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

Primary producers, such as green plants, capture only about 1% of the total incoming solar energy. In this problem, 1,000,000 J of sunlight is available. The 1% that is converted to net primary productivity (NPP) amounts to 1,000,000 × 0.01 = 10,000 J.

At each successive trophic level (primary consumer, secondary consumer, tertiary consumer), the ecological (trophic) efficiency is assumed to be 10%.

Thus, a primary consumer would receive 10% of 10,000 J = 1,000 J, a secondary consumer would get 10% of that = 100 J, and finally the tertiary consumer would receive 10% of 100 J = 10 J.

Destabilization of colloidal particles by neutralizing or reducing the repulsive forces among them is a fundamental step in water and wastewater treatment known as coagulation.

Chemical coagulants such as aluminum sulphate (alum) or ferric salts are added so that colloidal particles lose their surface charge and can then stick together. Once the particles are destabilized, gentle mixing or flocculation helps them form larger aggregates or flocs, which can then be removed by settling or other means.

The key word in the question is "destabilisation," which is distinct from flocculation: coagulation is the chemical charge-neutralization phase, while flocculation is the subsequent physical aggregation.

Various thermal structures of the atmosphere create characteristic plume behaviours:

(a) Inversion below and lapse (unstable or neutral) aloft → Lofting (II). A stable layer beneath the stack prevents the plume from moving downward, while the lapse region above allows the plume to rise and disperse upward.

(b) Strong lapse condition → Looping (III). Under highly unstable (super-adiabatic) conditions, the plume rises and sinks in oscillating loops due to strong vertical mixing.

(c) Lapse below and inversion above → Fumigation (I). The plume can move downward into the unstable air but is capped above by a stable inversion, forcing the pollutants downward.

(d) Weak lapse below and inversion aloft → Trapping (IV). In this scenario, the upper stable layer combines with a near-stable lower layer, and the plume remains confined in a thin vertical layer, effectively "trapping" the pollutants.

Elutriators separate particles from an air stream primarily by gravitational settling through a vertical chamber. The device slows down the flow enough that particles with sufficient terminal velocity will drop out of the gas stream.

Unlike electrostatic precipitators (which use electrostatic forces), bag houses (which use filtration), or super saturators (which involve condensation effects), elutriators exploit gravity as the main separating force. This principle relies on each particle's settling velocity, which depends on factors like size, shape, and density.

Different types of plastics have characteristic applications due to their physical and chemical properties.

(a) PETE (Polyethylene terephthalate) → Soft drink bottles (III). Because of PETE's clarity, strength, and gasbarrier properties, it is widely used in carbonated beverage containers.

(b) HDPE (High Density Polyethylene)→  Milk bottles (IV). Its high strength-todensity ratio and chemical resistance make it well-suited for milk jugs, detergent bottles, etc.

(c) PP (Polypropylene)→ Straw (I). Polypropylene has good rigidity, is relatively safe in contact with food/ beverages, and is easily moldable, making it common in straws and various caps.

(d) PS (Polystyrene) → Pharmaceutical bottles (II). Polystyrene can be used in certain rigid packaging applications, including some pharmaceutical or vitamin bottles and laboratory disposable ware.

In coalification (the progressive transformation of plant material to coal), the O/C atomic ratio generally decreases as one goes to more mature stages.

Wood and cellulose have high O/C ratios, while the macerals in coal (like huminite and vitrinite) show progressively lower O/C ratios as rank increases.

The question asks for the increasing order of O/C ratio, which means from smallest to largest. Among the listed materials: Vitrinite has the lowest O/C ratio, followed by huminite, then lignin, then wood, and finally cellulose has one of the highest O/С ratios.

So the sequence in ascending order is Vitrinite (a) < Huminite (b) < Lignin (c) < Wood (d) < Cellulose (e).

When two closely related species (such as Geospiza fuliginosa and Geospiza fortis) occur in allopatric populations (separate geographic locations), their beak depths are quite similar.

However, in sympatric populations (where they cooccur), competition for food resources can drive evolutionary divergence in beak morphology—a phenomenon called character displacement.

It is an adaptation that reduces niche overlap and direct competition by favouring individuals that exploit different food types or feeding strategies. This allows both species to coexist by minimizing direct resource competition.