NIOS Class 12 Environmental Science Chapter 9
INTEXT QUESTIONS 9.1
1. Make the list of plants used for medicinal purposes, along with the botanical names and the disease for which they are used.
Ans:
| Plant | Medicinal use |
| a. Cinchona officinalis | Treatment of malaria |
| b. Dititalis purspusla | Treatment of chronic heart disease |
| c. Vinca rosea | Treatment of cancer |
| d. Taxus brevifolia | Treatment of cancer |
2. What are the main functions of forests?
Ans: Protective function, productive function and regulative function.
3. List various timber-based industries.
Ans: Plywood manufacture, saw milling, paper and pulp, composite wood, Matches, man-made fibres, furniture, sports goods and particle boards.
INTEXT QUESTIONS 9.2
1. List the causes for deforestation.
Ans: Agriculture, shifting cultivation, demand for firewood and timber, and development projects
requiring land and raw materials.
2. Where is the Tehri power project?
Ans: Near Tehri town, at the junction of Bhagirathi and Bhilganga.
3. List the names of the Indian states where shifting cultivation is still practised.
Ans: Manipur, Meghalaya, Mizoram, Nagaland, Tripura, and the Andaman and Nicobar Islands.
4. Give reasons why the tribal communities were able to live in the forest without harming it.
Ans: Tribal people used ecologically sound agricultural practices, and the knowledge of such practices was passed on to the next generations for centuries.
- They grew multiple crops simultaneously for some years, and then plots were left to recover and grow back into forests.
- They have cultural and economic ties with the forest they live in and have the ability to sustain it and protect it.
5. What percentage of total wood produced in developing countries is utilized for fuel requirements? (Refer to Table 9.3).
Ans: 82%
INTEXT QUESTIONS 9.3
1. Name an endangered species in India.
Ans: Lion-tailed monkey
2. List the main causes for the depletion of wildlife.
Ans: Commercial exploitation
- Introduction of exotic species
- Habitat loss/ disturbance in habitat
- Domestication
- Use of pesticides
3. Name the mammal that is already extinct in India.
Ans: Cheetah
4. Name the mammal that was once common in Asia, but is now found in a few hundred kilometres at the Gir forest in India?
Ans: Asiatic Lion
5. Define biological diversity.
Ans: All forms of life, including plants, animals microorganisms in nature, constitute biological diversity.
INTEXT QUESTIONS 9.4
1. What is ‘desertification’?
Ans: Desertification can be defined as ‘the diminution or destruction of the biological potential of the land which can ultimately lead to desert-like conditions’.
2. List any three human activities that have resulted in desert formation.
Ans: Most of the deserts of recent origin have resulted from one or more of the following human activities.
- (i) Uncontrolled and overexploitation of grazing land, indiscriminate cutting of trees and forest resources leading to drought, soil erosion, and deterioration of soil fertility, which results in stunted plant growth.
- (ii) Excessive mining in arid and semi-arid regions for the extraction of minerals, coal or limestone, resulting in loss of trees and green cover, and leading to destruction of conditions conducive to vegetation growing.
- (iii) Uneconomic land use for agriculture by cultivation on marginal lands affecting adjacent fertile lands and causing soil erosion.
- (iv) Intensive and uneconomic exploitation of water resources leading to a fall in the water table, seepage and problems of excessive salinization of soil.
3. Name the two states where most of the deserts are found in India.
Ans: Rajasthan and Gujarat
4. Name a mammal, a bird and a plant that were once found in large numbers in the Thar Desert but are now on the list of endangered species.
Ans:
- Wild boar/wild ass – Mammal
- Great Indian Bustard – Bird
- Kehjri – Plant
TERMINAL EXERCISE
1. Write any three functions of the forest, which function you think is the most important, and why?
Ans: Functions of forests.
- Production of various types of wood, fruits and a wide range of compounds such as resins, alkaloids, essential oils, latex and pharmaceutical substances.
- Provides habitats for various organisms, conservation of soil and water, prevention of drought, shelter against wind, cold, radiation, noise, sounds, smells and sights.
- Absorption, storage and release of gases (most importantly carbon dioxide and oxygen), water,
- minerals, elements and radiant energy. All such functions improve the atmospheric and temperature conditions and enhance the economic and environmental value of the land. Forests also effectively regulate floods and drought, and all the biogeochemical cycles.
2. Discuss why deforestation is one of the most important factors for wildlife loss in the whole world.
Ans: The removal or damage of vegetation in a forest to the extent that it no longer supports its natural flora and fauna is called deforestation. Deforestation is one of the most serious and widespread environmental problems. Deforestation, coupled with desertification, has destroyed the natural treasure of the Earth to a large extent. The shrinkage of green cover has adverse effects on the stability of the ecosystem. Deforestation causes the elimination and disturbance of wildlife habitats or the selective destruction of habitat/ life forms. It also causes soil erosion and floods, climatic changes, and loss of wildlife. Loss of biodiversity during deforestation is immense because several unknown species of biota are lost forever from our planet.
3. Match the definition of words given in column A with column B
| Column A | Column B |
| (a) Rare species | i) A species is considered endangered when its numbers are few and its homeland is very small, or both, and if special protection is not given, it may become extinct |
| (b) Indeterminate species | ii) These are those species whose number is few, or they live in such small areas or such unusual environments (endemics), that they could quickly disappear. |
| (c) Endangered species | iii) These are the species whose numbers are greatly reduced from those of the recent past, and they are continuing to decrease. |
| (d) Depleted species | iv) Those species that seem to be in danger. |
Ans:
| Column A | Column B |
| (a) Rare species | ii) These are those species whose number is few, or they live in such small areas or such unusual environments (endemics), that they could quickly disappear. |
| (b) Indeterminate species | iv) Those species that seem to be in danger. |
| (c) Endangered species | i) A species is considered endangered when its numbers are few and its homeland is very small, or both, and if special protection is not given, it may become extinct |
| (d) Depleted species | iii) These are the species whose numbers are greatly reduced from those of the recent past, and they are continuing to decrease. |
4. Make a project on ‘habitat destruction and wildlife loss’ by giving at least five examples of five animal species and five plant species, and try to give a photograph/drawing of the species.
Ans: Do it yourself.
5. Make a list of extinct animal and plant species from India by going through various books and magazines.
Ans: Do it yourself.
6. ‘The development projects have harmed the tribal society the most.’ Give your views on the above statement.
Ans: Tribal people totally depended on forests for food, shelter and clothing; in turn, they also conserve the forests. Development projects often cause deforestation, the loss of forest areas where the tribal community resides. When the forest is lost, the tribal society is also losing its purpose and shelter. This is why the development projects have harmed the tribal society the most.
7. Discuss “deforestation results in desertification”.
Ans: Deforestation refers to the loss of tree cover; land that is permanently converted from forest to non-forest uses such as agricultural pasture, desert, and human settlement. Desertification is the diminution or destruction of the biological potential of the land, which can ultimately lead to desert-like conditions. Deforestation and desertification are two interlinked problems which have arisen from
The overexploitation of natural resources through human activities is causing irreparable damage to the Earth.
8. Write an essay on the importance of forests in human life. Support your answer with a diagram.
