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07_NATURAL RESOURCES – class 10

 

The Resources on the Earth

Major portion of the energy in India is generated from coal. It is estimated that India has around 120 billion tons of coal in reserve, enough to last for around 120 years. Huge reserves of petroleum have been found off the coast of Maharashtra and Gujarat.     The main natural resources of India are iron ore, bauxite and copper ore. India is one of the major producers of iron in the world. Iron ore is found all over India, the major contributors being the states of Bihar and Orissa. A quarter of all mining is carried out in the southern part of Orissa. Gold, silver, and diamonds make up a small part of other natural resources available in India. The gemstones are found in Rajasthan.

Natural resources are naturally occurring substances that are considered valuable in their relatively unmodified (natural) form. A commodity is generally considered a natural resource when the primary activities associated with it are extraction and purification, as opposed to creation. Thus, mining, petroleum extraction, fishing, and forestry are generally considered natural-resource industries, while agriculture is not.

Natural resources are often classified into renewable and non-renewable resources.

      Various energy resources are classified in two categories:

l    Non-renewable or conventional energy resources;

l    Renewable or non-convential energy resources.

l    Non-renewable or conventional energy resources.

      Conventional sources of energy are those which have been in use since a long time and have become a convention. Most of the energy which mankind has been using is derived directly or indirectly from the sun. Fossil fuels such as coal and petroleum are present in limited quantity and they cannot be renewed. Fossil fuels are nothing but energy-rich compounds of carbon which were originally made by the plants with the help of the sun’s energy. However, these conventional resources of energy produce a lot of air pollution and water pollution.

l    Renewable or non-conventional energy resources.

      Renewable energy resources are solar radiation, wind power, hydel power, biomass and nuclear power. Non-conventional energy resources are pollution free sources of energy. They can also be recycled or renewed in the nature. Our country has developed various devices for harnessing different non-conventional resources.

India will continue to experience an energy supply shortfall through the forecast period. This gap has been exacerbated since 1985, when the country became a net importer of coal. India has been unable to raise its oil production substantially in the 1990s. Rising oil demand of close to 10 percent per year has led to sizable oil import bills. In addition, the government subsidizes refined oil product prices, thus compounding the overall monetary loss to the government.

India’s rapidly growing economy will drive energy demand growth at a projected annual rate of 4.6 percent through 2010. This is the highest incremental energy demand rate of any major country.

 

Distribution of Natural Resources in various countries of the world

Country Natural resources
Australia bauxite, coal, iron ore, copper, tin, gold, silver, uranium, nickel, tungsten, mineral sands, lead, zinc, diamonds, natural gas, petroleum
Bangladesh natural gas, arable land, timber, coal
Brazil bauxite, gold, iron ore, manganese, nickel, phosphates, platinum, tin, uranium, petroleum, hydropower, timber
China coal, iron ore, petroleum, natural gas, mercury, tin, tungsten, antimony, manganese, molybdenum, vanadium, magnetite, aluminum, lead, zinc, uranium, hydropower potential (world’s largest)
India coal (fourth-largest reserves in the world), iron ore, manganese, mica, bauxite, titanium ore, chromite, natural gas, diamonds, petroleum, limestone, arable land
Nepal quartz, water, timber, hydropower, scenic beauty, small deposits of lignite, copper, cobalt, iron ore
Pakistan land, extensive natural gas reserves, limited petroleum, poor quality coal, iron ore, copper, salt, limestone
Russia wide natural resource base including major deposits of oil, natural gas, coal, and many strategic minerals, timber
note: formidable obstacles of climate, terrain, and distance hinder exploitation of natural resources
Saudi Arabia petroleum, natural gas, iron ore, gold, copper
Sri Lanka limestone, graphite, mineral sands, gems, phosphates, clay, hydropower
United Kingdom coal, petroleum, natural gas, iron ore, lead, zinc, gold, tin, limestone, salt, clay, chalk, gypsum, potash, silica sand, slate, arable land
United States coal, copper, lead, molybdenum, phosphates, uranium, bauxite, gold, iron, mercury, nickel, potash, silver, tungsten, zinc, petroleum, natural gas, timber

 

 

The Breath of life : Air

No element of the natural world is more essential to life than air, and no environmental task more critical than keeping it clean. Because electric power plants and motor vehicles are by far the biggest sources of air pollution and its myriad effects, from lung damage to acid rain to global warming.

Earth’s atmosphere is a layer of gases surrounding the planet Earth and retained by the Earth’s gravity. It contains roughly 78% nitrogen and 21% oxygen, with trace amounts of other gases such as water vapour. This mixture of gases is commonly known as air. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation and reducing temperature extremes between day and night.

The atmosphere has no abrupt cut-off. It slowly becomes thinner and fades away into space. There is no definite boundary between the atmosphere and outer space. Three-quarters of the atmosphere’s mass is within 11 km of the planetary surface. An altitude of 120 km (75 mi or 400,000 ft) marks the boundary where atmospheric effect become noticeable during re-entry. The Karman line, at 100 km (62 mi), is also frequently used as the boundary between atmosphere and space.

