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Biology 2 Marks Questions

Environmental Issues · Jharkhand Board (JAC) STD 12 Science (Jharkhand - English Medium). 95 questions.

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Question 12 Marks
How did a citizen group called Friends of Arcata Marsh, Arcata, California, USA, help to improve water quality of the marshland using Integrated Waste Water Treatment? Explain in four steps.
Answer
Wastewater including sewage can be treated in an integrated manner, by utilising a mix of artificial and natural processes.
  1. The conventional sedimentation, filtering and chlorine treatments are given. After this stage, lots of dangerous pollutants like dissolved heavy metals still remain.
  2. To combat this, an innovative approach was taken and the biologists developed a series of six connected marshes over 60 hectares of marshland.
  3. Appropriate plants, algae, fungi and bacteria were seeded into this area, which neutralise, absorb and assimilate the pollutants. Hence, as the water flows through the marshes, it gets purified naturally.
  4. The marshes also constitute a sanctury, with a high level of biodiversity in the form of fishes, animals and birds.
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Question 32 Marks
Why are there regular reminders to reduce the use of CFCs in the production of industrial and household appliances? Explain.
Answer
  • CFC adds to degradation of ozone layer in the stratosphere.
  • Ozone shields the earth by absorbing UV radiation from sun.
  • UV rays are highly injurious to organisms.
  • To prevent degradation of ozone layer (in stratosphere)/to maintain a balance between production and degradation of ozone in stratosphere.
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Question 42 Marks
List four benefits to human life by eliminating the use of CFCs.
Answer
  1. Delay in aging of skin.
  2. Prevent damage to skin cells.
  3. Prevent skin cancer.
  4. Prevent snow blindness/inflammation of cornea.
  5. Prevent cataract.
  6. Prevents ozone depletion.
  7. Prevents global warming.
  8. Reduces greenhouse effect.
  9. Reduces odd climatic changes or El Nino effect.
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Question 52 Marks
Plenty of algal bloom is observed in a pond in your locality.
  1. Write what has caused this bloom and how does it affect the quality of water.
  2. Suggest a preventive measure.
Answer
  1. Presence of large amounts of nutrients/Nitrogen/Phosphorus in water causes excessive growth of algae, depletes dissolved oxygen/imparts distinct colour to the water bodies/bloom-forming algae are extremely toxic/deteriorates water quality/fish mortality.
  2. Treatment of waste water before it reaches the pond/Integrated waste water treatment/avoiding using NPK fertilisers/use of organic or biodegradable manure/resort to organic farming.
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Question 62 Marks
Explain the relationship between green house gases and global warming.
Answer
Green house gases absorb a major fraction of infra red radiation, emitted by earth, and do not allow it to escape into space and reflects it back to earth, leading to considerable heating of earth and its atmosphere causing global warming.
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Question 72 Marks
Lower BOD of a water body helps reappearance of clean-water organisms. Explain.
Answer
Lowering of BOD results in decreased biodegradable material $\rightarrow$ reduced microbial decomposition $\rightarrow$ oxygen utilisation reduced $\rightarrow$ more Dissolved Oxygen (DO) available (clean water - organisms reappear.)
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Question 82 Marks
How e-wastes are being handled in our country? Write the correct solution for treating this waste.
Answer
E-wastes are being buried in landfills or incinerated. (manually)
Recycling, in the environment friendly manner.
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Question 92 Marks
Sewage discharge into a clean-water body leads to increased fish mortality. Explain.
Answer
Leads to increase in nutrients, promotes algal growth, increases BOD reduces dissolved oxygen. (aquatic animals deprived of oxygen leading to death), some bloom farming algae are extremely toxic to fish/other pollutants of sewage.
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Question 102 Marks
Name any two sources of e-wastes and write two different way for their disposal.
Answer
Two sources of e-waste are:
  1. Irreparable computers.
  2. Electronic items like mobile phones, television sets etc.
Two different way of disposal of e-Waste are:
  1. Damping the e-Waste into landfills.
  2. Incinerating e-Waste i.e. burning the e-Wastes completely into ashes.
These ways of disposal pose threat to the environment by releasing toxic substances into it, so recycling of e-Waste in an environment-friendly manner is the only solution its disposal.
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Question 112 Marks
How did Ahmed Khan, plastic sacks manufacturer from Bangalore, solve the ever-increasing problem of accumulating plastic waste?
