Day-633 | Daily MCQs | UPSC Prelims | ENVIRONMENT AND ECOLOGY

Answer: C
Explanation: Options 1, 2 and 3 are correct.
Bioindicators include biological processes, species, or communities and are used to assess the quality of the environment and how it changes over time. The lichens, earthworms, penguins, mosses and dragonfly have been noted to serve as bioindicators of mercury contamination in the environment.
Earthworms (E. foetida) are capable of accumulating Hg from solutions and soils, and this potential increases markedly in the presence of organic acids. In addition, evidence suggests that earthworms may be converting mercury associated with organic acids to its highly toxic, readily bioavailable form, methylmercury, in the intestinal tract.
Mercury is poisonous in all forms – inorganic, organic or elemental. Methyl mercury is a neurotoxicant: it can damage the developing brain as it crosses the placental and blood-brain barriers easily. The threat to the unborn is, therefore, of particular concern. It can also trigger depression and suicidal tendencies, paralysis, kidney failure, Alzheimer’s disease, speech and vision impairment, allergies, hypospermia and impotence. Even miniscule increases in methyl mercury exposures may adversely affect the cardiovascular system. It is also a possible carcinogen for humans.

Answer: C
Explanation: The carbonate compensation depth (CCD) is the particular depth level in the oceans where the rate of supply of calcium carbonate to the seafloor is balanced by the rate of dissolution. Carbonate particles cannot accumulate in the sediments where the seafloor is below this depth.
Statement 1 is correct: The aragonite compensation depth (ACD) is the compensation depth for aragonitic carbonates. Since aragonite is more soluble than calcite, the aragonite compensation depth is generally shallower than both the calcite compensation depth and the carbonate compensation depth (CCD).

Statement 2 is correct: Increasing atmospheric concentration of CO2 from combustion of fossil fuels are causing the CCD to rise, with zones of downwelling first being affected. Ocean acidification, which is also caused by increasing carbon dioxide concentrations in the atmosphere, will increase such dissolution and shallow the carbonate compensation depth on timescales of tens to hundreds of years.
The Global Ocean Modelling suggests that the CCD has already risen by nearly 100 m on average since pre-industrial times and will likely rise further by several hundred meters more this century.

Answer: A
Explanation:
Statements I and II are correct. Statement II explains statement I: Commonly known as bush crickets, the katydids mimic leaves and adopt leaf-like shapes, colours, and patterns to avoid detection by predators such as monkeys and bats. By blending in with their surroundings (using camouflage as their behavioural strategy), they enhance their chances of survival.
They are found in abundance in humid tropical areas. They belong to the family of insects called Tettigoniidae.

Answer: B
Explanation: A recent study has said a climate intervention strategy focused on decreasing water vapor (WV) concentrations near the tropopause and in the stratosphere could potentially cool down the rapidly heating up Earth. According to a study published in Science Advances, researchers at the National Oceanic and Atmospheric Administration (NOAA) and NASA plan to inject ice high up in the air so that water vapour in the upper atmosphere would get a bit drier and that could counteract a small amount of the human-caused warmth.
Notably, Water Vapour is a potent player in the Earth’s greenhouse effect that eventually leads to the increase in the planet’s surface temperature. Water vapour amplifies the warming of Earth’s surface caused by other greenhouse gases like carbon dioxide (CO2) and methane.
Water vapour is generated when the amount of methane and CO2 go up in the atmosphere, which leads to increased evaporation. Since warmer air holds more moisture, its concentration of water vapour increases. Specifically, this happens because water vapour does not condense and precipitate out of the atmosphere as easily at higher temperatures.
The climate scientists plan to send high-tech planes to inject ice particles about 11 miles (17 kilometres) high, just below the stratosphere, where the air slowly rises. Then the ice and cold air rise to where it’s coldest and get the water vapour to turn to ice and fall, dehydrating the stratosphere. It is being experimented as a geoengineering technique to counteract global warming due to excessive concentration of water vapour (a potent GHG).

Answer: C
Explanation: A keystone species is an organism that helps define an entire ecosystem. If the keystone species were to disappear from the ecosystem, no other species would be able to fill its environmental role. The ecosystem would be forced to radically change, allowing new and possibly invasive species to take over the habitat. Any organism, from plants to fungi, may be a keystone species. They are not always the largest or most abundant species in an ecosystem. However, almost all examples of keystone species are animals that have a huge influence on food webs.
The degrading status of the population of predators such as tigers from the ecosystem will have direct consequences on the stability of the whole forest ecosystem. The extinction of tigers will cause an increase in the population of deer. Overgrazing by deer will bring down the diversity and density of plant species. Ultimately, a number of plant-dependent species of birds and other animals will also suffer with the rise in invasive species.