Table Composition of atmospheric air

Gas relative percentage by volume
Nitrogen (N2) 78.09
Oxygen (O2) 20.93
Argon (A) 00.93
Carbon dioxide (CO2) 0.032
Miscellaneous 0.02

The air, which we breathe in is present in the first zone, 10 to 12 km from the surface of the earth. This zone of the atmosphere is called troposphere. Above the troposphere is the stratosphere which is above 30 km in height. This zone is rich in ozone gas which forms ozone layer. Such a layer of ozone is called ozonosphere.

Water

Competing demands for water are outstripping supply in many parts of the world, constraining development and laying the seeds for social tension and conflict. Water is vital to survival and is a key input to agriculture, industry and the maintenance of natural systems. Yet rainfall, rivers, lakes and groundwater aquifers are not always located where water demand arises. Moreover, industrial, municipal and agricultural pollution are decreasing the quality of available water sources, as is continued clearing of forests and draining of wetlands.

If current trends continue, it has been estimated that by 2025, two in every three people will be forced to survive in water-stressed conditions, subsisting on less than 50 litres per person per day.

Large-scale technical fixes to address water demand issues have reached an impasse. The social and environmental consequences of large dams have mobilized civil society in protest, even as their economic viability has increasingly come into question. Even institutional innovations aimed at resolving water supply shortfalls and over consumption–such as municipal water service privatization and full cost pricing–are fraught with controversy.

The limited quantity, increasing contamination and growing demand for water poses one of the key challenges to sustainable development. Successfully addressing the water puzzle in the next century will require doing more with less, “increasing the efficiency with which current needs are met and increasing the efficiency with which water is allocated among different uses.”

Water is a basic natural resource. It is a valuable national asset. It forms main requirement of human beings. Human beings depend on water for many purposes such as drinking, cooking, cleaning, agriculture, transportation, hydropower, etc. Water is of two types: salt water and fresh water. India has a very long coastline hence, it has a large source of saltwater of seas and oceans. Freshwater is an unlimited natural resource. Its quality is often degraded but not quantity. Freshwater is obtained from the following three natural sources:

l    Rainwater

l    Surface water (surface flow)

l    Ground water

The main sources of water are rainfall and snow which are a part of the hydrological cycle. The water resource of India have been estimated to an average run off in the river system of 1869 km3 and 432 km3 ground water.

 

Figure 6. 1 Hydrological cycle

In our country, the intensity of annual rainfall varies from region to region and accordingly we have four zones.

l    Wet zone. In this zone the annual rainfall is very high (i.e., over 200 cm).

l    Intermediate zone. In this zone the annual rainfall is quite heavy (i.e., from 100 to 200 cm).

l    Semiarid zone. In this zone the annual rainfall is moderate (i.e., from 50 to 100 cm).

l    Arid zone. In this zone the annual rainfall is very low (i.e., it ranges from 20 to 50 cm).

Surface water

India has rich water bodies consisting of rivers, lakes, streams and ponds. For example, in India surface flow occurs through 14 major river system such as Brahmani, Brahmputra, Cauvery, Ganga and Godavari.

Water level and water table.

The space between soil particles on the surface of earth is called pore spaces. In the top soil pore spaces are generally filled with both air and water. Water that percolates into the ground through the pore spaces of rocks is available as ground water. The porous rocks are saturated with water at a certain level below the surface; it is called zone of saturation. The upper level of the zone of saturation is called the water table. Thus, the depth in the soil where all the pore spaces of soil particles are saturated with water only, is called water table. The water table is expressed with reference to the mean sea level. The vertical distance from a place on the surface to the water table is called water level. The water table reaches the ground surface in the springs, permanent of perennial rivers, lakes and swamps and it is deeper on hill tops and in dry areas. The ground water provides, soil moisture for plant growth. It supplements water in streams and lakes. Ground water is frequently used for human consumption. The following factors tend to lower the water table at any given place :

l       scanty rainfall

l       use of more ground water

l       cutting of trees.

The gravitational water is important in causing the phenomenon called leaching. Leaching is the washing out of minerals, including nutrients. The level to which gravitational water drains is called water table. Water table may fluctuate in depth depending on rainfall. This is capillary water which forms the water table and is utilized by the plants.

Soil

Soil-types in India can be classified into three groups. The first group comprises of the alluvial, black and red soils, which are basically fertile and are arable and cultivatable.

The second group consists of the peaty and marshy, the saline and alkaline soils which are potentially arable.

The third group is the laterite and forest and hill soils, which are not at all suitable for cultivation.

The main alluvial area is found in the Indo-Gangetic plain and the Peninsular regions. The main crops are rice, sugarcane and wheat. Black soil is found in the northwestern regions and in the Deccan lava areas and Tamilnadu.

