Science M.C.Q. [1 M]

4. All of these.

Explanation:

Waste from industries into water bodies pollutes the water bodies as majority of the waste is non-biodegradable. Sewage waste which is mostly from houses is also directed into water bodies. Runoff water from farms carries along with it chemicals of fertilizers and pesticides thus again polluting the water bodies.

The conversion of atmospheric nitrogen into ammonia NH₃ is known as nitrogen fixation. Bacteria that perform nitrogen fixation are either free living or they may form symbiotic associations with other organisms.

NITROGEN CYCLE: It is a process by which nitrogen is converted into various chemical forms and is made available to living organisms. There are various steps in a nitrogen cycle. Nitrogen fixation takes place by the action of microbes, inert nitrogen breaks down in the air and combines with oxygen to form nitrous oxide. Nitrifying bacterias in the soil take up this atmospheric nitrogen and make it available for plants. Plants get this nitrogen. Later when they decay, the nitrogen is returned back into the environment. In the soil there are some denitrifying bacterias too, they break down nitrate and release nitrogen into the atmosphere thus they end the nitrogen cycle.

4. Rows of trees and shrubs.

Explanation:

Wind breaks are rows of trees and shrubs on land to prevent erosion of soil by high speed wind.

4. 2.5%

Explanation:

Only 2.5 percent of total water is found as fresh water which occurs in lakes and rivers.

2. Arid zone.

Explanation:

Arid zone is characterized by areas of low rainfall and desert. Rajasthan and Gujarat fall in this zone.

3. Carbon dioxide.

Explanation:

Carbon dioxide traps the infrared rays and prevent heat from escaping the earth’s atmosphere. This causes the temperature of earth to rise which is known as global warming.

4. Itai-itai.

Explanation:

Cadmium poisoning in drinking water of Japan from a river basin resulted in itai-itai disease in people of Japan. The symptoms included kidney disorders, anemia, pain and bone fractures.

1. Take an empty plastic bottle.
2. Pour 5-10ml water into it and close the bottle tightly with a cap.
3. Shake the bottle well and then place it in the sun for 10 minutes.
4. Now, open the cap of the bottle and allow some smoke from the lighted incense stick to enter the bottle.
5. Quickly close the bottle tightly with the cap.
6. Press the bottle hard between your hands as much as possible.
7. After few seconds release the bottle. Press the bottle again as hard as you can.

This simple experiment replicates, on a very small scale, the happenings when air with a very high content of water vapour goes from a region of high pressure to a region of low pressure. When bottle containing water is kept in the sun, the water evaporates and air inside the bottle gets saturated with water vapour. When the bottle is pressed between your hands, the pressure inside becomes high and air inside the bottle moves in a region of low pressure. It expands and cools. The smoke particles act as 'nuclei' on which water vapours condense in the form of tiny droplets. When you release the pressure, the air inside the bottle becomes foggy. When bottle is again pressed, the fog will disappear. It is so because due to high pressure condensed water vapours will fall down and collect as water at the bottom of the bottle. When the experiment is repeated without smoke inside the bottle, one will not observe foggy air inside the bottle as smoke particles are absent and nothing is available in air to act as ‘nucleus’ for water vapours to condense as tiny droplets.

1. NO₂

Explanation:

Photochemical smog is formed in atmosphere when ozidized volatile organic compounds react with nitrogen oxide.

4. All of these.

Explanation:

Methane, carbon dioxide and chlorofluorocarbons, all of them are greenhouse gases that trap the infrared rays and thus trap the heat, not allowing it to escape the earth’s surface, hence contributing to greenhouse effect.

2. Sulphur dioxide.

Explanation:

Lichens are sensitive to Sulphur dioxide because they have efficient absorption systems due to which they rapidly accumulate Sulphur from high levels of Sulphur dioxide in air.

4. Solar radiation.

Explanation:

Solar energy is a renewable form of energy that cannot be exhausted ever. Radiations from sun are solar radiation so they are too inexhaustible and sustainable form of energy. Fossil fuels, minerals and soil are non-renewable sources. Once lost, they cannot be replenished.

1. Sunlight.

Explanation:

Green plants are producers in an ecosystem i.e. they produce food. The food obtained from plants is utilized by all the other components of an ecosystem. Hence, Green plants are ultimate source of energy.

