UKPSC Biology: Biological Classification, Monera, Fungi & Plant Diversity (Solved PYQs & Notes)

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1 UKPSC Biology (Unit 4): Biological Classification, Monera, Fungi & Plant Diversity

1.1 1.High-Yield Micro-Notes

1.2 2. Important facts you should know:

1.3 3. Master Questions

1.4 Contact Oracle IAS:

1.4.1 Call/WhatsApp 9997453844 for details

1.4.2 Join Our Preparation program:

UKPSC Biology (Unit 4): Biological Classification, Monera, Fungi & Plant Diversity

Part of the UKPSC General Science & Technology Revision Series.

1.High-Yield Micro-Notes

Taxonomic Systems & Plant Phylogeny: Plant classification systems are categorized by taxonomic philosophy: Artificial (Carolus Linnaeus, based on superficial floral traits like stamen count in Systema Naturae), Natural (George Bentham and Joseph Dalton Hooker, detailed in Genera Plantarum, emphasizing overall morphological and natural structural affinities), and Phylogenetic (Engler & Prantl; John Hutchinson, based on evolutionary ancestry). Bryophytes (mosses, liverworts) lack vascular tissues and are termed “amphibians of the plant kingdom” because while they grow on terrestrial damp substrate, their flagellated antherozoids require ambient liquid water for fertilization.
Zoological Misnomers & Arthropod Biology: Fireflies belong to class Insecta (order Coleoptera, family Lampyridae), emitting light through bioluminescence (enzymatic oxidation of luciferin catalyzed by luciferase in the presence of ATP and Mg²⁺). Termites (order Blattodea / Isoptera) are colloquially termed “white ants”, though they are phylogenetically distinct from true ants (order Hymenoptera). Termites feed on woody cellulose and rely on symbiotic gut flagellates (Trichonympha) and endosymbiotic bacteria to synthesize cellulase.
Chemical Signaling & Molecular Genetics: Unlike systemic endocrine endohormones that circulate internally through bloodstream networks, pheromones are ectohormones secreted outside the organism’s body into the external environment to elicit behavioral or physiological responses (alarm, mating, trail marking) in conspecific individuals. At the molecular level, a gene is a specific segment of DNA containing nucleotide sequences that encode functional RNAs or polypeptide chains.
Microbial Applied Biotechnology: Bacillus thuringiensis (Bt) is a gram-positive, spore-forming soil bacterium utilized globally as a biological insecticide (bio-pesticide); during sporulation, it synthesizes crystalline inclusion bodies composed of insecticidal endotoxins (Cry proteins) that form pores in the alkaline midgut of lepidopteran, dipteran, and coleopteran pests. Fermentation of milk into nutritional curd and yogurt relies on Lactic Acid Bacteria (LAB), predominantly Lactobacillus species (Lactobacillus acidophilus, Lactobacillus bulgaricus, Lactococcus lactis), whereas post-pasteurization spoilage and enzymatic rancidity of refrigerated raw milk are driven by psychrotrophic proteolytic bacteria, especially Pseudomonas species.

2. Important facts you should know:

Organism / Taxonomic Entity	Scientific Identity / Classification	Functional Mechanism / Ecological Role
Firefly	Insect (Coleoptera: Lampyridae)	Bioluminescent abdominal lantern via luciferin-luciferase oxidation.
Termite (“White Ant”)	Insect (Blattodea / Isoptera)	Cellulose digestion via intestinal symbiotic protozoa (Trichonympha).
Bryophytes	Non-vascular Embryophytes (Mosses/Liverworts)	Amphibians of plant kingdom; require external water for swimming sperm.
Bentham & Hooker System	Natural Taxonomic System (Genera Plantarum)	Classifies seed plants (phanerogams) based on natural morphological affinities.
Bacillus thuringiensis (Bt)	Soil Bacterium (Phylum Bacillota)	Microbial bio-insecticide producing crystalline delta-endotoxin (Cry proteins).
Pheromones	Volatile Chemical Ectohormones	Exocrine chemical communication altering social/mating behavior of conspecifics.
Lactobacillus sp.	Lactic Acid Bacteria (LAB)	Ferments milk lactose into lactic acid, coagulating milk casein into curd.
Pseudomonas sp.	Psychrotrophic Proteolytic Bacterium	Causes spoilage in refrigerated stored milk via heat-stable lipases and proteases.

