UPSC Static Quiz – Environment : 13 March 2026

Solution: B

• Statement 1 is correct. High species diversity generally enhances ecosystem stability, resilience, and resistance to disturbances. Diverse communities possess multiple species performing similar ecological roles (functional redundancy). If one species declines due to disturbance, others can compensate, helping maintain ecosystem functioning. This concept is often linked with mature or climax ecosystems where complex interactions among species contribute to long-term stability.
• Statement 2 is incorrect. The description given actually refers to dominant species or foundation species, which influence community structure due to their abundance or biomass. Indicator species, in contrast, are species whose presence, absence, or abundance reflects specific environmental conditions, such as pollution levels, habitat quality, or climate change.
• Statement 3 is correct. Edge species are species that thrive in the ecotone (transition zone) between two ecological communities or biomes, such as the boundary between a forest and grassland. These zones often support higher diversity due to the edge effect, where species from both adjoining ecosystems coexist along with specialized edge-adapted species.

Solution: B

• Invasive species are a major driver of ecological disruption.
• Statement 1 is correct; this is known as the “Enemy Release Hypothesis.” In their native range, their population is kept in check by specific predators and diseases, but in a new habitat, they escape these homeostatic controls, allowing for exponential growth.
• Statement 2 is correct; invasive species do more than just compete for food. For instance, some invasive plants like Lantana can change the fire regime of a forest, while others can alter the nitrogen-fixing capacity of the soil, making it inhospitable for native flora.
• Statement 3 is incorrect; while the introduction of a new species technically increases the species count by one in the very short term, the long-term effect is usually a sharp decrease in species richness as the invasive species outcompetes and displaces numerous native species, often creating a “monoculture.” Invasive species management is particularly difficult because they often possess a wide range of tolerance for varied environmental conditions.

Solution: B

• Hibernation is a complex physiological state of metabolic slowdown. During this period, animals like bears rely on internal energy sources.
• Option (b) is the correct answer. Bears accumulate significant fat reserves before entering dormancy. While most of their energy comes from white fat, they possess specialized brown fat (brown adipose tissue) that is highly efficient at generating heat. When a bear wakes up intermittently—a process called arousal—the metabolism of this brown fat helps quickly raise the body temperature without the need for muscle shivering, which would consume too much energy.
• This mechanism is a vital survival strategy that allows the animal to maintain a minimum core temperature even in sub-zero environments. Unlike “true” hibernators who may stay dormant for months without waking, bears are “light” sleepers. Their ability to generate heat internally from stored fat is what allows them to survive food scarcity in winter. Disruptions to this cycle, such as climate change leading to warmer winters or lack of snow, can force the animal to exhaust these fat reserves too quickly, leading to starvation or increased foraging in human settlements.

Solution: D

Benzene is a natural part of crude oil and a known human carcinogen. Benzene exposure arises from both outdoor and indoor sources. Automobile exhaust and petrol filling stations are major ambient contributors due to fuel combustion and vapour release. Tobacco smoke is one of the largest indoor sources of benzene exposure. In addition, benzene is widely used as a solvent or chemical intermediate in producing varnishes, resins, plastics, and polyurethane foams. Off-gassing from varnished furniture, cushions, mattresses, insulation foams, and other polyurethane-based consumer products can release benzene or benzene-related volatile organic compounds into indoor air, particularly under heat, aging, or poor ventilation.

Solution: D

• Statement 1 is correct: Bioventing is an in-situ (on-site) technique that delivers oxygen to the unsaturated zone (above the water table) to help native soil bacteria break down pollutants like petroleum hydrocarbons.
• Statement 2 is correct: Biobarriers (or biowalls) are in-situ systems where a permeable trench is filled with microbes; as groundwater flows through, the microbes degrade the plume, allowing clean water to pass.
• Statement 3 is correct: Phytoremediation is the broad term for using plants (like sunflowers or poplars) to clean up soil or water; it includes processes like phytoextraction (taking up toxins like heavy metals into plant tissues) and phytostabilization (locking toxins in the roots).
• These biological methods are often preferred because they are cost-effective and environmentally friendly compared to traditional excavation.