2. Mercury.

Explanation:

Paper industry uses fuels and during of fuels like coal releases mercury that is a toxic chemical.

The continuous process by which nitrogen is exchanged between organisms and the environment is called nitrogen cycle. Nitrogen is an essential nutrient, needed to make amino acids and other important organic compounds, but most organisms cannot use free nitrogen, which is abundant as a gas in the atmosphere.

Nitrogen cycle involves the following steps:

1. Nitrogen fixation: This process involves the conversion of atmospheric nitrogen into nitrates, which are soluble in water. This is done by various nitrogen fixing bacteria.

Example: Rhizobium, blue green algae and bacterium Azotobacter.

2. Ammonification: It is the process of decomposing complex, dead organic matter into ammonia. This is done by microorganisms living in the soil.

3. Nitrification: It is the process of conversion of ammonia into nitrites and then into nitrates. This is done by nitrifying bacteria.

Example: Nitrosomonas and Nitrobacter.

4. Denitrification: It is the process of reducing nitrates present in the soil to release nitrogen back into the atmosphere.

Example: Pseudomonas.

The decomposers help in decomposing the dead bodies of plants and animals, and hence act as cleansing agents of environment. The decomposers also help in putting back the various elements of which the dead plants and animals were made, back into the soil, air and water for reuse by the producers like crop-plants, e.g. the decomposers like purifying bacteria and fungi decompose the dead plants and animal bodies into ammonia. This ammonia is converted into nitrates by nitrifying bacteria present in soil. These nitrates act as fertilizer in the soil and are again absorbed by the plants for their growth. Thus, the nitrates act as fertilizer in the biosphere so that the process of life may go on and on like an unending chain.

3. At place of interaction of lithosphere, hydrosphere and atmosphere.

Explanation:

Biosphere constitutes all the living beings and their relationships along with their interaction with lithosphere, hydrosphere and atmosphere.

The ozone layer is a deep layer in the stratosphere, encircling the Earth, which has large amounts of ozone in it. This layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun. Ozone is a special form of oxygen, made up of three oxygen atoms rather than the usual two oxygen atoms.

It is formed when some type of radiation or electrical discharge separates the two atoms in an oxygen molecule (O₂), which can then individually recombine with other oxygen molecules to form ozone (O₃).

Reduction in the concentration of ozone layer is called ozone depletion. Ozone depletion is caused by certain chemicals called ozone depleting substances. They include chlorofluoro carbons, methyl bromide, nitrogen oxides and chlorine.

Effects of ozone depletion: Depleting ozone layer allows more ultraviolet (UV) radiations to pass through it, which reach the earth's surface. These UV rays cause various harmful effects on human beings, animals, plants and environment such as:

1. Skin cancer.
2. Damage of eyes.
3. Damage of immune system.
4. Decreased crop yields.

2. 1985

Explanation:

Ozone hole was discovered in 1985 over Antarctic by Joe Farman, Brian Gardiner and Jonathan Shanklin.

Break down of bigger rocks into smaller mineral particles is called weathering.

It is of three types:

1. Physical weathering: Various climatic factors such as temperature, wind, rain water, ice, snow, glaciers and running water contribute to physical weathering. Water and high temperature cause corrosive humidity and bring about unequal expansion and contraction of rocks, facilitating their break down.

2. Chemical weathering: It involves a variety of chemical processes, such as hydrolysis, hydration, oxidation and reduction. The breakdown of complex compounds by the carbonic acids present in water and acidic substances derived from the decomposition of organic matter in soil, are examples of chemical weathering.

3. Biological weathering: Is done by living organisms such as lichens and bryophytes. They create small crevices which deepen to form cracks in the rocks. Cracks gradually widen and cause slow fragmentation and eventually pulverisation of rocks.

2. Inexhaustible resource.

Explanation:

Air is inexhaustible resource. It is present in an abundant amount and will not ever run out or deplete.

1. Bacteria and fungi.

Explanation:

Bacteria and fungi are microorganisms that decompose the dead and decaying matter.

2. Rajendra Singh.

Explanation:

Rajendra Singh is popularly known as water man of India. He is a water conservationist from Alwar, Rajasthan.

4. All the above.

Explanation:

All the elements of life support system are inter-related, inter-dependent, inter-connected. Food chain and food web are clear examples of this.