Black soil is especially suited for cotton. Red soil is particularly rich in potash and is found in northern and central India. The peaty and marshy soils are found in the Bengal deltas, Saline and alkaline soils in the semi-arid regions of Bihar, U.P, Gujarat, Punjab and Rajasthan. Desert soils are found in the minimum rain receiving areas of Gujarat, Punjab and Rajasthan. Laterite soil is common in the low hills of Andhra, Karnataka, Kerala, Madhya Pradesh, Orissa and Assam.

There are two crop seasons: Kharif and Rabi. The major Kharif crops are rice, jowar, maize, cotton, sugarcane, sesame and groundnut. The Rabi crops are wheat, jowar, barley, gram, rapeseed and mustard and the summer crops are rice, maize, groundnut and some cash crops.

Soil can be defined as the weathered uppermost crust of earth which is mixed with organic material and in which animals and microorganisms live and plants grow. Thus, any soil typically consists of the following four components:

l       The inorganic materials (i.e., mineral particles) which are derived from parent rocks.

l       The organic materials (i.e., humus) which is derived from dead organisms by their decomposition.

l       The air and water occupying the pores between the soil particles which are loosely packed (i.e., soil, water and soil atmosphere).

l       Organisms (the biological system) such as bacteria, fungi, algae, protozoans, rotifers, nematodes, earthworms, snails, ants, ticks, scolopendra, millipede, etc. Soil provides mechanical anchorage to plants, i.e., roots of higher plants grow into the soil in search of water and nutrients.

Minerals

For our industrial, technological and cultural growth, we have required and still need a great variety of inorganic materials, all of which comes from the earth’s crust. Chief among them are the ores which are used in large scale to yield metals, such as iron, aluminum, copper, tin, nickel, silver, gold, platinum, etc. Some of the metals are required in the form of catalysts and hardners such as vanadium, tungsten and molybdenum. Finally there are non-metallic materials (minerals) which are vital to industrial growth such as sand, gravel, cement, fluxes (e.g., borax), clay, salt, sulphur, phosphorus, diamonds, gems, coal and the by-products of petroleum refining (petrol, kerosene, lubricants, etc.).

Minerals form exhaustible non-renewable or ‘stock’ natural resources, since, they can only be extracted from earth’s crust once. Mineral deposits are formed slowly over millions of years and once used cannot be regenerated.

Thus, coal, petroleum, iron, aluminum, copper, silver and gold are some very important natural mineral resources to the mankind. For example, the coal and petroleum (both called fossil fuels) have been our useful sources of energy. They are widely used in transport, agriculture and industry (e.g., car, buses, trucks, tractors, generators, etc.). However, the metals, non-metals, mineral fuels and lubricants are non-renewable unlike air or water. Since they are not renewable so we cannot maintain these resources.

Figure 6. 2 Indian maps of minerals and metal resources

India has a large number of economically useful minerals and they constitute one-quarter of the world’s known mineral resources. About two-thirds of its iron deposits lies in a belt along Orissa and Bihar border. Other hematite deposits are found in Madhya Pradesh, Karnataka, Maharastra and Goa. Magnetite iron-ore is found in Tamilnadu, Bihar and Himachal.

India has the world’s largest deposits of coal. Bituminous coal is found in Jharia and Bokaro in Bihar and Ranigunj in West Bengal. Lignite coals are found in Neyveli in Tamilnadu.

Next to Russia, India has the largest supply of Manganese. The manganese mining areas are Madhya Pradesh, Maharastra and Bihar-Orissa area. Chromite deposits are found in Bihar, Cuttack district in Orissa, Krishna district in Andhra and Mysore and Hassan in Karnataka. Bauxite deposits are found in western Bihar, southwest Kashmir, Central Tamilnadu, and parts of Kerala, U.P, Maharastra and Karnataka.

India also produces third quarters of the world’s mica. Belts of high quality mica are, Bihar, Andhra and Rajasthan. Gypsum reserves are in Tamilnadu and Rajasthan. Nickel ore is found in Cuttack in Orissa and Mayurbanj in Bihar.

      Copper ore bearing areas are Agnigundala in Andhra, Singhbum in Bihar, Khetri and Dartiba in Rajasthan and parts of Sikkhim and Karnataka.

The Ramagiri field in Andhra, Kolar and Hutti in Karnataka are the important gold mines.

The Panna diamond belt is the only diamond producing area in the country, which covers the districts of Panna, Chatarpur and Satna in Madhya Pradesh, as well as some parts of Banda in Uttar Pradesh.

      Petroleum deposits are found in Assam and Gujarat. Fresh reserves were located off Bombay. The potential oil bearing areas are, Assam, Tripura, Manipur, west Bengal, Punjab, Himachal, Kutch and the Andamans.

India also possesses the all-too valuable nuclear uranium as well as some varieties of rare earths.

