1. Which taxonomic aid consists of a pair of contrasting characters arranged in couplets used for identifying unknown organisms?
Correct Answer: B (Taxonomic Key)
A key is an analytical taxonomic tool based on contrasting pairs of characters called couplets, where each individual statement is known as a lead.
A key is an analytical taxonomic tool based on contrasting pairs of characters called couplets, where each individual statement is known as a lead.
2. Nostoc and Anabaena fix atmospheric nitrogen inside specialized, thick-walled, non-photosynthetic anaerobic cells called:
Correct Answer: B (Heterocysts)
Heterocysts lack oxygen-evolving Photosystem II and have thick walls impermeable to oxygen, creating the anaerobic conditions required by nitrogenase enzyme to fix dinitrogen.
Heterocysts lack oxygen-evolving Photosystem II and have thick walls impermeable to oxygen, creating the anaerobic conditions required by nitrogenase enzyme to fix dinitrogen.
3. Euglenoids (e.g., Euglena) lack a rigid cellulose cell wall; instead, their flexible protein-rich outer covering is called a:
Correct Answer: A (Pellicle)
Euglenoids possess a protein-rich flexible boundary layer called a pellicle beneath the plasma membrane, enabling cell flexibility and characteristic euglenoid movement.
Euglenoids possess a protein-rich flexible boundary layer called a pellicle beneath the plasma membrane, enabling cell flexibility and characteristic euglenoid movement.
4. Which of the following edible fungi belongs to the class Ascomycetes?
Correct Answer: B (Morchella and Tuber)
Morels (Morchella) and truffles (Tuber) are delicacy edible fungi belonging to Ascomycetes. Agaricus (mushrooms) and bracket fungi belong to Basidiomycetes.
Morels (Morchella) and truffles (Tuber) are delicacy edible fungi belonging to Ascomycetes. Agaricus (mushrooms) and bracket fungi belong to Basidiomycetes.
5. Agar-agar, a solidifying agent widely used in microbiology media and ice-cream preparation, is extracted from red algae genera:
Correct Answer: A (Gelidium and Gracilaria)
Agar is a sulfated hydrocolloid polysaccharide commercially harvested from red seaweeds Gelidium and Gracilaria.
Agar is a sulfated hydrocolloid polysaccharide commercially harvested from red seaweeds Gelidium and Gracilaria.
6. The branched, creeping, green, filamentous juvenile stage produced directly from a germinating moss spore is the:
Correct Answer: B (Primary protonema)
In moss life cycles (e.g., Funaria, Polytrichum), the haploid spore germinates into a filamentous green creeping protonema stage, which later buds into the leafy gametophore.
In moss life cycles (e.g., Funaria, Polytrichum), the haploid spore germinates into a filamentous green creeping protonema stage, which later buds into the leafy gametophore.
7. “Horsetails” belonging to Pteridophyta are represented by the genus:
Correct Answer: C (Equisetum)
Equisetum belongs to the pteridophyte class Sphenopsida and is commonly called the horsetail or scouring rush due to its ribbed silica-encrusted jointed stems.
Equisetum belongs to the pteridophyte class Sphenopsida and is commonly called the horsetail or scouring rush due to its ribbed silica-encrusted jointed stems.
8. Cnidoblasts (stinging cells) containing nematocysts are used for anchorage, defense, and prey capture in:
Correct Answer: B (Coelenterata)
Cnidarians possess specialized stinging cells called cnidocytes (containing toxin-filled nematocyst capsules) on their tentacles and body walls.
Cnidarians possess specialized stinging cells called cnidocytes (containing toxin-filled nematocyst capsules) on their tentacles and body walls.
9. Which of the following is an exclusive pseudocoelomate animal with an unsegmented round body?
Correct Answer: C (Ascaris lumbricoides)
Phylum Aschelminthes (roundworms like Ascaris, Wuchereria) uniquely possesses a false coelom (pseudocoelom) where the mesoderm is scattered in pouches between ectoderm and endoderm.
Phylum Aschelminthes (roundworms like Ascaris, Wuchereria) uniquely possesses a false coelom (pseudocoelom) where the mesoderm is scattered in pouches between ectoderm and endoderm.
10. Cyclostomes (e.g., Petromyzon – Lamprey, Myxine – Hagfish) are primitive jawless vertebrates that:
Correct Answer: B (Circular suctorial mouth without jaws, lack paired fins and scales)
Class Cyclostomata comprises ectoparasitic marine jawless vertebrates with a sucking circular mouth, 6–15 pairs of gill slits, and a cartilaginous cranium and vertebral column.
Class Cyclostomata comprises ectoparasitic marine jawless vertebrates with a sucking circular mouth, 6–15 pairs of gill slits, and a cartilaginous cranium and vertebral column.
11. Stilt roots supporting the plant arise from the lower basal nodes of stems in:
Correct Answer: B (Maize and Sugarcane)
Stilt roots are aerial adventitious support roots emerging from the lower nodes of maize and sugarcane stems. Banyan trees produce hanging prop roots from branches.
Stilt roots are aerial adventitious support roots emerging from the lower nodes of maize and sugarcane stems. Banyan trees produce hanging prop roots from branches.
12. In pea and sweet pea flowers, the type of aestivation where a large posterior petal (standard) overlaps two lateral wings, which in turn overlap two anterior keel petals, is:
Correct Answer: D (Vexillary)
Vexillary (papilionaceous) aestivation is characteristic of family Fabaceae: 1 large standard (vexillum) + 2 lateral wings (alae) + 2 fused keel (carina) petals.
Vexillary (papilionaceous) aestivation is characteristic of family Fabaceae: 1 large standard (vexillum) + 2 lateral wings (alae) + 2 fused keel (carina) petals.
