Science M.C.Q. [1 M]

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

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

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.

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.

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

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.

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.

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.

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

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

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.

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

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

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

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.

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.

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

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

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

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.

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.

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

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.

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.

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.

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

Nitrosomonas and Nitrobacter are bacteria that carry out nitrification.
Nitrosomonas oxidize ammonia into nitrite. Nitrobacter break down nitrite into nitrate.

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.

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

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.

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.

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:

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

Eutrophication is a phenomenon that occurs in water bodies. Excess of nutrients result in algal blooms which stops the penetration of light into the water body and the aquatic plants are thus unable to perfrom photosynthesis.

The introduction of chemicals, particulate matter, or biological materials into the atmosphere that cause harm or irritate living organisms or damage the natural environment is known as air pollution.
The major causes of air pollution can be in the form of solid particles, liquid droplets, or gas. There are many different chemical substances that contribute to air pollution. These chemicals come from a variety of sources. Among the many types of air pollutants are nitrogen oxides, carbon monoxides, and organic compounds that can evaporate and enter the atmosphere.
Air pollutants have sources that are both natural and human. Humans contribute substantially more to the air pollution problem. Forest fires, volcanic eruptions, wind erosion, pollen dispersal, evaporation of organic compounds, and natural radioactivity are all among the natural causes of air pollution. Though some pollution comes from these natural sources, most pollution is the result of human activity. The biggest causes are the operation of fossil fuel-burning, power plants and automobiles that combust fuel.
Effects of air pollution on human beings:

1. SPM (suspeneded particulate matter) causes asthma, bronchitis and allergic cold.
2. Pollutant gases cause irritation in eyes, throat and lungs. Heart related diseases tend to increase.
3. Hydrocarbon vapours not only damage the internal organs but also cause cancer.

Soil formation in nature takes place by weathering of rocks by mechanical, chemical and biological methods.

1. Physical/ Mechanical: Breakdown of rocks into smaller pieces. The rocks get heated up during the day and it cools down during night. This expansion and contraction due to heating and cooling of rocks lead to splitting of rocks. Water might enter the rocks in the cracks made by expansion and contraction. When this water freezes, the rocks widen and thus rocks break.
2. Chemical: It occurs when rocks are worn away by chemical changes like the chemicals released by lichens. These chemicals cause the rock surface to powder own which forms layers of soil.
3. Biological: Disintegration of rocks by activities of living organisms like plant grow in the cracks of rocks thus breaking the rocks.

1. Take a beaker full of water, a beaker full of soil and a closed bottle containing a thermometer.
2. Keep them in bright sunlight for three hours.
3. Now, measure the temperature of all three vessels and also take the temperature reading in shade at the same time.
4. You will observe that the temperature of the soil and sand is more than that of water in bright sunlight because sand and soil gets heated by solar radiations faster than the water.
5. Therefore, land would become hot faster than the sea.
6. You will also observe that the temperature of air in shade is different from the temperature of soil, sand and water in bright sunlight because of the direct effect of radiations.

Winds erode away lose soil, heavy rains also wash away soil that is loosely bound. If the fields are left fallow for long , since there will be no plants to hold the soil the soil easily gets eroded away by wind and water.

Burning of fossil fuels like coal, natural gas and oil for fulfilling various needs is a major source of air pollution. The gases that are released on the burning of these compounds results in air pollution.

Sulphur dioxide is a gas that dissolves in water and produces acidic ions that are highly reactive. When lichen absorb this gas, it disrupts photosynthesis, inhibits reproduction and other activities.

The process of evaporation of water and falling on the land as rain and later flowing back into the sea via rivers is known as the water-cycle.
Water Cycle: Water in the atmosphere is converted into water vapor by the heat from sunlight i.e. water evaporates and turns into water vapour. Also, water vapour is present in the atmosphere from plants by transpiration from leaves. This water vapour condenses in the atmosphere and forms cloud. When enough water vapour has condensed, it falls down on earth in the form of rainfall. This water flows into water bodies or seeps underground.

Clouds form when water condenses in the sky. They are formed in troposphere because nearly all of the water vapour and dust particles in atmosphere are in the troposphere.

Natural resources are living and non-living components of nature which are used by humans to meet their requirements. Since natural resources are available only from the Earth, they are called Earth resources.
Based on their abundance, natural resources are of two main types, inexhaustible and exhaustible.

1. Inexhaustible natural resources: They are natural resources which occur in such abundance that they are not likely to get exhausted despite continuous use, e.g., air, water, solar energy.
2. Exhaustible natural resources: They are natural resources which are available in limited quantity. They may to get depleted by continuous and indiscriminate human consumption. Exhaustible resources are of two kinds, renewable and non-renewable.