Energy

The key energy challenge facing India today is preventing bottlenecks in energy supply from constraining economic growth. Due to rising consumption and higher world oil prices, the Indian government is faced with debilitating oil import costs. Between 1992 and 1997, India estimates that it needs 140,000 megawatts (MW) of new electricity generation capacity. In the last five-year plan (1992-1997), though, India installed less than 60 percent of its targeted capacity. This shortfall is anticipated to increase as foreign investors continue to encounter difficulty in moving ahead with their independent power projects.

l    Natural gas is India’s most important potential alternative to coal. India is planning to make widespread use of natural gas in power generation and in the industrial and residential sectors. Projected demand will require large volumes of gas pipeline and liquefied natural gas (LNG) imports.

l    India’s oil demand has risen to 1.6 million barrels per day (b/d), or more than twice domestic output. Almost half of India’s trade deficit is due to petroleum imports, the cost of which also limits capital that could be invested in the economy. India is hoping to restrain demand by gradually raising product prices to international levels.

l    India’s heavy reliance on highly polluting coal makes development and installation of Clean Coal Technology (CCT) a high priority. However, CCT is expensive to implement and questions have arisen on how to spread the costs of such technology.

 

Table: Power generation in India

Source Electricity production (MW)
Thermal power (solar energy) 70,200
Hydel power 23,800
Nuclear power 2,700
Wind power 1,150
Biomass power 256

 

 

In 1995, coal accounted for 63.3 percent of India’s primary energy production. In the same year, petroleum accounted for 18.6 percent, hydroelectricity 8.9 percent, natural gas 8.2 percent, and nuclear power 1 percent.

l    India’s electricity is generated overwhelmingly by coal (70 percent). Hydroelectricity ranks a distant second (about 25 percent), followed by natural gas, nuclear power, oil, and renewables, which account for the remaining 5 percent.

l    The current fuel mix is expected to change slightly through the forecast period ending in 2010. Coal (65%) is projected to remain roughly the same as in 1995, while hydro (14%) and natural gas (10%) will have higher shares of total production. Oil production will decline sharply, however, to only a 9 percent share.

l    Overall, India’s energy production was around 8.8 quadrillion Btu (quads) in 1995. By 2010, India’s energy output is expected to reach 16.4 quads. In comparison, China’s total energy production was 11.7 quads in 1970, 35.6 quads in 1995, and is forecast to rise to 64 quads by 2010.

Indian Fauna

There are around 500 varieties of mammals, 2000 species of birds and 30,000 types of insects and a wide variety of fish, amphibians and reptiles are found in the country according to the latest census estimate.

Popular mammals include the elephant, the famous white lions and some common lions, the Royal bengal tiger, rhinos, wild bisons some varieties from the cat family, deer, monkeys, wild goats, etc. Elephants are found in the     sparsely populated hill areas of Karnataka, Kerala and Orissa.

Figure 6. 3 KING OF ANIMALS
THE MAJESTIC LION
Lions are found in the rocky hills and forests of the Gir area of Gujarat, Tigers in the Sunderbans and the Brahmaputra valley. The famous Project Tiger is a scheme financed by the government of India to safeguard the tiger in its habitat in nine selected reserves. Indian Fauna also include the wild ass of Rajasthan, Nilgiri Langur, Lion-tailed macaque, Nilgiri mongoose and Malaber civer of the southern hills and the spotted deer. Leopards are found in many forests, Wolves roam the open country.

A huge number of snake varieties, lizards and crocodiles account for the reptile count. Snakes include the deadly king cobras to the equally poisonous Kraits. Scorpions and insects are plenty in this country. Disease carrying mosquitoes and destructive locusts are to be found. Useful insects include the bees, silkworms and the Lac insect.

Bird-Life in India is rich and colorful. The birds include the beautiful peacock to the parrots, and thousands of immigrant birds. Other common Indian birds are pheasants, geese ducks, mynahs, parakeets, pigeons, cranes, and hornbills. India now maintains 80 national parks, 441 wildlife sanctuaries and 35 zoological gardens.

 

FLORA

Thanks to its wide range of climatic conditions, India has a rich variety of vegetation that no other country in this world can boast of. According to the distribution of the flora, India can be classified into, Western Himalayas, Eastern Himalayas, Assam, Indus Plain, Ganga Plain, Deccan, Malabar and the Andamans.

Indian flora varies from the Western Himalayan and Assamese, from the species of the Indus Plain to those of the gangetic plain, from the Deccan and Malabar to the vegetation of the Andamans. The floral wealth ranges from the Alpine to the temperate thorn, from the coniferous to the evergreen, from scrubs to deciduous forests, from thick tropical jungles to cool temperate woods.

The Western Himalayan region is abound in Chirpine and other conifers deodar, blue pine, spruce, silver fir, and junipers. The Eastern Himalayan region consists of oaks, laurels, maples, rhododendrons, alder, and birch and dwarf willows. The Assam region is full of evergreen forests with lots of bamboo and tall grasses.

The Indus plain supports very scanty vegetation and the Ganges Plain is under cultivation. The Deccan region is full of scrubs and mixed deciduous forests. The Malabar region is under commercial crops like coconut, betel, pepper, coffee and tea. Andaman region is abounding in evergreen and mangrove forests.

