Free Man and His Environment MCQs with Answers

341. The relationship in which one organism gets benefit and the other is not affected is called

• A. Mutualism
• B. Commensalism
• C. Predation
• D. Parasitism

Explanation: The relationship in which one organism gets benefit and the other is not affected is called commensalism.

342. During successions, the first organisms that develop on bare rock are:

• A. Lichens
• B. Shrubs
• C. Moss
• D. Herbs

Explanation: Lichens: This option is the correct answer. Lichens are the first organisms that typically colonize and establish on bare rock during primary succession. Lichens are a symbiotic association between fungi and algae or cyanobacteria. They can tolerate extreme environmental conditions and play a vital role in breaking down rock surfaces, contributing to the formation of soil for other plants to establish.

343. The trophic level of a herbivore in a given food web is:

• A. 1
• B. 3
• C. 4
• D. 2

Explanation: D option is the correct answer. The trophic level of a herbivore is generally at the second level. Herbivores are primary consumers that directly feed on plants or algae, which occupy the first trophic level as primary producers. The energy flow in a food chain typically starts with primary producers, followed by herbivores at the second trophic level.

344. The organisms of the third trophic level are:

• A. Primary consumer
• B. Primary producer
• C. Tertiary consumer
• D. Secondary consumer

Explanation: Secondary consumers belong to trophic level three, they feed on primary consumers.

345. The ultimate source of energy in an ecosystem is

• A. Photosynthesis
• B. Sun
• C. Plants
• D. Water

Explanation: Sun is the ultimate source of energy because it is the source of most of the energies on Earth. It provides solar energy, it is responsible for photosynthesis in plants and also provides vitamin D to humans.

346. All the food chains and food webs begin with:

• A. Detritus
• B. Herbivores
• C. Green plants
• D. Omnivores

Explanation: The living part of the food chain always begins with plant life, as plants are the only organisms that get their energy from a nonliving source, Sun. We know that the Sun is the ultimate source of energy because it does not depend on anything else.

347. The change from bare rock or open area is rapid, especially in the initial stages and follows a series of recognizable and hence predictable stages. This process is called

• A. Pioneers
• B. Xerosere
• C. Succession
• D. Secondary succession

Explanation: A broad definition of succession states: 'Ecological succession is the process by which the mix of species and habitat in an area changes over time. Gradually, these communities replace one another until a "climax community" is reached.' (via news.uchicago.edu) This fits the description provided in the question hence it's the correct option.

348. How denitrification does occur in soils?

• A. Bacterial reduction of NO3- ions to N2 gas.
• B. Active uptake of Nitrate ions by plant roots
• C. Drainage of manure from fields
• D. Leaching of nitrate ions

Explanation: Denitrification is a natural soil microbial process where nitrate ions are converted to nitrogen gas which is then lost to the atmosphere. Denitrification occurs when soil bacteria use nitrate for their respiration in place of oxygen in the air.

349. What is the drawback of nuclear energy?

• A. It causes radiation pollution
• B. It is very expensive
• C. It is not long lasting
• D. It pollutes the air

Explanation: Explanation:One of the major drawbacks of nuclear energy is the risk of radiation pollution in the event of accidents, such as the Chernobyl and Fukushima disasters, which can have devastating impacts on the environment and human health.This option is not correct because while the initial cost of building nuclear power plants can be high, the cost of generating electricity from nuclear energy is relatively low.This option is also incorrect because nuclear energy can provide a long-lasting source of energy, as the fuel used in nuclear reactors can last for many years.This option is also incorrect because nuclear energy does not emit air pollutants such as carbon dioxide, sulfur dioxide, or nitrogen oxides, which are associated with air pollution.

350. _ are bioindicators of air pollution.

• A. Cyanobacteria
• B. Mycorrhizae
• C. Fungi
• D. Lichens

Explanation: Explanation:Correct answer is lichen as they are used as an bioindicator specifically for air pollution. Cyanobacteria are not typically used as bioindicators of air pollution, as they are more commonly found in aquatic environments such as lakes and oceans. Mycorrhizae are symbiotic associations between fungi and the roots of plants. While they can play a role in soil health, they are not typically used as bioindicators of air pollution. Fungi are important decomposers in the ecosystem, but they are not typically used as bioindicators of air pollution.