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Q1. Mention the effect of global warming on the geographical distribution of stenothermals like amphibians.

Solution

Due to global warming, stenothermals like amphibians would either migrate or die due to change in the temperature.

Q2. Write about the 3R technology in waste management.

Solution

We can follow the 3R approach - reduce, reuse and recycle - for effective waste management. Reduce: One can reduce the amount of solid waste at the source itself. Example: Use of less paper and less plastic carry bags. Reuse: One can use plastic bottles and jars, aluminium foils and plastic bags over and over again, before recycling or disposing them of. Recycle: Used and discarded materials like plastic, glass, paper and metal are sent to the respective industries, where they can be converted into other useful products.

Q3. State the differences between biodegradable and non-biodegradable wastes.

Solution

Differences between biodegradable and non-biodegradable wastes: Biodegradable wastes Non-biodegradable wastes 1. These wastes can be broken down into non-poisonous substances by the action of microorganisms like bacteria and earthworms. 1. These wastes cannot be broken down into harmless substances by any biological processes. 2. Biodegradable substances change their form and structure over time and become harmless. 2. Non-biodegradable substances remain unchanged over a long period of time. 3. They do not pollute the environment. 3. Some of them remain inert and begin to accumulate in our surroundings, while others cannot be made less toxic easily and hence keep on polluting the environment. Examples: Spoilt food, vegetable peels, tea leaves, wood, grass, paper, leather, cotton, cattle dung etc. Examples: Glass bottles, metal cans, polythene bags, synthetic fibres, radioactive wastes, plastics and pesticides like DDT etc.    

Q4. Describe electrostatic precipitator by a diagram.

Solution

Electrostatic precipitators are extremely efficient devices which remove about 99% of particulate matter present in the industrial and thermal power exhausts. They have charged plates which are connected to the ground. The electrode wires are provided with high voltage electric current which produce a corona that releases electrons. These electrons attach to the dust particles giving them a negative charge. The collecting particles are grounded and attract the charged dust particles. The velocity of air between the plates must be low enough to allow the dust to fall.      

Q5. Name any three gases contributing to the greenhouse effect.  

Solution

Carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄) are greenhouse gases which contribute to the greenhouse effect. These gases are transparent to sunlight but can trap the heat and keep the Earth’s surface warm.  

Q6. DDT content in the water of a lake which supplies drinking water to nearby villages is 0.003 ppm. The kingfishers of that area were reported to have 2 ppm of DDT. Why has the concentration of DDT increased in these birds? What harm will this cause to the bird population? Name the phenomenon.

Solution

DDT is a toxic substance which gets accumulated in the organisms at each trophic level. As it cannot be metabolised or excreted, the concentration of DDT increases at each trophic level. As kingfishers are present at the highest trophic level, the concentration of DDT is highest in them. The high concentration of DDT disturbs calcium metabolism in birds, causes thinning of eggshell and their premature breaking, and eventually, causes a decline in the bird population. The phenomenon is called biomagnification.

Q7. What are radioactive elements? How do radiations affect the body cells?

Solution

Elements which emit radiations as they disintegrate are called radioactive elements. Examples: Radium, thorium and uranium. Non-ionising radiations inactivate biochemicals including DNA and RNA. Ionising radiations break up the macromolecules.

Q8. What is polyblend? Why did plastic manufacturers think of producing polyblend? Write its usefulness.

Solution

Polyblend is a fine powder of recycled modified plastic. It was produced by plastic manufacturers in order to recycle plastic waste. When blended with bitumen, polyblend can be used to lay roads which have increased road life.

Q9. How is snow blindness caused in humans?

Solution

The cornea of the human eye absorbs UV-B radiation. High dose of UV-B can cause inflammation of the cornea called snow blindness. Such exposure may permanently damage the cornea.  

Q10. What is an ozone shield?

Solution

The thin layer of ozone which surrounds the Earth’s atmosphere and prevents harmful UV rays from reaching the Earth’s surface is called the ozone shield.

Q11. What is the Amrita Devi Bishnoi Wildlife Protection Award given for?

Solution

The Amrita Devi Bishnoi Wildlife Protection Award is given to individuals or communities from rural areas which have shown extraordinary courage and dedication in protecting wildlife.

Q12. Why is it desirable to use unleaded petrol in vehicles fitted with catalytic converters?

Solution

The presence of lead in petrol inactivates catalysts such as platinum, palladium and rhodium which convert harmful pollutants like CO, unburnt hydrocarbons and nitric oxide into lesser harmful pollutants like C0₂, H₂0 and N₂.