Figure 6. 4 Tea Plantations India’s original vegetation was mainly deciduous forest because of her tropical location. It is unfortunate that the forest cover has been reduced to 13% of the total surface area.

Of the deciduous trees sal and teak are the most important. Sal is found in eastern India and it is used for buildings because it is resistant to termites and fire. Deodars, Pines, cedars, firs and spruce are found in the foothills of the Himalayas. Sandalwood is found in Karnataka and Tamilnadu. Coconut palms are dominant in Kerala.

Use of forests

Forests contribute to the economic development of our country by providing goods and services to the people and industry. They are intimately linked with our culture and civilization. Forests are useful to us for the following reasons:

l    Forests provide timber for the building and furniture. For the cane-furniture the canes (rattans) too are obtained from the forests.

l    Forests provide raw materials for the paper industry, board industry, plywood industry, etc.

l    Forests provide fodder (food) for cattle, sheep, goat and camels.

l    Forests yield bamboos which is called ‘poor man’s timber’ Industrially bamboos are used as a raw material in paper and rayon industry.

l    Forests give protection to the wild life (or wild animals).

l    Forests provide protection from adverse (injurious) effects of solar radiation.

Wild life

      The native population of a community make up its wildlife. The term wildlife means all those naturally occurring animals, plants and their species which are not cultivated, domesticated and tamed. Indian subcontinent possesses a rich and diverse wildlife fauna. The Indian fauna includes variety of animal life such as mammals, birds, reptiles, fishes, insects, molluscs, etc.

India boasts a wide variety of flora and fauna which are diversified in nature and which depend upon the geography of the region.

National parks and sanctuaries are administered at the state level and are promoted by them as a tourist attraction, which earns them sufficient revenue to keep the sanctuaries running. Most of the sanctuaries provide well are at least optimum accommodation and other facilities but they had to be booked in advance. Some parks even provide modern guest houses. Usually van and jeep rides and also boat trips are arranged to give the visitors a good view of the animals in their natural habitats. Watchtowers and hides are also available.

Some of the notable parks and sanctuaries of India are listed below :

CORBETT NATIONAL PARK

This park in Uttranchal is famous for its tigers. Other wild lives include cheetahs, deer, elephants, leopards, and sloth bears. The park has good scenery with sal and hardwood trees. There are numerous watch towers and daytime photography is allowed.

SUNDERBANS WILDLIFE SANCTUARY

This reserve in West Bengal is to the southeast of the city of Calcutta. It contains the mangrove forests of the Gangetic delta. It is an important haven for tigers but it also includes fishing cats and a wide variety of birds. It is accessible by a boat ride only.

KAZIRANGA NATIONAL PARK

This park in Assam is famous for its one-horned rhinos which are almost extinct now but for a few. The park is full of tall grasses and swampy areas. The rhinos can be spotted around the swampy areas, bathing. Egrets and other birds are also found here.

RANTHAMBORE NATIONAL PARK

Ranthambore or Sawai Madhopur in Rajasthan is smaller in size when compared to most of the parks in India. It is famous for its lake tigers but nowadays the number has dwindled thanks to large-scale poaching in these areas. It is located on the Mumbai- Delhi rail-line and is 160 kms by road from Jaipur.

KANHA NATIONAL PARK

This is one of the spectacular and most exciting parks for wildlife in India and is in Madhya Pradesh. Originally it was conceived to protect the swamp deers also called Barasinghas but now it also includes tigers, chitals, blackbucks, langurs and leopards.

PERIYAR WILDLIFE SANCTUARY

This is a large and scenic park in Kerala state built around an artificial lake. It is famous for its large elephant population. Others include the wild dogs, Nilgiri Langurs, otters, tortoise, and hornbills.

Management and Replenishment of Natural resources

Our natural resources are being used continuously by human beings. With the explosion of human population and subsequent technology advancement, the natural resources have been extensively exploited. This tread is posing a danger of gross scarcity of those natural resources which are exhaustible in nature e.g., coal, petroleum. Therefore there is an urgent need that natural resources be used rationally, equitably and with due consideration of their replaceability. Carefully, logically and ethically. Such an approach of use of natural resources forms the concept of management and conservation of natural resources. Thus, management and conservation mean scientific utilization of resources while maintaining their sustained yield and quality.

Biogeochemical Cycles

      A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic, but stable system. These interactions consist of a transfer of matter and energy between the different components of the biosphere. Let us look at some processes involved in the maintenance of the above balance.

The movement of nutrient elements through the living and non-living components of the biosphere or any other ecosystem, is called biogeochemical cycle or cycle of matter.

The term ‘biogeochemical cycle’ indicates that chemicals circulate through life (bio) and through earth (geo) again and again (cycles).