2. Infrared rays.

Explanation:

Greenhouse effect is caused by infrared rays. Gases like carbon dioxide absorb infrared rays, thereby increasing the temperature of earth and hence causing greenhouse effect.

2. 23–25km

Explanation:

Ozone layer or ozonosphere occurs in the stratosphere. It is generally lowest at the equator and highest in polar regions. It is present to a height of 23-25kms over the equator.

2. Dissolved oxygen.

Explanation:

Eutrophication leads to algal blooms in water bodies thus blocking the penetration of sunlight in the water bodies. Hence the plants do not get sufficient sunlight to carry out photosynthesis hence oxygen is not produced.

4. All of the above.

Explanation:

Biotic components refer to all the living components. Prodcers, consumers and decomposer, all are living components in an ecosystem.

2. Loam.

Explanation:

Loamy soil contains a small amount of organic material hence it is best suited for plant growth.

2. Infrared rays.

Explanation:

Greenhouse gases trap infrared rays and stop them from escaping the earth’s surface thus causing global warming.

3. Carbon dioxide.

Explanation:

Carbon dioxide traps infrared rays and prevent them from escaping the earth’s surface thereby increasing the temperature of earth and resulting in global warming.

1. Rhizobium.

Explanation:

Rhizobium is a gram -ve bacteria that fixes nitrogen. Nif gene occurs in Rhizobium.

4. All the above.

Explanation:

Suspended Particulate Matter (SPM)are finely divided matter particles that cause aur pollution. They may be dispersed into air by combustion or industrial processes. Dust, soot and smoke, flash are all Suspended Particulate Matter.

3. Ammonia into nitrite.

Explanation:

Nitrosomonas are rod shaped bacteria that oxidize ammonia into nitrite. Nitrosomonas are useful in bioremediation.

Living organisms need water because it plays a vital role in the reactions taking place within organism’s cells and body. Water acts as a universal solvent, providing a medium for the chemical reactions to occur. Substances are also transported from one part of body to the other in the dissolved state. Therefore, it is necessary for the organisms to maintain a distinct level of water within their bodies in order to stay alive. Terrestrial life forms require fresh water because their bodies cannot tolerate or get rid of the high amounts of the dissolved salts in saline water. So, water sources need to be easily accessible to animals and plants to survive on land. Thus, availability of water decides not only the number of individuals of each species that are able to survive in a particular area, but it also decides the diversity of life there.

3. Mercury.

Explanation:

Mercury contaminated water in Japan lead to the outspread of Minamata disease when people consumed this water polluted with high levels of mercury.

1. Land faster than the water bodies.

Explanation:

Land absorbs more heat because they are darker, hence heat up faster than water bodies by absorbing solar radiations. Water bodies on the other hand reflect most of the solar radiation that fall on it thus not getting heated faster.

1. Producers.

Explanation:

Green plants are the producers as they produce their own food by photosynthesis.

Soil pollution is caused by solid wastes and chemicals. The slag heaps from mines spoil the beauty of sites of mines. Pulp and paper mills, sugar mills, oil refineries, power plants, chemicals fertilizer manufacturing units, iron and steel plants, plastic and rubber producing complexes are some major contributions to soil pollution. Most industrial furnaces and thermal power stations produce fly ash, which is a grey, powdery residue of unburnt material, and causes pollution. This fly ash hampers the growth of crop plants and also decreases crops of orchards. Domestic waste also adds a large amount of solid wastes. Modern farming practices involve the use of large amounts of fertilizers and pesticides. Use of these substances over long period of time can destroy the soil structure by killing the soil microorganisms that recycle nutrients in the soil. It also kills the earthworms which are helpful in making the rich humus. Fertile soils can quickly become barren if sustainable practices are not followed.

1. Global warming.

Explanation:

Greenhouse is related to global warming. Greenhouse gases absorb infrared radiations and stop it from escaping the earth’s surface which results in increase in temperature of earth, thus causing global warming.

4. Hydroelectric power plants.

Explanation:

Water flowing through through dams spin the turbine plates to generate electricity. There is no air or water pollution caused by hydroelectric power plant.

4. Nitrosomonas and Nitrobacter.

Explanation:

Nitrosomonas and Nitrobacter are bacteria that carry out nitrification.

