1. Which taxonomic aid provides an index to the plant species found in a particular area, containing actual accounts of habitat and distribution?
Correct Answer: A (Flora)
Flora contains the actual account of habitat and distribution of plants of a given area. Manuals provide information for identification of names of species, while Monographs contain information on any one taxon.
Flora contains the actual account of habitat and distribution of plants of a given area. Manuals provide information for identification of names of species, while Monographs contain information on any one taxon.
2. Mycoplasmas are unique among prokaryotes because they:
Correct Answer: B (Completely lack a cell wall and can survive without oxygen)
Mycoplasmas are the smallest living cells known; they completely lack a cell wall, are pleomorphic, can survive without oxygen, and are pathogenic in animals and plants.
Mycoplasmas are the smallest living cells known; they completely lack a cell wall, are pleomorphic, can survive without oxygen, and are pathogenic in animals and plants.
3. Which group of fungi produces endogenous sexual spores called ascospores inside sac-like asci?
Correct Answer: B (Ascomycetes)
Ascomycetes produce sexual ascospores endogenously within asci, whereas Basidiomycetes produce basidiospores exogenously on basidia.
Ascomycetes produce sexual ascospores endogenously within asci, whereas Basidiomycetes produce basidiospores exogenously on basidia.
4. Lichens are considered excellent bioindicators of air pollution because they:
Correct Answer: B (Are extremely sensitive to SO2 and do not grow in polluted areas)
Lichens represent symbiotic mutualism between an alga (phycobiont) and a fungus (mycobiont) and serve as natural pollution indicators, especially for SO2.
Lichens represent symbiotic mutualism between an alga (phycobiont) and a fungus (mycobiont) and serve as natural pollution indicators, especially for SO2.
5. The photosynthetic pigments Chlorophyll a, Chlorophyll d, and phycoerythrin are characteristic of:
Correct Answer: C (Rhodophyceae)
Red algae (Rhodophyceae) contain chlorophyll a, chlorophyll d, and high levels of r-phycoerythrin, allowing them to absorb blue-green light in deep ocean waters.
Red algae (Rhodophyceae) contain chlorophyll a, chlorophyll d, and high levels of r-phycoerythrin, allowing them to absorb blue-green light in deep ocean waters.
6. In gymnosperms, the endosperm tissue is:
Correct Answer: A (Haploid and formed before fertilization)
In gymnosperms, the female gametophyte directly serves as the nutritive endosperm and is haploid (n), formed prior to fertilization. In angiosperms, it is triploid (3n) via triple fusion.
In gymnosperms, the female gametophyte directly serves as the nutritive endosperm and is haploid (n), formed prior to fertilization. In angiosperms, it is triploid (3n) via triple fusion.
7. Which of the following is a non-parasitic, free-living flatworm capable of high regeneration?
Correct Answer: C (Planaria)
Planaria is a free-living freshwater flatworm belonging to Platyhelminthes that possesses immense true physiological regeneration capacity.
Planaria is a free-living freshwater flatworm belonging to Platyhelminthes that possesses immense true physiological regeneration capacity.
8. An open circulatory system with a body cavity called hemocoel and chitinous exoskeleton is found in:
Correct Answer: B (Arthropoda)
Arthropods (e.g., insects, crabs, spiders) have jointed appendages, a tough chitinous exoskeleton, and an open circulatory system draining into a hemocoel.
Arthropods (e.g., insects, crabs, spiders) have jointed appendages, a tough chitinous exoskeleton, and an open circulatory system draining into a hemocoel.
9. In Urochordata (e.g., Ascidia, Salpa), the notochord is:
Correct Answer: A (Present only in the larval tail)
In Urochordata, the notochord is restricted to the tail of the free-swimming larva and disappears during retrogressive metamorphosis. In Cephalochordata, it extends head-to-tail throughout life.
In Urochordata, the notochord is restricted to the tail of the free-swimming larva and disappears during retrogressive metamorphosis. In Cephalochordata, it extends head-to-tail throughout life.
10. Poison sting (trygon) and electric organs (torpedo) are specialized modifications seen in:
Correct Answer: A (Chondrichthyes)
Cartilaginous fishes (Chondrichthyes) include Torpedo (which possesses electric organs derived from branchial muscles) and Trygon (stingray, which possesses a venomous tail spine).
