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Q1. (i) Write any three reasons for cutting trees in forests. (ii) How does carbon dioxide cause global warming?

Solution

(i) The reasons for cutting trees in forests are:a. Procuring land for cultivationb. Building houses and factoriesc. Making furniture or using wood as fuel(ii) Carbon dioxide traps the heat rays reflected by the earth and causes global warming by increasing the temperature on the earth.

Q2. What are the functions of an ecosystem?

Solution

The functions of an ecosystem are:(i) Transfer of matter and energy.(ii) Fixation of solar energy.

Q3. (i) Name the following:(a)The gradual conversion of the fertile land into deserts due to deforestation.(b)The overall increase in the temperature of the earth due to greater concentration of carbon dioxide in atmosphere.(c)Clearing of forests and using that land for other purposes. (ii) How does carbon dioxide cause global warming?

Solution

(i) (a) Desertification.(b) Global warming.(c) Deforestation.(ii) Carbon dioxide traps the heat rays reflected by the earth and causes global warming by increasing the temperature on the earth.

Q4. (i) Discuss any two problems that can arise if deforestation continues.(ii) What is the relation between deforestation and obtaining fuel?

Solution

(i) If deforestation continues, rainfall and soil fertility will decrease. In addition, there will be increased chances of natural calamities such as floods and droughts.(ii) Trees are cut down in several countries especially the developing ones, where wood is used as firewood or turned into charcoal, used for cooking and heating purposes which leads to deforestation.

Q5. (i) There was massive destruction of a large forest area due to forest fires. A few years later, severe droughts were experienced in that region. Explain how the massive deforestation led to droughts.(ii) Which of the following cannot be caused by deforestation? Why? (a) Desertification (b) Severe droughts (c) Increase in soil fertility (d) Global warming

Solution

(i) The fewer trees remaining after deforestation utilizes less carbon dioxide during photosynthesis resulting in its increased amount in the atmosphere. This will lead to global warming as carbon dioxide traps the heat rays reflected by the earth. The increase in temperature on the earth disturbs the water cycle and may reduce rainfall. This could cause droughts.(ii) Increase in soil fertility cannot be caused by deforestation. Deforestation causes large amount of soil erosion, due to which the lower, hard and rocky layers get exposed. The fertile soil gets washed away during soil erosion. Hence, soil fertility gets reduced and is not increased during deforestation.

Q6. We have read about floods being caused by deforestation. Explain how.

Solution

Deforestation leads to a decrease in the water holding capacity of the soil. The movement of water from the soil surface into the ground i.e. infiltration rate, is reduced. This causes floods.

Q7. Reena visited her native place land after 20 years. She was shocked to see the earlier lush green land now barren and desert-like. Her parents informed her that this was caused by large-scale deforestation. Could this be true? Explain how.

Solution

Yes. Trees prevent soil erosion, hence cutting of trees results in more soil erosion. Removal of the top layer of the soil exposes the lower, hard and rocky layers. This soil has less humus and is less fertile. Gradually the fertile land gets converted into deserts.

Q8. List 5 factors which disturb biodiversity.

Solution

Factors which disturb biodiversity:

Poaching

Agriculture

Deforestation

Urbanisation

Industrialisation 

Q9. In which of the protected areas can one find the presence of tribal people along with the natural flora and fauna?

Solution

In a biosphere reserve, one can find the presence of tribal people living in harmony with the flora and fauna.

Q10. Differentiate between endemic and endangered species.

Solution

    Endemic species Endangered species Species which are found exclusively in a particular area Species which are in danger of becoming extinct Examples: Sal, bulbul, forest owlet Examples: African wild dog, blue whale, giant panda, snow leopard      

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