Answer
Collected plastic wastes - recycled - powdered - to form polyblend, blended with bitumen, used in road laying, increased road life by a factor of three/more durable.
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Question 122 Marks
Mention the major cause of air pollution in metro cities. Write any three ways by which it can be reduced.
Answer
Automobiles,
Using catalytic converters, application of stringent pollution level norms, switching over to CNG as fuel, phasing out old vehicles, using unleaded petrol, using low sulphur petrol or diesel.
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Question 132 Marks
How does an electrostatic precipitator work to remove particulate pollutants released from the thermal power plants?
Answer
Electrode wires at several thousand volts produce a corona that releases electrons, electrons attach to dust particles, (dust particles) become negatively charged, are attracted to collecting plates, low velocity of air help settling of dust.
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Question 142 Marks
Explain accelerated eutrophication. Mention any two consequences of this phenomenon.
Answer
Accelerated eutrophication is addition of effluents from industries and homes that accelerates the ageing of a lake.Consequences are destruction of aquatic life/decreased dissolved oxygen, algal bloom.
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Question 152 Marks
Explain the cause of algal bloom in a water body. How does it affect an ecosystem?
Answer
Effluents from home/industries/chemical fertilisers/agriculture/sewage, bring or add nutrients to the water body which enhances algal growth.Effects - Reduces oxygen content/BOD increases. Deterioration of water quality, affects all aquatic life forms, toxicity of water increases.
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Question 162 Marks
A crane had DDT level as 5 ppm in its body. What would happen to the population of such birds? Explain giving reasons.
Answer
Population of birds decreases, DDT can neither be metabolised nor be excreted, interferes with calcium metabolism causing thinning of egg shells, premature breaking of egg shells.
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Question 172 Marks
DDT content in the water of a lake that supplies drinking water to the nearby villages, is found to be 0.003 ppm. The kingfishers of that area are reported to have 2 ppm of DDT. Why has the concentration increased in these birds? What harm will this cause to the bird population? Name the phenomenon.
Answer
DDT neither excreted nor metabolised, interferes with Calcium metabolism, decline in bird population/due to thinning of egg shell/premature breaking of eggs, biomagnification.
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Question 182 Marks
Thermal power plants are inevitable in industrial and densely populated country like ours. What harm do they do to the environment? Also, mention any precaution that could be taken to save our environment.
Answer
Release particulate and gaseous air pollutants, hot thermal waste, kills organism sensitive to high-temperature indigenous flora and fauna lost, Use of electrostatic precipitator.
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Question 192 Marks
What is eutrophication? Explain its consequences on the life of plants and animals in such water bodies.
Answer
Eutrophication: Excessive enrichment of water bodies with nutrients (due to inflow of waste water) causes profuse growth of algae.(algal bloom), releases toxins in water cause oxygen deficiency in water.
Growth of algae inhibited due to toxins, aquatic animals (fish) may die due to toxicity or lack of oxygen/loss of species.
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Question 202 Marks
Explain the relationship between biotic potential and environmental resistance.
Answer
Biotic potential: Inherent/ physiological capacity of an organism to reproduce/ increase in number, is only realised when environmental conditions are non-limiting.Environmental resistance: Nature keeps a check on the expression of Biotic potential/population size, all factors that keep a check on population size constitute environmental resistance.
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Question 212 Marks
Is global warming real, only a theory or speculation?
Answer
Global warming is real and has been with us for sometime, increasingly during the past two decades, but gradually for more than a hundred years. The reality of it is seen in direct temperature measurements and also in the melting of glaciers in low latitudes, permafrost decay in Alaska and the decrease in sea-ice cover in Arctic.
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Question 222 Marks
What are the effects of waste water of thermal power plants if disposed directly into water bodies?
Answer
Thermal water waste if disposed directly into water bodies eliminates or reduces the number of organisms sensitive to high temperature, and may change the growth of plants and fish in extremely cold areas after causing damage to the native flora and fauna.
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Question 232 Marks
Mention two important problems relating to nuclear energy.
Answer
  1. Radiation from nuclear material/ waste is extremely harmful for the living organisms. It causes mutations at high rate and also increases the risk of cancer.
  2. Nuclear energy contributes a very small amount of emissions into the atmosphere which can cause many environmental problems such as global warming. Uranium is not burned in a nuclear power plant as coal is so there are no emissions from it.
