phosphates and sulphates of potassium. They may reach the ground water through leaching or may be carried to rivers, lakes and ponds. 

Excess of nitrates from fertilizers run down into ponds, lakes, streams etc. It leads to think blooms of algae. As a result, plenty of oxygen from water by these algae. This leads to suffocation of aquatic organisms. The increased productivity of lake and pond etc. due to this nutrient enrichment is called cultured eutrophication or cultural eutrophication or accelerated eutrophication. 

Q.7. What are green house gases? 

Ans : The temperature of Earth is maintained by reradiated infra-red radiations by CO₂, CH₄, O₃, NO and NO₂ and slightly by water vapours in atmosphere. These gases prevent heat from escaping to our space, so are functionally comparable to glass panels of a green house and are called green house gases (GHGS) and the mechanism is called as green house effect. 

Q.8. Define reforestation. 

Ans : Reforestation can be defined as the natural phenomenon of restoring a forest that once existed but was renewed at some point of time in the past. We can follow to get the earlier existed status by planting trees for the conservation of biodiversity as it was. 

(D) . Short Answer Questions (2 Marks Each) : 

Q.1. State two adverse effects of air pollution? 

Ans : The two adverse effects of air pollution are : 

(a) The photochemical smog is responsible for bleaching the foliage of certain plants. 

(b) Peroxy acyl nitrates cause eye irritation and respiratory problems. 

Q.2. What is the major cause of atmospheric pollution in metros of India? How automobile emission can be controlled? 

Ans : The major causes of atmospheric pollution in metros of India are : 

(a) The smoke containing CO₂ and CO is released from the incomplete combustion of fuels in vehicles, homes, factories etc. 

(b) Benzpyrene is produced from Tobacco smoking, industries and automobile exhausts which is carcinogenic in nature. 

The automobile exhausts or emissions can be controlled by using lead free petrol or diesel and catalytic converters must be filled in their automobiles.

Q.3. Why CNG is considered better than diesel? 

Ans : CNG is better than diesel because its combustion releases less pollutants. Moreover it is cheaper can not be siphoned off by the thieves and cannot be adulterated. Presently, all the buses of DTC and Private agencies and auto rickshaws in Delhi are being run on CNG. 

Q.4. Suggest measures for control of noise pollution. 

Ans : Noise pollution can be controlled by : 

(a) Construction of sound proof rooms for noisy machines in mills or industries.

(b) Radio, Transistors, Speaker should be kept at low volume. 

(c) Use of Horn should be banned near the Hospital, school etc. 

(d) Sound box is prefered in place of Loud speaker in any party in night time. 

(e) Noise producing industries, aerodrome, railway station, markets, bus stand, Truck Terminals should be away from human habitation.

(f) Regular checking, greezing, oiling should be done for scooter, motor cycle, other sound producing machineries. 

(g) Legal steps can be taken for the control of noise. 

Q.5. Write a short note on water pollution. 

Ans : Water pollution can be defined as the addition of organic, inorganic, biological or radiological substances or factor which degrade the quality of water and not supporting the life i.e. unfit for use. 

The water pollution may be due to : 

(a) Domestic effluents. 

(b) Industrial effluents. 

(c) Surface run-off.

(d) Waste heat. 

The water pollution can be controlled by : 

(a) Treatment of waste water. 

(b) Recycling of wastes. 

(c) Controlled use of Pesticides and fertilizers. 

(d) Reverse osmosis. 

(e) Checking the thermal pollution. 

(f) By growing water hyacinth. 

Q.6. How can we control global warming? 

Ans : Global warming can be controlled by : 

(a) Minimise the use of fossil fuel. 

(b) Reducing deforestation. 

(c) Plantation and conserving biodiversity. 

(d) By avoiding AC, Freeze etc. 

Q.7. Why Jhum cultivation is considered as major cause of environmental degradation of northeast India? 

Ans : Jhum cultivation is very popular in North East India specially in the hilly areas. But it has believed that Jhum cultivation has contributed to deforestation. In this practice, the farmers cut down the trees, vegetations of the forest and burnt. Due to cleaning of top vegetation the hill soils become loose and causes soil erosion. Finally it causes environmental degradation. Hence, Jhum is considered as the major cause of environmental degradation. 

