NIOS Class 12 Environmental Science Chapter 14
INTEXT QUESTIONS 14.1
1. Why do you think environmental issues are of global significance?
Ans: Increased human activity, urbanisation, and industrialisation are rapidly deteriorating the environment, affecting the life-supporting system. The developmental discrepancies in different regions of the world pose a serious threat to our common global environment, leading to complex environmental issues. Moreover, the environment has no frontiers, no geographical boundaries.
2. Enumerate at least 3 environmental issues that confront us today.
Ans: The important global environmental issues are:
- Greenhouse effect and global warming
- Biodiversity loss
- Desertification
- Depletion of the ozone layer
- Acid rain
- Oil spills
- Dumping of hazardous wastes
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’s surface.
4. Why is the greenhouse effect called so?
Ans: The greenhouse effect is called so because it stimulates similar conditions that one encounters in a glass greenhouse. A greenhouse is a glass chamber in which plants are grown to provide them warmth by trapping sunlight. Sunlight passes through the glass, and it gets absorbed inside, releasing heat radiation. However, this heat radiation can not escape through glass. Thus, even on a cold winter day, the inside of a greenhouse can become quite warm to support plant growth. The phenomenon of heat buildup inside a glass chamber from the absorption of solar radiation is called the greenhouse effect.
5. Which kind of radiation is not reflected back out of the atmosphere, causing greenhouse effect?
Ans: Infrared
6. Name four greenhouse 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: The main reasons for biodiversity loss are loss of habitat, pollution, overuse of resources, introduction of foreign species and environmental degradation.
3. How does high-technology fishing affect marine biodiversity?
Ans: Improved technologies, such as radar/sonar/electronic equipment/navigation, aid help locating shoals of fish very accurately. It ensures capture efficiency.
- It results in large-scale fishing of newer species. It results in depriving larger fish/mammals/ aquatic birds of their prey. It affects the food chain.
- Improved and substantial aquacultural practices lead to the capture of more fish than they can reproduce. It leads to loss of biodiversity.
- Fish farms destroy large mangrove trees. It causes loss of fish sheltering in the vicinity of submerged roots of mangrove.
4. How does a species lose its habitat?
Ans: Due to the growing human population, wetlands are being made dry through landfills, as the demand for land increases. Natural forests are cleared for industry, agriculture, dams, habitation, recreational sports, etc. As a consequence, every plant and animal species occupying that ecosystem is temporarily or permanently affected.
5. What kinds of activities promote desertification?
Ans: Some of the principal causes which promote desertification are:
- Over-cultivation,
- Overgrazing,
- Deforestation, and
- Salt accumulation due to irrigation.
6. Which kind of sowing is better in the long term: ploughing or tractor–sowing?
Ans: Tractor-sowing.
7. What is a desert?
Ans: The land that has lost its productivity (ability to grow plants) 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 there in an ozone molecule?
Ans: Three
3. How do volcanoes contribute to O3 depletion?
Ans: During volcanic eruptions, a significant amount of chlorine may be released in the stratosphere, which is harmful to the ozone layer.
4. Which kinds of anthropogenic activities are most dangerous to ozone-shield?
Ans: Any event which releases chlorine atoms into the atmosphere can cause severe ozone destruction, because chlorine atoms in the stratosphere can destroy ozone very efficiently.
5. Name some harmful effects of UV radiation on human beings.
Ans: Harmful effects on humans
beings
- Increase the susceptibility to skin cancer
- Increase cataract
- Damage DNA
- Damage cornea
- Cause retinal diseases
- Suppers human immune systems
INTEXT QUESTIONS 14.4
1. Name two acids that are present in acid rain.
Ans: H2SO4– Sulphuric acid, HNO3– Nitric acid.
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/sperm) of the organisms cannot survive. It affects the life cycle. Leading to generation/population loss. Death or their inability to increase in numbers affects aquatic food chains in acidic water bodies, causing severe ecosystem imbalances.
Acidic lake waters may kill bacteria/microbes/planktons, and the acidic lakes become unproductive and lifeless. Such acidic and lifeless ponds/lakes adversely affect fisheries and livelihood.
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 a danger to life forms.
Ans: The slow nuclear radiations can also emanate from a variety of sources, viz, nuclear reactors, laboratories, hospitals, and direct exposures to radiation for diagnostic purposes (eg X-rays).
2. Enlist some harmful effects of nuclear radiation on human beings.
Ans: Nuclear radiation can cause: childhood leukaemia, miscarriage, underweight babies, infant deaths, increased susceptibility to AIDS and other immune disorders and increased criminality.
INTEXT QUESTIONS 14.6
1. What is the effect of oil spills on algal blooms?
Ans: Oil spills also either poison or suffocate algal blooms, which makes the water body deficient in oxygen. This oxygen-deficient water is responsible for the deaths of an enormous number of fish/marine life.
2. What is the harmful impact of an oil spill on marine life?
Ans: Within hours of an oil spill, the fish, shellfish, and plankton die due to suffocation and metabolic disorders. Within a day of an oil spill, birds and sea mammals die. The death of these organisms severely damages marine ecosystems.
INTEXT QUESTIONS 14.7
1. Give four important characteristics that make any substance hazardous.
Ans: Any hazardous substance could exhibit any one or more of the following characteristics:
- Toxicity
- Ignibility
- Corrosivity
- Reactivity (explosive)
2. What is a very hazardous substance?
Ans: Any substance that could have serious, irreversible health effects from a single exposure is
called a very hazardous substance.