13. A flower with radial symmetry that can be divided into equal halves in any radial plane passing through the center (e.g., Mustard, Datura, Chilli) is:
Correct Answer: A (Actinomorphic)
Actinomorphic flowers exhibit radial symmetry (Mustard, Datura, Chilli). Zygomorphic flowers exhibit bilateral symmetry along a single vertical plane (Pea, Gulmohar, Bean, Cassia).
Actinomorphic flowers exhibit radial symmetry (Mustard, Datura, Chilli). Zygomorphic flowers exhibit bilateral symmetry along a single vertical plane (Pea, Gulmohar, Bean, Cassia).
14. Sclereids (stone cells) with narrow lumens providing mechanical strength are found in:
Correct Answer: B (Gritty pulp of fruits like guava, pear, and sapota)
Sclereids are spherical, oval, or cylindrical dead sclerenchyma cells with thick lignified walls and narrow pits that create the gritty texture in guava and pear pulp.
Sclereids are spherical, oval, or cylindrical dead sclerenchyma cells with thick lignified walls and narrow pits that create the gritty texture in guava and pear pulp.
15. In dicot stems, the vascular cambium originates during secondary growth from:
Correct Answer: B (Intrafascicular cambium and interfascicular medullary ray cells)
A continuous vascular cambium ring in dicot stems forms when the primary intrafascicular cambium joins with the interfascicular cambium formed by dedifferentiated medullary rays.
A continuous vascular cambium ring in dicot stems forms when the primary intrafascicular cambium joins with the interfascicular cambium formed by dedifferentiated medullary rays.
16. Which animal tissue is characterized by cells resting on an extracellular basement membrane without blood vessels?
Correct Answer: A (Epithelial tissue)
Epithelial tissue features tightly packed cells with minimal intercellular matrix resting on an acellular basement membrane; it is avascular and relies on underlying connective tissue diffusion.
Epithelial tissue features tightly packed cells with minimal intercellular matrix resting on an acellular basement membrane; it is avascular and relies on underlying connective tissue diffusion.
17. In the respiratory system of frogs, positive pressure breathing forces air into the lungs by movements of the:
Correct Answer: B (Buccopharyngeal cavity floor)
Frogs lack a diaphragm and true thoracic ribs; pulmonary respiration uses the buccopharyngeal floor as a force pump (positive pressure breathing) to push air into the lungs.
Frogs lack a diaphragm and true thoracic ribs; pulmonary respiration uses the buccopharyngeal floor as a force pump (positive pressure breathing) to push air into the lungs.
18. The structural and functional units of frog kidneys that filter waste and produce urine are:
Correct Answer: B (Nephrons)
Frogs possess paired, elongated, dark red mesonephric kidneys composed of structural and functional units called nephrons/uriniferous tubules that excrete urea.
Frogs possess paired, elongated, dark red mesonephric kidneys composed of structural and functional units called nephrons/uriniferous tubules that excrete urea.
19. How many pairs of cranial nerves arise directly from the brain of a frog?
Correct Answer: A (10 pairs)
Amphibians (frogs) and fishes possess 10 pairs of cranial nerves. Amniotes (reptiles, birds, and mammals) possess 12 pairs of cranial nerves.
Amphibians (frogs) and fishes possess 10 pairs of cranial nerves. Amniotes (reptiles, birds, and mammals) possess 12 pairs of cranial nerves.
20. The middle ear cavity of a frog contains a single hearing ossicle that transmits sound vibrations to the inner ear, called the:
Correct Answer: C (Columella auris)
The frog middle ear houses a single auditory bone called the columella auris (homologous to the mammalian stapes), which spans from the tympanum to the fenestra ovalis.
The frog middle ear houses a single auditory bone called the columella auris (homologous to the mammalian stapes), which spans from the tympanum to the fenestra ovalis.
21. In bacterial cells, specialized infoldings of the plasma membrane that function in respiration, cell wall formation, and DNA replication are:
Correct Answer: C (Mesosomes)
Mesosomes are membranous invaginations in prokaryotes in the form of vesicles, tubules, and lamellae that house respiratory enzymes and assist in cell division and DNA replication.
Mesosomes are membranous invaginations in prokaryotes in the form of vesicles, tubules, and lamellae that house respiratory enzymes and assist in cell division and DNA replication.
22. The primary site for post-translational modification and glycosylation of proteins and lipids into glycoproteins and glycolipids is the:
Correct Answer: C (Golgi apparatus)
Proteins synthesized by the RER enter the Golgi apparatus for post-translational glycosylation and sorting into secretory vesicles or lysosomes.
Proteins synthesized by the RER enter the Golgi apparatus for post-translational glycosylation and sorting into secretory vesicles or lysosomes.
23. In mitochondria, the folding of the inner membrane into shelf-like cristae functions to:
Correct Answer: B (Increase the surface area for oxidative phosphorylation)
Cristae are extensive folds of the inner mitochondrial membrane that expand the surface area for electron transport complexes and ATP synthase particles.
Cristae are extensive folds of the inner mitochondrial membrane that expand the surface area for electron transport complexes and ATP synthase particles.
24. The 80S eukaryotic cytoplasmic ribosome dissociates into which two ribonucleoprotein subunits?
Correct Answer: B (60S and 40S)
Eukaryotic cytoplasmic 80S ribosomes dissociate into a 60S large subunit (containing 28S, 5.8S, and 5S rRNAs) and a 40S small subunit (containing 18S rRNA).
Eukaryotic cytoplasmic 80S ribosomes dissociate into a 60S large subunit (containing 28S, 5.8S, and 5S rRNAs) and a 40S small subunit (containing 18S rRNA).
25. Which unsaturated fatty acid contains 20 carbon atoms including the carboxyl carbon?
Correct Answer: B (Arachidonic acid)
Palmitic acid is a saturated fatty acid with 16 carbons. Arachidonic acid is a polyunsaturated fatty acid with 20 carbon atoms (including the carboxyl carbon).
