Free Man and His Environment MCQs with Answers

271. Which of the following is a secondary pollutant?

• A. PAN
• B. Aerosol
• C. CO
• D. CO 2

Explanation: The formation of secondary pollutants is influenced by a combination of factors, including the presence of primary pollutant emissions, meteorological conditions, sunlight, and the concentration of precursor compounds in the atmosphere. The secondary pollutants are more toxic than the primary ones. Nitrogen oxides and hydrocarbons react photochemically to produce peroxyacyl nitrates and ozone. Peroxyacyl nitrates are produced due to photochemical reactions between nitrogen oxides and unsaturated hydrocarbons.

272. The maximum biomagnification would be in which of the following in the case of an aquatic ecosystem?

• A. Zooplankton
• B. Phytoplanktons
• C. Fishes
• D. Birds

Explanation: Heavy metals and persistent pesticides (e.g., chlorinated hydrocarbons like DDT) pass into the food chain and increase in amount per unit weight of organisms with the rise in trophic level due to their accumulation in fat. The phenomenon is called biomagnification/ bioconcentration/biological amplification, e.g., 0.003 parts per billion of DDT in water becomes 0.003 ppm in phytoplankton, 0.04 ppm in zooplankton, 0.5 ppm in clams and small fish, 2.0 ppm in predator fish and 25 ppm in fish-eating birds like seagulls.

273. Which of the following is the use of lichens in case of pollution?

• A. They promote pollution
• B. Lichens are not related to pollution
• C. They treat the polluted water
• D. They act as bioindicators of pollutions

Explanation: Lichen biomonitoring has been widely used in environmental research and air quality assessment. It provides valuable insights into the impact of pollutants on ecosystems and human health. Lichens are particularly useful in areas where air quality monitoring equipment may be limited, and they offer a cost-effective and non-invasive way to assess pollution levels over time. Lichens are very sensitive to SO2 pollution. They are completely destroyed at places where there is SO2 pollution in the atmosphere. Therefore, they act as very good indicators of SO2 pollution.

274. The supersonic jets cause pollution by the thinning of the:

• A. O2 layer
• B. O3 layer
• C. CO2 layer
• D. SO2 layer.

Explanation: Supersonic jets, like the Concorde, can potentially contribute to environmental pollution, particularly in the upper atmosphere. Depletion of the ozone is due to the action of sunlight over pollutants that release chemicals (e.g., chlorine) to destroy ozone. Ozone-depleting substances react with the ozone present in the stratosphere and destroy the same. The major ODS are chlorofluorocarbons (14% of total depletion), nitrogen oxides (3.5% of total depletion), sulphur dioxide, halon, carbon tetrachloride, methyl chloroform, chlorine, etc. Many of these are being released by jets flying in the stratosphere and rockets being fired into space. A major contributor of these gases is the USA.

275. Which one of the following organisms is used as an indicator of water quality?

• A. Azospirillum
• B. Escherichia
• C. Eichhornia
• D. Chlorella

Explanation: E.coli is the most common indicator of water pollution. It naturally occurs in the intestines of human beings and animals. They are commonly found in sewage and if E.coli are detected in water, it is indicative of faecal contamination. So if E.coli are detected in drinking water it indicates a serious health risk and that water should not be used for drinking.

276. If there was no CO2 in the earth's atmosphere, the temperature of earth's surface would be:

• A. Higher than the present
• B. Dependent on the amount of oxygen in the atmosphere.
• C. Same as present
• D. Less than the present

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 longwave 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 the 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 the atmosphere. This causes the greenhouse effect.

277. Carbon monoxide is a pollutant because it:

• A. Reacts with haemoglobin
• B. Makes the nervous system inactive
• C. Reacts with O2
• D. Inhibits glycolysis

Explanation: Carbon monoxide is produced due to incomplete combustion, metallurgical operations and naturally by plants as well as animals. Carbon monoxide has 200 times more affinity to haemoglobin as compared to oxygen. Carbon monoxide combines with haemoglobin and forms a stable compound called carboxyhaemoglobin. At 50 ppm, CO converts 7.5% of haemoglobin into carboxy­haemoglobin within 8 hours. It impairs oxygen transport resulting in headaches, decreased vision, cardiovascular malfunction and asphyxial.

278. How does the carbon monoxide emitted by automobiles prevent the transport of oxygen in the body tissues?

• A. By forming a stable compound with haemoglobin.
• B. By obstructing the reaction of oxygen with haemoglobin.
• C. By changing oxygen into carbon dioxide.
• D. By destroying the haemoglobin.

Explanation: Carbon monoxide (CO) prevents the transport of oxygen in the body tissues by interfering with the oxygen-carrying capacity of hemoglobin, the protein in red blood cells responsible for transporting oxygen. When carbon monoxide is inhaled, it enters the bloodstream through the lungs. In the bloodstream, CO has a much higher affinity for hemoglobin than oxygen. This means that CO molecules preferentially bind to hemoglobin over oxygen. When CO binds to hemoglobin, it forms a compound called carboxyhemoglobin (COHb). Carboxyhemoglobin has a stronger bond with hemoglobin than oxyhemoglobin (the form of hemoglobin that carries oxygen). As a result, COHb accumulates in the bloodstream, displacing oxyhemoglobin.

279. The most common indicator organism that represents polluted water is:

• A. Vibrio
• B. Entamoeba histolytica
• C. E.coli
• D. P. typhi

Explanation: E.coli is the most common indicator of water pollution. It naturally occurs in the intestines of human beings and animals. They are commonly found in sewage and if E.coli are detected in water then it indicates faecal contamination. So if E.coli are detected in drinking water it indicates a serious health risk and that water should not be used for drinking.

280. In coming years, skin related disorders will be more common due to:

• A. Water pollution
• B. Depletion of ozone layer
• C. Pollutants in air
• D. Use of detergents

Explanation: Ozone layer or shield is present in stratosphere. It functions as a shield against strong UV radiations coming from sun. UV radiations are very harmful and may cause mutations in living organisms. Thinning of ozone layer increases the amount of UV radiations reaching the earth. It would increase occurrence of cataract, skin cancers, dimming of eye sight, photoburning, deficient functioning of immune system, etc.