Q.8. Explain Joint Forest Management. 

Ans : Joint Forest Management committees have been set up as a partnership between the Government and local communities to recover degraded forests. It involves the people’s role in the development and protection of forests so for 17 states have issued their resolutions for 8. J.F.M. 

It involves the management of forests in following manner : 

(a) State forest Department and voluntary village community should work together. 

(b) Village community etc. are entitled for share prescribed by state Government. 

(c) Ownership should not given to beneficiary. 

(d) The working scheme should be prepared in consultation with beneficiaries. 

(e) Grazing in such area is not permitted. 

(E). Short Answer Questions (3 Marks Each) : 

Q.1. How the Bishnois of Rajasthan tried to save tree? 

Ans : The king of Rajasthan in 1731 ordered his minister to arrange matured wood for the construction of his new place. Following the order of king, the minister along with the workers went to the village forest to collect wood. But the forest were mutually occupied by the Bishnois. Although the Bishnois were found in jungle but they never destroied the forest. A Bishnoi woman Amrita Devi showed courage in front of the ministers by hugging a tree and daring kings men to kill her before cutting down the tree. But king’s men ignored her place and cut down the tree along with her. After this her three daughters and hundreds of Bishnois followed the Amritas and thus lost their lives saving trees. 

Q.2. Discuss the functioning of catalytic converter. 

Ans : It has been established that installation of catalytic converters can slash carbon monoxide emission from 90 grams to 3.4 grams per mile run. These catalytic converters have metals like platinum, palladium and rhodium which act as catalysts. These convert the unburnt hydrocarbons to CO₂ and H₂O, CO to CO₂ ; Nitric oxide to nitrogen gas. So catalytic converter reduce the emission of pollutant gases.

Q.3. State the effects of noise as an air pollutant. 

Ans : Air (prevention and control of pollution) act was enacted on 29th March, 1981 and was amended in 1987 to include noise as an air pollutant. Noise can cause psychological and physiological disorders in human. Noise affects the development of embryo, Noise causes sleeplessness, increased heart beating, feeling of fatigue etc. 

Q.4. What do you understand by biomagnifications? How it affects 4. the top carnivores? 

Ans : The toxic waste substances, often present in industrial waste may flow from lower group of organisms to higher group through the aquatic food chain. This phenomenon is called as biomagnification. A toxic substance accumulated by an organism can not be metabolised or excreted and is thus passed on to the next higher trophic level.

Generally the small aquatic insects consume the toxic substance first. These are consumed by small insectivorous organisms which are consumed by the large fishes or other aquatic animals. These are consumed by the carnivores and Top carnivores finally. Thus the toxic substances can pass over to the top carnivores through the food chain. 

By the biomagnification, the pollutants from water to top carnivores are spreading. 

Q.5. Explain the process of Eutrophication. 

Ans : The surface run off from field of inorganic fertilizers, pesticides, insecticides, manures bring heavy loads of pollutants into natural water bodies. 

Fertilizers include nitrates, phosphates and sulphates of potassium. They may reach the ground water through hatching or may be carried to rivers, lakes and ponds. 

Excess of nitrates from fertilizers run down into pond, lakes, streams etc. It leads to thick blooms of algae. As a result, plenty of oxygen is used from water by these algae. This leads to suffocation of aquatic organisms. The increased productivity of lake and pond etc. due to the nutrient enrichment is called Eutrophication. 

Through eutrophication is a natural phenomenon, still the carelessness of human being enhances it. 

Q.6. Discuss how green house effect causing global warming. 

Ans : Earth’s temperature is maintained by reradiated infrared radiations by CO₂, CH₄, O₃, NO and NO₂ and slightly by water vapours in atmosphere. These gases prevent heat from escaping to outer space, so are called green house gases (GHGS) and called the phenomenon as green house effect. The CO₂ is added to atmosphere mainly by burning of fossil fuels, volcanic activities and respirations. 

It is estimated that more than 18×10¹² tonnes of CO₂ is being produced annually from the fossil fuels only. Not only CO₂, CFCS and oxides of nitrogen and methene also exert green house effect. CO₂ increases the earth atmosphere by 50% while CFCS are responsible for another 20% increase. 