Palmitic acid is a saturated fatty acid with 16 carbons. Arachidonic acid is a polyunsaturated fatty acid with 20 carbon atoms (including the carboxyl carbon).
26. In the quaternary structure of adult human hemoglobin, how many polypeptide subunits are linked together?
Correct Answer: B (Four subunits: two alpha chains and two beta chains)
Adult hemoglobin (HbA) is a tetrameric quaternary protein composed of two alpha-globin and two beta-globin subunits, each coordinated with an iron-containing heme prosthetic group.
Adult hemoglobin (HbA) is a tetrameric quaternary protein composed of two alpha-globin and two beta-globin subunits, each coordinated with an iron-containing heme prosthetic group.
27. An enzyme that catalyzes the hydrolytic cleavage of C-O, C-N, or C-C bonds with the addition of water belongs to enzyme class:
Correct Answer: C (Hydrolases)
Hydrolases (Class 3) catalyze the hydrolysis of ester, ether, peptide, glycosidic, and C-C bonds using water molecules (e.g., digestive enzymes).
Hydrolases (Class 3) catalyze the hydrolysis of ester, ether, peptide, glycosidic, and C-C bonds using water molecules (e.g., digestive enzymes).
28. Recombination nodules indicating the exact sites of crossing over between non-sister chromatids appear during:
Correct Answer: C (Pachytene)
During the pachytene stage of meiotic Prophase I, multi-protein recombination nodules assemble along the synaptonemal complex to mediate reciprocal crossing over.
During the pachytene stage of meiotic Prophase I, multi-protein recombination nodules assemble along the synaptonemal complex to mediate reciprocal crossing over.
29. What is the correct chronological sequence of mitotic phases?
Correct Answer: A (Prophase -> Metaphase -> Anaphase -> Telophase)
Mitotic karyokinesis follows an invariant four-stage sequence: Prophase (condensation), Metaphase (equatorial alignment), Anaphase (chromatid segregation), and Telophase (nuclear reconstruction).
Mitotic karyokinesis follows an invariant four-stage sequence: Prophase (condensation), Metaphase (equatorial alignment), Anaphase (chromatid segregation), and Telophase (nuclear reconstruction).
30. Interkinesis is the brief transitional resting stage that occurs between:
Correct Answer: B (Meiosis I and Meiosis II)
Interkinesis is a short interphase-like stage separating Telophase I and Prophase II during which no DNA replication occurs.
Interkinesis is a short interphase-like stage separating Telophase I and Prophase II during which no DNA replication occurs.
31. In the chloroplast thylakoid membrane, the enzyme NADP+ reductase is located on the:
Correct Answer: B (Stroma side of the thylakoid membrane)
NADP+ reductase is situated on the stromal surface of the thylakoid membrane, consuming stromal protons along with electrons from ferredoxin to generate NADPH in the stroma.
NADP+ reductase is situated on the stromal surface of the thylakoid membrane, consuming stromal protons along with electrons from ferredoxin to generate NADPH in the stroma.
32. The enzyme RuBisCO acts as an oxygenase when the ratio of:
Correct Answer: A (O2 to CO2 is high and temperature is high)
Elevated temperatures decrease CO2 solubility more than O2 and alter RuBisCO’s active site conformation, favoring oxygenase activity and driving photorespiration in C3 plants.
Elevated temperatures decrease CO2 solubility more than O2 and alter RuBisCO’s active site conformation, favoring oxygenase activity and driving photorespiration in C3 plants.
33. Which enzyme is completely ABSENT in the mesophyll cells of C4 plants, forcing initial carboxylation via PEPcase?
Correct Answer: B (RuBisCO)
In C4 plants, mesophyll cells lack RuBisCO and possess PEPcase, whereas bundle sheath cells contain RuBisCO and lack PEPcase.
In C4 plants, mesophyll cells lack RuBisCO and possess PEPcase, whereas bundle sheath cells contain RuBisCO and lack PEPcase.
34. When succulent xerophytic plants (CAM plants like pineapple, Opuntia) fix CO2 at night using PEPcase, the mechanism is known as:
Correct Answer: C (Crassulacean Acid Metabolism)
CAM plants open stomata at night (scotoactive stomata) to fix CO2 into malic acid via PEPcase, storing it in vacuoles to run the Calvin cycle during daytime with closed stomata.
CAM plants open stomata at night (scotoactive stomata) to fix CO2 into malic acid via PEPcase, storing it in vacuoles to run the Calvin cycle during daytime with closed stomata.
35. The single oxidation-reduction reaction in glycolysis that generates NADH + H+ involves the conversion of:
Correct Answer: C (Glyceraldehyde-3-phosphate to 1,3-Bisphosphoglycerate)
PGAL dehydrogenase oxidizes glyceraldehyde-3-phosphate and phosphorylates it using inorganic phosphate (Pi), reducing NAD+ to NADH + H+.
PGAL dehydrogenase oxidizes glyceraldehyde-3-phosphate and phosphorylates it using inorganic phosphate (Pi), reducing NAD+ to NADH + H+.
36. For every molecule of FADH2 oxidized through the mitochondrial electron transport chain, how many ATP molecules are synthesized?
Correct Answer: B (2 ATP)
FADH2 feeds electrons directly into Complex II (ubiquinone), bypassing Complex I; this pumps fewer protons across the inner membrane, generating 2 ATP vs. 3 ATP per NADH.
FADH2 feeds electrons directly into Complex II (ubiquinone), bypassing Complex I; this pumps fewer protons across the inner membrane, generating 2 ATP vs. 3 ATP per NADH.
37. Cyanide poison stops cellular aerobic respiration and causes rapid death by inhibiting which electron transport complex?
Correct Answer: D (Complex IV)
Cyanide binds tightly to the heme iron and copper centers in Cytochrome c oxidase (Complex IV), halting electron transfer to terminal oxygen and shutting down ATP synthesis.
Cyanide binds tightly to the heme iron and copper centers in Cytochrome c oxidase (Complex IV), halting electron transfer to terminal oxygen and shutting down ATP synthesis.
38. The phenomenon of apical dominance, where the growing apical bud suppresses lateral axillary bud outgrowth, is mediated by:
Correct Answer: A (Auxin produced at shoot tips)
Auxin produced by the shoot apex flows basipetally to inhibit lateral bud expansion. Removing the apex (decapitation) relieves inhibition and stimulates bushy branching.
Auxin produced by the shoot apex flows basipetally to inhibit lateral bud expansion. Removing the apex (decapitation) relieves inhibition and stimulates bushy branching.
39. Bolting (rapid internode elongation just prior to flowering in rosette plants like cabbage and beet) is chemically induced by:
Correct Answer: B (Gibberellins)
Exogenous gibberellin application stimulates rapid internodal cell division and elongation, inducing bolting and flowering in rosette species.
Exogenous gibberellin application stimulates rapid internodal cell division and elongation, inducing bolting and flowering in rosette species.
40. The process by which differentiated parenchyma cells that regained dividing capacity undergo maturation again into specialized secondary xylem/phloem is:
Correct Answer: C (Redifferentiation)
Redifferentiation is the process where dedifferentiated secondary meristematic cells (e.g., vascular cambium) mature again into non-dividing functional tissues like secondary xylem.
Redifferentiation is the process where dedifferentiated secondary meristematic cells (e.g., vascular cambium) mature again into non-dividing functional tissues like secondary xylem.
41. The volume of air that remains inside the conductive airways (trachea, bronchi, bronchioles) and does not take part in gas exchange is called:
Correct Answer: A (Anatomical dead space volume)
About 150 mL of inhaled tidal air remains in the conducting respiratory tract (dead space) and does not contact respiratory alveolar surfaces for gas exchange.
About 150 mL of inhaled tidal air remains in the conducting respiratory tract (dead space) and does not contact respiratory alveolar surfaces for gas exchange.
42. In red blood cells, when bicarbonate ions (HCO3-) diffuse out into plasma, chloride ions (Cl-) move into RBCs to maintain electrical neutrality, a mechanism known as:
Correct Answer: C (Chloride shift)
Hamburger’s chloride shift exchanges intracellular HCO3- for extracellular Cl- across the erythrocyte membrane via band-3 anion exchanger proteins.
Hamburger’s chloride shift exchanges intracellular HCO3- for extracellular Cl- across the erythrocyte membrane via band-3 anion exchanger proteins.
43. Normal human cardiac output averages ~5 liters/min. It is calculated mathematically as:
Correct Answer: A (Stroke Volume x Heart Rate)
Cardiac Output = Stroke Volume (~70 mL) x Heart Rate (~72 beats/min) = ~5040 mL/min (approx. 5 Liters per minute).
Cardiac Output = Stroke Volume (~70 mL) x Heart Rate (~72 beats/min) = ~5040 mL/min (approx. 5 Liters per minute).
44. The bundle of His and Purkinje fibers are specialized cardiac muscle fibers that rapidly conduct electrical impulses across the:
Correct Answer: C (Interventricular septum and ventricular myocardium)
The AV bundle (Bundle of His) travels through the interventricular septum and branches into Purkinje fibers across both ventricular walls to coordinate simultaneous contraction.
The AV bundle (Bundle of His) travels through the interventricular septum and branches into Purkinje fibers across both ventricular walls to coordinate simultaneous contraction.
45. Which hormone synthesized by the heart atrial walls acts as a potent vasodilator and stimulates renal Na+ excretion when blood pressure rises?
Correct Answer: D (Atrial Natriuretic Factor)
ANF is secreted by atrial myocytes in response to high blood volume/pressure. It causes vasodilation and natriuresis (Na+ excretion), counteracting the RAAS axis.
ANF is secreted by atrial myocytes in response to high blood volume/pressure. It causes vasodilation and natriuresis (Na+ excretion), counteracting the RAAS axis.
46. The presence of glucose (Glucosuria) and ketone bodies (Ketonuria) in human urine is a clinical indicator of:
Correct Answer: B (Diabetes mellitus)
Insulin hyposecretion in diabetes mellitus causes hyperglycemia that exceeds renal thresholds, resulting in glucosuria and ketoacidosis from fat breakdown.
Insulin hyposecretion in diabetes mellitus causes hyperglycemia that exceeds renal thresholds, resulting in glucosuria and ketoacidosis from fat breakdown.
47. The pectoral girdle in humans consists of two bones on each side:
Correct Answer: B (Scapula and Clavicle)
Each half of the human pectoral girdle consists of a flat triangular dorsal bone (scapula with glenoid cavity) and a curved S-shaped collarbone (clavicle).
Each half of the human pectoral girdle consists of a flat triangular dorsal bone (scapula with glenoid cavity) and a curved S-shaped collarbone (clavicle).
48. Synovial fluid present in the synovial cavity of freely movable joints (e.g., ball and socket, hinge) functions to:
Correct Answer: B (Lubricate articulating cartilage surfaces)
Synovial fluid is a viscous hyaluronic acid-rich fluid secreted by the synovial membrane that cushions and lubricates articulating bone ends during movement.
Synovial fluid is a viscous hyaluronic acid-rich fluid secreted by the synovial membrane that cushions and lubricates articulating bone ends during movement.
49. The electrical synapse differs from a chemical synapse because in an electrical synapse:
Correct Answer: B (Pre- and post-synaptic membranes in direct contact via gap junctions)
In electrical synapses, ionic currents flow directly through gap junctions with near-zero synaptic delay, allowing faster transmission than chemical synapses.
In electrical synapses, ionic currents flow directly through gap junctions with near-zero synaptic delay, allowing faster transmission than chemical synapses.
50. Grave’s disease (Exophthalmic goiter) is an autoimmune hyperthyroid disorder characterized by:
Correct Answer: B (Enlarged thyroid, elevated BMR, weight loss, and protruding eyeballs)
Graves’ disease produces autoantibodies that stimulate TSH receptors, triggering thyroid hypersecretion, elevated BMR, tachycardia, weight loss, and proptosis/exophthalmos.
Graves’ disease produces autoantibodies that stimulate TSH receptors, triggering thyroid hypersecretion, elevated BMR, tachycardia, weight loss, and proptosis/exophthalmos.
51. The phenomenon of “Double Fertilization” in angiosperms was first discovered by:
Correct Answer: B (S.G. Nawaschin)
Sergei Nawaschin (1898) first documented double fertilization (syngamy + triple fusion) while studying Lilium and Fritillaria species.
Sergei Nawaschin (1898) first documented double fertilization (syngamy + triple fusion) while studying Lilium and Fritillaria species.
52. In an angiosperm ovule, the stalk that attaches the ovule body to the placenta is called the:
Correct Answer: A (Funiculus)
The ovule is attached to the ovarian placenta by the funicle stalk. The junction point where the funicle fuses with the ovule body is called the hilum.
The ovule is attached to the ovarian placenta by the funicle stalk. The junction point where the funicle fuses with the ovule body is called the hilum.
53. In non-albuminous (exalbuminous) seeds, the endosperm is:
Correct Answer: B (Completely consumed by the developing embryo)
Exalbuminous seeds (e.g., peas, beans, groundnuts) consume all endosperm reserves during embryogenesis, storing food within fleshy cotyledons instead.
Exalbuminous seeds (e.g., peas, beans, groundnuts) consume all endosperm reserves during embryogenesis, storing food within fleshy cotyledons instead.
54. Which male reproductive accessory gland is single, chestnut-sized, surrounds the proximal urethra, and secretes a slightly alkaline fluid?
Correct Answer: B (Prostate gland)
The prostate is an unpaired gland situated at the base of the bladder surrounding the urethra. Seminal vesicles and bulbourethral glands are paired structures.
The prostate is an unpaired gland situated at the base of the bladder surrounding the urethra. Seminal vesicles and bulbourethral glands are paired structures.
55. During human oogenesis, the number of primary follicles in each ovary at puberty decreases through atresia to approximately:
Correct Answer: B (60,000 to 80,000)
Of the ~2 million primary oocytes formed during embryonic development, follicular atresia leaves only 60,000–80,000 viable primary follicles in each ovary by menarche.
Of the ~2 million primary oocytes formed during embryonic development, follicular atresia leaves only 60,000–80,000 viable primary follicles in each ovary by menarche.
56. The follicular (proliferative) phase of the human menstrual cycle is characterized by endometrial repair and thickening driven by rising levels of:
Correct Answer: B (Estrogen)
During the proliferative phase (days 6–13), granulosa cells of developing follicles secrete estrogen, stimulating rapid mitotic repair of the functional endometrium.
During the proliferative phase (days 6–13), granulosa cells of developing follicles secrete estrogen, stimulating rapid mitotic repair of the functional endometrium.
57. The cleavage divisions of the human zygote are described as:
Correct Answer: A (Holoblastic, unequal, and indeterminate)
Because human eggs are microlecithal/alecithal, cleavage is complete (holoblastic) across the cell, generating blastomeres through mitotic divisions without cellular growth.
Because human eggs are microlecithal/alecithal, cleavage is complete (holoblastic) across the cell, generating blastomeres through mitotic divisions without cellular growth.
58. The structural and functional units formed by interdigitating chorionic villi with maternal uterine tissue are the:
Correct Answer: B (Placenta)
Fetal trophoblastic chorionic villi interdigitate with the maternal endometrium (decidua basalis) to form the placenta, facilitating nutrient exchange and hormone secretion.
Fetal trophoblastic chorionic villi interdigitate with the maternal endometrium (decidua basalis) to form the placenta, facilitating nutrient exchange and hormone secretion.
59. Progestasert and LNG-20 are examples of:
Correct Answer: C (Hormone-releasing IUDs)
Progestasert and LNG-20 release synthetic progestogens, making the endometrium unsuitable for implantation and thickening cervical mucus to block sperm entry.
Progestasert and LNG-20 release synthetic progestogens, making the endometrium unsuitable for implantation and thickening cervical mucus to block sperm entry.
60. In an In Vitro Fertilization (IVF) clinic, the direct laboratory injection of a single spermatozoon into an ovum’s cytoplasm is known as:
Correct Answer: C (ICSI)
ICSI is a micro-manipulation technique where a selected sperm cell is directly injected into an unfertilized oocyte in vitro, forming an embryo for transfer.
ICSI is a micro-manipulation technique where a selected sperm cell is directly injected into an unfertilized oocyte in vitro, forming an embryo for transfer.
61. In human genetics, the inheritance of the Holandric (hypertrichosis of ear pinna) trait is carried exclusively on the:
Correct Answer: B (Y chromosome)
Y-linked (holandric) genes reside on the non-homologous segment of the Y chromosome and are transmitted exclusively from father to male offspring.
Y-linked (holandric) genes reside on the non-homologous segment of the Y chromosome and are transmitted exclusively from father to male offspring.
62. Which aneuploid chromosomal disorder in humans results from an extra copy of chromosome 21 (Trisomy 21)?
Correct Answer: C (Down’s syndrome)
Down’s syndrome (47 chromosomes: 45 autosomes + XX/XY) is caused by meiotic non-disjunction of chromosome pair 21, resulting in developmental delays and characteristic physical features.