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Question 242 Marks
Humans, as well as other animals, have been dumping their wastes into the environment for thousands of years. What is the reason that this appears to be such a problem today?
Answer
The human population is increasing rapidly, producing more wastes, and a significant amount of the wastes are non-biodegradable.
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Question 252 Marks
Why is it necessary to reduce sulphur from petroleum products?
Answer
It is necessary to reduce sulphur from petroleum products because sulphur dioxide formed as a result of fuel combustion is highly hazardous for our environment. It has significant impact on human health and is a major cause of acid rain.
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Question 262 Marks
Write an account on Montreal Protocol.
Answer
The Montreal Protocol is an agreement which was signed on $16^{th}$ September 1987 at Montreal (Canada) by 27 countries and became effective in 1989. It is an international treaty to limit the production and use of ozone-depleting substances like chlorofluorocarbons (CFCS) and to implement the use of alternatives to CFCS.
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Question 272 Marks
Name the various green house gases? Give their percentage contribution to global warming.
Answer
  • Methane, CFCs (Chloroflurocarbons) and nitrous oxide.
  • $CO_2$ contributes 60% of total global warming.
  • Methane contributes 20%.
  • CFCs contribute 14%.
  • Nitrous oxide 6%.
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Question 282 Marks
Mention the two major environmental issues of global nature.
Answer
  1. Increasing greenhouse effect.
  2. Depletion of ozone in the stratosphere.
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Question 292 Marks
Write a note on deforestation and enumerate it's consequences.
Answer
People's Participation in Conservation of Forests:
  1. In 1731, a Bishnoi woman, Amrita Devi (Jodhpur) showed, exemplary courage by hugging a tree and prevented it from cutting. Her three daughters and hundreds of other Bishnois, followed her and lost their lives, while saving trees. The Government of India has recently instituted the Amrita Devi Bishnoi Protection Award for individuals or communities from rural areas that have shown extraordinary courage and dedication to save trees.
  2. Chipko Movement started in Garhwal Himalayas in 1974, is primarily aimed to save trees and forests. Local women protected the trees by hugging them.
  3. Government of India in 1980s has introduced the concept of Joint Forest Management (JFM) to work closely with local communities in forest conservation. In return, the communities get benefits of various forest products (e.g. fruits, gum, rubber, medicine, etc.), thus enabling sustainable development of forest.
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Question 302 Marks
What are the problems associated with e-waste?
Answer
(e-wastes) comprise the damaged electronic goods and irreparable computers E-wastes release many toxins like lead, mercury, cadmium, etc, in soil and water. These toxins thus, get accumulated in biological chains of organisms.
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Question 312 Marks
Differentiate between bad and good ozone.
Answer
Serial Number
Good ozone
Bad ozone
i
The ‘stratospheric ozone' is also known as “Good Ozone."
The ‘Tropospheric Ozone’ is also known as “bad ozone”
ii
UV radiation with wavelengths between 280 and 315 nanometers called UV-B, and is damaging to almost all forms of life.
Ozone at ground level is a harmful pollutant. Ozone pollution is a concern during the summer months, when the weather conditions needed to form it lots of sun, hot temperatures normally occur.
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Question 322 Marks
Mention the consequences of deforestation.
Answer
  1. Increased concentration of carbon dioxide, leading to global warming.
  2. Loss of biodiversity due to habitat destruction.
  3. Soil erosion.
  4. Disturbance to hydrological cycle.
  5. Desertification in extreme cases.
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Question 332 Marks
The figure given below shows relative contributions of various greenhouse gases to the total global warming.
  1. Name the gases (a) and (b).
  2. Explain how increase in greenhouse gases in earth's atmosphere leads to melting of ice caps.
Answer
  1.  
  1. Nitrous oxide $\left(\mathrm{N}_2 \mathrm{O}\right)$.
  2. Methane $\left(\mathrm{CH}_4\right)$.
  1. Greenhouse gases cause global warming (increase in the earth's temperature), which causes melting of ice caps.
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Question 342 Marks
Why are the environmentalists worried about the considerate increase in the level of greenhouse gases? List the different greenhouse gases other than carbon dioxide.
Answer
  • Increase in the level of greenhouse gases will lead to heating of the Earth and result in global warming.
  • Environmentalists believe that the increased temperature is leading to deleterious changes in the environment and resulting in odd climatic changes (El Nino effect), melting of polar ice caps, etc.
