(a) Define air pollution. Explain the types, sources, consequences and control measures of air pollution. 20 (b) Define…

Air Pollution: Types, Sources, Consequences, and Control

The World Health Organization defines air pollution as the contamination of indoor or outdoor environments by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. Physically, air pollutants exist as particulate matter (PM₂.5, PM₁₀, soot) or gaseous pollutants (SO₂, NOₓ, CO). By origin, they are classified into primary pollutants, which are directly discharged into the atmosphere (e.g., SO₂, unburnt hydrocarbons), and secondary pollutants, which form through atmospheric chemical interactions (e.g., tropospheric ozone, peroxyacetyl nitrate in photochemical smog).

Sources are twofold. Natural sources comprise volcanic eruptions releasing sulfur compounds, forest fires emitting smoke, and aeolian dust storms. Anthropogenic sources include vehicular combustion emissions, fossil-fuel thermal power stations, metallurgical processing, chemical industries, and biomass burning such as agricultural stubble.

The consequences are systemic. In humans and animals, particulate and gaseous inhalation impairs alveolar gas exchange, leading to chronic obstructive pulmonary disease (COPD), asthma, and cardiovascular stress. Environmentally, the oxidation of atmospheric SO₂ and NOₓ produces sulfuric and nitric acids, precipitating as acid rain. Acid deposition alters freshwater and soil pH, leaches vital cationic nutrients (Ca²⁺, Mg²⁺), mobilizes toxic aluminum ions, and accelerates aquatic eutrophication. Concurrently, greenhouse gases (CO₂, CH₄) enhance radiative forcing, driving global warming and disrupted precipitation regimes.

Control measures require combined approaches:

• Legislative: Implementation of statutory frameworks like the Air (Prevention and Control of Pollution) Act, 1981, and vehicular transition to Bharat Stage VI (BS-VI) emission norms.
• Technological: Industrial installations of electrostatic precipitators (ESPs) and fabric filters to arrest fly ash; wet scrubbers to neutralize acidic gases like SO₂; and vehicular three-way catalytic converters to oxidize CO and hydrocarbons while reducing NOₓ.
• Biological: Establishing green belts around industrial corridors using tolerant plant species (Ficus religiosa, Azadirachta indica) that act as vegetative particulate sinks and bio-filters.

Pheromones and Alarm Spreading in Animals

Karlson and Lüscher (1959) defined pheromones as substances secreted to the outside by an individual and received by a second individual of the same species, in which they release a specific behavioral or developmental response. They differ from interspecific semiochemicals, namely allomones (which favor the emitter) and kairomones (which favor the receiver).

Alarm pheromones coordinate anti-predator defenses through a causal cascade: noxious stimuli or tissue injury induces immediate exocrine secretion; the chemical volatile disperses along a concentration gradient; it binds to chemoreceptors on the antennae or olfactory sensilla of conspecifics; and signal transduction triggers rapid neuro-motor reflex behaviors such as aggression, aggregation, or flight.

• Honeybees (Apis mellifera): Autotomy of the sting apparatus during defense releases isoamyl acetate and 2-heptanone, eliciting defensive flight and targeted recruitment of guard bees toward the intruder.
• Ants (Formica spp.): When alarmed, workers emit formic acid and undecane from their poison and Dufour's glands, triggering frantic running, jaw-gaping, and aggressive biting within the colony.
• Fishes (Superorder Ostariophysi): Mechanical injury to specialized epidermal club cells releases the alarm substance Schreckstoff (containing hypoxanthine-3-N-oxide). Olfactory detection by nearby shoal members induces rapid escape dives, schooling, or freezing at the benthic substrate.
• Aphids: Predation by ladybird beetles triggers the secretion of (E)-β-farnesene from the cornicles, causing surrounding colony members to release their stylets and drop off the host plant.

DNA Fingerprinting and Forensic Applications

Developed by Sir Alec Jeffreys (1984) and pioneered in India by Lalji Singh, DNA fingerprinting (profiling) identifies unique individual genetic configurations based on polymorphic, non-coding, highly variable tandemly repeated DNA sequences.

The standard molecular mechanism follows a definitive sequence:

1. Extraction: High-molecular-weight genomic DNA is isolated from biological trace evidence (blood, semen, hair follicles, epithelial buccal swabs).
2. Amplification and Cleavage: Extracted DNA is digested using restriction endonucleases targeting Variable Number of Tandem Repeats (VNTRs), or specific Short Tandem Repeats (STRs) are amplified via Multiplex Polymerase Chain Reaction (PCR).
3. Separation: The resulting fragments are resolved according to molecular size through polyacrylamide gel or automated capillary electrophoresis.
4. Blotting and Hybridization: In classical RFLP-VNTR analysis, fragments are transferred onto nitrocellulose membranes via Southern blotting and hybridized with radioactive or fluorescent locus-specific probes.
5. Detection: Autoradiography or laser-induced fluorescence generates a discrete pattern of bands (DNA profile) unique to the individual, except in monozygotic twins.

In forensic science, the technique provides decisive evidence across multiple domains:

• Criminal Identification: Matches biological evidence from crime scenes to suspects in violent crimes, as decisively demonstrated in the Nirbhaya case.
• Paternity and Kinship Disputes: Resolves parentage conflicts based on the Mendelian inheritance of half-maternal and half-paternal STR alleles.
• Exoneration: Secures the release of wrongfully convicted individuals through retrospective DNA testing of preserved evidence.
• Disaster Victim Identification (DVI): Facilitates the identification of severely degraded human remains in plane crashes, natural disasters, or mass casualties by matching STR profiles with reference family databases.
• Wildlife Forensics: Utilized by institutions such as the Wildlife Institute of India (WII) to trace poached tiger skins, elephant ivory, and venison to specific geographical populations, curbing illegal wildlife trafficking.

Integrated chemical ecology and molecular genetics thus provide essential mechanistic frameworks for wildlife conservation, ecological management, and forensic jurisprudence.