UGC NTA NET/JRF Exam, Environmental Sciences, September-2024

In a hydropower plant, the main factors that determine the power capacity are the flow rate of water and the available head (the vertical drop or potential energy difference). Flow rate (Q) signifies the volume of water passing through the turbines per unit time.

Head (H) denotes the pressure difference due to the height of water above the turbines. The power (P) is often represented by the simplified expression P = p × g × Q × H  × n, where p is density of water, g is gravitational acceleration, and n is the efficiency factor.

The length of the penstock, size of the reservoir, or the distance from the intake to the forebay do not directly fix the capacity in terms of maximum power output, although they can influence losses and energy availability.

The penstock length is relevant for friction losses, the reservoir size helps regulate flow availability over time, and the intake-forebay distance is an engineering or layout factor. However, none of these directly define the rated or maximum power capacity. Hence, (b) flow rate and (d) head are the key parameters.

Mechanical defense is best exemplified by the hedgehog, which uses its spines to protect against predators. Chemical defense is common in octopuses that release ink (a chemical deterrent) to confuse or repel predators.

Aposematic coloration involves bright or conspicuous coloration that warns predators of potential toxicity or unpalatability, as seen in the cinnabar moth. Cryptic coloration, or camouflage, allows animals to blend into their environment, a strategy observed in bushcrickets.

The listed pairs match these defensive strategies with their known examples: (a) mechanical defense → hedgehog (II), (b) chemical defense → octopus (I), (c) aposematic coloration → cinnabar moth (IV), (d) cryptic coloration → bushcrickets (III).

Parthenium hysterophorus, Chromolaena odorata, and Mikania micrantha all belong to the family Asteraceae (also known as the daisy or sunflower family). They are known invasive species that cause ecological and economic damage in many regions.

Salvinia molesta is an aquatic fern belonging to the family Salviniaceae, and Lantana camara is a member of the family Verbenaceae. Therefore, only (a) Parthenium hysterophorus, (b) Chromolaena odorata, and (c) Mikania micrantha are from Asteraceae.

From lower to higher moisture content, solid waste categories often follow a scale in which "trash" contains predominantly dry materials like old furniture, cardboard, and similar items.

"Rubbish" is also largely dry, though it can include some less-dry contents. "Refuse" is a more general category that can contain mixed wastes with somewhat higher moisture content.

"Garbage" is usually food or kitchen waste with a significantly higher water content. "Animal solids and organic  waste" typically exhibit the highest moisture content of the listed categories. Therefore, trash < rubbish < refuse < garbage < animal solids and organic waste translates to (b) < (a) < (d) < (c) < (e).

Acidification of lake water can lead to mobilization and release of toxic aluminum (Al³⁺) ions, which harm aquatic life.

Coniferous foliage tends to be more acidic and can produce runoff that is more acidic than the precipitation itself due to the chemical characteristics of the needles and associated organic acids.

Lakes with granitic bedrock offer minimal buffering capacity because granite lacks substantial amounts of alkaline minerals such as carbonates.

Deciduous foliage does not necessarily increase acidity, and thin and impermeable soils do not provide better buffering capacity. Thicker soils with neutralizing components would be more effective for buffering. Hence, (a), (c), and (d) are correct.

According to the India State of Forest Report (2021), the areas covered by different forest types in increasing order of geographical area are as follows:

(c) Scrub occupies the smallest area, approximately 2.8%.
(d) Tree Cover follows, covering around 3.0%.
(e) Very Dense Forest covers 3.0%.
(a) Moderately Dense Forest covers a larger area of about 9.38%.
(b) Open Forest has the largest area, covering around 9.26%.
So, the correct order is Scrub (c), Tree Cover (d), Very Dense Forest (e), Moderately Dense Forest (a), and Open Forest (b).

Geostrophic winds occur when the Coriolis force due to Earth's rotation balances the horizontal pressure gradient force. As a result, the wind flows parallel to isobars, which means it is oriented at a right angle to the direction of the pressure gradient.

This wind pattern is commonly observed at higher altitudes in the midlatitudes, where friction with the surface is negligible, allowing near-perfect geostrophic balance.

In the optical remote sensing bands, the wavelength range 0.52-0.62 µm (green region) is often used for assessing vegetation vigor, as healthy green vegetation is highly reflective in this band.

The 1.55-1.75 µm range (a Short-Wave Infrared band) is sensitive to moisture content in soils and vegetation. The thermal infrared region of 10.4-12.5 um is employed for thermal mapping, identifying heat patterns, and assessing surface temperatures.

The 2.08-2.35 um range (SWIR2) is valuable in discriminating mineral and rock types because many minerals show distinctive absorption features in that range.

Thus the correct pairing is: (a) 0.52-0.62 µm→ vegetation vigour (II), (b) 1.55-1.75 µm → soil moisture (III), (c) 10.4-12.5 µm → thermal mapping (IV), (d) 2.08-2.35 µm → mineral/rock (I).

Photochemical smog primarily forms from nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of strong sunlight and sufficiently high temperatures (above approximately 25°C).

When sunlight interacts with these precursor pollutants, a complex chain of photochemical reactions leads to the formation of groundlevel ozone and other oxidants that characterize photochemical smog.

Sulphur dioxide and water vapour are not the central ingredients for photochemical smog, making NOx and VOCs the key reactive species under high temperature.

Under India's National Action Plan on Climate Change (NAPCC), the Department of Science and Technology (DST) is responsible for coordinating two missions: (b) the National Mission for Sustaining the Himalayan Ecosystem and (d) the National Mission on Strategic Knowledge for Climate Change.

The mission on Enhanced Energy Efficiency is largely under the Bureau of Energy Efficiency (Ministry of Power), Sustainable Agriculture is under the Ministry of Agriculture, and Sustainable Habitat is overseen by the Ministry of Housing and Urban Affairs. Hence, only (b) and (d) fall under DST's purview.