  • The different greenhouse gases are methane, chlorofluorocarbons and nitrous oxide other than carbon dioxide.
  • The melting of polar ice caps may increase the sea level in due course of time and many coastal areas may become submerged.
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Question 352 Marks
What are the three major kinds of impurities in domestic wastewater?
Answer
Following are the three major kinds of impurities in domestic wastewater.
  1. Suspended impurities.
  2. Colloidal materials.
  3. Dissolved materials.
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Question 362 Marks
Why does biomagnification occur with certain substances? Name two such substances.
Answer
Biomagnification is increase in the concentration of certain toxic substances at successive trophic levels; this happens because these substances can neither be metabolised nor excreted, but get accumulated and passed on to the next higher trophic level, e.g. Mercury and DDT.
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Question 372 Marks
Enumerate the ill-effects of the PM 2.5 on human health.
Answer
When these fine particulate matter is inhaled deep into the lungs, it causes:
  1. Breathing and respiratory problems.
  2. Irritation and inflammation of the lungs.
  3. Damage to the lungs leading to premature death.
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Question 382 Marks
What do you understand by algal bloom?
Answer
Presence of large amount of nutrients in water bodies causes excessive growth of planktonic algae that causes colouration of water is called algal bloom. It causes deterioration of water quality and fish mortality.
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Question 392 Marks
Is it true that if the dissolved oxygen level drops to zero the water will become septic? Given example which could lower the dissolved oxygen content of an aquatic body.
Answer
Yes, the water become septic if the dissolved oxygen drops to zero. Organic pollution (biodegradable) is an example.
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Question 402 Marks
Suggest any four control measures of noise pollution.
Answer
  • By using sound-adsorbent materials.
  • Delimiting horn free zones near hospitals, schools etc.
  • Playing loudspeaker only in permissible limits and limiting the timings after
  • Which loudspeaker can not be played.
  • Having permissible sound levels of crackers.
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Question 412 Marks
List any two adverse effects of particulate matter on human health.
Answer
When particulate matter inhaled deep into the lungs they cause:
  1. Breathing and respiratory symptoms.
  2. Irritation.
  3. Inflammations.
  4. Damage to the lungs and premature death.
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Question 422 Marks
All of a sudden a great many dead fish are found floating on the surface of a pond. What might be the cause of such a fish kill?
Answer
It is likely that eutrophication has occurred in the pond. If so, large algal blooms can result from the excess nutrients. As this dead organic matter falls to the lower depths, decomposers consume the organic matter, but deplete the $O_2$ of water, which kills fish.
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Question 432 Marks
Study the given aquatic food chain and answer the questions that follow:
  1. Give reasons why there is a continuous increase in the DDT content in different trophic levels of the chain.
  2. Name the phenomenon responsible for themincrease in DDT content.
Answer
  1. The DDT concentration increases because:
  • It cannot be metabolised.
  • It is not excreted, but is passed on to the next higher trophic level.
  1. The phenomenon is called biomagnification.
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Question 442 Marks
Eichhornia crassipes is an alien hydrophyte introduced in India. Mention the problems posed by this plant.
Answer
Eichhornia crassipes (water hyacinth) is the world's most problematic aquatic weed. It grows abundantly in eutrophic water bodies and imbalances water ecosystem. It blocks the water, ways and growth of other organisms due to its excessive growth.
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Question 452 Marks
Answer the following:
  1. What depletes ozone in the stratosphere? How does this affect human life?
  2. What is El Nino effect? Explain how it accounts for biodiversity loss.
Answer
  1. Ozone in the stratosphere is depleted by CFCS, i.e. chlorofluorocarbons, released primarily from refrigerators and other industrial emissions. This affects the human life as it leads to more exposure of UV radiation, which is considered to be harmful for health.
  2. Effects of UV Rays:
    1. Damage to DNA and leads to mutation.
    2. Damage to the skin cells.
    3. Ageing of the skin.
    4. Various types of cancers.
  3. El Nino is abnormal warming of surface ocean water in the Eastern Pacific Ocean. During El Nino, there is movement of warm water to East which causes bleaching and death of coral reefs. It changes the route of migration of birds, fishes and whales thereby increasing the risk for them. It is also known to be responsible for sudden changes in rainfall pattern and drought. All this makes El Nino, a factor for biodiversity loss.
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Question 462 Marks
Explain how the inflow of large amount nutrients like phosphates and nitrates into the water body drastically affect the aquatic life there. Name the phenomenon responsible.