The biogeochemical cycles are of two types :

  1. Gaseous cycles
  2. Sedimentary cycles.
  3. Gaseous cycles. In the gaseous cycles, the reservoir for the nutrient elements is the atmosphere (air) or hydrosphere (water). Gaseous cycles are quick and relatively perfect systems in that the elements remain in circulation more or less uniformly. The four most abundant elements in the living systems – nitrogen, carbon oxygen and hydrogen have predominantly gaseous cycles.
  4. Sedimentary cycles. In the sedimentary cycles, the reservoir for the nutrient elements is the sediments of the earth. These cycles are slow and less perfect systems in that the elements may get locked in the reservoir pool and go out of circulation for long periods. Phosphorous, sulphur, potassium and calcium have sedimentary cycles.

 

THE WATER-CYCLE (Hydrological Cycle)

     You have seen how the water evaporates from the water bodies and subsequent condensation of this water vapour leads to rain. But we don’t see the seas and oceans drying up. So, how is the water returning to these water bodies? The whole process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known as the water-cycle. This cycle is not as straight-forward and simple as this statement seems to imply. All of the water that falls on the land does not immediately flow back into the sea. Some of it seeps into the soil and becomes part of the underground reservoir of fresh-water. Some of this underground water finds its way to the surface through springs. Or we bring it to the surface for our use through wells or tube- wells. Water is also used by terrestrial animals and plants for various life-processes.

Let us look at another aspect of what happens to water during the water-cycle. As you know, water is capable of dissolving a large number of substances. As water flows through or over rocks containing soluble minerals, some of them get dissolved in the water. Thus rivers carry many nutrients from the land to the sea, and these are used by the marine organisms.

THE NITROGEN-CYCLE

Nitrogen gas makes up 78% of our atmosphere and nitrogen is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins. Nitrogen is found in other biologically important compounds such as alkaloids and urea too. Nitrogen is thus an essential nutrient for all life-forms and life would be simple if all these life-forms could use the atmospheric nitrogen directly. However, other than a few forms of bacteria, life-forms are not able to convert the comparatively inert nitrogen molecule into forms like nitrates and nitrites which can be taken up and used to make the required molecules. These ‘nitrogen-fixing’ bacteria may be free-living or be associated with some species of dicot plants. Most commonly, the nitrogen-fixing bacteria are found in the roots of legumes (generally the plants which give us pulses) in special structures called root- nodules. Other than these bacteria, the only other manner in which the nitrogen molecule is converted to nitrates and nitrites is by a physical process. During lightning, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain. These are then utilised by various life- forms.

What happens to the nitrogen once it is converted into forms that can be taken up and used to make nitrogen-containing molecules? Plants generally take up nitrates and nitrites and convert them into amino acids which are used to make proteins. Some other biochemical pathways are used to make the other complex compounds containing nitrogen. These proteins and other complex compounds are subsequently consumed by animals. Once the animal or the plant dies, other bacteria in the soil convert the various compounds of nitrogen back into nitrates and nitrites. A different type of bacteria converts the nitrates and nitrites into elemental nitrogen. Thus, there is a nitrogen-cycle in nature in which nitrogen passes from its elemental form in the atmosphere into simple molecules in the soil and water, which get converted to more complex molecules in living beings and back again to the simple nitrogen molecule in the atmosphere.

THE CARBON-CYCLE

       Carbon is found in various forms on the Earth. It occurs in the elemental form as diamonds and graphite. In the combined state, it is found as carbon dioxide in the atmosphere, as carbonate and hydrogen- carbonate salts in various minerals, while all life-forms are based on carbon-containing molecules like proteins, carbohydrates, fats, nucleic acids and vitamins. The endoskeletons and exoskeletons of various animals are also formed from carbonate salts. Carbon is incorporated into life-forms through the basic process of photosynthesis which is performed in the presence of Sunlight by all life-forms that contain chlorophyll. This process converts carbon dioxide from the atmosphere or dissolved in water into glucose molecules. These glucose molecules are either converted into other substances or used to provide energy for the synthesis of other biologically important molecules.

The utilisation of glucose to provide energy to living things involves the process of respiration in which oxygen may or may not be used to convert glucose back into carbon dioxide. This carbon dioxide then goes back into the atmosphere. Another process that adds to the carbon dioxide in the atmosphere is the process of combustion where fuels are burnt to provide energy for various needs like heating, cooking, transportation and industrial processes. In fact, the percentage of carbon dioxide in the atmosphere is said to have doubled since the industrial revolution when human beings started burning fossil fuels on a very large scale. Carbon, like water, is thus cycled repeatedly through different forms by the various physical and biological activities

 

THE GREENHOUSE  EFFECT

      Recall the reading taken by you under (iii) in Activity 14.1. Heat is trapped by glass, and hence the temperature inside a glass enclosure will be much higher than the surroundings. This phenomenon was used to create an enclosure where tropical plants could be kept warm during the winters in colder climates. Such enclosures are called greenhouses. Greenhouses have also lent their name to an atmospheric phenomenon. Some gases prevent the escape of heat from the Earth. An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase world- wide and this is called the greenhouse effect. Carbon dioxide is one of the greenhouse gases. An increase in the carbon dioxide content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.