3. Master Questions

Q1. The luminescent nocturnal organism commonly known as the ‘Fire-fly’ belongs zoologically to the class of:

[UKPSC Mains 2002-03] [Direct Fact]

(a) Mollusca

(b) Insecta

(d) Nematoda

Q2. The wood-boring social insects popularly designated by the vernacular misnomer ‘White Ants’ are:

[UKPSC Mains 2002-03] [Direct Fact]

(a) True Formicid Ants

(b) Red Fire Ants

(d) Black Carpenter Ants

Q3. In fundamental cellular biology and genetics, a ‘Gene’ is structurally defined as:

[UKPSC Pre 2016] [Direct Fact]

(a) A distinct functional segment of DNA

(b) A permanent composite segment of DNA and histone protein

(d) The entire eukaryotic nuclear chromosome

Q4. Which terrestrial plant division is universally characterized as the ‘amphibians of the plant kingdom’ owing to their obligate dependence on water for fertilization?

[UKPSC AE 2013] [Direct Fact]

(a) Bryophytes

(b) Pteridophytes

(d) Gymnosperms

Q5. The comprehensive ‘Natural System’ of angiosperm plant classification, widely adopted across Commonwealth herbaria and published in Genera Plantarum, was propounded by:

[UKPSC AE 2013] [Direct Fact]

(a) Carolus Linnaeus

(b) George Bentham and Joseph Dalton Hooker

(d) John Hutchinson

Q6. The microbial spoilage and off-flavor breakdown of stored liquid dairy milk under cold storage is primarily triggered by heat-resistant proteolytic enzymes produced by:

[UKPSC UDA/LDA Pre 2003] [Direct Fact]

(a) Lactobacillus

(b) Aspergillus

(d) Staphylococcus

Q7. Pheromones, which are released into the surrounding air to communicate mating readiness or alarm among social insects, are classified as:

[UKPCS Lower Pre 2021] [Direct Fact]

(a) Phytohormonal Growth Regulators

(b) Endocrine Endohormones

(d) Neural Neurotransmitters

Q8. In sustainable integrated pest management and agricultural biotechnology, the soil-dwelling bacterium Bacillus thuringiensis (Bt) is utilized as a:

[UKPSC Pre 2012] [Direct Fact]

(a) Biofertilizer for non-symbiotic nitrogen fixation

(b) Biological insecticide (Bio-pesticide)

(d) Chemical soil fumigant

Q9. The beneficial fermentative bacterial genus found in high concentrations in homemade curd, responsible for converting milk lactose into lactic acid, is:

[UKPSC FRO/ACF Pre 2019] [Direct Fact]

(a) Salmonella species

(b) Lactobacillus species

(d) Streptomyces species

4. Master Explanations & Answer Key

Ans. (b)

Direct Answer: The firefly is a soft-bodied beetle classified under the order Coleoptera and class Insecta (phylum Arthropoda), possessing jointed walking legs and paired elytra wings.
Exam Trap / Distractor Alert: Despite the colloquial suffixes “-fly” and “glow-worm” (often applied to flightless females and larvae), fireflies are true beetles and are not related to annelid worms, molluscs, or nematodes.
High-Yield Extra Facts: Bioluminescence in fireflies is a “cold light” reaction with over 90% quantum energy efficiency; the oxidation of luciferin is catalyzed by luciferase in specialized abdominal light organs called lanterns.

Ans. (c)

Direct Answer: Termites are termed “white ants” because of their pale, soft-bodied appearance and social colony structure; however, they belong to the order Blattodea (epifamily Termitoidae) and are phylogenetically closer to cockroaches than to true ants (order Hymenoptera).
Exam Trap / Distractor Alert: True ants have elbowed antennae and a narrow “wasp waist” (petiole constriction between thorax and abdomen), whereas termites have moniliform (bead-like) antennae and a broad waist without a petiole.
High-Yield Extra Facts: Termites cannot digest crystalline plant cellulose directly; they rely on mutualistic flagellated trichomonad protozoans (Trichonympha) and gut endosymbionts to enzymatically hydrolyze cellulose into metabolizable short-chain fatty acids.

Ans. (a)

Direct Answer: A gene is a specific functional locus and nucleotide sequence of Deoxyribonucleic Acid (DNA) that carries instructions for synthesizing a functional macromolecule (a polypeptide chain or functional transfer/ribosomal RNA).
Exam Trap / Distractor Alert: While eukaryotic DNA is packaged around octameric basic histone proteins to form chromatin nucleosomes, the gene itself consists strictly of the underlying informational DNA sequence, not the structural histone packing scaffold.
High-Yield Extra Facts: The term “gene” was coined in 1909 by Danish botanist Wilhelm Johannsen to designate the fundamental Mendelian units of biological heredity.