Cartilaginous fishes (Chondrichthyes) include Torpedo (which possesses electric organs derived from branchial muscles) and Trygon (stingray, which possesses a venomous tail spine).
11. Stems modified into green, flattened photosynthetic structures of unlimited growth in arid regions (e.g., Opuntia) are called:
Correct Answer: A (Phylloclades)
Phylloclades are flattened (Opuntia) or cylindrical (Euphorbia) green photosynthetic stem modifications with distinct nodes and internodes. Phyllodes are flattened petiole modifications (Australian Acacia).
Phylloclades are flattened (Opuntia) or cylindrical (Euphorbia) green photosynthetic stem modifications with distinct nodes and internodes. Phyllodes are flattened petiole modifications (Australian Acacia).
12. In a racemose inflorescence:
Correct Answer: A (Main axis continues to grow and flowers borne in acropetal succession)
In racemose inflorescences, the main peduncle shows continuous indeterminate growth, bearing younger flowers toward the apex (acropetal succession).
In racemose inflorescences, the main peduncle shows continuous indeterminate growth, bearing younger flowers toward the apex (acropetal succession).
13. Axile placentation with multilocular ovaries containing ovules attached to a central axis is observed in:
Correct Answer: C (Tomato, Lemon, and China rose)
In axile placentation, the ovary is syncarpous and multilocular, with placentas located along the central column (e.g., Solanaceae, Rutaceae, Malvaceae).
In axile placentation, the ovary is syncarpous and multilocular, with placentas located along the central column (e.g., Solanaceae, Rutaceae, Malvaceae).
14. Which dead mechanical tissue has narrow elongated cells with pointed tapering ends and heavily lignified thick walls with pits?
Correct Answer: C (Sclerenchyma fibres)
Sclerenchyma fibers are dead, thick-walled, elongated tapering cells with narrow lumens and heavily lignified cell walls providing mechanical rigidity.
Sclerenchyma fibers are dead, thick-walled, elongated tapering cells with narrow lumens and heavily lignified cell walls providing mechanical rigidity.
15. In a dicotyledonous root, the vascular bundles are:
Correct Answer: A (Radial with exarch xylem arrangement)
Dicot roots show radial, diarch to tetrarch (2–4) vascular bundles with exarch xylem (protoxylem toward periphery). Monocot roots have polyarch bundles (>6).
Dicot roots show radial, diarch to tetrarch (2–4) vascular bundles with exarch xylem (protoxylem toward periphery). Monocot roots have polyarch bundles (>6).
16. Dense regular connective tissue where collagen fibers are oriented in parallel bundles between rows of fibers is found in:
Correct Answer: B (Tendons and Ligaments)
Dense regular connective tissue features parallel arrays of collagen fibers, as seen in tendons (connecting muscles to bones) and ligaments (connecting bones to bones).
Dense regular connective tissue features parallel arrays of collagen fibers, as seen in tendons (connecting muscles to bones) and ligaments (connecting bones to bones).
17. In the mouth of a frog, teeth are:
Correct Answer: B (Homodont, acrodont, and polyphyodont)
Frogs possess homodont (identical shape), acrodont (attached to surface of jaw bone), and polyphyodont (replaced multiple times) teeth on the upper jaw and vomer bones.
Frogs possess homodont (identical shape), acrodont (attached to surface of jaw bone), and polyphyodont (replaced multiple times) teeth on the upper jaw and vomer bones.
18. The vascular connection in frogs between the liver and intestine, and between the kidneys and lower body parts, are respectively:
Correct Answer: B (Hepatic portal system and Renal portal system)
Frogs possess both a hepatic portal system (gut to liver) and a renal portal system (hind limbs/lower body to kidneys).
Frogs possess both a hepatic portal system (gut to liver) and a renal portal system (hind limbs/lower body to kidneys).
19. In male frogs, the paired copulatory (nuptial) pads used to grip females during amplexus are located on the:
Correct Answer: A (First digit of the forelimbs)
Male frogs show sexual dimorphism by having vocal sacs and a thickened nuptial (copulatory) pad on the first digit of each forelimb during the breeding season.
