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The natural resources that cannot be renewed or replenished by natural processes are called non-renewable resources. Examples: Coal and petroleum

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Plantations cannot make up for the loss of primary forests because these forests have evolved over centuries. Moreover, forests consist of a vast variety of organisms that are not present in planted forests.

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Natural causes of deforestation are:

(a) Droughts
(b) Floods
(c) Storms
(d) Forest fires

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Human activities that cause deforestation are:

(a) Extraction of timber
(b) Production of paper
(c) Fuel wood
(d) Shifting cultivation

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Forests protect soil as the leaves of plants cover the soil and protect it from direct impact of rain. Also, the roots of the plants keep soil in place. Thus, soil erosion is prevented.

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Consequences of deforestation are:

(a) It causes soil erosion.
(b) It can lead to floods and droughts.
(c) It can alter the climate of a place.

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Coal, petroleum and natural gas are called fossil fuels because they are formed by the fossilisation of the living organisms or remains of plants and animals that are trapped between layers of rocks.

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Commercial energy refers to the energy that is bought or sold. It includes energy obtained from coal, petroleum and natural gas.

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The products of destructive distillation of coal are coal tar, coal gas, coke and ammoniacal liquor. Ammoniacal liquor is used for production of fertilisers.

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Alternative sources of energy that can be used for generation of electricity are biomass energy, solar energy, wind energy, geothermal energy and hydroelectricity.

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Following measures can be taken to bring down the number of trees being cut annually for the production of paper:

(a) Reducing wasteful consumption of paper
(b) Recycling of paper, i.e., using the waste paper to make a new paper

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Affects of deforestation on climate are:

(a) It can cause global changes in the weather pattern by increasing the amount of carbon dioxide in the air.
(b) It can cause a worldwide increase in temperature, leading to global warming.

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Petroleum and natural gas are formed by the decomposition of the remains of marine organisms by the bacteria and get deposited under the layers of sediments. Under the earth, a part of the product of decomposition got liquefied (petroleum) and other got converted into gas (natural gas) due to high temperature and pressure.

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Shifting cultivation is a method of agriculture in which a forest is converted into crop land and pastures. In this method, a part of the forest is cleared by cutting the vegetation and burning it for growing crops on the cleared land. After the soil gets exhausted, the farmers move onto the other parts of the forest.
Shifting cultivation has destroyed forests in South and Central America. This also causes the soil to get exhausted and due to increasing population, the soil does not get adequate time (20$-$25 years) to restore and gain its fertility.

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Large-scale logging for timber destroys forests in the following ways:

(a) Timber is used for making houses, furniture, crates, etc. With increase in population, the demand for timber has also increased. This has destroyed large parts of forests.
(b) Trees are cut down with electrical machines for industrial uses. This has destroyed forests in various ways. For every cubic metre of timber removed, about double that quantity of forest is destroyed.

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Deforestation of mountains, slopes and uplands causes water to rush down to the rivers. This causes the rivers to overflow and lower lands get flooded. Example: Deforestation of Himalayas has been causing floods in India, Bangladesh and Pakistan every year.
Forests hold water and deforestation causes water to rush down very fast. Because of this, the uplands get deprived of water, soon after the rains. This leads to droughts in the uplands.
Example: Deforestation of Himalayas in India has changed the perennial streams into seasonal streams that run out of water soon after the monsoon.

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Following stages are involved in the formation of coal:

(a) Peat: It is the first stage and has the lowest content of carbon. It is the most inferior type of coal and is formed by the decomposition of plant remains, buried under swamps, by anaerobic bacteria.

(b) Carbonisation: It is a process by which the carbon content of coal increases. Peat got pushed under the ground by earthquakes and volcanic eruptions. It experienced a high pressure and temperature as it sank, and this drove out gaseous product from the remains, increasing the carbon content. The deeper the remains sank, the more is their carbon content.
Anthracite is the best quality of coal with highest carbon content.

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1. For the rural poor in developing countries, fuelwood is the primary source of energy.
2. The process by which the carbon content of coal increases is called carbonisation.
3. Energy derived from animal excreta and plant waste is called biomass energy.
4. A natural fountain of hot water and steam is called a geyser.
5. A worldwide increase in temperature is called global warming.
6. Petrol made from sources other than petroleum is called synthetic petrol.

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(a) stabilised

In recent years, the total forest cover in our country has stabilised.

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(a) north-eastern India

Shifting cultivation is practised in north-eastern India.

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(c) 65

Coal fulfils about 65 percent of the energy requirement of our country.

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(b) carbon black

Carbon black is a product of natural gas.