Ans. (a)

Direct Answer: Bryophytes (including mosses like Funaria and liverworts like Marchantia) are termed the “amphibians of the plant kingdom” because they thrive on moist terrestrial land yet require a film of ambient water for their biflagellate male antherozoids to swim to the archegonium for fertilization.
Exam Trap / Distractor Alert: Pteridophytes (ferns) also require water for fertilization, but they are true vascular plants with xylem and phloem; Bryophytes are non-vascular plants (embryophytes) lacking specialized vascular tissues.
High-Yield Extra Facts: Sphagnum (peat moss) has a high water-retention capacity and is used as packing material for transporting living plants; decayed layers of Sphagnum form peat, which is used as fuel and a soil conditioning substrate.

Ans. (b)

Direct Answer: George Bentham and Sir Joseph Dalton Hooker formulated the widely adopted “Natural System” of seed plant classification, published in their three-volume landmark work Genera Plantarum (1862–1883).
Exam Trap / Distractor Alert: Carolus Linnaeus devised an artificial sexual system based on stamen and pistil characteristics; Adolf Engler, Karl Prantl, and John Hutchinson developed phylogenetic systems rooted in evolutionary lineages.
High-Yield Extra Facts: The Bentham and Hooker system classified seed plants into Dicotyledones, Gymnospermae, and Monocotyledones, placing gymnosperms between dicots and monocots—an arrangement modified in modern phylogenetic classifications.

Ans. (c)

Direct Answer: Psychrotrophic species of Pseudomonas (notably Pseudomonas fluorescens and Pseudomonas fragi) dominate the microflora of cold raw milk; they secrete heat-stable extracellular proteases and lipases that survive pasteurization and cause bitter flavors, curd coagulation, and spoilage during refrigerated storage.
Exam Trap / Distractor Alert: Lactobacillus species are beneficial fermenting bacteria used purposefully to acidify milk into curd, yogurt, and cheese; Pseudomonas represents the spoilage organism in industrial dairy refrigeration.
High-Yield Extra Facts: Psychrotrophic bacteria are cold-tolerant microbes capable of growing at low refrigeration temperatures (≤ 7 °C), even though their optimum growth temperature is 20–30 °C.

Ans. (c)

Direct Answer: Pheromones are chemical substances secreted externally by an animal’s exocrine glands into the environment, where they act as ectohormones that trigger specific behavioral, physiological, or developmental reactions in other members of the same species.
Exam Trap / Distractor Alert: Endohormones (such as insulin, adrenaline, or thyroid hormones) are secreted into internal body fluids and the vascular system to regulate homeostatic functions within the individual that produces them; pheromones act externally on other individuals.
High-Yield Extra Facts: Common examples of insect pheromones include bombykol (mating attractant secreted by female silkworm moths, Bombyx mori), alarm pheromones in worker honeybees (isoamyl acetate), and formic acid trail pheromones in foraging ants.

Ans. (b)

Direct Answer: Bacillus thuringiensis (Bt) is a soil-dwelling bacterium used as a biological microbial insecticide; during sporulation, it produces parasporal protein crystals containing delta-endotoxins (Cry and Cyt toxins) that disrupt the digestive tract of target insect pests.
Exam Trap / Distractor Alert: Bt is a biopesticide, not a nitrogen-fixing biofertilizer like Rhizobium or Azotobacter; it provides targeted biological control without contaminating soil with persistent chemical insecticide residues.
High-Yield Extra Facts: Genetic engineers transferred the cry genes from Bacillus thuringiensis directly into the nuclear genome of cotton to create transgenic Bt cotton, protecting the crop against lepidopteran bollworm infestations.

Ans. (b)

Direct Answer: Curd contains an abundance of Lactic Acid Bacteria (LAB), predominantly belonging to the genus Lactobacillus (including Lactobacillus acidophilus, Lactococcus lactis, and Lactobacillus bulgaricus).
Exam Trap / Distractor Alert: Salmonella and Escherichia coli are pathogenic enteric bacteria that cause food poisoning, gastroenteritis, and typhoid; they are contaminants, not the beneficial fermenters in commercial dairy curd.
High-Yield Extra Facts: During curd formation, Lactobacillus metabolizes milk lactose into lactic acid; the resulting drop in pH destabilizes and coagulates the milk protein casein, transforming liquid milk into semi-solid curd while synthesizing B-complex vitamins (especially Vitamin B12).

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Hemant Bhatt is a B. Tech from Pantnagar University and has studied Social Sciences at SciencesPo, Paris. He teaches at Oracle IAS, Dehradun. He has given 5 UPSC mains back to back along with 2 interviews.
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