OR
'Fish mortality increases with the influx of nutrients in a freshwater body.' Write two reasons. How will the influx of nutrients affect the BOD level of this water body?

OR
How is it that the mortality rate of fish increases downstream from the point of sewage discharge into a water body? Explain.
Answer
  • The nutrients like phophates and nitrates in the sewage stimulate the excess growth of planktonic algae and cause algal blooms. \
  • Some bloom-forming algae secrete toxic chemicals that affect humans and other aquatic animals like fish.
  • They deteriorate the water quality and cause fish mortality.
  • When they die, the decomposers acting on them use oxygen and there is increased BOD and depletion of oxygen, which also causes mortality of aquatic animals like fish.
  • The phenomenon is called accelerated eutrophication.
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Question 472 Marks
What is meant by ozone hole? Which unit is used for measuring ozone thickness?
Answer
  • Ozone layer is a protective shield in stratosphere. Its depletion over a part of the atmosphere is called ozone hole which will result in an increased UV radiations reaching the earth surface.
  • Dobson Units (D.U.)
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Question 482 Marks
How has DDT caused decline in bird population?
Answer
High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing decline in bird populations.
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Question 492 Marks
What is meant by Jhum cultivation? Explain how it is responsible for deforestation.
Answer
In Jhum cultivation, farmers clear the trees of the forest 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, farmers move to another area and this process is repeated. Thus, in north-eastern states of India, this practice has caused major deforestation.
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Question 502 Marks
Differentiate between biodegradable and non biodegradable wastes.
Answer
Differences:
Biodigradable wastes
Non-biodegradable wastes
These are the wastes which can be broken down into simpler, harmless, (sometimes useful) substances by the action of living organisms through decomposition.
These are the wastes which cannot be broken down into simpler or harmless substances by the action of living organisms.
  • Non-biodegradable wastes are more harmful, as they tend to remain as such for many years on the surface of earth; this type of wastes must be reduced significantly.
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Question 512 Marks
The figure below shows the relative contribution of four greenhouse gases to global warming:
  1. Identify the gases A and C.
  2. Why are these four gases called the greenhouse gases?
Answer
  1.  
  • A-Carbon dioxide
  • C-Chlorofluorocarbons.
  1.  
  • Since these gases are responsible for the greenhouse effect, i.e. heating of the earth's surface, by absorbing the infrared radiation of the earth they are called greenhouse gases.
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Question 522 Marks
What is cultural eutrophication?
Answer
Cultural eutrophication is a form of water pollution. When eutrophication is accelerated due to human activities; it is called cultural eutrophication.
For example: Addition of excessive fertilisers into lakes results in cultural eutrophication.
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Question 532 Marks
How can we control global warming?
Answer
Global warming can be controlled by:
  1. Cutting down the use of fossil fuels.
  2. Improving the efficiency of energy usage.
  3. Planting trees and avoiding felling of trees.
  4. Controlling the growth of population.
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Question 542 Marks
Name two metals used in a catalytic converter. How do they help in keeping the environment clean?
OR
State the function of catalytic converters in automobiles. Name any two metals used in these converters.
Answer
  • As the exhaust passes through the catalytic converter, the unburnt hydrocarbons are converted into carbon dioxide and water, carbon monoxide and nitric oxide are converted into carbon dioxide and nitrogen gas.
  • The metals include rhodium, platinum and palladium.
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Question 552 Marks
  1. On seeing bad state of roads in your locality, as a student, you have recommended to the Municipal corporation to use polyblend.
  1. What is poly blend? Point out its raw material.
  2. How will it be advantageous?
  1. What are e-wastes? Explain the method of their disposal.
Answer
  1.  
  1. It is a fine powder of recycled modified plastic.
This mixture is mixed with bitumen used to lay roads:

Raw material: Plastic film waste.
  1. Blends of polyblend and bitumen, when used to lay roads, enhances the bitumen's water repellent properties and helps to increase road life by a factor of three.
  1. Irreparable computers and other electronic goods are known as e-wastes = 1
Burried in landfills or incinerated.
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Question 562 Marks
The figure given below shows the relative contribution of four greenhouse gases to global warming.