Q13. Mention how e-waste is produced and disposed of. Write the solution for its treatment.

Solution

Discarded electrical appliances such as old television sets, computers, radios, mobile phones, fluorescent tubes, medical instruments, toys and lead acid batteries all fall into the category of e-wastes. E-wastes are either buried in landfills or incinerated. Recycling under skilled supervision is the only solution for the treatment of e-wastes. 

Q14. How can pollution by auto exhaust be minimised?

Solution

Pollution by auto exhaust can be minimised by taking the following steps: (i) Use of CNG as a fuel instead of petrol and diesel. (ii) Use of catalytic converter in vehicles. (iii) Use of lead-free petrol. (iv) Use of multipoint fuel injection engine.

Q15. Thermal power plants are inevitable in an industrial and densely populated country. What harm do they do to the environment? Also, mention any precaution which could be taken to save our environment.

Solution

Thermal power plants release particulate and gaseous pollutants into the air which cause harmful effects. These pollutants can cause: (i) Breathing or respiratory problems when inhaled. (ii) Irritation, inflammation and damage to the lungs and premature death. Precautionary measures to save the environment include the use of electrostatic precipitators, which remove about 99% of the particulate matter from the exhaust.

Q16. Why is CNG considered a better fuel than diesel for automobiles?

Solution

CNG is considered as a better fuel than diesel for automobiles because it burns most efficiently, is cheaper and cannot be emptied by thieves and adulterated like petrol or diesel.

Q17. What is meant by an ozone hole?

Solution

Depletion of the ozone layer widely in the stratosphere, particularly over the Antarctic region, resulted in the formation of a thinned ozone layer called the ozone hole.

Q18. Name any four toxic compounds found in defunct ships.

Solution

The toxic compounds found in defunct ships include asbestos, polychlorinated biphenyls (PCB), tributylin (TBT) and mercury.

Q19. What is integrated organic farming?

Solution

Integrated organic farming is a cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients for other processes.

Q20. How do automobiles fitted with catalytic converters reduce air pollution? Suggest the best fuel for such vehicles.

Solution

Catalytic converters have expensive metals like platinum, palladium and rhodium as catalysts. As exhaust emission passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, while carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas. Unleaded petrol is the best fuel for automobiles fitted with catalytic converters to reduce air pollution.

Q21. Why is Eichhornia crassipes regarded as ‘Terror of Bengal’?

Solution

Eichhornia crassipes is an aquatic weed which grows fast and abundantly in water bodies with excess of nutrients and causes an imbalance in the water ecosystem. It results in oxygen depletion causing eutrophication, leading to the death of aquatic life.

Q22. Why are lichens regarded as pollution indicators?

Solution

Lichens are regarded as pollution indicators because they are sensitive to sulphur dioxide (SO₂) and do not grow in polluted areas. Their presence indicates the absence of pollution in an area, and their absence indicates that the area is polluted.

Q23. Which is the most common and abundant greenhouse gas? Discuss the effect of this gas on the growth of plants.

Solution

Carbon dioxide is the most common and abundant (60%) greenhouse gas. As the concentration of carbon dioxide increases, the growth of plants increases by 30% in a short period. At higher concentration of CO₂, stomata close, and hence, the rate of transpiration gets reduced.

Q24. Why is nuclear waste said to be an extremely potent pollutant?

Solution

The radiations emitted by nuclear waste are dangerous to organisms as they can cause mutations at a high rate. At high doses, nuclear radiation is lethal, but at lower doses, it creates various disorders such as cancer. Therefore, nuclear waste is said to be an extremely potent pollutant. 

Q25. Explain how solid waste can be disposed of.

Solution

Different ways of solid waste disposal are 1. Waste segregation: At the household level, the wastes are first separated into dry and wet solid wastes. The wastes are then stored in separate containers.  2. Composting: The rotting and conversion of organic waste into manure is known as composting. The household garbage as well as farmland wastes can all be converted into useful compost. 3. Vermicomposting : The method which involves the use of worms to decompose the wastes is called vermicomposting. The earthworms can degrade or decompose the wastes such as domestic waste, cow dung, coconut thresh etc. in few days. 4. Secured landfill: Secured landfill is the best disposal option for solid wastes, particularly, hazardous wastes. It prevents leaching of waste. 5. Deep well injection method: A well is drilled into the dry porous material below the groundwater. Hazardous waste liquids are pumped into the well. They soak into the porous material and, in this way, remain isolated indefinitely. 6. Pyrolysis: The process of pyrolysis transforms hazardous organic materials into gaseous components, small quantities of liquid and coke. It is possible to generate gas and electricity through the process of pyrolysis. 7. Incineration: Hazardous biomedical wastes, such as discarded medicines, toxic drugs, human anatomical wastes, blood, pus, microbiological and biotechnological wastes etc., are usually disposed of by incineration. It helps to reduce the weight and volume of waste and converts these toxic wastes into less toxic or even non-toxic substances. 8. Recycling: E-wastes can be recycled in specifically built facilities or manually to recover important metals.