3. Is plastic burning hazardous? Why?
Ans: Yes, plastic burning is hazardous as it contains polythene, polypropylene, polyesters, etc., that release harmful gases upon burning. It causes ecological pollution as well.
4. What are phytosanitary products? How are they harmful?
Ans: Insecticides, pesticides, fungicides, herbicides, etc, are phytosanitary products. They enter the soil as runoff and pollute the water table, affecting aquatic life. They are carcinogenic and can cause renal failure.
TERMINAL EXERCISE
1. Name an introduced weed in India.
Ans: Parthenium, Argemone and Lantana are the common weeds of foreign origin in our country.
2. Name two greenhouse gases.
Ans: Carbon dioxide (CO2) and Methane (CH4)
3. Name any two compounds that are harmful to the ozone layer.
Ans: Hydrogen oxide (HOx), Methane (CH4), Hydrogen gas (H2), Nitrogen oxides (NOx). Chlorine monoxide (ClO).
4. Which has been the most disastrous nuclear accident so far?
Ans: Nuclear attacks on Hiroshima and Nagasaki in Japan during World War II.
5. Name one phytosanitary product.
Ans: Insecticides and pesticides.
6. Mention various (at least 5) global environmental issues?
Ans: The important global environmental issues are:
- Greenhouse effect and global warming
- Biodiversity loss
- Desertification
- Depletion of the ozone layer
- Acid rain
- Oil spills
- Dumping of hazardous wastes
7. Why are environmental issues of global concern?
Ans: Increased human activity, urbanisation, and industrialisation are rapidly deteriorating the environment, affecting the life-supporting system. The developmental discrepancies in different regions of the world pose a serious threat to our common global environment, leading to complex environmental issues. Moreover, the environment has no frontiers, no geographical boundaries.
8. Why should we avoid the use of CFCs and such compounds?
Ans: In the stratosphere, chlorine atoms from CFCs react with ozone to form chlorine monoxide and an oxygen molecule.
Cl + O3—> ClO + O2
Chlorine monoxide may then react with oxygen atoms to release more chlorine atoms:
2ClO + O2—> 2Cl + 2O2
One chlorine atom can break down 1,00,000 ozone molecules.
9. Explain briefly:
(a) Compare the effects of tropospheric and stratospheric ozone on life on our planet.
(b) Suggest strategies to cope with green greenhouse effect.
(c) How does canal-based irrigation contribute to desertification?
(d) Chlorine atom causes the ozone hole
(e) Harmful effects of UV radiation on human beings.
(f) Perils of nuclear disasters
(g) “Environmental problems need global intervention”.
Ans:
(a) Compare the effects of tropospheric and stratospheric ozone on life on our planet.
The stratospheric ozone is a protective layer that prevents UV radiation from penetrating to the Earth’s surface. On the other hand, tropospheric ozone is a harmful compound that pollutes the air. This is a secondary product produced by various gases such as CFCs or nitrogen oxides.
(b) Suggest strategies to cope with the greenhouse effect.
The following steps would be useful in reducing the emission/release of greenhouse gases into the atmosphere:
- Increased fuel efficiency of power plants and vehicles;
- Development/implementation of solar energy/non-fossil fuel alternatives;
- Halting deforestation;
- Supporting and undertaking tree-planting (afforestation);
- Reduce air pollution.
(c) How does canal-based irrigation contribute to desertification?
Canal-based irrigation water brings salts dissolved in it. Even the best quality of irrigation water contains 200-500 ppm of salts. The water evaporated, but the dissolved salt keeps on accumulating, which makes the soil more salty. Saline accumulation in excessive soils prevents retards plant growth. Land devoid of plant cover easily becomes desertified. Accumulation of excessive salt in soil or salinisation
makes the soil unfit for agriculture.
(d) Chlorine atom causes the ozone hole
Ans: In the stratosphere, chlorine atoms from CFCs react with ozone to form chlorine monoxide and oxygen molecules.
Cl + O3—> ClO + O2
Chlorine monoxide may then react with oxygen atoms to release more chlorine atoms:
2ClO + O2—> 2Cl + 2O2
One chlorine atom can break down 1,00,000 ozone molecules.
(e) Harmful effects of UV radiation on human beings.
Harmful effects on human beings
- Increase the susceptibility to skin cancer
- Increase cataract
- Damage DNA
- Damage cornea
- Cause retinal diseases
- Suppers human immune systems
(f) Perils of nuclear disasters
Such low-dose radiation could have a substantial impact on life forms and ecosystems.
Continued small-dose exposure to nuclear radiation is very harmful. It can cause:
- childhood leukemia
- Miscarriage
- Underweight babies
- Infant deaths
- Increased susceptibility to AIDS and other immune disorders, and increased criminality.
Underground bomb testing releases radiation in very small doses of radionuclides that enter the water in the soil. This radioactive water is taken by plants through their roots. The radioactivity enters the food chain when such plants are eaten by animals and humans. Such radioactivity has been detected even in the milk.
(g) “Environmental problems need global intervention”.Ans: Increased human activity, urbanisation, and industrialisation have led to the rapid deterioration of the environment. This has severely affected the life-supporting system. The developmental discrepancies in different regions of the world pose a serious threat to our common global environment. Consequently, we are confronted with complex environmental issues deserving attention. Pollution, ozone hole, greenhouse effect, desertification, loss of biodiversity, oil spills, nuclear disasters, and hazardous waste management are some of the global environmental problems that need immediate collective attention.
Additional Study Materials
- Chapter 10 Environmental Pollution
- Chapter 12 Environment and Health
- Chapter 13 Disasters and Their Management
