Free Man and His Environment MCQs with Answers

281. What does MAB stand for?

• A. Mammals and biosphere
• B. Mammals and biology programme
• C. Man and biology programme
• D. Man and biosphere programme.

Explanation: The man and biosphere programme is an international biological programme of UNESCO (United Nations Educational Scientific and Cultural Organisation) which was started in 1971. MAB has studied the human environment, the impact of human interference and pollution on biotic and abiotic environments and conservation strategies for the present as well as the future.

282. Phosphate pollution is caused by:

• A. Sewage and phosphate rock.
• B. Sewage and agricultural fertilizers.
• C. Phosphate rock only.
• D. Agricultural fertilizers only.

Explanation: Phosphate pollution is indeed primarily caused by the release of phosphates into the environment from various sources, with sewage and agricultural fertilizers being two significant contributors. Phosphate is an important compound of fertilizers that are added to crop fields and then are passed down to water bodies during rains through run off. It is also present in sewage that is dumped into the water body. This can bring about the dense growth of water plants especially the algae and cause an algal bloom. This algal bloom leads to oxygen depletion in water bodies and causes death of aquatic life.

283. If we uncover half of the forests covering the earth, which crisis will come about first?

• A. Some species will be extinct
• B. Population and ecological imbalance will rise up
• C. Energy crisis will occur
• D. The remaining forests will maintain this imbalance.

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.

284. The toxic effect of carbon monoxide is due to its greater affinity for haemoglobin as compared to oxygen approximately by:

• A. 200 times
• B. 1000 times
• C. 2 times
• D. 20 times

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 hemoglobin as compared to oxygen. Carbon monoxide combines with hemoglobin of blood and forms a stable compound called carboxyhemoglobin. At 50 ppm, CO converts 7.5% of hemoglobin into carboxy­ hemoglobin within 8 hours. It impairs oxygen transport resulting in headache, decreased vision, cardiovascular malfunction and asphyxial.

285. Which of the following isotopes is most dangerous to Homo sapiens?

• A. Phosphorus­-32
• B. Strontium-­90
• C. Cesium­-137
• D. Iodine-­131

Explanation: Strontium-90 (Sr-90) is a radioactive isotope of strontium, and it is indeed considered dangerous due to its potential health risks associated with exposure to ionizing radiation. One of the main concerns with strontium-90 is its chemical similarity to calcium. When released into the environment, strontium-90 can be absorbed by living organisms, particularly in the form of strontium ions, which can replace calcium ions in bones. As a result, it tends to accumulate in bone tissues, where it can irradiate the bone marrow and cause damage to blood-forming cells.

286. A dental disease characterized by mottling of teeth is due to the presence of which chemical element in drinking water?

• A. Fluorine
• B. Boron
• C. Mercury
• D. Chlorine

Explanation: The dental disease characterized by mottling of teeth is known as "dental fluorosis." It is caused by the excessive presence of the chemical element "fluoride" in drinking water. Dental fluorosis is a cosmetic condition that affects the appearance of teeth, leading to white or brown spots, streaks, or pitting on the tooth enamel. It occurs when individuals are exposed to high levels of fluoride during the development of their teeth, typically in childhood. The condition is most often associated with the consumption of water with elevated natural fluoride levels or the use of excessive fluoride-containing dental products.

287. Which of the following is the main factor of desertification?

• A. Over­-grazing
• B. Tourism
• C. Irrigated agriculture
• D. All of these

Explanation: Desertification means a process of spread of desert that occurs due to degradation of environment, cutting of trees, soil erosion etc. It can be natural or man made. The main causes for desertification are overcultivation of poor soils, overgrazing by animals, excessive cutting of fuelwood and inappropriate irrigation practises resulting in salinization. Among them overgrazing is the most important factor as it causes maximum effect.

288. Which among the following is likely to have the highest levels of D.D.T. depositions in its body?

• A. Sea gull
• B. Phytoplankton
• C. Eel
• D. Crab

Explanation: DDT is non-­biodegradable and is not metabolized within the body of an organism rather it accumulates in the fat tissues therefore its concentration goes on increasing from one trophic level to another of a food chain, highest amount being present in top consumer i.e., it shows biomagnification. In an aquatic food chain seagull is the top carnivore therefore will possess highest concentration of DDT.

289. Sounds above what level are considered hazardous noise pollution?

• A. Above 80 dB
• B. Above 30 dB
• C. 50 dB
• D. 20 dB

Explanation: The level at which sounds are considered hazardous noise pollution depends on both the intensity of the sound and the duration of exposure. Sound intensity is typically measured in decibels (dB). Prolonged exposure to sound levels of 85 decibels or above can potentially lead to hearing damage over time. Noise level is expressed on a logarithmic scale of decibels. The baseline noise levels in the community vary around 40 dB. International standards prescribe a maximum of 50 dB for day and 40 dB for night time in a residential area. Noise over 115 dB is regarded as highly avoidable. The World Health Organization (WHO) recommends an industrial noise limit of 75 dB.

290. Ultraviolet radiations from sunlight causes a reaction that produces:

• A. Fluorides
• B. Carbon monoxide
• C. Sulphur dioxide
• D. Ozone

Explanation: Ozone is generated in the lower atmosphere during the formation of photochemical smog when nitrogen dioxide splits to produce reactive oxygen atoms which combine with molecular oxygen. Oxygen molecules split under ultraviolet radiations to produce oxygen atoms which combine with molecular oxygen to form ozone. It is this gas which forms the protective ozone umbrella in the stratosphere and shield life from biocidal high energy radiations. It can also damage DNA molecules and cause carcinogenesis.