UPSC Static Quiz – Environment : 4 May 2026

Solution: C

Many benthic species are crucial to the marine ecosystem. They filter the water and keep seas, rivers and lakes clean by eating dead organisms. Some species are an important food source for other creatures or are harvested by humans. Benthics like soft corals, seaweed and seagrasses provide some of the main ocean habitats.

Solution: B

Statement 3 is incorrect.

Kelps cover 25 percent of the world’s coastlines and provide food and shelter for fish, invertebrates and marine mammal species. They also offer crucial services such as carbon sequestration and erosion control, according to scientists.

But kelps are increasingly threatened by climate change, eutrophication and shoreline development, among other human-induced stressors.

One such threat is from bryozoa, moss animals that grow as mats on kelps. They drive the seaweed to sink into the seafloor and disintegrate.

The outbreak can be linked to high temperatures. For example, in 2015, researchers observed an expansive outbreak of bryozoa. These observations coincided with ‘the blob’, a marine heat wave that emerged across the northeast Pacific Ocean, according to a report.

Dense kelp beds in warmer and less wave-exposed sites are more susceptible to bryozoan outbreaks.

Seaweeds are farmed as they have industrial applications. They can be harvested to extract biostimulants for plant growth. They also can help in long-term carbon sequestration and regeneration of ocean habitats.

Solution: B

Statement 3 is incorrect.

Phytoplankton are photosynthesizing microscopic biotic organisms that inhabit the upper sunlit layer of almost all oceans and bodies of fresh water on Earth. They are agents for “primary production”, the creation of organic compounds from carbon dioxide dissolved in the water, a process that sustains the aquatic food web.

Phytoplankton are crucially dependent on minerals. These are primarily macronutrients such as nitrate, phosphate or silicic acid, whose availability is governed by the balance between the so-called biological pump and upwelling of deep, nutrient-rich waters.

Phytoplankton depend on B Vitamins for survival.

They are found in all water systems, including marine or brackish or fresh.

Solution: B

Option 2 and 4 is correct.

Everything that surrounds or affects an organism during its life time is collectively known as its environment which comprises both living (biotic) and non-living (abiotic) components. The environment is not static. Both biotic and abiotic factors are in a flux and keep changing continuously.

Solution: A

Statement 1 is incorrect.

Energy pyramids represent energy flow through trophic levels. An energy pyramid usually shows rates of energy flow through trophic levels, not absolute amounts of energy stored.

Energy pyramids are always upright (biomass pyramids can be inverted), that is, narrower at each successive level (unless organisms enter the ecosystem from elsewhere). This pattern reflects the laws of thermodynamics, which tell us that new energy can’t be created, and that some must be converted to a not-useful form (heat) in each transfer.