Free Man and His Environment MCQs with Answers

291. The most hazardous metal pollutant of automobile exhausts is:

• A. Mercury
• B. Cadmium
• C. Lead
• D. Copper

Explanation: Lead (Pb) is released by the combustion of petrol because tetraethyl lead is used as an antiknocking agent in petrol. This lead is very harmful and causes plumbism or lead poisoning, which disturbs the nervous system, liver, kidneys in adults and also causes brain damage in children. About 150 to 400 mg of lead is stored in the body of an average adult and blood levels average about 25 mg/100 ml. An increase to 70 mg/100 ml of blood is generally associated with clinical symptoms. Hence a level of 30 mg/100 ml should be considered alarming.

292. Minerals and metals are:

• A. Biodegradable resources.
• B. Renewable resources.
• C. Non-­renewable resources.
• D. Renewable and non-renewable resources.

Explanation: Minerals and metals are generally considered non-renewable resources, meaning that they are finite and cannot be replaced on a human timescale. These resources are formed over geological time through natural processes, and their extraction for human use occurs at a much faster rate than their formation.

293. Domestic waste constitutes:

• A. Non-biodegradable pollution.
• B. Biodegradable pollution.
• C. Effluents
• D. Air pollution

Explanation: Domestic waste constitutes biodegradable pollution. These are also called non­-conservative pollutants. These are decomposed chemically or by activity of microorganisms into harmless products and are recycled back into the atmosphere.

294. A major aerosol pollutant in jet plane emissions is:

• A. Sulphur dioxide
• B. Carbon monoxide
• C. Methane
• D. Fluorocarbon

Explanation: Aerosols are chlorofluoro­-hydrocarbon compounds released into the air with force in the form of vapour. The main source of aerosols is the emission of jet planes, where fluorocarbons are used. These chlorofluorocarbons deplete the ozone layer in the higher atmosphere. These CFC's have produced a hole in the ozone layer.

295. Deforestation will decrease:

• A. Soil erosion
• B. Land slides
• C. Soil fertility
• D. Rainfall

Explanation: Deforestation will affect the earth in different ways. Due to destruction of natural habitats, many species will get extinct. Man will be deprived of the benefits of trees and wild animals. Soil erosion will be increased. Floods and drought will become more frequent. There will also be a change in climate. Deforestation will also decrease the atmospheric humidity which will affect rainfall and makes the air hot. Economy of the forest dwelling people will be deteriorated and wild life will be adversely affected.

296. Soil conservation is the:

• A. Conversion of sterile soil into fertile soil
• B. Aeration of soil
• C. Erosion of soil
• D. Protection against loss of soil

Explanation: Soil conservation is to conserve fertile soil from losses like heavy rainfall, drainage, high wind, flood, drought etc. Soil is the top cover of the Earth in which plants can grow. The rotation of crops, contour ploughing and use of proper fertilizers help in maintaining the fertility of the soil. Plantation of trees, controlled grazing of grasslands, reforestation and prevention of forests fires will protect the erosion of topsoil. The regulation of water resources to prevent floods will help not only in soil conservation but will also supply an adequate water supply in periods of drought.

297. Which enzyme is first used in nitrogen fixation?

• A. Nitrogenase
• B. Nitroreductase
• C. Transferase
• D. Transaminase.

Explanation: The correct enzyme used in the process of nitrogen fixation is "nitrogenase." Nitrogenase is the enzyme responsible for catalyzing the conversion of atmospheric nitrogen (N2) into ammonia (NH3) during the process of nitrogen fixation. This enzyme is essential for making nitrogen available to plants and other organisms in a biologically useful form.Nitroreductases are a group of enzymes that catalyze the reduction of nitro groups (-NO2) to amino groups (-NH2) in certain chemical reactions. While they are involved in nitrogen metabolism, they are not directly related to nitrogen fixation.Transferases are a broad class of enzymes that transfer functional groups (e.g., methyl, acetyl, phosphate) from one molecule to another. While transferases play vital roles in various cellular processes, they are not specifically involved in nitrogen fixation. Transaminases, also known as aminotransferases, are a group of enzymes that catalyze the transfer of an amino group (-NH2) from one molecule to a keto acid, forming a new amino acid and a different keto acid. They are involved in amino acid metabolism and synthesis but not directly related to nitrogen fixation. In summary, nitrogenase is the enzyme directly responsible for catalyzing the conversion of atmospheric nitrogen into ammonia during nitrogen fixation, making it crucial for the nitrogen cycle and supporting life on Earth.

298. The present population of the world is about:

• A. 15 trillion
• B. 6 billion
• C. 500 million
• D. 100 million

Explanation: As this question appeared in 1997, so the population of world in mid 1997 was 5, 840, 324, 240 i.e., approximately 6 billion.

299. The presence of lichen in an area indicates the

• A. Absence of air pollution
• B. Nutrient content of the area
• C. Rich biodiversity of the area
• D. Beginning of ecosystem degradation

Explanation: Lichens are bioindicators that can provide information about the environmental conditions of an area. They are bioindicators of air pollution. So option A is correct. Therefore, the correct answer is that the presence of lichen indicates the absence of air pollution in the area. The other options are incorrect, as lichen presence does not indicate the nutrient level of the area, the overall biodiversity of the area, or the beginning of ecosystem degradation. Options B, C, and D are incorrect.

300. The ideal place for the conservation and protection of snow leopard is:

• A. Zoo garden
• B. National park
• C. Botanical garden
• D. Wildlife corridors

Explanation: The ideal place for the conservation and protection of snow leopards is a national park. National parks are designated areas that allow animals to live in their natural habitat with legal protection, which is crucial for species like the snow leopard that require large territories. Zoos and botanical gardens do not provide the necessary environment for wild animals, focusing instead on education and plant conservation, respectively. Wildlife corridors are vital for connecting habitats but do not serve as primary conservation areas.