  1. Identify the gases A and C.
  2. Why are these four gases called greenhouse gases?
Answer
  1. A-Carbon dioxide $\left(\mathrm{CO}_2\right)$ C-Chlorofluorocarbons (CFCS).
  2. These four gases (i.e. $\mathrm{CO}_2, \mathrm{CH}_4, \mathrm{~N}_2, \mathrm{O}$ and CFCs) are called greenhouse gases, as they absorb infrared radiations emitted by the earth's surface.
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Question 572 Marks
Write down the various constituents of municipal and industrial waste (Sewage).
Answer
It is released. from petroleum. paper manufacturing, metal and chemical manufacturing industries into water bodies. The industrial effluents contain toxic heavy metals like mercury, cadmium, copper, Iead, etc.
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Question 582 Marks
Name any one green house gas and its possible source of production on a large scale. What are the harmful effects of it?
Answer
$CO_2$ and Methane.$CO_2$ levels are increasing due to burning of fossil fuels, and harmful effects are leading to Global Warming.
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Question 592 Marks
Why are landfills not really much of a solution, to dispose solid wastes?
Answer
  1. The amount of garbage generated, especially in metros is so much that the landfills are getting filled very fast.
  2. There is also danger of seepage of chemicals, which can pollute the underground water resources.
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Question 602 Marks
What is hybrid vehicle technology. Explain the advantages with a suitable example.
Answer
Vehicle running on dual mode like petrol and CNG are hybrid vehicle. As CNG is a green fuel there is conservation of fossil fuel and reduction in the environmental pollution.
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Question 612 Marks
Use of lead-free petrol or diesel is recommended to reduce the pollutants emitted by automobiles. What role does lead play?
Answer
Tetraethyllead is added to petrol or diesel to reduce knocking in engine. Knocking severely damages the engine. But lead in this compound poses several environmental and health hazards.
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Question 622 Marks
It is a common practice to plant tree and shrubs near the boundary walls of building. What purpose do they serve?
Answer
The plant growing near the boundary wall act as barrier for sound pollution and act as dust catchers.
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Question 632 Marks
How do chlorofluorocarbons destroy ozone layer?
Answer
Chlorofluorocarbons (CFCs) break down in the presence of UV rays and produce active chlorine. The chlorine atoms break down ozone into molecular $O^2$, thereby depleting ozone layer.
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Question 642 Marks
What is integrated organic farming?
Answer
It is a cyclic, zero waste procedure, where waste products from one process are cycled as nutrients for other processes. This allows the maximum utilisation of resource and increases the efficiency of production.
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Question 652 Marks
What is integrated organic farming? Mention its advantages.
Answer
  • It is a cyclical, zero-waste procedure, where waste products from one process are cycled in as nutrients/ resources for other processes.
  • This allows the maximum utilisation of resources and increases the efficiency of production.
  • Cattle excreta is used as manure as well as for generating biogas that can be used for lighting and cooking.
  • Crop wastes are decomposed too and used as manure.
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Question 662 Marks
What are Euro II norms?
Answer
  • Sulphur be controlled at 350ppm in diesel and 150ppm in the petrol.
  • Aromatic hydrocarbons are to be contained at 42% of concerned fuel.
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Question 672 Marks
What would be the impact on the environment around a thermal power plant if its electrostatic precipitator stops functioning? Give a reason.
Answer
Electrostatic precipitators remove 99% of the particulate matter present in the exhaust of a thermal power plant.
In its absence, they will remain in the air as pollutants.
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Question 682 Marks
Mention the advantages of using EcoSan toilets or ecosanitation.
Answer
  1. The human excreta can be recycled to form manure and thereby reduce the use of chemical fertilisers.
  2. A large quantity of water can be saved.
  3. It is a hygienic method of disposal of human excreta.
  4. This method is efficient and cost-effective too.
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Question 692 Marks
Will climate change bring benefits to some areas?
Answer
As a result of global warming and climate change, regions such as Siberia will likely to become warmer and more habitable. The growing seasons in some regions will lengthen, as spring will arrive earlier and winter frosts set in later.
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Question 702 Marks
What are secondary pollutants? Give two examples.
Answer
Pollutants which are formed by reaction between the primary pollutants in the presence of sunlight are called secondary pollutants.
Examples: Proxy-acyl nitrate (PAN) and Ozone.
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Question 712 Marks
What can be the effect of discharging hot (thermal) water into a water body on the organisms in it?
Answer
  1. A number of organisms will die that are sensitive to high temperature.
  2. Hot water will reduce oxygen content of water and thus increased BOD will affect the aquatic animals.
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Question 722 Marks
How does a scrubber function?