THE OXYGEN-CYCLE

     Oxygen is a very abundant element on our Earth. It is found in the elemental form in the atmosphere to the extent of 21%. It also occurs extensively in the combined form in the Earth’s crust as well as also in the air in the form of carbon dioxide. In the crust, it is found as the oxides of most metals and silicon, and also as carbonate, sulphate, nitrate and other minerals. It is also an essential component of most biological molecules like carbohydrates, proteins, nucleic acids and fats (or lipids).

But when we talk of the oxygen-cycle, we are mainly referring to the cycle that maintains the levels of oxygen in the atmosphere. Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen. Oxygen is returned to the atmosphere in only one major process, that is, photosynthesis. And this forms the broad outline of the oxygen-cycle in nature.

Though we usually think of oxygen as being necessary to life in the process of respiration, it might be of interest to you to learn that some forms of life, especially bacteria, are poisoned by elemental oxygen. In fact, even the process of nitrogen-fixing by bacteria does not take place in the presence of oxygen.

Ozone Layer

      Elemental oxygen is normally found in the form of a diatomic molecule. However, in the upper reaches of the atmosphere, a molecule containing three atoms of oxygen is found. This would mean a formula of O and this is called ozone. Unlike the normal diatomic molecule of oxygen, ozone is poisonous and we are lucky that it is not stable nearer to the Earth’s surface. But it performs an essential function where it is found. It absorbs harmful radiations from the Sun. This prevents those harmful radiations from reaching the surface of the Earth where they may damage many forms of life.

Recently it was discovered that this ozone layer was getting depleted. Various man-made compounds like CFCs (carbon compounds having both fluorine and chlorine which are very stable and not degraded by any biological process) were found to persist in the atmosphere. Once they reached the ozone layer, they would react with the ozone molecules. This resulted in a reduction of the ozone layer and recently they have discovered a hole in the ozone layer above the Antartica. It is difficult to imagine the consequences for life on Earth if the ozone layer dwindles further, but many people think that it would be better not to take chances. These people advocate working towards stopping all further damage to the ozone layer.

 

 

 

 

 

 

 

exercise

 

Very Short Answer Questions

  1. What is water table?
  2. Name an animal which is facing extinction in India.
  3. What is Leaching?
  4. What is meant by monoculture?
  5. Name any two threatened species of India.

 

Short Answer Questions

  1. What do you mean by soil fertility?
  2. Name any two renewable sources of energy.
  3. How do trees prevent soil erosion?
  4. Write short note on national parks.
  5. What are the main steps that are being taken for the conservation of wild life in India?
  6. Define the following terms:
  7. a) photoperiod b) green manure    c) organic farming  d) concentrates
  8. e) roughage
  9. Mention one advantage and one disadvantage of green revolution.
  10. What nutrients do we get from: cereals and pulses?
  11. How many nutrients are required in lesser quantities and what are they commonly called?
  12. Why even excess application of manure doesnot cause pollution?
  13. Give one disadvantage of fertilizer.
  14. Name one crop which can tolerate waterlogging in field and one which cannot?
  15. What happens when a matured wheat crop is irrigated?
  16. A farmer grows gram crop between two cereal crops. What agricultural practice Is being followed?
  17. Give one word:
  18. a) A toxic substance effective against insects.
  19. b) A fungal disease of wheat crop
  20. c) A common weed
  21. d) A weedicide
  22. e) One natural insecticide
  23. f) Name one HYV of cow and one of buffalo.
  24. Name two exotic varieties of cow.
  25. What are the indications for diseased cattle?
  26. Why special care of broiler is taken?
  27. During heavy rains in a village, the rain water carried excess of nitrogen compounds into the river. What can be the consequence of this process.?
  28. Name two indigenous breeds of poultry.
  29. Define inland fishery.
  30. How is pisciculture different from apiculture?
  31. Name two fresh water fishes.
  32. What two products do we obtain from honey bees?
  33. How are HYV of poultry advantageous over local breeds?
  34. What is pasturage and how is it related to honey production?
  35. How will you distinguish between capture fishery, inland fishery and aquaculture?
  36. Name the Italian bee variety used for honey production and mention two reasons for why its preferred over other varieties?
  37. Define composite fish culture and mention its advantage.
  38. How are broilers and layers different from each other?
  39. Mention four main features of a good cattle shelter.
  40. Pick the odd one out and give reason:
  41. a) Gir ,sahiwal, red sindhi, jersey
  42. b) Aseel, basra, chattisgarh, white leghorn.
  43. Suppose you are incharge of a grain store. Mention two indications to find out the presence of pests in the godown.
  44. Give reason:
  45. a) legumes are desirable during crop rotation
  46. b) Excessive irrigation of crops should be avoided.
  47. Classify the various plant nutrients according to their sources.
  48. Crop variety improvement is a must. Justify by giving three reasons.
  49. How is a compost different fron vermicompost?
  50. Pick the odd one out wiyh reason:
  51. a) mullets, pearl spots, oyster, bhetki
  52. b) sardine, rohu, Bombay duck, tuna
  53. Name the surface , middle zone and bottom feeders in composite fish culture.

