UPSC Static Quiz – Environment : 9 April 2026

Solution: B

• Oceanic productivity is the foundation of the marine food web.
• Statement 1 is correct; while rainforests are often called the “lungs of the planet,” phytoplankton in the oceans produce an equivalent, if not greater, share of global oxygen through photosynthesis.
• Statement 2 is incorrect because equatorial open oceans are often “biological deserts.” This is due to thermal stratification, where warm surface water creates a barrier (thermocline) that prevents nutrients from deeper layers from mixing upward. In contrast, polar regions can be highly productive during summer blooms when light is abundant.

Statement 3 is correct; upwelling occurs when winds push surface water away, allowing cold, nutrient-dense water from the deep to rise. This fuels the growth of phytoplankton, supporting massive fisheries in regions like the coast of Peru or the Arabian Sea. Understanding these oceanic mechanisms is essential for global carbon budget modeling.

Solution: C

• Statement I is correct; acidification is a major global threat to marine calcifiers.
• Statement II provides the correct chemical explanation; CO2 reacts with seawater to form carbonic acid, which reduces the availability of carbonate ions needed for coral skeletons.

However, Statement III is incorrect; ocean acidification is caused by the absorption of atmospheric CO2 (from fossil fuel combustion), not by terrestrial fertilizer runoff. While runoff causes “eutrophication” (algal blooms), it is not the primary driver of global ocean pH reduction.

Solution: C

• Echolocation, also known as biosonar, is a biological sensory system used by several animals to perceive their environment.
• Statement (c) is correct because echolocation involves an animal emitting high-frequency sound calls and then listening to and analyzing the echoes that return from various objects in the environment. This allows the animal to locate, range, and identify obstacles, prey, or other features even in total darkness.
• While most commonly associated with bats and toothed whales (dolphins), it is also used by some small mammals like shrews and tenrecs, and nocturnal birds such as the oilbird and certain cave-dwelling swiftlets.

The animal measures the time delay between the sound emission and the returning echo to calculate the distance to an object. This capability is particularly vital for animals that live or hunt in environments where vision is limited, such as dark caves, murky waters, or deep forests. Echolocation provides a “sound picture” that helps these animals navigate and forage with high precision.

Solution: B

• Statement 1 is correct. Ecological Dominance occurs when certain species have a disproportionate influence on the community due to their biomass, numbers, or functional role.
• Statement 2 is incorrect. Diurnal fluctuations refer to changes that occur within a 24-hour cycle (day and night), such as the shifting activity of diurnal (daytime) and nocturnal (nighttime) animals. Seasonal changes that occur over the course of a year are related to Periodicity.

Statement 3 is correct. An ecological community is not just a collection of species; it is an organized unit where organisms are interlinked through various biological interactions. These include positive interactions like mutualism, negative ones like competition and predation, and others like parasitism. These interactions provide the community its distinct structure and functional stability.

Solution: C

• Statement 1 is correct. Coral reefs are physical barriers that break the energy of incoming waves. When reefs die and erode, coastal areas become far more vulnerable to erosion and destruction from cyclones and tsunamis.
• Statement 2 is correct. While often overshadowed by forests, reefs play a role in the carbon cycle. They utilize calcium carbonate to build their skeletons. When reefs degrade, this process is disrupted, and the “feedback loop” can affect the ocean’s ability to regulate CO2 levels.
• Statement 3 is correct. Reefs are the “rainforests of the sea.” Although they cover less than 1% of the ocean floor, they are home to a quarter of all marine life. Their collapse triggers a domino effect through the food chain.
• Statement 4 is incorrect. The loss of color is not just aesthetic. Many marine species rely on the complex structures and specific visual cues of a healthy reef for camouflage, mating, and protection. When a reef bleaches and is eventually covered in turf algae, the entire habitat architecture changes, disrupting the breeding and survival of countless species.