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Page No 240:

Question 1:

What is deforestation? List some of the common effects of deforestation.

Answer:

Clearing of forests cover on a large scale leading to degradation of forests is called deforestation. Forests are degraded continually due to natural or human related activities. Some of the effects of deforestation are increase in global temperature, scanty rainfall, altered climatic patterns, soil erosion, landslides and floods. 

Page No 240:

Question 2:

Differentiate between afforestation and deforestation.

Answer:

Sl.No Afforestation Deforestation
1. Large scale planting of saplings is called afforestation. Degradation of forests due to large scale felling of trees is called deforestation.
2. Helps in conserving and renewing the forests resources. Results in the complete destruction of forest resources.

Page No 240:

Question 3:

List some major consequences of over-extraction of fossil fuels.

Answer:

The consequences of over extraction of fossil fuels are :
a) Exhaustion of existing reserves
b) Threat to organisms and bio-diversity and
c) Air pollution.

Page No 240:

Question 4:

Name any four renewable sources of energy.

Answer:

The four renewable sources of energy are:

1. Wind Energy
2. Solar Energy
3. Hydroelectric Energy and
4. Nuclear Energy

Page No 240:

Question 1:

Describe the various uses of forests to human beings.

Answer:

Forests are useful to mankind in several ways:

a. Forests are home to various plants, animals insects and birds
b. Forests provide us with many useful products such as timber, paper, medicines and oil
c. Forests help in preventing soil erosion and landslides
d. Forests help in regulating the climate and help in keeping a check on global warming.

Page No 240:

Question 2:

Explain the various causes and effects of deforestation.

Answer:

Clearing of forests on a large scale to fulfil ever increasing human requirements is called deforestation. Causes of deforestation are:
    a. Increasing requirement of wood due to rising population
    b. Felling of trees to create agricultural lands due to rapid urbanization
    c. Overgrazing
Deforestation can lead to complete destruction of forest resources causing many adverse effects, some of which are desertification and soil erosion, landslides, destruction of various biological species, scanty rainfall and increase in global temperature.

Page No 240:

Question 3:

Describe some practices that could be followed for conserving our forests.

Answer:

Forests are an important natural resource and human beings depend on forest for fulfilling various requirements either directly or indirectly. Thus, we should take certain steps in conserving our forest. They are:

1. Planting trees on a large scale on vacant land. This practice is called afforestation.
2. Trampling and overgrazing of growing plants by the cattle should be avoided.
3.  Measures should be taken to control and prevent forest fires.
4. Various awareness programmes should be conducted by schools, organizations and through television advertisements, on the importance of forests and their natural resources.
5. A larger number of botanical gardens and forest reserves should be established. 

Page No 240:

Question 4:

Explain the various consequences of over-extraction of fossil fuels.

Answer:

An extreme use of the fossil fuels such as coal, gas and petroleum, to satisfy the requirements of the ever increasing human population, all over the world has led to their over-extraction. The consequences of over extraction of fossil fuels are:
a. Exhaustion of existing reserves: The over-extraction of fossil fuels depletes the Earth of its reserves and if this continues, we will face a severe energy crisis in the near future.
b.Air pollution: Burning the fuels such as coal and petroleum, releases greenhouse gases into the atmosphere causing global warming. Pollutants such as carbon monoxide, sulphur oxides and nitrogen oxides are also released into the air causing air pollution.
c. Threat to organisms:  Coal contains toxic metals such as mercury which when released into atmosphere settles in water with the passage of time. This water enters the aquatic animals such as fishes, which in turn can harm other animals and humans who consume them.

Page No 240:

Question 5:

Describe any four renewable sources of energy.

Answer:

The following are the renewable sources of energies.
a. Solar energy:  Sun is the ultimate source of energy. The heat from the sun is absorbed with the help of solar panels and solar cells and converted into heat, light and electrical energies.
b.Nuclear energy:  This energy is produced by the splitting and fusing of the nuclei of atoms. Nuclear power plants release huge amounts of heat energy through this process which is used to produce steam for driving generators.
c. Hydroelectric energy: This energy is produced from water bodies such as rivers. The dams built across them help in generating electricity by passing the running water through turbine generators.
d.Wind energy: Wind turbines are used to generate electricity from strong winds. Wind energy produced from the wind turbines can drive generators.

Page No 240:

Question 1:

Write one word for the following.

1. Continual degradation of forests ....................
2. Large-scale planting of saplings ....................
3. Afforestation done on deforested land ....................

Answer:

1. Deforestation
2. Afforestation
3. Reforestation

Page No 240:

Question 1:

Which of these benefits human beings and the environment?
(a) Soil erosion
(b) Landslides
(c) Forests
(d) Pollution

Answer:

(c) Forests
Forests are a valuable natural resource beneficial to both human beings and environment.

Page No 240:

Question 2:

Forests are felled due to
(a) urbanization
(b) requirement for wood
(c) flood
(d) both (a) and (b)

Answer:

(d) both (a) and (b)
Forests are felled due to rapid urbanization and for requirement of wood

Page No 240:

Question 3:

Large-scale planting of saplings is called
(a) deforestation
(b) afforestation
(c) overgrazing
(d) erosion

Answer:

(b) Afforestation
Planting of saplings on a large scale is called afforestation.

Page No 240:

Question 4:

Over-extraction of fossil fuels is leading to
(a) overgrazing
(b) urbanization
(c) air pollution
(d) afforestation

Answer:

(c) Air pollution
Air pollution is one of the major consequences of over-extraction of fossil fuels.

Page No 240:

Question 5:

Energy can be derived from
(a) dams on water bodies
(b) strong winds
(c) the sun
(d) all of these

Answer:

(d) all of these
Energy can be derived from the Sun, dams on water bodies and also from strong winds.

Page No 240:

Question 1:

Match the following.

Column A Column B
Floods Global warming
Climate change Harmful to animals
Afforestation Hydroelectric energy
Mercury Planting saplings
Water Impact of deforestation

Answer:

Sl.No Column A Column B
1. Floods Impact of deforestation
2. Climate change Global warming
3. Afforestation Planting Saplings
4. Mercury Harmful to animals
5. Water Hydroelectric energy



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