Q26. State the difference between radioactive waste and municipal solid waste.

Solution

Difference between radioactive waste and municipal solid waste   Radioactive waste Municipal solid waste 1. Waste of nuclear energy which are non-usable and possess radioactivity are called radioactive waste. 1. Waste generated from domestic, industrial and commercial activities is called municipal solid waste.  2. Radiations emitted from nuclear wastes can cause mutations and extreme damage to organisms. 2. Radiations are not emitted from municipal solid waste. 3. Radioactive wastes are generally disposed of in secured landfills and through the deep well injection method. 3. Municipal solid wastes are generally disposed of in sanitary landfills, through pyrolysis and incineration.  Examples: Leftovers of nuclear material used in the production of electricity, for diagnosis and treatment of disease and for other purposes. Examples: Paper, leather, textile, rubber, glass etc.    

Q27. (a) What is El Nino effect? Explain how it accounts for biodiversity loss. (b) Explain any three measures which you as an individual would take to reduce environmental pollution.

Solution

(a) The El Nino effect refers to uneven climatic changes due to rise in temperature. It leads to increased melting of polar ice caps as well as other places like the Himalayan snow caps. This results in the rise in the sea level which can submerge many coastal areas, thus resulting in biodiversity loss. (b) Measures to reduce environmental pollution: (i) Use of renewable energy resources (ii) Use of television and other instruments at low pitch (iii) Minimum use of fossil fuels (iv) No tobacco smoking (v) Planting more trees

Q28. State the major causes of air pollution in metro cities. Write any three ways in which it can be reduced.

Solution

The major causes of air pollution in metro cities are (i) Smoke from forest fires, volcanic eruptions etc. (ii) Decomposition of garbage resulting in the release of unwanted gases into the atmosphere. (iii) Burning of fossil fuels in automobiles and industries release particulate air pollutants. (iv) Use of unleaded petrol. (v) Gaseous waste or particulate by-products of various industries. Control measures of air pollution: (i) Use of electrostatic precipitators to remove particulate matter from industries and thermal power plants. (ii) Use of scrubber to remove gases like S0₂. (iii) Use of catalytic converters in automobiles to reduce the emission of poisonous gases.

Q29. (a) What depletes ozone in the stratosphere? How does this affect human life? (b) Explain biomagnification of DDT in an aquatic food chain. How does it affect the bird population?

Solution

(a) Chlorofluorocarbons (CFCs) are mainly responsible for the depletion of ozone in the stratosphere. Once released in the troposphere, CFCs reach the stratosphere and produce ‘active chlorine’ in the presence of ultraviolet (UV) radiation. These radicals, through a chain reaction, destroy the ozone by converting it into oxygen. Excess dose of UV-B radiations damages DNA causing mutation, skin cancer, snow blindness, cataract and ageing of skin. (b) If DDT leaches from agricultural fields, it enters the nearby water body. The concentration of DDT in the water body is low (0.003 ppm). The pesticide enters the food chain and gets accumulated in zooplankton (0.04 ppm) and thereby its concentration goes on increasing at different trophic levels of the food chain from the small fish (0.5 ppm), large fish (2 ppm) to finally the fish-eating birds (5 ppm). Concentration of DDT increases along the food chain, reaching the highest level in the top carnivore bird. The increased concentration of DDT in birds disturbs calcium metabolism. The egg shells become thin, resulting in premature breaking. Consequently, there is a decline in the bird population.

Q30. What was the purpose of the concept of Joint Forest Management (JFM)?

Solution

The Government of India in 1980s introduced the concept of Joint Forest Management (JFM) so as to work closely with the local communities for the protection and management of forests. In return, the communities got the benefit of various forest products such as fruits, gum, rubber, medicine etc. In this way, the forest can be conserved in a sustainable manner.