Male frogs show sexual dimorphism by having vocal sacs and a thickened nuptial (copulatory) pad on the first digit of each forelimb during the breeding season.
20. The common chamber in frogs into which the alimentary canal, urinary bladder, and reproductive ducts all empty is the:
Correct Answer: B (Cloaca)
The cloaca is a common terminal chamber in amphibians that receives fecal matter, urine, and gametes before they exit through the cloacal aperture.
The cloaca is a common terminal chamber in amphibians that receives fecal matter, urine, and gametes before they exit through the cloacal aperture.
21. The bacterial cell envelope consists of a tightly bound three-layered structure comprising, from outermost to innermost:
Correct Answer: A (Glycocalyx -> Cell Wall -> Plasma Membrane)
The prokaryotic envelope consists of an outer glycocalyx (slime layer or capsule), a middle peptidoglycan cell wall, and an inner selectively permeable plasma membrane.
The prokaryotic envelope consists of an outer glycocalyx (slime layer or capsule), a middle peptidoglycan cell wall, and an inner selectively permeable plasma membrane.
22. The major site for active ribosomal RNA (rRNA) transcription and synthesis in eukaryotic cells is the:
Correct Answer: B (Nucleolus)
The nucleolus is a non-membrane-bound subnuclear compartment dedicated to transcribing rRNA and assembling ribosomal subunits.
The nucleolus is a non-membrane-bound subnuclear compartment dedicated to transcribing rRNA and assembling ribosomal subunits.
23. In plant cells, the central vacuole is bounded by a single semi-permeable membrane that transports ions against concentration gradients into the vacuole, named the:
Correct Answer: A (Tonoplast)
The tonoplast is the single membrane bounding the plant vacuole. Active transport across the tonoplast makes solute concentrations higher in the sap than in the cytoplasm.
The tonoplast is the single membrane bounding the plant vacuole. Active transport across the tonoplast makes solute concentrations higher in the sap than in the cytoplasm.
24. Chloroplast plastids that store fats and oils in plant seeds are called:
Correct Answer: B (Elaioplasts)
Leucoplasts are non-pigmented storage plastids: Amyloplasts store starch, Elaioplasts store oils/lipids, and Aleuroplasts store proteins.
Leucoplasts are non-pigmented storage plastids: Amyloplasts store starch, Elaioplasts store oils/lipids, and Aleuroplasts store proteins.
25. A heterocyclic nitrogenous base linked to a pentose sugar via an N-glycosidic bond without a phosphate group is called a:
Correct Answer: B (Nucleoside)
A nitrogen base + pentose sugar = Nucleoside (e.g., adenosine). Adding a phosphate group via an ester bond forms a Nucleotide (e.g., adenylic acid).
A nitrogen base + pentose sugar = Nucleoside (e.g., adenosine). Adding a phosphate group via an ester bond forms a Nucleotide (e.g., adenylic acid).
26. In the tertiary folding of globular proteins, which of the following non-covalent interactions contributes to structure stabilization?
Correct Answer: D (All of the above)
Tertiary protein structure is stabilized by hydrophobic interactions, hydrogen bonds, ionic electrostatic bonds, and covalent disulfide bridges between cysteine residues.
Tertiary protein structure is stabilized by hydrophobic interactions, hydrogen bonds, ionic electrostatic bonds, and covalent disulfide bridges between cysteine residues.
27. The lock-and-key and induced-fit models explain that enzymes increase biochemical reaction rates primarily by:
Correct Answer: B (Lowering the activation energy barrier of the transition state)
Enzymes stabilize the transient transition state complex, significantly lowering the activation energy required without altering the overall free energy change (delta G).
Enzymes stabilize the transient transition state complex, significantly lowering the activation energy required without altering the overall free energy change (delta G).
28. The phase of the cell cycle during which histone proteins are synthesized and centrosome duplication occurs in animal cells is:
Correct Answer: B (S phase)
During S phase, nuclear DNA replication occurs alongside histone protein synthesis, and the cytoplasmic centrosome duplicates.
