NCERT MOST IMPORTANT QUESTIONS CLASS – 12 | BIOLOGY IMPORTANT QUESTIONS | CHAPTER – 16 | ENVIRONMENTAL ISSUES | EDUGROWN |

In This Post we are  providing Chapter- 16 ENVIRONMENTAL ISSUES NCERT MOST IMPORTANT QUESTIONS for Class 12 BIOLOGY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS  can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter

NCERT MOST IMPORTANT QUESTIONS ON ENVIRONMENTAL ISSUES

Question 1.
Define pollution. Compare the biodegradable and non-biodegradable pollutants.
Answer:
Pollution: “Environmental pollution is an unfavorable alteration of our surroundings largely as a by-product of man’s actions through direct or indirect effects of changes in energy patterns, radiation levels, chemical and physical conditions and abundance of organisms.”

Differences between biodegradable and non-biodegradable pollutants:

Biodegradable Pollutants	Non-biodegradable Pollutants
1. These wastes can be broken down into harmless substances naturally.	1. These cannot be broken down into harmless substances naturally.
2. The disposal of biodegradable wastes is easy and therefore, maintains balance in the ecosystem. Example. Cattle dung	2. Their disposal is not easy and is a problem. Example. D.D.T., plastics.

Question 2.
What is air pollution? List various air pollutants.
Answer:
Air pollution: The release of harmful materials into the air is called air or atmospheric pollution. It is the degradation of air quality and atmospheric conditions.

Air pollutants include gaseous materials, suspended particles, and radioactive substances.
1. The gaseous pollutants of the air come from combustion in motor vehicles and industries. These include CO, C0₂, NO, N0₂, S0₂, S0₃, hydrocarbons, fluorides, and photochemical oxidants such as peroxyacetyl nitrate (PAN), ozone (0₃), and aldehydes. PAN is a secondary pollutant formed in the air by the interaction between nitrogen oxides and hydrocarbons in the presence of sunlight. It is more toxic than the primary pollutants. An increase in toxicity by the reaction among pollutants is called synergism.

2. The particulate contaminants of air also come from industries and automobiles. These include fly-ash, soot, metal dust, cotton fibers, asbestos, fibers, lead, aerosols (chlorofluorocarbons or CFCs), polychlorinated biphenyls (PCBs), tobacco smoke, smog, pollen, spores, cysts, and bacteria.
(in) Radioactive substances released by nuclear explosions and war explosives are also very harmful air pollutants.

Question 3.
Define a pollutant. How many types of pollutants are there?
Answer:
Pollutant: It is a substance (e.g. dust, smoke), chemical (e.g. S0₂), or factor (e.g. heat, noise) that on release into the environment has an actual or potentially adverse effect on human interests. A pollutant can also be defined as a constituent in the wrong amount, at the wrong place, or at the wrong time.

Question 4.
What measures do you suggest to control pollution from automobile exhaust?
Answer:
Control of pollution from automobile exhaust:

1. Efficient engines can reduce the number of unburnt hydrocarbons from vehicuLar emissions.
2. Use of cataLytic converters to convert harmful gases to harmless.
3. Use of good quality fuel.
4. Unleaded petroL can reduce the amount of lead in the exhaust.
5. The use of CNG (compressed natural gas) Lowers the toxic contaminants in the exhaust.

Question 5.
Blends of polyblend and bitumen, when used, help to increase road life by a factor of three. What is the reason?
Answer:
Polyblend is a fine powder of recycled modified plastic. The binding property due to increased cohesion and enhanced water-repelling property of plastic makes the road last longer besides giving added strength to withstand more loads.

This is because:

• Plastic increases the melting point of the bitumen which would prevent it from melting in India’s hot and extremely humid climate, where temperature frequently crosses 45°C.
• Rainwater will not seep through because of the plastic in the tar.

Question 6.
“Indiscriminate human activities have strengthened the greenhouse effect resulting in Global Warming.” Give the relative contribution of various Greenhouse Gases in the form of a pie chart and explain the rate of the energy of sunlight reaching the earth’s surface contributing towards Global Warming. (CBSE Sample Paper 2020)
Answer:
a)
(b) Rate of the energy of sunlight:

• Clouds and gases reflect one-fourth of incoming solar radiations.
• Some of the energy is absorbed by clouds and gases.
• Thus only half of the solar energy falls on the surface of the earth.
• The small amount of energy is reflected back.
• Earth surface re-emits heat in the form of infrared radiations.
• The major fraction of solar energy is absorbed by atmospheric gases.

Question 7.
How does a scrubber function?
Answer:
Scrubber: A scrubber can remove gases like sulfur dioxide. In a scrubber, the exhaust is passed through a spray of water or lime. Water dissolves gases and lime reacts with sulfur dioxide to form a precipitate of calcium sulfate or sulfite.

Question 8.
Discuss the causes and effects of global warming.
Answer:
Global warming: The increase in global mean temperature due to the enhanced greenhouse effect is called global warming.

Effects of global warming:
1. Effect on weather and climate.
(а) The average temperature of the earth may increase by 1.4° to 5.8°C by the year 2100.
(б) Winter precipitation may decrease at lower altitudes.
(c) Frequency of droughts, floods may increase.
(d) Climatic change is a threat to human health in tropical and subtropical countries.

2. Sea level change. Sea level had been raised by 1 to 2 mm per year during the 20th century. It is predicted that by the year 2100, the global mean sea level can increase up to 0.88 m over the 1990 level. Global warming may contribute to sea-level rise due to the thermal expansion of the ocean.

3. Effect on a range of species distribution. Vegetation may extend 250-600 km poleward with a global rise in temperature by 2 to 5°C during the 21st century.

4. Effect on food production. Increased temperature will cause an eruption of plant diseases and pests and vast growth of weeds.

Question 9.
Show the relative contribution of greenhouse gases to total global warming.
Answer:
Greenhouse gases:

The relative contribution of various greenhouse gases to total Global warming.

Question 10.
Make a chart illustrating the kinds of water pollutants.
Answer:
Classification of water pollutants: