DHR - BRET PYQs Sept 2021

Immunology & Environmental Toxicology

Which one of the following is a mammal?

Whales are fully aquatic mammals within order Cetacea, warm-blooded, viviparous, lactating with mammary glands, breathing air via lungs and blowhole. In contrast sharks, trout, salmon are fishes, poikilothermic, oviparous, respiring through gills, lacking mammalian characteristics entirely.

Ref: Campbell Biology, 11th Edition, Chapter 34, Vertebrates; also Pough et al., Vertebrate Life, Chapter 10, Mammals discusses marine mammals like whales versus fishes such as sharks trout salmon, mammalian traits versus piscine features, published by Pearson Education.

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Immunology & Environmental Toxicology

Which of the animals are referred to as solipeds?

Solipeds, also called solidungulates, refer to equids possessing single hoofed digit per limb as adaptation for running. Horse, donkey, zebra belong to this group. Dogs are digitigrade, cattle are artiodactyl cloven-hoofed, poultry possess scaly feet, none are solipeds.

Ref: Banerjee, Textbook of Animal Husbandry, 8th Edition, Chapter 9, Equine Husbandry and Getty, Sisson and Grossman's Anatomy of Domestic Animals, Volume 1 discusses solipeds solidungula classification, single-hoofed equids like horse versus ruminants and carnivores, published by Oxford IBH.

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Immunology & Environmental Toxicology

The practice of painless killing of laboratory animal to relieve pain after experimentation is called:

Euthanasia literally means good death, employing humane, painless methods such as anesthetic overdose after experimentation to avoid suffering. CPCSEA guidelines mandate approved euthanasia methods. Dissection is anatomical study, post mortem and autopsy are examinations after death, not methods of killing.

Ref: Committee for Purpose of Control and Supervision of Experiments on Animals CPCSEA Guidelines; also Sikes et al., Guidelines of American Society of Mammalogists, Chapter on Laboratory Animal Care covering euthanasia versus dissection, necropsy, autopsy definitions, published by ILAR Journal and Government of India.

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Immunology & Environmental Toxicology

Which of the following insect can be used for production of formic acid?

Red wood ants, Formica rufa group, possess abdominal formic acid glands spraying 20-60% formic acid for defense. Historically distilled from crushed ants. Bed bugs, crickets, locusts do not produce substantial formic acid; hence red ants are the commercial and traditional source.

Ref: Hölldobler and Wilson, The Ants, Chapter 7, Chemical Communication and Defense; discusses formic acid production in Formicinae ants, especially Formica and Oecophylla red ants, defensive secretion, published by Harvard University Press Belknap Press.

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Immunology & Environmental Toxicology

Natural insecticide obtained from Neem tree is:

Azadirachtin, tetranortriterpenoid limonoid from Azadirachta indica neem seeds, acts as antifeedant, growth disruptor and repellent against many pests. Nicotine derives from tobacco, ecdysone is insect molting hormone, malathion synthetic organophosphate, not neem-derived insecticides.

Ref: Isman, Annual Review of Entomology and Schmutterer, The Neem Tree: Source of Unique Natural Products for Integrated Pest Management, Chapter 3, Azadirachtin chemistry; also Taiz Plant Physiology discusses neem limonoids as natural insecticides, published by Wiley-VCH.

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Immunology & Environmental Toxicology

Which plant part is modified into pitcher in pitcher plant?

In Nepenthes pitcher plants, lamina of leaf is modified into jug-shaped pitcher with lid formed from leaf apex for trapping insects. Digestive enzymes inside supplement nitrogen in nutrient-poor soils. Root, stem, flower lack such carnivorous adaptation; leaf modification underlies carnivory.

Ref: Raven, Evert, Eichhorn, Biology of Plants, 8th Edition, Chapter 32, Modified Leaves and Carnivorous Plants discusses Nepenthes pitcher leaf modification, insectivorous adaptation to nitrogen-poor habitats, versus stem or root modifications, published by W.H. Freeman.