Answer
Scrubbers are generally employed in removing gaseous pollutants. In a scrubber, the exhaust is passed through a spray of water or lime. Water dissolve gases and line reacts with sulphur dioxide to form a precipitate of calcium sulphate or sulphite.
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Question 732 Marks
How is waterlogging caused? How does it affect the crop plants?
Answer
  • Irrigation without proper drainage causes waterlogging
  • Waterlogging draws the salts to the surface of soil and the salts may get collecting on the roots.
  • The increased concentration of salts is inimical to the growth of crop plants.
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Question 742 Marks
It has been recorded that the temperature of the earth's atmosphere has increased by 0.6°C.
  1. What has caused this increase?
  2. Explain its consequences. Write a note on deforestation and enumerate it's consequences.
Answer
  1. Increase in the level of greenhouse gases $(CO_2$, CFCS, etc.$)$ in the atmosphere allow the heat waves to reach earth, but prevent their escape and thus, the earth becomes warm.
  2. Effects of increased temperature are:
  1. Leads to deleterious changes in environment, resulting into odd climatic changes such as El Nino effect.
  2. Melting of polar ice caps which will cause the rise in sea level and many coastal areas may also get submerged.
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Question 752 Marks
Is it true that carpets and curtains/ drapes placed on the floor or wall surfaces can reduce noise level. Explain briefly?
Answer
Yes, It is true that carpets and curtains/ drapes placed on the floor or wall surfaces can reduce noise level. These objects are made of fibres and fibres can absorb sound waves thus reduce noise level.
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Question 762 Marks
Differentiate between ‘bad’ ozone and ‘good’ ozone.
Answer
S. No.
Bad ozone
Good ozone
(i)
The ozone found in the lower atmosphere is called bad ozone.
The ozone found in the stratosphere is called good ozone.
(ii)
It harms both plants and animals.
It absorbs UV radiation and protects the living organisms from its harmful effects.
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Question 772 Marks
Is it true, that carpets and curtains oblique drapes placed on the floor or wall surfaces can reduce noise level? Explain briefly.
Answer
Yes, it is true, that placing/ using carpets on floor and curtains on wall surface, windows, reduces noise level. This is because the curtains on wall surface and carpet acts as muffling device and absorb sounds of moderate level.
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Question 782 Marks
Suggest any four remedial/control measures of noise pollution.
Answer
Control of Noise Pollution:
  1. Establishment of horn-free zones around schools and hospitals.
  2. Use of acoustic materials in the wall of homes located in high sound zones.
  3. Silencers must be fitted to automobiles and industrial gadgets.
  4. Use of sound absorbent materials or mufflers in industries.
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Question 792 Marks
Which one gas is most abundant out of the four commonest greenhouse gases? Discuss the effect of this gas on the growth of plants.
Answer
Carbon dioxide is the most abundant (60 percent) among greenhouse gases. With doubling of concentration growth of plants (carbon dioxide fixing) increases by 30 percent in shortterm period. At higher concentration of $CO_2$, stomata close and hence transpiration rate will be reduced.
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Question 802 Marks
What is "greenhouse effect"? How is this phenomenon used for growing plants, especially in winter?
Answer
  • The 'greenhouse effect' is a phenomenon that occurs in a greenhouse, where the glass panel lets the light in, but does not allow the heat to escape, consequently, the inside of the greenhouse warms up.
  • Thus, the small glasshouse (greenhouse) is used for growing plants in winter, when it is very cold outside.
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Question 812 Marks
Enumerate the major causes of deforestation.
Answer
  1. Conversion of forest to agricultural land.
  2. Felling of tress for timber, firewood, etc.
  3. Jhum Cultivation.
  4. Clearing forests to make living areas.
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Question 822 Marks
  1. What are the after effects of the degradation of ozone?
  2. How does it affect human health?
Answer
  1. In the absence of ozone which acts as a shield and absorbs the UV-rays, the UV rays reach the earth surface; UV rays are highly injurious to living organisms as it damages DNA and proteins.
  2. In humans it causes:
  1. Cataract, snowblindness and damage to cornea.
  2. Damage to skin cells, aging of skin and skin cancers.
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Question 832 Marks
Why are e-wastes recycled in the developing countries? What is the problem associated with it?
Answer
  • E-wastes are recycled in the developing countries, as they recover some costly elements like copper, gold, nickel, silicon, etc.