 

 

Long Answer Questions

  1. Give a brief account of pollutants of air.
  2. Water is essential for life. Justify the statement.
  3. Mention some methods of pollution control.
  4. What are fossil fuels and why should they be used most economically? What alternative sources of energy would you suggest?
  5. Differentiate between water table and water level.
  6. Green revolution is like two faces of a coin . Explain in detail.
  7. Write a note on prevention of animal diseases.
  8. Mention the various preventive measures to be taken in account during grain storage.
  9. Biological control methods should be preferred for protecting crops. Why?
  10. Compare mixed and intercropping. Also mention their advantages

 

 

  1. Define the environment .
  2. Name two green house gases?
  3. Name two chemicals that are deplating ozone layers?
  4. What is water pollution?
  5. Name the nitrogen – fixing bacteria.
  6. What is soil erosion?
  7. Name two combined forms of carbon?
  8. What is nitrifications?
  9. What is top soil?
  10. What are the diseases caused by air pollution?

 

Short type Questions

  1. Name the type of soil based on size of particles and on nutrient and nature.
  2. How does carbon exist in all life forms?
  3. What Is humus?
  4. What is bad ozone and good ozone?
  5. What is bio-geo chemical cycle?
  6. How does atmosphere helps in climate control?
  7. What is air – pollution? How is it caused?
  8. How do fossil fuel cause air pollution?
  9. State in brief the role of photosynthes is and respiration in carbon cycle in nature.
  10. How can lichen help in indication the pollutants in air?

 

Long answer type questions

  1. How is soil formed by sun, water, wind and living organisms?
  2. List any three human activities which would lead to an increase in the carbon-dioxide context for air?
  3. How are winds caused and what decides the breeze to be gentle, strong wind or a terrible storm?
  4. How does atmosphere helps in climate control?
  5. What is global warming/

 

Long answer type questions

  1. Explain water cycle with diagram.
  2. Explain the importance of ozone to mankind.
  3. How does oxygen occur in nature? Explain oxygen-cycle in nature.
  4. Give the existence of nitrogen in nature and define all the terms involved in it.
  5. Explain the Biosphere.

 

Objective type questions

  1. The micro organisms which helps in the formation of soil is

(a)      bacteria                                    (b)      moss

(c)      lichen                                       (d)      both (b) and (c)

  1. The life supporting – zone of earth is

(a)      lithosphere                               (b)      hydrosphere

(c)      atmosphere                               (d)      biosphere

  1. Molecules of protein contain-

(a)      carbon                                      (b)      Nitrogen

(c)      Oxygen                                     (d)      All of them

  1. Nitrogen fixation can be done by

(a)      Industries                                 (b)      Rhizobium

(c)      Lightning                                  (d)      All of the above

  1. Greenhouse gases are

(a)      CO2                                                                      (b)      CH4

(c)      CFC                                          (d)      All of the above

 

Value based questions

  1. Nancy and parents had to postpones their trip to Indonasia because of cancellation of all flights to the country last December. She found out the reason to persistent ‘SMOG’ in the country.

(a)      What is smog?

(b)      How does it effect human beings?

(c)      What could be your/Nancy’s contribution as an individual towards      controlling such a situation.

  1. A priest of temple collected dried garland holy old books and some statues. He asked his son to throw in the river, But instead of throwing, he buried them in the soil.

(a)      In the situation above, who wins your support, the priest or the son? Justify your answer by giving two reasons.

(b)      What are the values reflected in the behaviour of son?

 

 

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WORKSHEET – 1

 

  1. How is our atmosphere different from atmospheres on Venus and Mars?
  2. How does the atmosphere act as a blanked.
  3. What causes winds?
  4. How are clouds formed?
  5. List any three human.

 

WORKSHEET – 2

 

  1. Why do organisms need water?
  2. What are major source of fresh water in the city/town/village where you live?
  3. Do you know of any activity which may be polluting this water source?
  4. What is carbon cycle?
  5. Write short notes on nitrogen cycle.

 

WORKSHEET – 3

 

  1. Why is atmosphere essential for life.
  2. Why is water essential for life?
  3. What is green house effect.
  4. Draw a flow chart of carbon-cycle.
  5. How is soil formed.

 

WORKSHEET – 4

 

  1. What is soil erosion?
  2. What are the methods of preventing or reducing soil erosion?
  3. Name two biologically important compounds that contain both oxygen and nitrogen?
  4. List any three human activities which would lead to an increase in the carbon dioxide for air?
  5. What are the two forms of oxygen found in the atmosphere.

 

WORKSHEET – 5

 

  1. Define nitrification and denitrification?
  2. What is bad ozon and good ozon?
  3. State two harmful effects of ozone hole or ozone layer depletion?
  4. What is top soil?
  5. What is biosphere and air pollution.

 

 

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