Down’s syndrome (47 chromosomes: 45 autosomes + XX/XY) is caused by meiotic non-disjunction of chromosome pair 21, resulting in developmental delays and characteristic physical features.
63. In beta-thalassemia, the synthesis of beta-globin chains is impaired due to a mutation in the HBB gene located on:
Correct Answer: B (Chromosome 11)
Beta-thalassemia is controlled by a single HBB gene on chromosome 11. Alpha-thalassemia is controlled by two linked genes (HBA1 and HBA2) on chromosome 16.
Beta-thalassemia is controlled by a single HBB gene on chromosome 11. Alpha-thalassemia is controlled by two linked genes (HBA1 and HBA2) on chromosome 16.
64. In a DNA molecule, the purine Guanine pairs with the pyrimidine Cytosine through:
Correct Answer: B (Three hydrogen bonds)
According to Watson-Crick base pairing rules, Adenine pairs with Thymine via two hydrogen bonds (A = T), and Guanine pairs with Cytosine via three hydrogen bonds (G === C).
According to Watson-Crick base pairing rules, Adenine pairs with Thymine via two hydrogen bonds (A = T), and Guanine pairs with Cytosine via three hydrogen bonds (G === C).
65. The discontinuous replication of DNA on the lagging strand (3′ to 5′ template) produces short fragments called:
Correct Answer: A (Okazaki fragments)
Because DNA polymerase synthesizes only in the 5′ to 3′ direction, the lagging strand is replicated discontinuously as short Okazaki fragments, which are covalently joined by DNA ligase.
Because DNA polymerase synthesizes only in the 5′ to 3′ direction, the lagging strand is replicated discontinuously as short Okazaki fragments, which are covalently joined by DNA ligase.
66. The genetic code is described as “unambiguous and specific” because:
Correct Answer: B (One codon codes for only one amino acid)
Unambiguous means each triplet codon specifies exactly one amino acid. Degeneracy means multiple codons can code for the same amino acid.
Unambiguous means each triplet codon specifies exactly one amino acid. Degeneracy means multiple codons can code for the same amino acid.
67. The technique of DNA Fingerprinting was originally developed by:
Correct Answer: B (Alec Jeffreys)
Sir Alec Jeffreys developed DNA fingerprinting using Variable Number of Tandem Repeats (VNTRs) as hybridization probes to profile individual DNA polymorphisms.
Sir Alec Jeffreys developed DNA fingerprinting using Variable Number of Tandem Repeats (VNTRs) as hybridization probes to profile individual DNA polymorphisms.
68. The eyes of an octopus and the eyes of a mammal (human) have different developmental origins but perform similar vision functions, exemplifying:
Correct Answer: B (Analogy arising from convergent evolution)
Octopus and mammalian eyes share different retinal structures and embryological origins but perform the same visual function, demonstrating convergent evolution.
Octopus and mammalian eyes share different retinal structures and embryological origins but perform the same visual function, demonstrating convergent evolution.
69. Random, non-directional fluctuations in allele frequencies that occur purely by chance in small populations are known as:
Correct Answer: C (Genetic Drift)
Genetic drift refers to chance alterations in allele frequencies that disproportionately affect small, isolated breeding populations (e.g., founder and bottleneck effects).
Genetic drift refers to chance alterations in allele frequencies that disproportionately affect small, isolated breeding populations (e.g., founder and bottleneck effects).
70. Which fossil hominid had a cranial capacity of ~1400 cc, lived 100,000 to 40,000 years ago, used animal hides for clothing, and buried their dead?
Correct Answer: C (Neanderthal man)
Neanderthals possessed a 1400 cc brain volume, inhabited near East and Central Asia, used clothing hides, and practiced intentional burial rites.
Neanderthals possessed a 1400 cc brain volume, inhabited near East and Central Asia, used clothing hides, and practiced intentional burial rites.
71. Typhoid fever is caused by Salmonella typhi and is clinically characterized pathologically by:
Correct Answer: B (Sustained high fever, stomach pain, and intestinal perforation)
Salmonella typhi infects the small intestine through contaminated food and water, causing sustained high fever (39°–40°C), stomach cramps, and ulceration/perforation.
Salmonella typhi infects the small intestine through contaminated food and water, causing sustained high fever (39°–40°C), stomach cramps, and ulceration/perforation.
72. Which type of immunity is long-lasting and produced when a person’s own immune system responds to an antigen encountered via natural infection or vaccination?
Correct Answer: A (Active immunity)
Active immunity develops when the host generates its own antibodies and memory B/T cells in response to living or attenuated antigens, providing durable immunological protection.
Active immunity develops when the host generates its own antibodies and memory B/T cells in response to living or attenuated antigens, providing durable immunological protection.
73. Enzyme-Linked Immunosorbent Assay (ELISA) is primarily used for the preliminary screening of:
Correct Answer: C (HIV / AIDS infection)
ELISA is the primary serological screening assay used to detect antibodies generated against the Human Immunodeficiency Virus (HIV).
ELISA is the primary serological screening assay used to detect antibodies generated against the Human Immunodeficiency Virus (HIV).
74. Malignant tumors exhibit metastasis, which refers to the:
Correct Answer: B (Sloughing of cells to form distant secondary tumors)
Metastasis is the spread of malignant tumor cells through circulation to colonize distant organs, representing a hallmark of advanced cancer.
Metastasis is the spread of malignant tumor cells through circulation to colonize distant organs, representing a hallmark of advanced cancer.
75. The alkaloid “Nicotine” present in tobacco stimulates which endocrine organ to release adrenaline and noradrenaline into the blood?
Correct Answer: B (Adrenal gland)
Nicotine stimulates nicotinic acetylcholine receptors in the adrenal medulla, triggering catecholamine release that elevates systemic blood pressure and heart rate.
