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Q1. Strontium-90 accumulates in the

• 1) Bone
• 2) RBCs
• 3) Brain
• 4) WBCs

Solution

Strontium-90 accumulates in the bone and may cause bone cancer.

Q2. The figure below shows the relative contribution of four greenhouse gases to global warming.       (i) Identify the gases A and C. (ii) Why are these four gases called greenhouse gases?

Solution

(i) A recent survey has revealed 60%, 20%, 14% and 6% of warming effect of CO₂, CH₄, CFCs and N₂O. So, according to the figure, Gas A is carbon dioxide (C0₂) and Gas C is chlorofluorocarbon (CFC). (ii) These gases in the atmosphere are transparent to sunlight but can trap heat and keep the Earth’s surface warm. They are responsible for the greenhouse effect and are therefore called greenhouse gases.

Q3. The term biomagnification refers to the

• 1) Growth of organisms due to food consumption
• 2) Blowing up of environmental issues by man
• 3) Increase in population size
• 4) Increase in the concentration of non-degradable pollutants as they pass through the food chain

Solution

An increase in the concentration of toxic materials at each trophic level of a food chain is called biomagnification or biological magnification.

Q4. Oysters are used for the accumulation of which radioactive material?

• 1) ⁵⁶Zn
• 2) ⁵⁵Fe
• 3) ⁶⁵Zn
• 4) ⁶⁵Fe

Solution

Certain organisms can take up radioactive materials and accumulate them without facing any danger. Oysters can accumulate ⁶⁵Zn.

Q5. 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.  

Q6. The pH of acid rain is below

• 1) 4.6
• 2) 7
• 3) 6.5
• 4) 6

Solution

Acid rain is precipitation with a pH less than 5. It is a mixture of H₂SO₄ and HNO₃. Acid rain occurs due to sulphur dioxide and nitrogen oxide produced by the combustion of fossil fuels, industries, power plants etc.

Q7. In radioactivity, beta particles are

• 1) Mesons
• 2) Neutrons
• 3) Electrons
• 4) Protons

Solution

In radioactivity, beta particles are electrons and alpha particles are protons. 

Q8. Which of the following accounts for more than 50% of air pollutants?

• 1) Oxides of sulphur
• 2) Smoke
• 3) Carbon monoxide
• 4) Carbon dioxide

Solution

Carbon monoxide accounts for more than 50% of the air pollutants.

Q9. The Montreal protocol which calls for appropriate action to protect the ozone layer from human activities was passed in the year

• 1) 1986
• 2) 1985
• 3) 1987
• 4) 1988

Solution

On 16^th September 1987, twenty-seven industrialised countries signed an agreement called the Montreal Protocol to limit the production and use of ozone-depleting substances like chlorofluorocarbons (CFCs) and to implement the use of alternatives to CFCs.

Q10. In India, Van Mahotsava is held during

• 1) October and December
• 2) January and March
• 3) February and July
• 4) June and September

Solution

In India, Van Mahotsava is a festival during which plants are planted. It is held in February and July since 1950.

Q11. Which of the following is a secondary pollutant?

• 1) SO₂
• 2) NO₂
• 3) NO
• 4) PAN

Solution

Secondary pollutants are formed by the interaction with primary pollutants. PAN or peroxyacyl nitrate is a secondary pollutant, while NO, NO₂ and SO₂ are examples of primary pollutants.

Q12. Atomic weapons use

• 1) Uranium-165
• 2) Uranium-265
• 3) Uranium-235
• 4) Uranium-135

Solution

Atomic weapons use uranium-235 and plutonium-239.

Q13. Which of the following is not a greenhouse gas?

• 1) O₃
• 2) N₂O
• 3) SO₂
• 4) CFC

Solution

The increase in mean global temperature of the Earth due to increased concentration of greenhouse gases like carbon dioxide (CO₂), methane (CH₄), chlorofluorocarbons (CFCs) and nitrous oxide (N₂O) is called the greenhouse effect.

Q14. Carbon dioxide is called a greenhouse gas because it is

• 1) Transparent to both sunlight and heat
• 2) Transparent to heat but traps sunlight
• 3) Transparent to sunlight but traps heat
• 4) Used in a greenhouse to increase plant growth

Solution

The greenhouse gases in the atmosphere are transparent to sunlight but can trap heat and keep the Earth’s surface warm. These gases include CO₂, CH₄, CFCs and N₂O. They are called radiatively active gases as they can absorb long wave infrared radiation.

Q15. IPCC regularly assesses the concentrations of greenhouse gases and studies its impact on global warming. According to recent surveys, which gas contributes maximum towards the warming effect?

• 1) CH₄
• 2) N­₂­O
• 3) CO₂
• 4) CFC

Solution

According to a recent survey by the IPCC, CO­_2­ contributes to about 60% of the total warming in greenhouse effect.

Q16. The ozone is thickest at the

• 1) Tropic of Capricorn
• 2) Tropic of Cancer
• 3) Equator
• 4) Poles

Solution

The ozone is thickest at the poles and thinnest at the equator.

Q17. PCBs are a class of chemicals which cause water pollution. Expand PCBs.