These gases radiate heat energy which heated up earth’s surface once again. This cycle is repeated many a time. It is known warming. 

The negative impacts of global warming are : 

(a) Polar ice caps will melt and causes unexpected flood. 

(b) Deserts are likely to increase. 

(c) One third of the global forest might be swept away. 

Q.7. Write an essay on ozone depletion and its effect on biota. 

Ans : In the stratosphere, the uv-radiation causes photodissociation of ozone into O₂ and O. But O₂ and O quickly recombine to form O₃. The thickness of the vertical column of stratospheric O₃ layer, condensed to standard temperature and pressure, averages 0.29 cm above equator and may exceed 0.40 cm above the poles at the end of winter season. 

This layer acts as the Ozone layer protecting the biota of earth from harmful effects of strong uv-radiations. Absorption of uv-radiations by ozone layer ally with its thickness. Therefore, maximum amount increases exponent of uv-radiation passing through the atmosphere reaches the earth surface in the tropics and this amount decreases towards the poles. 

During the period 1956-70, the spring time O₃ layer thickness above Antarctica varied from 280 to 325 D.U (Dobson Unit ; IDU = 1 ppb). The thickness was reduced to 225 DU in 1979 and 136 DU in 1985. Later, the O, layer thickness continued to decline to about 94 DU in 1994. The decline in spring time ozone layer thickness is termed as ozone hole. 

CFCs, CH₄ and N₂O escape into the atmosphere and cause destruction of O₃ there. Most damaging iš the effect of CFCs which produce “active chlorine” in the presence of UV. radiations. These radicals catalytically destroy ozone, converting it into oxygen. CH₄ and N₂O also cause ozone destruction through a complicated series of reactions. 

Ozone depletion cause cataract, skin cancer, malfunction of the organs etc.

(F). Long Answer Questions (5 Marks Each) : 

Q.1. Explain a method of removal of particulate matter in air. 

Ans : Particulate mater of polluted air can be separated by two types of devices called – arresters and scrubbers. 

(i) Arresters are again of different types like :

(a) ESPs (Electrostatic Precipitators) : These are electrical devices which separate the particulate matter on the basis of their charges. In then, the electrically charged particulate wastes are attracted on oppositely charged electrode wires of collecting surfaces. These can remove the particles even in the size range of 5-20 mm and can remove them to the extent of 99%. 

(b) Cyclone Separator : In this, an incoming dust-laden gas stream is transformed into a combined vortex from which centrifugal forces tend to drive the suspended particles to the wall of the body of the separator. 

(c) Bag House Filters : In this, dust-laden fumes are passed through the filtering devices formed of porous mats of polyester, teflon, polyamide, wool, cloth, fabric, cellulose etc. The particles are held by the filters while the clean gas pass through them. 

(ii) Scrubbers : These are formed of dry or act packing material and are used to separate dust particles and toxic gases from air. In this, the polluted air is forced into serubbers while a counter current of water is passed through a spray tower at the top. Spray tower releases drops of water or lime from a number of spray nozzles. Water drops remove the particulates as well as toxic gases.

Q.2. What is solid waste? Discuss a case study of remedy for plastic waste. 

Ans : The wastes of air house hold like paper, non used packets, foods, etc. are termed as solid wastes. All these solid wastes may be of 3 types- 

(i) Biodegradable Solid Waste : It includes the paper, throwing of vegetables etc. 

(ii) Recyclable Solid Waste : It includes paper, some plastic bottles etc. 

(iii) Non-biodegradable Waste : If includes the polythene materials, coloured materials etc which never mixed with environment. . 

Altafur Rahman, a 60 years old plastic packet manufacturer in Guwahati had managed to find the ideal solution of to the ever increasing problem of plastic waste. He was producing plastic bags for about 20 years. He was creating the problem in the environment in the Guwahati town. The plastic packets through in the drain causes blocked to the drain. He was at the top of News paper for his affect. 

Bishal sing a student of class X of PVSH had invented a technique for recycling the plastic and to build the sleeper of Railways. Govt. of India had found the idea was innovative and hence he was awarded by best child scientist and practically solved the problem of plastic bags. (All the characters are hypothetical).

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