Nicotine stimulates nicotinic acetylcholine receptors in the adrenal medulla, triggering catecholamine release that elevates systemic blood pressure and heart rate.
76. The large holes in “Swiss Cheese” are produced by carbon dioxide released during fermentation by the bacterium:
Correct Answer: B (Propionibacterium sharmanii)
Propionibacterium sharmanii produces large volumes of CO2 gas during cheese ripening, creating characteristic cavernous eyes/holes in Swiss cheese.
Propionibacterium sharmanii produces large volumes of CO2 gas during cheese ripening, creating characteristic cavernous eyes/holes in Swiss cheese.
77. The immunosuppressive medication Cyclosporin A administered to kidney transplant recipients is harvested from the fungus:
Correct Answer: B (Trichoderma polysporum)
Cyclosporin A, an immunosuppressive cyclic peptide that prevents graft rejection by inhibiting T-cell activation, is produced by the fungus Trichoderma polysporum.
Cyclosporin A, an immunosuppressive cyclic peptide that prevents graft rejection by inhibiting T-cell activation, is produced by the fungus Trichoderma polysporum.
78. During biological sewage treatment, microbial flocs consist of:
Correct Answer: B (Masses of aerobic bacteria with fungal filaments)
In secondary aeration tanks, aerobic bacteria enmesh with fungal hyphae to form flocs that consume dissolved organic matter and lower wastewater BOD.
In secondary aeration tanks, aerobic bacteria enmesh with fungal hyphae to form flocs that consume dissolved organic matter and lower wastewater BOD.
79. The biological control agent effective against several soil-borne plant root fungal pathogens is:
Correct Answer: A (Trichoderma species)
Trichoderma is a free-living rhizosphere fungus that suppresses root rot pathogens through mycoparasitism and antibiotic production.
Trichoderma is a free-living rhizosphere fungus that suppresses root rot pathogens through mycoparasitism and antibiotic production.
80. The fungal symbiont in a Mycorrhiza (e.g., genus Glomus) benefits the host plant primarily by absorbing which limiting nutrient from soil?
Correct Answer: B (Phosphorus)
Mycorrhizae (such as Glomus) absorb inorganic phosphorus from deficient soils and transfer it to the plant, while providing drought tolerance and root pathogen resistance.
Mycorrhizae (such as Glomus) absorb inorganic phosphorus from deficient soils and transfer it to the plant, while providing drought tolerance and root pathogen resistance.
81. The first discovered restriction endonuclease that cuts DNA at a specific 6-base-pair recognition site is:
Correct Answer: B (Hind II)
Hind II (isolated from Haemophilus influenzae) was the first restriction endonuclease discovered, characteristically cleaving DNA at a specific 6-bp sequence.
Hind II (isolated from Haemophilus influenzae) was the first restriction endonuclease discovered, characteristically cleaving DNA at a specific 6-bp sequence.
82. In pBR322 plasmid, insertion of foreign DNA at the BamHI site leads to insertional inactivation of the gene conferring resistance to:
Correct Answer: B (Tetracycline)
The BamHI restriction site is located within the tetracycline-resistance gene (tetR); inserting passenger DNA here inactivates tetR, rendering recombinants tetracycline-sensitive.
The BamHI restriction site is located within the tetracycline-resistance gene (tetR); inserting passenger DNA here inactivates tetR, rendering recombinants tetracycline-sensitive.
83. To isolate pure genomic DNA from bacterial cells, the cell wall is enzymatically digested using:
Correct Answer: A (Lysozyme)
Bacterial peptidoglycan walls are degraded with Lysozyme, plant cellulose walls with Cellulase, and fungal chitin walls with Chitinase.
Bacterial peptidoglycan walls are degraded with Lysozyme, plant cellulose walls with Cellulase, and fungal chitin walls with Chitinase.
84. The precipitate of pure DNA threads obtained after adding chilled ethanol to a lysate is collected via:
Correct Answer: B (Spooling)
Chilled ethanol precipitates DNA as fine insoluble white fibers that can be wound out on a glass rod in a process known as spooling.
Chilled ethanol precipitates DNA as fine insoluble white fibers that can be wound out on a glass rod in a process known as spooling.
85. The crystalline Bt protein protoxin is converted into its active toxic form inside the insect gut due to:
Correct Answer: B (Alkaline pH of the midgut)
Bt crystal proteins are inactive protoxins that dissolve only in the alkaline pH of the insect midgut, where gut proteases cleave them into pore-forming toxins.
Bt crystal proteins are inactive protoxins that dissolve only in the alkaline pH of the insect midgut, where gut proteases cleave them into pore-forming toxins.
86. In tobacco plants transformed by RNAi against Meloidogyne incognita, the introduced Agrobacterium vector was engineered to produce:
Correct Answer: B (Both sense and anti-sense RNA that form regulatory dsRNA)
Expressing both sense and antisense strands produces double-stranded RNA (dsRNA), which initiates RNA interference to silence homologous parasite mRNA upon ingestion.
Expressing both sense and antisense strands produces double-stranded RNA (dsRNA), which initiates RNA interference to silence homologous parasite mRNA upon ingestion.
87. Proinsulin synthesized in human beta cells contains an extra connecting polypeptide that is absent in mature insulin, called:
Correct Answer: C (C-peptide)
Proinsulin contains A, B, and connecting C peptides; proteolytic removal of the C-peptide leaves the A and B chains linked by disulfide bonds in mature insulin.
Proinsulin contains A, B, and connecting C peptides; proteolytic removal of the C-peptide leaves the A and B chains linked by disulfide bonds in mature insulin.
88. The permanent cure for Adenosine Deaminase (ADA) deficiency can be accomplished by:
Correct Answer: B (Introducing functional ADA gene into bone marrow stem cells at early embryonic stages)
Adult lymphocyte infusions require periodic repeats because lymphocytes have finite lifespans. Transforming hematopoietic stem cells during early development provides a permanent cure.
Adult lymphocyte infusions require periodic repeats because lymphocytes have finite lifespans. Transforming hematopoietic stem cells during early development provides a permanent cure.
89. Human alpha-1-antitrypsin synthesized by transgenic animals is used for the clinical management of:
Correct Answer: C (Emphysema)
Transgenic animals synthesize therapeutic proteins such as human alpha-1-antitrypsin, a protease inhibitor used to treat emphysema.
Transgenic animals synthesize therapeutic proteins such as human alpha-1-antitrypsin, a protease inhibitor used to treat emphysema.
90. In 1997, an American multinational company attempted to patent Indian Basmati rice through the US Patent Office after crossing it with:
Correct Answer: B (Semi-dwarf varieties)
The company crossed traditional Indian Basmati with semi-dwarf lines and claimed patent rights over the hybrid variety, sparking international biopiracy challenges.
The company crossed traditional Indian Basmati with semi-dwarf lines and claimed patent rights over the hybrid variety, sparking international biopiracy challenges.
91. The female wasp and fig tree relationship, where the wasp pollinates the fig and the fig provides oviposition sites for wasp larvae, illustrates:
Correct Answer: B (Mutualism with obligate co-evolution)
Fig and wasp exhibit tight mutualistic co-evolution: a specific wasp species can pollinate only its partner fig species while using developing seeds as larval nurseries.
Fig and wasp exhibit tight mutualistic co-evolution: a specific wasp species can pollinate only its partner fig species while using developing seeds as larval nurseries.
92. In a triangular-shaped population age pyramid, the proportion of pre-reproductive individuals is:
Correct Answer: A (Very high, indicating an expanding population)
A broad base of pre-reproductive individuals creates a triangular age pyramid, reflecting high birth rates and rapid population expansion.
A broad base of pre-reproductive individuals creates a triangular age pyramid, reflecting high birth rates and rapid population expansion.
93. Ecological succession that starts in a newly formed freshwater pond or bare flooded reservoir is termed:
Correct Answer: B (Hydrosere)
Hydrarch succession (hydrosere) begins in aquatic habitats (lakes/ponds) and progresses through phytoplankton, submerged, floating, reed-swamp, and marsh-meadow stages to reach a mesic forest climax.
Hydrarch succession (hydrosere) begins in aquatic habitats (lakes/ponds) and progresses through phytoplankton, submerged, floating, reed-swamp, and marsh-meadow stages to reach a mesic forest climax.
94. The fraction of total organic biomass synthesized by green plants that remains available for consumption by heterotrophs is:
Correct Answer: B (Net Primary Productivity)
NPP represents the net biomass stored by autotrophs after deducting metabolic respiration losses (R), which serves as the energy foundation for herbivores and decomposers.
NPP represents the net biomass stored by autotrophs after deducting metabolic respiration losses (R), which serves as the energy foundation for herbivores and decomposers.
95. In a single large oak tree supporting thousands of herbivorous insects that are parasitized by thousands of hyperparasites, the pyramid of numbers is:
Correct Answer: B (Inverted)
A single tree producer (1) supports numerous herbivorous insects, which support larger populations of hyperparasites, resulting in an inverted pyramid of numbers.
A single tree producer (1) supports numerous herbivorous insects, which support larger populations of hyperparasites, resulting in an inverted pyramid of numbers.
96. Across continents, when species-area relationships are evaluated for large taxonomic assemblages, the regression slope Z value steepens to:
Correct Answer: B (0.6 to 1.2)
While small regional survey slopes fall within Z = 0.1–0.2, continental-scale analyses steepen to Z = 0.6–1.2 (e.g., 1.15 for tropical frugivorous birds).
While small regional survey slopes fall within Z = 0.1–0.2, continental-scale analyses steepen to Z = 0.6–1.2 (e.g., 1.15 for tropical frugivorous birds).
97. The catastrophic loss of tropical rainforest cover from historically 14% of Earth’s land surface down to less than what percentage today illustrates severe habitat loss?
Correct Answer: B (Less than 6%)
Tropical rainforests that once covered >14% of Earth’s land area now cover <6% due to deforestation and agricultural expansion in the Amazon and Southeast Asia.
Tropical rainforests that once covered >14% of Earth’s land area now cover <6% due to deforestation and agricultural expansion in the Amazon and Southeast Asia.
98. Which flightless bird species became extinct from the island of Mauritius in recent centuries due to human over-exploitation?
Correct Answer: A (Dodo)
The flightless Dodo bird became extinct in Mauritius. The Quagga went extinct in Africa, the Thylacine in Australia, and the Steller’s sea cow in Russia.
The flightless Dodo bird became extinct in Mauritius. The Quagga went extinct in Africa, the Thylacine in Australia, and the Steller’s sea cow in Russia.
99. Which of the following is an example of an Ex-situ (off-site) biodiversity conservation facility?
Correct Answer: C (Botanical Garden, Seed Bank, and Zoological Park)
Ex-situ conservation preserves endangered organisms outside their natural habitat in controlled facilities like botanical gardens, zoos, and cryopreservation banks.
Ex-situ conservation preserves endangered organisms outside their natural habitat in controlled facilities like botanical gardens, zoos, and cryopreservation banks.
100. In 2002, the World Summit on Sustainable Development where 190 countries committed to achieving a significant reduction in current biodiversity loss was held in:
Correct Answer: B (Johannesburg, South Africa)
Ten years after the 1992 Earth Summit in Rio, the 2002 World Summit on Sustainable Development convened in Johannesburg, South Africa, reaffirming global conservation goals.
Ten years after the 1992 Earth Summit in Rio, the 2002 World Summit on Sustainable Development convened in Johannesburg, South Africa, reaffirming global conservation goals.