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Immunology & Environmental Toxicology

Induction of cell division activity and delay in senescence is caused by:

Cytokinins, N6-substituted adenine derivatives, promote cytokinesis, cell division in shoot and root meristems, and inhibit chlorophyll degradation delaying leaf senescence. Gibberellins drive stem elongation, auxins mediate apical dominance, ethylene promotes senescence and abscission, opposite to cytokinin action.

Ref: Taiz, Zeiger, Møller, Murphy, Plant Physiology and Development, 6th Edition, Chapter 21, Cytokinins chapter discusses cell division induction, Richmond-Lang effect delaying senescence, difference from gibberellin, auxin and ethylene roles, published by Sinauer Associates Oxford University Press.

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Immunology & Environmental Toxicology

Which of the following best describes a pattern of idealized population growth that is restricted by limiting factors?

Logistic growth incorporates carrying capacity K, showing sigmoid curve where per capita growth declines as population nears K due to resource limitation, competition. Exponential model assumes unlimited resources, unrealistic long term. Thus logistic best describes density-dependent growth constrained by environmental limits.

Ref: Bowler, Begon et al., Ecology: From Individuals to Ecosystems, 4th Edition, Chapter 5, Population Ecology explains logistic growth model, carrying capacity, density-dependent regulation versus exponential growth model under ideal conditions, published by Wiley-Blackwell.

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Immunology & Environmental Toxicology

A host plant produces a toxin that is lethal to aphids feeding on its leaves. Over time, some of the aphids become immun

Reciprocal evolutionary pressure where plant evolves novel defensive toxins and herbivore evolves resistance exemplifies coevolution. Aphids developing immunity selecting for new plant toxins represents antagonistic coevolutionary arms race, not parasitism alone, mutualism cooperation, or commensalism where one partner remains unaffected.

Ref: Futuyma, Evolution, 3rd Edition, Chapter 11, Coevolution; also Thompson, The Geographic Mosaic of Coevolution discusses plant-herbivore chemical arms races, reciprocal selection, antagonistic coevolution illustrated by toxins and resistance, published by Sinauer Associates and University of Chicago Press.

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Immunology & Environmental Toxicology

Itai-Itai disease is associated with which metal poisoning?

Itai-Itai disease, first reported in Toyama Japan, results from chronic cadmium exposure contaminating rice via mining effluents. Cadmium accumulates in kidneys causing proximal tubular dysfunction, calcium loss, osteomalacia and severe bone pain. Silver, mercury, palladium cause different toxi-syndromes.

Ref: Klaassen, Casarett and Doull's Toxicology: The Basic Science of Poisons, 9th Edition, Chapter 23, Toxic Effects of Metals discusses cadmium-induced Itai-Itai disease, renal osteomalacia in Japan, contrasted with mercury Minamata disease, published by McGraw-Hill Education.

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Immunology & Environmental Toxicology

Which of the following is a secondary air pollutant?

Secondary pollutants form in atmosphere via chemical reactions of primary emissions. Tropospheric ozone arises from photochemical oxidation of NOx and VOCs under sunlight, not directly emitted. Sulphur dioxide, carbon monoxide, nitrogen dioxide are primary pollutants released directly from combustion sources.

Ref: Seinfeld and Pandis, Atmospheric Chemistry and Physics, 3rd Edition, Chapter 6, Photochemical Smog and Secondary Pollutants explains tropospheric ozone formation from NOx-VOCs versus primary gases SO2, CO, published by Wiley-Interscience.

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Immunology & Environmental Toxicology

Which of the following is most commonly applied in automobile exhaust system?

Catalytic converters contain platinum, palladium, rhodium catalysts converting CO, hydrocarbons, NOx into CO2, nitrogen, water vapor, substantially reducing vehicular emissions. Wet/dry scrubbers and electrostatic precipitators serve industrial stack gas cleaning, not mobile exhaust systems, hence unsuitable for automobiles.

Ref: Cooper and Alley, Air Pollution Control: A Design Approach, 4th Edition, Chapter 13, Mobile Source Control; and Masters and Ela Environmental Engineering discuss catalytic converter chemistry for automobile exhaust treatment versus industrial scrubbers and ESPs, published by Waveland Press.

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