Free Man and His Environment MCQs with Answers

241. A scrubber in the exhaust of a chemical industrial plant removes:

• A. Gases like sulphur dioxide.
• B. Particulate matter of the size 5 micrometer or above.
• C. Gases like ozone and methane.
• D. Particulate matter of the size 2.5 micrometer or less.

Explanation: Dust separation is carried out by scrubbers. They are of two types, dry and wet. Both can be used to separate particulate matter by passing through dry or wet packing material but more commonly they are employed in removing gaseous pollutants like SO2. Scrubbers are widely used to remove sulfur dioxide (SO2) pollutants from industrial emissions. SO2 is a major air pollutant that is primarily produced through the combustion of fossil fuels, such as coal and oil. It is a key contributor to air pollution and can have adverse effects on the environment and human health. Scrubbers, specifically designed for SO2 removal, help mitigate these impacts by capturing and neutralizing the SO2 emissions.

242. Kyoto protocol was endorsed at:

• A. CoP -­ 6
• B. CoP ­- 4
• C. CoP -­ 3
• D. CoP ­- 5.

Explanation: Kyoto protocol is an international treaty to reduce emission of greenhouse gases which was adopted at the third session of the Conference of Parties (CoP ­- 3) to the UNFCCC (United Nations Framework Convention on Climate Change) in 1997, in Kyoto, Japan.

243. The climate of the world is threatened by the:

• A. Decreasing amount of atmospheric oxygen.
• B. Increasing amount of atmospheric carbon dioxide.
• C. Decreasing amount of atmospheric carbon dioxide.
• D. Increasing concentration of atmospheric oxygen.

Explanation: Carbon dioxide is a greenhouse gas with a warming effect of 60%. Greenhouse gases are essential for keeping the earth warm and hospitable. They prevent a substantial part of long wave radiations emitted by the earth to escape into space and radiate a part of this energy back to the earth. The phenomenon is called greenhouse flux. Because of greenhouse flux, the mean annual temperature of earth is 15°C. Recently the concentration of greenhouse gases has started rising that is resulting in increasing the mean global temperature. It is called global warming. Deforestation has reduced carbon dioxide assimilation. The excess remains in the air. Excessive use of fossil fuel is adding more CO 2 to atmosphere. This causes the greenhouse effect.

244. In an area where DDT had been used extensively, the population of birds declined significantly because:

• A. Birds stopped laying eggs.
• B. Earthworms in the area got eradicated.
• C. Cobras were feeding exclusively on birds.
• D. Many of the birds eggs laid, did not hatch.

Explanation: Higher amounts of DDT disturb calcium metabolism of birds resulting in thinning of egg shells and their premature breaking that kills the embryos. Thus many of the eggs laid by birds did not hatch.

245. Which one of the following is a wrong statement?

• A. Most of the forests have been lost in tropical areas.
• B. Ozone in upper part of atmosphere is harmful to animals.
• C. Greenhouse effect is a natural phenomenon.
• D. Eutrophication is a natural phenomenon in freshwater bodies.

Explanation: Ozone present in upper atmosphere forms a distinct layer that is known as ozone layer. Ozone layer is necessary for the survival of life on earth as it blocks harmful UV rays of sun from reaching earth's surface.

246. Measuring Biochemical Oxygen Demand (BOD) is a method used for:

• A. Estimating the amount of organic matter in sewage water.
• B. Working out the efficiency of oil driven automobile engines.
• C. Measuring the activity of Saccharomyces cerevisiae in producing curd on a commercial scale.
• D. Working out the efficiency of RBCs about their capacity to carry oxygen.

Explanation: Biochemical oxygen demand (BOD) is the amount of oxygen taken up by microorganisms that decompose organic waste matter in water. It is therefore used as a measure of the amount of certain types of organic pollutant in water.

247. Eutrophication is often seen in:

• A. Deserts
• B. Fresh water lakes
• C. Ocean
• D. Mountains

Explanation: Eutrophication is the excessive growth of algae, plants and animals in water bodies due to the nutrient enrichment particularly with nitrogen and phosphate. Nutrients present in sewage, agricultural wastes and fertilizers cause dense growth of plants and planktonic algae. The excessive growth of planktonic algae that cause colouration of water is called algal bloom, which is toxic to animals and humans. Eutrophic water bodies also support excessive growth of floating plants. Algal blooms and floating plants cut off light form submerged plants, resulting in their death. There is drastic decrease in oxygen replenishment inside water. Non­-availability of oxygen results in the death of aquatic animals such as fish, which further adds to organic loading of water. Decomposition is replaced by putrefraction which is anaerobic, leading to absence of oxygen in water and death of aquatic animals.

248. "Good ozone" is found in the:

• A. Mesosphere
• B. Troposphere
• C. Stratosphere
• D. Ionosphere

Explanation: Bad ozone is formed in the lower atmosphere (troposphere) that harms plants and animals. Good ozone is found in the upper part of the atmosphere called the stratosphere and it acts as a shield absorbing ultraviolet radiation from the sun. UV rays are highly injurious to living organisms since DNA and proteins of living organisms preferentially absorb UV rays and its high energy breaks the chemical bonds within these molecules.

249. A renewable exhaustible natural resource is:

• A. Coal
• B. Petroleum
• C. Minerals
• D. Forest

Explanation: Exhaustible resources are those natural resources which are likely to be exhausted or diminished as a result of their continuous use. These are further of two types - renewable and non­ renewable. Forest is a renewable exhaustible resource which can be again generated or produced artificially or naturally. Coal, petroleum and minerals are non­-renewable exhaustible natural resources which cannot be again produced or generated.

250. What happens when domestic sewage mixes with river water?

• A. Small animals like rats will die after drinking river water.
• B. The increased microbial activity releases micronutrients such as iron.
• C. The increased microbial activity uses up the dissolved oxygen.
• D. The river water is still suitable for drinking as impurities are only about 0.1%.

Explanation: When sewage mixes with a water body, microorganisms present in it biodegrade the organic matter of the sewage using oxygen. This results in a sharp decline in dissolved oxygen which may cause mortality of aquatic creatures. Gradually, however, dissolved oxygen increases in concentration with the completion of biodegradation of sewage matter.