Question 1

Which of the following is an example of a renewable energy source that does not produce greenhouse gas emissions?

Accepted Answer

Renewable energy sources like solar, wind, hydroelectric, and geothermal power generate electricity without burning fossil fuels and thus produce minimal to zero greenhouse gas emissions during operation.

Question 2

Which of the following is the primary greenhouse gas responsible for climate change, contributing approximately 75% of global warming?

Accepted Answer

Carbon dioxide (CO₂) is the most significant anthropogenic greenhouse gas, accounting for roughly 75% of radiative forcing from long-lived greenhouse gases. It is released primarily through fossil fuel combustion, deforestation, and industrial processes.

Question 3

The process by which plants convert sunlight into chemical energy stored in glucose is called:

Accepted Answer

Photosynthesis is the biochemical process in which chlorophyll-containing plants, algae, and some bacteria use light energy to synthesize organic compounds (glucose) from carbon dioxide and water, releasing oxygen as a byproduct.

Question 4

Which of the following is a biodegradable pollutant that can be naturally decomposed by microorganisms?

Accepted Answer

Biodegradable pollutants are organic substances that can be broken down by natural biological processes (bacterial decomposition) within a reasonable timeframe. Examples include food waste, paper, and sewage.

Question 5

The layer of the atmosphere closest to Earth's surface, where weather occurs and most living organisms exist, is called:

Accepted Answer

The troposphere is the lowest layer of Earth's atmosphere, extending approximately 8–18 km above the surface (lower at poles, higher at equator). It contains 80% of atmospheric mass and is where weather, clouds, and precipitation occur.

Question 6

Which of the following is the primary greenhouse gas responsible for climate change, and what is its approximate concentration in the Earth's atmosphere as of 2024?

Accepted Answer

Carbon dioxide (CO₂) is the primary anthropogenic greenhouse gas driving climate change. As of 2024, atmospheric CO₂ concentration has exceeded 420 ppm (parts per million), having risen from pre-industrial levels of ~280 ppm. This increase is primarily due to fossil fuel combustion, deforestation, and industrial processes. CO₂ remains in the atmosphere for centuries, making it the most significant long-term climate forcing agent.

Question 7

Which of the following processes describes the conversion of ammonia (NH₃) to nitrate (NO₃⁻) by bacteria in the soil?

Accepted Answer

Nitrification is the process by which ammonia (NH₃) is oxidized to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by nitrifying bacteria such as Nitrosomonas and Nitrobacter. This is a crucial step in the nitrogen cycle, making nitrogen available to plants.

Question 8

Which of the following gases is primarily responsible for the depletion of the ozone layer in the Earth's stratosphere?

Accepted Answer

Chlorofluorocarbons (CFCs) are the primary cause of ozone layer depletion. When CFCs reach the stratosphere, UV radiation breaks them down, releasing chlorine atoms that catalytically destroy ozone molecules. One chlorine atom can destroy up to 100,000 ozone molecules.

Question 9

Which of the following is the primary source of nitrogen fixation in terrestrial ecosystems?

Accepted Answer

Nitrogen-fixing bacteria, particularly those in the genus Rhizobium (which form symbiotic relationships with legume plants), are the primary source of nitrogen fixation in terrestrial ecosystems. These bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), making it available to plants.

Question 10

Which of the following biomes is characterized by permafrost, low precipitation, and sparse vegetation such as lichens and mosses?

Accepted Answer

The tundra biome is characterized by permafrost (permanently frozen ground), extremely low temperatures, low precipitation (100-250 mm annually), and sparse vegetation dominated by lichens, mosses, and dwarf shrubs. It is found in Arctic and subarctic regions.

Question 11

Which of the following is the primary cause of eutrophication in freshwater bodies?

Accepted Answer

Eutrophication is primarily caused by excessive nutrient input, particularly nitrogen and phosphorus, from agricultural runoff, sewage, and detergents. These nutrients promote algal blooms, which deplete oxygen and create dead zones, harming aquatic life.

Question 12

Which of the following is the primary greenhouse gas responsible for the majority of anthropogenic climate change, and what is its atmospheric concentration (in ppm) as of 2024?

Accepted Answer

Carbon dioxide (CO₂) is the most significant anthropogenic greenhouse gas, accounting for approximately 75% of radiative forcing from long-lived greenhouse gases. As of 2024, atmospheric CO₂ concentration has exceeded 420 ppm (measured at Mauna Loa Observatory), up from ~280 ppm in pre-industrial times.

Question 13

The Montreal Protocol (1987) successfully addressed the depletion of which atmospheric layer, and which chemical compound was primarily responsible for this damage?

Accepted Answer

The Montreal Protocol targeted ozone (O₃) depletion in the stratosphere. Chlorofluorocarbons (CFCs), particularly CFC-11 and CFC-12, were the primary culprits. One chlorine atom from a CFC molecule can destroy ~100,000 ozone molecules. The protocol phased out CFCs and related halons, leading to measurable ozone recovery since the 2000s.

Question 14

In the context of ecosystem succession, which of the following best describes the difference between primary and secondary succession, and what is the key limiting factor in primary succession?

Accepted Answer

Primary succession occurs on bare, lifeless substrate (e.g., volcanic rock, glacial moraines) with no pre-existing soil or seed bank. Secondary succession occurs on disturbed land with existing soil and seed sources (e.g., after forest fire or abandonment of farmland). The key limiting factor in primary succession is soil formation—pioneer species (lichens, mosses) must first colonize rock and begin weathering to create soil.

Question 15

Which of the following biogeochemical cycles is primarily driven by bacterial processes, and which bacteria are responsible for converting atmospheric nitrogen (N₂) into ammonia (NH₃)?

Accepted Answer

The nitrogen cycle is primarily driven by bacteria. Nitrogen-fixing bacteria (e.g., Rhizobium, Azotobacter, Nostoc) convert atmospheric N₂ into ammonia (NH₃) through the enzyme nitrogenase. This is the critical first step because most organisms cannot directly utilize atmospheric N₂. Nitrifying bacteria then oxidize ammonia to nitrite and nitrate, which plants can absorb.

Question 16

Which of the following statements correctly describes the relationship between biodiversity and ecosystem stability, and what is the primary mechanism by which high biodiversity increases ecosystem resilience?

Accepted Answer

High biodiversity increases ecosystem resilience through functional redundancy and niche complementarity. Functional redundancy means multiple species perform similar ecological functions; if one species is lost, others can compensate. Niche complementarity means different species utilize different resources, reducing competition and increasing overall productivity. Ecosystems with high biodiversity recover faster from disturbances (resilience) and maintain more stable productivity (stability).

Question 17

Which of the following biogeochemical cycles is primarily driven by bacterial denitrification in anaerobic soil conditions?

Accepted Answer

Denitrification is a microbial process where nitrate (NO₃⁻) is reduced to nitrogen gas (N₂) and released into the atmosphere. This occurs in anaerobic (oxygen-poor) environments such as waterlogged soils, sediments, and the deep ocean. Denitrifying bacteria like Pseudomonas and Bacillus carry out this process as part of the nitrogen cycle. This is a critical mechanism for returning nitrogen to the atmosphere and completing the nitrogen cycle.

SSC MTS Environment & Ecology

Environment & Ecology— Rules & Concept

Key Points to Remember

Exam-Specific Tips

Environment & Ecology — Practice Questions

60-Second Revision — Environment & Ecology