• 1) Polychlorinated biphosphates
• 2) Polycarbonated biphenyls
• 3) Polychlorinated biphenyls
• 4) Polycarbonated biphosphates

Solution

PCBs are polychlorinated biphenyls. 

Q18. Expand PAN.

• 1) Peroxyacetyl nitrite
• 2) Peroxyacyl nitrate
• 3) Peroxyacetyl nitrate
• 4) Peroxyacyl nitrite

Solution

PAN - Peroxyacyl nitrate is a type of photochemical oxidant.

Q19. Byssinosis is caused by

• 1) Cotton fibres
• 2) Stone particles
• 3) Dust particles
• 4) Asbestos

Solution

Asbestos causes asbestosis. Stone particles cause silicosis. Cotton fibres cause byssinosis. Dust particles cause lung fibrosis or pneumoconiosis.

Q20. On a global scale, which country has the highest loss of top soil?

• 1) Italy
• 2) England
• 3) China
• 4) India

Solution

On a global scale, the loss of top soil is maximum (about 18.5%) in India.

Q21. What is meant by Jhum cultivation? Explain how it is responsible for deforestation.

Solution

In Jhum cultivation, farmers clear the trees of the forest area and burn the plant remains. The ash of the burnt vegetation contains minerals and is used as fertiliser. The land is then used for farming or cattle grazing. After cultivation, the farmers move to another area and this process is repeated. This practice has caused major deforestation in north eastern states of India.

Q22. Which of the following pollutants reduces the oxygen-carrying capacity of blood in humans?

• 1) Carbon monoxide
• 2) Carbon dioxide
• 3) Lead
• 4) Mercury

Solution

Carbon monoxide binds to haemoglobin and reduces the oxygen-carrying capacity of blood.

Q23. The Chipko movement was launched for the protection of

• 1) Livestock
• 2) Wetlands
• 3) Grasslands
• 4) Forests

Solution

The Chipko Movement was started in 1973 at Gopeshwar town of Chamoli district to check the felling of trees by contractors. The peasant women of Reni village protested by embracing the trees to prevent them from being felled.

Q24. The Earth Summit was held at

• 1) Rio de Janeiro, Brazil
• 2) Kyoto, Japan
• 3) Montreal, Canada
• 4) London, England

Solution

The Earth Summit was held at Rio de Janeiro, Brazil, in 1992.

Q25. Checking of reradiating heat by atmospheric dust, O₃, CO₂ and water vapour is called

• 1) Greenhouse effect
• 2) Ozone layer effect
• 3) Solar effect
• 4) Radioactive effect

Solution

The atmospheric cover of the Earth acts like glass walls of a greenhouse. It absorbs most of the incoming solar radiations from the Sun and reradiates them to the Earth’s surface. However, it prevents the long wave infrared radiation emitted by the Earth’s surface to escape into space. In this way, the atmosphere acts as a greenhouse, trapping the heat.

Q26. 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.

Q27. Allethrin is a

• 1) Fertiliser
• 2) Growth hormone
• 3) Herbicide
• 4) Insecticide

Solution

Allethrins are a group of synthetic compounds used in insecticides. They are synthetic pyrethroids which are found naturally in the Chrysanthemum flower.

Q28. 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.

Q29. 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.      

Q30. Greenhouse gases are capable of absorbing

• 1) Short wave radio waves
• 2) Short wave infrared radiation
• 3) Long wave infrared radiation
• 4) Long wave radio waves

Solution

Greenhouse gases are capable of absorbing long wave infrared radiation and hence are also known as radiatively active gases.

Q31. 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.

Q32. 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.

Q33. 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.

Q34. Pollution from animal excreta and organic waste from the kitchen can be most profitably minimised by

• 1) Using them directly as biofertilisers
• 2) Storing them in underground storage tanks
• 3) Vermiculture
• 4) Using them for producing biogas

Solution

Biodegradable wastes like animal excreta and organic waste from the kitchen can be used in biogas plants to generate biogas and manure. Biogas is a cheap source of fuel and the manure can be used as a cheap fertiliser.

Q35. What is reforestation?

Solution

Reforestation is the process of restoring a forest which once existed but was removed at some point of time in the past.

Q36. (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.

Q37. Study the graph given below and answer the questions which follow:       (i) What is the relationship between dissolved oxygen and biochemical oxygen (BOD)? (ii) Mention their effect on aquatic life in the river.

Solution

(i) BOD refers to the amount of oxygen required to decompose the organic matter present in one litre of water. Thus, greater the BOD, lesser will be the dissolved oxygen content in sewage discharge. (ii) Effects on aquatic life: (a) It causes high mortality of aquatic animals. (b) The excessive nutrients facilitate algal growth causing algal bloom.

Q38. 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.

Q39. 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.

Q40. 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. 

Q41. Write the differences between BOD and COD.

Solution

Differences between BOD and COD   BOD COD 1. BOD refers to Biochemical Oxygen Demand. 1. COD refers to Chemical Oxygen Demand. 2. BOD is the oxygen required for the decomposition of unit mass of organic matter by microbes. 2. COD is the oxygen required for the chemical oxidation of unit mass of reduced organic and inorganic matter. 3. It is comparatively lower. 3. It is comparatively higher. 4. Involves only aerobic decomposer microbes. 4. Involves chemical oxidants.