• Renewable resources: They are exhaustible resources which get replenished regularly. These are both living and non-living resources which can replenish themselves by quick recycling, e.g., forests, wildlife, soil and underground water. Renewable resources can last for ever if they are used responsibly.
• Non-renewable resources: They are exhaustible resources which once used cannot be replenished. Thus, these resources are non-living and cannot replenish themselves by recycling and replacement. If not used carefully they will ultimately get exhausted. Their increased consumption results in quicker exhaustion, e.g., minerals, fossil fuels such as coal and petroleum.

Contamination of water bodies with undesirable substances like fertilizers, pesticides or poisonous substances, thus degrading the water quality and making it unfit for drinking and other purposes is defined as water pollution. Water pollution occurs from organic pollutants like detergents that are a part of domestic waste, insecticides from farm runoff. Inorganic water pollutants include heavy metals, fertilizers, chemical wastes from industries. Industrial waste into water bodies pollutes the water bodies as majority of the waste is non biodegradable. Industries also use water for cooling in various operations and later return this hot water to water-bodies therby causing thermal pollution. Sewage waste which is mostly from houses is also dumped into rivers or lakes. Runoff water from farms carries along with it chemicals of fertilizers and pesticides thus again polluting the water bodies.

Terrace farming and intensive cropping, both are helpful in preventing soil erosion. Terrace reduces the speed of water moving across the soil surface which reduces soil erosion. Also, Terrace farming allows more intensive cropping which thus binds the soil and prevents soil erosion.

Winds transport the rocks. During the transport abrasion occurs i.e. the rocks are scraped off as a result of friction between the rocks and sediment particles.

Fertilizers run of from crop fields lead to accumulation of the chemicals in water bodies which results in algal blooms. These alagal blooms thus block the sunlight from penetrating into the aquatic bodies. The aquatic plants thus do not get sunlight to synthesize food and oxygen, thus causing Eutrophication.

Various methods of rain water harvesting are as follows:

1. Surface runoff harvesting- Rainwater that flows off from surface is collected and used to recharge aquifers.
2. Roof top rainwater harvesting- Roof acts as a catchment where the rainwater is collected. This collected water is stored in a tank or diverted to artificial recharge system.

Methods:

1. Terrace, courtyard, paved or unpaved ground acts as catchment that receive rainfall directly. This rainwater is carried down through UV resistant water pipes or drains to a storage system. The water that is received in the first shower is flushed off to avoid contamination from the roof/ atmosphere. Then, filters are used for treatment of water to remove turbidity, color and microorganisms. The filters are very importan in keeping the rainwater in the storage tank.
2. Another method involves collecting the water from roof of a building and diverting it to a storage tank. Water from the storage tank can be used for secondary purposes such as washing and gardening. It is the most effective way of rainwater harvesting.
3. Ground water aquifers can be recharged by various kinds od structures to ensure that the water percolates in the ground. Recharge pits, trenches, sak ways, percolation tanks, recharging of bore and dug wells are some of the common recharging methods.

Soil is a mixture of small particles of rocks and humus (i.e., organic matter obtained from decaying of living organisms or their wastes). Temperature variations due to radiations of the sun, rain water, winds and living organisms influence the formation of soil from the rocks involving two processes: weathering and paedogenesis. Breakdown of bigger rocks into small, fine soil particles is called weathering. It may occur due to physical, chemical or biological means. Under the influence of solar radiations, rocks heat up and expand. At night, these rocks cool down and contract. Since all the parts of rocks do not expand and contract at the same rate, cracks appear in the rocks and ultimately the large rocks breakdown into smaller pieces. Flow of water through or over the rocks makes the cracks bigger. Flowing/ falling water also has an erasing effect on the rocks. On freezing the water expands in rock crevices and breaks the rocks. Similarly, strong winds continue to rub against hard rocks and erode them. Growth of lichens, mosses and other plants also influence the formation of soil by eroding the rocks over which they are growing.
Paedogenesis: This process concludes the decomposition by bacteria and fungi, during which organic materials are broken down, leading to humification and mineralization. Detritivores such as nematods, earthworms, etc., consume organic matter and add excretory nitrogen to it. Thus, addition of organic matter (humus) from dead and decomposed plants and animals, is the final stage in soil formation.

Lichens and mosses release chemicals on rocks that cause them to powder down and form layers of soil. Roots of plants in the cracks of rock cause the rock to expand and break.

Fertilizers contain chemicals. High amount of fertilizers leads to increased amounts of chemicals which kill the microroganisms that recycle nutrients which also degrades the soil structure. Fertilizers in soil when transported or carried off by water into water bodies, result in algal blooms in aquatic bodies thus causing eutrophication.

Very low winter temperatures in the Antarctic stratosphere leads to appearance of ozone hole over AntaMediums rctica due to formation of polar stratospheric clouds.

This is because its molecules are not in direct contact with one another. Heat conduction occurs best through substances whose molecules are in contact with one another. So air is a bad conductor of heat.

Percolation tanks and wells are made to percolate the surface water so that it reacharges ground water level which supples drinking water.

Chlorofluorocarbons are inorganic compounds that contain only carbon. They are widely used in refrigerators, aerosol propellants and formation of foam.