Free Man and His Environment MCQs with Answers

301. A group of environmental biologists work for the establishment of forests in the previously barren lands. The effort of these biologists exemplies:

• A. Reduction
• B. Recycling
• C. Afforestation
• D. Deforestation

Explanation: The correct answer is Afforestation. This term refers to the process of creating a forest, especially on land that was not previously forested, which aligns with the work of the environmental biologists in the scenario. Deforestation is incorrect because it involves clearing trees, not establishing them. Reduction and Recycling are unrelated to the process of planting trees on barren lands.

302. In fresh water bodies, eutrophication occurs due to the accumulation of:

• A. Toxic gases
• B. Heavy metals
• C. Plastic garbage
• D. Inorganic nutrients

Explanation: Eutrophication is the process by which a body of water becomes overly enriched with minerals and nutrients, leading to excessive growth of algae and plants. The primary contributors to this process are inorganic nutrients like nitrates and phosphates, often from agricultural runoff or wastewater discharge. These nutrients provide the essential elements for plant growth, resulting in an imbalance in the aquatic ecosystem. Toxic gases, heavy metals, and plastic garbage are environmental pollutants, but they do not contribute to the nutrient-based process of eutrophication. Toxic gases affect air quality, heavy metals can poison water and organisms, and plastic garbage leads to physical contamination and harm to marine life, but none of these cause the nutrient enrichment that defines eutrophication.

303. Secondary sewage treatment is mainly due to

• A. Mechanical processes
• B. Biological processes
• C. Physical processes
• D. Chemical processes

Explanation: This is usually done with the help of microorganisms(bacteria), hence it is called biological treatment. The microorganisms feed on the organic matter present in the wastewater thereby reducing the organic load of the wastewater and purifying the water.

304. Which one of the following stage of sewage treatment consists of temporarily holding the sewage in a quiescent basin where heavy solids can settle to the bottom while oil, grease and lighter solids float to the surface?

• A. primary
• B. secondary
• C. tertiary
• D. Quaternary

Explanation: The stage of sewage treatment described is called "primary sedimentation." It involves holding the sewage in a quiescent basin, allowing heavier solids to settle to the bottom (forming sludge) and lighter solids like oil and grease to float to the surface (forming scum). This stage is not called "primary treatment" because primary treatment typically refers to the initial phase of sewage treatment, which involves physical processes such as screening to remove large objects and grit, followed by primary sedimentation. So, primary sedimentation is part of the primary treatment stage, but it's specifically referred to as "primary sedimentation" to distinguish it from other processes within primary treatment.

305. The graph shows the relationship between the number of lichens and the levels of sulfur dioxide pollution. It indicates that as the sulfur dioxide levels increase, the number of lichen decreases. Which one of following is the best conclusion drawn from the above graph?

• A. Sulfur dioxide is an essential nutrient for lichen growth
• B. Lichens are good pollution indicators
• C. Lichens use sulfur dioxide in photosynthesis
• D. Sulfur dioxide has relation with lichen growth

Explanation: Sulfur dioxide (SO2) can actually have a significant impact on lichen growth and health. Lichens are sensitive to air pollution, including sulfur dioxide, which can cause damage to their tissues and inhibit their growth. High levels of sulfur dioxide in the air can lead to the decline or death of lichen populations in affected areas. Therefore, sulfur dioxide does have a direct relation to lichen growth, albeit in a negative way, as it can be detrimental to their health and survival.

306. What is formed by a series of complex reactions of ozone with water in the troposphere that are driven by sunlight?

• A. O radical
• B. H radical
• C. OH radical
• D. H3O radical

Explanation: The complex reactions of ozone with water in the troposphere that are driven by sunlight produce OH radical, which is a highly reactive species that can participate in various atmospheric reactions.

307. Which of the following is not a primary pollutant of the troposphere?

• A. Carbon dioxide
• B. Sulfur dioxide
• C. Carbon monoxide
• D. Ammonia

Explanation: Carbon dioxide is not considered a primary pollutant of the troposphere because it is a natural component of the atmosphere and is essential for photosynthesis and plant growth. Primary pollutants are directly emitted into the atmosphere and can cause harm to human health and the environment. Sulfur dioxide, carbon monoxide, and ammonia are all examples of primary pollutants.

308. Which one of the following pairs is wrongly matched?

• A. Yeast ­- Ethanol
• B. Streptomycetes ­- Antibiotic
• C. Coliforms ­- Vinegar
• D. Methanogens ­- Gobar gas

Explanation: Coliform bacteria are a commonly used bacterial indicator of the sanitary quality of foods and water. They are not involved in the production of vinegar.

309. Which one of the following pairs is not correctly matched?

• A. Streptomyces- Antibiotic
• B. Serratia-Drug addiction
• C. Spirulina Single-celll protein
• D. Rhizobium­-Biofertilizer

Explanation: Serratia marcescens is considered a harmful human pathogen that has been known to cause urinary tract infections, wound infections, and pneumonia. Serratia bacteria also have many antibiotic resistance properties which may become important if the incidence of Serratia infections dramatically increases.

310. One of the major difficulties in the biological control of insect pests is that

• A. The method is less effective as compared with the use of insecticides.
• B. The practical difficulty of introducing the predator to specific areas.
• C. The predator develops a preference to other diets and may itself become a pest.
• D. The predator does not always survive when transferred to a new environment.

Explanation: Insect enemies play an important role in nature for managing the phytophagous insect pests and keep a balance. It is just possible that predators of a particular plant pest are unable to get established and multiply in a particular environment. In such cases, the predators are reared in the laboratory and let off at a particular time when the pests are about to threaten the crops. And then this practice becomes expensive.