  • Recycling in developing countries involves manual participation and workers are exposed to the toxic substances and get certain respiratory diseases.
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Question 842 Marks
How do air pollutants harm the living beings?
Answer
Air pollutants:
  1. Cause breathing and respiratory disorders in humans and other animals.
  2. Some air pollutants cause allergic responses.
  3. Reduce the growth rate and yield of crop plants.
  4. Cause premature death of plants.
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Question 852 Marks
How do catalytic converters work?
Answer
Platinum, palladium and rhodium metals act as catalysts in catalytic converters. Catalytic converters are fitted into automobiles. When poisonous gases pass through these converters unburnt hydrocarbons get converted into carbon dioxide and water. Carbon monoxide and nitric oxide also change to $CO_2$ and$N_2$ gass.
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Question 862 Marks
Study the graph given below and answer the questions that follow:
  1. What is the relationship between dissolved oxygen and biochemical oxygen demand (BOD)?
  1. Mention their effect on aquatic life in the river.
Answer
  1. When BOD is high, dissolved $O_2$ is less/ inversely proportional.
  2. If dissolved $O_2$ is less and BOD is high, aquatic organisms die.
If dissolved $O_2$ is more and BOD is low, fresh water organisms reappear.
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Question 872 Marks
Describe Chipko Movement.
Answer
Chipko movement was started in Garhwal, Himalayas in 1974 by Shri Sundar Lal Bahuguna to prevent cutting down of trees. The leaders of Chipko Movement believe in 5 Fs-food, fodder, fuel, fertilisers and fibres provided by the forest.
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Question 882 Marks
Name any one of the green house gases and its possible source of production on a large scale. What are the harmful effects of it?
Answer
$\mathrm{CO}_2$ and Methane. $\mathrm{CO}_2$ levels are increasing due to burning of fossil fuel leading to global warming.
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Question 892 Marks
Name any two places where it is essential to install electrostatic precipitators. Why is it required to do so?
Answer
Limitation of using electrostatic precipitator is that it only works on gravitational settling method. Velocity of air between the plates is maintained low to allow the dust to fall in.
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Question 902 Marks
Thermal power plants are inevitable in an industrial and densely populated country like ours. What harm do they do to the environment? Also mention any precautions that could be taken to save our environment.
Answer
The smoke stacks of thermal power plants release particulate and gaseous air pollutants.These pollutants when inhaled deep into the lungs can cause:
  1. Breathing or respiratory disorders.
  2. Irritation, inflammations and damage to lung alveoli and
  3. Premature death.
Control measure: By use of electrostatic precipitators, 99% of the particulate matter can be removed.
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Question 912 Marks
Draw a labelled diagram of a scrubber and mention its use to remove pollutants.
Answer

It is used to remove harmful gases like $SO_2$ from the industrial exhausts. The exhaust is passed through a spray of lime or water. Water dissolves the gases and lime reacts with $SO_2$ to form a precipitate of calcium sulphate and sulphide.
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Question 922 Marks
How does global warming pose a threat to the coastal areas of the earth? Explain.
Answer
  • The global warming is resulting in odd climatic changes and leading to melting of polar ice caps and other snow caps of mountains like Himalayas.
  • Over many years, this will result in a rise in sea level, which can submerge the coastal areas.
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Question 932 Marks
What is an 'algal bloom'? State its cause and any two harmful effects.
Answer
  • Algal bloom refers to the excessive growth of planktonic algae in water bodies.
  • It is caused by the presence of large amounts of nitrates and phosphates in the water.
  • Its harmful effects include:
  1. Fish mortality and deterioration of water quality
  2. Some bloom-forming algae are toxic to humans and other animals.
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Question 942 Marks
A person has inhaled air having particulate pollutants of size less than 2.5 micrometers in diameter. What could be the impact of their pollutants on his respiratory system?
Answer
Particulate pollutants inhaled deep into the lungs cause irritation, inflammation, damage to the lungs, and premature death.
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Question 952 Marks
  1. Expand CFC.
  2. How does it reduce ozone to oxygen?
Answer
  1. Chlorofluorocarbons.
  2. In stratosphere, UV rays act on CFCs thereby releasing Cl, which degrades ozone, releasing molecular oxygen. Cl atoms act merely as catalyst and are not consumed in the reaction. A single chlorine atom can convert 1 lakh molecules of ozone into oxygen.
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