NIOS Class 12 Environmental Science Chapter 14 Global Environmental Issues

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NIOS Class 12 Environmental Science Chapter 14 Global Environmental Issues

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Environmental Science Chapter 14 Global Environmental Issues Solutions, NIOS Senior Secondary Course Environmental Science Solutions for All Chapter, You can practice these here.

Global Environmental Issues

Chapter: 14

Module 4: Contemporary Environment issues

Textual Question Answer

INTEXT QUESTIONS 14.1

1. Why do you think environmental issues are of global significance? 

Ans: Because environment has no frontiers, no geographical boundaries.

2. Enumerate at least 3 environmental issues that confront us today.

Ans: Pollution, O3-hole, greenhouse effect, biodiversity loss, desertification, problems related to dumping of hazardous wastes, nuclear disasters, oil spills (Any three).

3. Define global warming.

Ans: Global warming is defined as a natural or human induced increase in the average global temperature of the atmosphere near the earth surface.

4. Why is green-house effect called so?

Ans: Because it stimulates similar conditions that one encounters in a glass green house.

5. Which kind of radiations are not reflected back out of atmosphere causing green-house effect? 

Ans: Infrared.

6. Name four green-house gases.

Ans: CFC, methane, nitrogen oxides, CO₂.

INTEXT QUESTIONS 14.2

1. List different components of biodiversity.

Ans: Species biodiversity, generic biodiversity, ecosystem biodiversity.

2. Why does biodiversity loss occur? 

Ans: Because of loss of habitat, overuse, introduction of foreign species.

3. How does high-technology fishing affect marine biodiversity? 

Ans: Because, they help locate shoals of fish very accurately and efficiently.

4. How does a species lose its habitat? 

Ans: When its habitat is destroyed to make way to housing, industry, agriculture, sports etc.

5. What kinds of activities promote desertification? 

Ans: Over cultivation, over grazing, deforestation, salting due to irrigation.

6. Which kind of sowing is better in long term: ploughing or tractor – sowing?

Ans: Tractor-sowing.

7. What is a desert? 

Ans: The land that has lost the productivity capacity is called a desert.

INTEXT QUESTIONS 14.3

1. Which kind of electromagnetic waves are screened by ozone in the stratosphere? Give their wavelength.

Ans: Ultraviolet, 200-400 nm.

2. How many oxygen atoms are these in an ozone molecule?

Ans: Three.

3. How do volcanoes contribute to O₃ depletion? 

Ans: By releasing significant amount of chlorine.

4. Which kinds of anthropogenic activities are most dangerous to ozone-shield? 

Ans: Any activity that release chlorine atoms into the atmosphere.

5. Name some harmful effects of UV radiation on human-being.

Ans: Causes skin cancer, retinal diseases, damage cornea etc.

INTEXT QUESTIONS 14.4

1. Name two acids that are present in acid rain.

Ans: H₂SO₄, HNO₃.

2. How does acid rain affect aquatic life? 

Ans: Acid rain lowers the pH of water in which the organism lives. At low pH gametes (egg/sperms) of the organisms cannot survive. It affects the life cycle. Leading to generation/population loss.

3. Use of which type of fuel will help in preventing acid rain? 

Ans: Solar / nuclear energy.

INTEXT QUESTIONS 14.5

1. Enumerate the sources of slow nuclear radiations that can pose danger to life forms.

Ans: nuclear reactors, laboratories, hospitals, diagnostic X-rays.

2. Enlist some harmful effects of nuclear radiation on human being.

Ans: Any substance that could have serious, irreversible health after affects from a single dose of exposure.

INTEXT QUESTIONS 14.6

1. What is the affect of oil spills on algal blooms?

Ans: It may either poisonous or suffocate, damage marine ecosystem.

2. What is the harmful impact of oil spill on marine life? 

Ans: Lack of oxygen in the water body is responsible for the deaths of enormous number of fish or marine life.

INTEXT QUESTIONS 14.7

1. Give four important characteristics that make any substance hazardous.

Ans: From nuclear reactors, laboratories, hospitals and direct exposure to radiation for diagnostic purposes (X-rays).

2. What is a very hazardous substance? 

Ans: Quick devastating effect on human and other life forms. Slow effect – childhood leukemia, miscarriages, infant mortality, increased susceptibility to AIOs.

3. Is plastic burning hazardous. Why?

Ans: It suffocates them, poisons them.

4. What are phytosanitary products? How are they harmful?

Ans: Phytosanitary products are pesticides/insecticides used to protect plants. They are harmful as they pollute soil, water and can cause health hazards.”

TERMINAL EXERCISE

1. Name an introduced weed in India.

Ans: Parthenium.

2. Name two green-house gases.

Ans: Carbon Dioxide (CO₂) and Chlorofluorocarbons (CFCs).