Nitrosomonas oxidize ammonia into nitrite. Nitrobacter break down nitrite into nitrate.

2. Physical phenomena.

Explanation:

Sun’s energy heats up rocks to a high temperature which causes them to expand. When temperature falls, these rock contract. This continuous expansion and contraction causes the rock layer to wear off. And hence results in weathering of rocks.

3. Lithosphere.

Explanation:

Lithosphere is the upper part of the earth consisting f crust and solid part of mantle. It contains rocks, minerals and soil.

4. All of these.

Explanation:

Water pollution occurs from organic pollutants like detergents, insecticides. Inorganic water pollutants include heavy metals, fertilizers, chemical wastes from industries. Bacteria, viruses and fungi that contaminate water are biological causes.

4. All of these.

Explanation:

Forest destruction results in all of the above mentioned effects.

• Animals lose their habitat when forests are cut down
• The soil losens when trees are cut down as roots of the trees no longer exist to hold the soil which hence results in floods and soile erosion by wind and water.

1. Rocks.

Explanation:

Soil is a thin layer of sediments and fine particles covering the earth’s surface. It is mainly formed from weathering of rocks by various processes.

Sources of water pollution:

1. Sewage: Organic wastes are contributed as domestic and commercial sewage by food processing plants, dairy farms, piggeries, poultry farms, slaughter houses, breweries, tanneries, etc. Animal excreta is discharged into fields or dumped into pits reaches water bodies through run off and leaching, particularly during the rainy season.

2. Industrial wastes: Effluents of mills and industries such as paper mills, petroleum refineries, etc., contain large quantities of harmful chemicals including acids, alkalis and heavy metals (e.g., mercury salts from paper industries) that are discharged into water bodies (rivers and lakes).

3. Synthetic soaps and detergents: Water containing soaps and detergents is discharged from houses and certain factories.

4. Fertilizers and pesticides: Fertilizers and pesticides are being used excessively in the fields to increase crop production. These are washed by rainwater into water bodies and pollute them.

5. Petroleum oil: Drilling and shipping operations are common in the oceans. Leakage of petroleum oil during such operations or due to accidents results in water pollution.

6. Solid particles: Rain erodes soil and carries silt to water. Tiny suspended particles of clay and dust also settle in water from air. These soil particles cause turbidity.

7. Thermal pollution: Discharge of hot water from industries and thermal plants into water body changes the normal temperature of the water. The content of oxygen decreases. Reduced oxygen content kills aquatic animals and reduces the rate of decomposition of organic matter which, therefore, accumulates.

Harmful effects of Water pollution:

1. Human diseases: Diseases such as typhoid, cholera, dysentery, jaundice and hepatitis are caused due to water pollution.

2. Disturbance in ecological balance: All types of water pollutants affect the life forms living in the water. These pollutants can encourage the growth of some life forms and harm some other life forms hence affecting the balance between various organisms.

3. Removal of desirable substances from water bodies: With increase in the amount of organic wastes in water, bacteria multiply rapidly and use up the available oxygen. Lack of oxygen kills the fish and other animals.

Atmosphere is divided into five distinct layers: Troposphere, stratosphere, mesosphere, thermosphere and exosphere.

1. Troposphere is the lowest region of atmosphere which contains air and is subject of differential heating. It extends from the surface of the earth upto 8-20kms. Many important climatic events such as cloud formation, lightning, thundering etc all takes place in the troposphere.
2. The Stratosphere extends from the top of the troposphere up to around 31 miles (50km) above the Earth's surface. In this region the temperature increases with height. Heat is produced due to the formation of ozone.
3. The mesosphere extends from the top of the stratosphere to about 53 miles (85km) above the earth. The gases, including the oxygen molecules, continue to become thinner and thinner with height.
4. Above the mesosphere the thermosphere extends up to near 375 miles (600km) above the earth. This layer is known as the upper atmosphere. As such, incoming high energy ultraviolet and x-ray radiation from the sun, absorbed by the molecules in this layer, causes a large temperature increase.
5. Exosphere exists above the thermosphere.

1. Nitrogen cycle:

2. Carbon cycle:

2. Aeolian.

Explanation:

Aeolian soil are wind deposited sand and silt sized particles. They have no coarse fragments.