3. Name any two compounds that are harmful to ozone layer.

Ans: Chlorofluorocarbons (CFCs) and Methane (CH₄).

4. Which has been the most disastrous nuclear accident so far.

Ans: The most disastrous nuclear accident in history is the nuclear disaster at Chernobyl Nuclear Reactor, Kiew, Chernobyl, USSR, on April 26, 1986.

5. Name one phytosanitary product.

Ans: Insecticides.

6. Mention various (at least 5) global environmental issues?

Ans: Important global environmental issues are as follows:

(i) Greenhouse effect.

(ii) Global warming. 

(iii) Biodiversity loss.

(iv) Desertification.

(v) ozone layer depletion.

7. Why are environmental issues of global concerns?

Ans: Environmental issues are affecting the globe as a whole. It is industrialization and urbanization that brought about many developmental activities around the world for human welfare. As these developmental activities were not on par with environmental conservation, human welfare activities posed a serious threat to the environment. Thus environmental issues are of global concern.

8. Why should we avoid use of CFCs and such compounds?

Ans: Any event, which releases chlorine atoms into the atmosphere, can reduce the thickness of ozone. It is because chlorine atoms in the stratosphere can destroy ozone very efficiently. In the stratosphere, chlorine atoms from CFCS react with ozone to form chlorine monoxide and an oxygen molecule. Chlorine monoxide may then react with oxygen atoms to release more chlorine atoms.

One chlorine atom can break down 1,00,000 ozone molecules. Hence it is advisable to avoid the use of CFCs and other chlorine emitting compounds.

9. Explain briefly:

(a) Compare the effects of tropospheric and stratospheric ozone on life in our planet.

Ans: Tropospheric ozone is a toxic compound that can not be breathed in. Its concentration should not exceed a few parts per billion. It is a secondary pollutant, as it is produced from other pollutants like NOx.

Stratospheric ozone is beneficial to life as it protects us from the effects of harmful UV rays. Tropospheric and stratospheric ozone have opposite effects on life on earth. When the former is harmful, the latter is useful.

(b) Suggest strategies to cope with green house effect.

Ans: The steps to reduce the emission of greenhouse gases are as follows:

(i) Increase fuel efficiency of power plants and vehicles

(ii) Use of solar energy/non-fossil fuel alternatives

(iii) Promoting afforestation

(iv) Preventing deforestation

(v) Reduce air-pollution.

(c) How does canal-based irrigation contribute to desertification?

Ans: Modern irrigation techniques like canal-based irrigation can bring a lot of salts to the land. Salt accumulation can lead to desertification. As the need for food increased, agriculture had to be extended to areas with little water access. The water is supplied to these growing areas by artificial means and improved irrigation methods. Such water brings salts dissolved in it. Even the best quality of irrigation water contains 200-500 ppm of salts. Water used for irrigation is lost from the agricultural field through evaporation and transpiration by crop plants. After evaporation, salts get accumulated. Accumulation of excessive salt in soil or salinization makes the soil unfit for agriculture.

(d) Chlorine atom causes ozone-hole.

Ans: In the stratosphere, chlorine atoms from CFCs react with ozone to form chlorine monoxide and an oxygen molecule. Chlorine monoxide may then react with oxygen atoms to release more chlorine atoms:

One chlorine atom can break down 1,00,000 ozone molecules. 

Chlorine atom splits the ozone molecules causing the reduction in the thickness of OZone called ozone depletion. Thus, UV rays can easily penetrate the earth’s atmosphere and cause health hazards.

(e) Harmful effect of UV radiations on human being.

Ans: The harmful effects of UV rays on human beings are as follows:

(i) Increased susceptibility to skin cancer.

(ii) Cataract.

(iii) Damage DNA.

(iv) Damage cornea.

(v) Cause retinal diseases.

(vi) Suppress human immune systems.

(f) Perils of nuclear disasters.

Ans: Nuclear radiations have an impact on life forms and ecosystems. Continued small dose exposure to nuclear radiation is very harmful. 

It can cause:

(i) Childhood leukemia.

(ii) Miscarriage.

(iii) Underweight babies.

(iv) Infant mortality.

(v) Increased susceptibility to AlDS.

Nuclear leakage can cause radioactivity in water bodies, plants, etc., and thereby it can enter the food chain affecting all the living organisms.

(g) “Environmental problems need global intervention”.

Ans: We all need to cooperate at the individual, domestic, local level to conserve the environment. National and international level interventions are to be made to maintain our environment clean and sustainable globally. It is the increased human activity, urbanization, industrialization that have led to the rapid destruction of the environment. This has adversely affected the life-supporting system. The developmental activities without the protection of the environment in different regions of the world pose a serious threat to our common global environment. Thus, we are confronted with complex environmental issues deserving attention from a global perspective.