During S phase, nuclear DNA replication occurs alongside histone protein synthesis, and the cytoplasmic centrosome duplicates.
29. Dissolution of the synaptonemal complex begins and X-shaped chiasmata become visible during which meiotic stage?
Correct Answer: C (Diplotene)
In Diplotene, the synaptonemal complex dissolves and homologous chromosomes separate except at crossover sites, forming visible X-shaped chiasmata.
In Diplotene, the synaptonemal complex dissolves and homologous chromosomes separate except at crossover sites, forming visible X-shaped chiasmata.
30. In plant cell cytokinesis, division of the cytoplasm occurs by formation of a cell plate that grows:
Correct Answer: B (Centrifugally from center to outside)
Animal cells divide centripetally via a contracting actin cleavage furrow. Plant cells divide centrifugally via a phragmoplast/cell plate growing outward to meet lateral walls.
Animal cells divide centripetally via a contracting actin cleavage furrow. Plant cells divide centrifugally via a phragmoplast/cell plate growing outward to meet lateral walls.
31. The primary electron acceptor from Photosystem II in the light-harvesting complex is:
Correct Answer: A (Pheophytin)
When P680 in PS II is photo-excited, it transfers an electron to pheophytin (a chlorophyll lacking magnesium), which passes it down to plastoquinone.
When P680 in PS II is photo-excited, it transfers an electron to pheophytin (a chlorophyll lacking magnesium), which passes it down to plastoquinone.
32. Which mineral ions are essential for the catalytic water-splitting complex (oxygen-evolving complex) in PS II?
Correct Answer: B (Manganese and Chlorine)
The oxygen-evolving complex requires a catalytic cluster of Manganese (Mn) ions, along with Chloride (Cl-) and Calcium (Ca2+), to oxidize water into O2, 4H+, and 4e-.
The oxygen-evolving complex requires a catalytic cluster of Manganese (Mn) ions, along with Chloride (Cl-) and Calcium (Ca2+), to oxidize water into O2, 4H+, and 4e-.
33. RuBisCO exhibits both carboxylase and oxygenase activity. Photorespiration is initiated when RuBisCO binds oxygen (O2), producing:
Correct Answer: B (One molecule of 3-PGA and one of 2-Phosphoglycolate)
When oxygen binds to RuBisCO, 5-carbon RuBP is cleaved into one 3-carbon 3-PGA molecule and one 2-carbon 2-phosphoglycolate molecule, initiating photorespiration.
When oxygen binds to RuBisCO, 5-carbon RuBP is cleaved into one 3-carbon 3-PGA molecule and one 2-carbon 2-phosphoglycolate molecule, initiating photorespiration.
34. Blackman’s Law of Limiting Factors (1905) states that if a chemical process is affected by more than one factor, its rate is determined by the:
Correct Answer: B (Factor which is nearest to its minimal value)
According to Blackman, when a process is governed by multiple variables, the rate is limited by the single factor nearest to its minimum threshold.
According to Blackman, when a process is governed by multiple variables, the rate is limited by the single factor nearest to its minimum threshold.
35. During glycolysis, the enzyme Enolase converts 2-phosphoglycerate (2-PGA) into high-energy phosphoenolpyruvate (PEP) by releasing:
Correct Answer: B (A water molecule)
Enolase catalyzes a dehydration reaction converting 2-phosphoglycerate into high-energy phosphoenolpyruvate (PEP) by removing one molecule of water.
Enolase catalyzes a dehydration reaction converting 2-phosphoglycerate into high-energy phosphoenolpyruvate (PEP) by removing one molecule of water.
36. In alcoholic fermentation by yeast, pyruvate is decarboxylated to acetaldehyde and then reduced to ethanol by the enzymes:
Correct Answer: B (Pyruvate decarboxylase and Alcohol dehydrogenase)
Pyruvate decarboxylase converts pyruvate to acetaldehyde and CO2, and alcohol dehydrogenase reduces acetaldehyde to ethanol using NADH.
Pyruvate decarboxylase converts pyruvate to acetaldehyde and CO2, and alcohol dehydrogenase reduces acetaldehyde to ethanol using NADH.
37. In the Krebs cycle, how many molecules of NADH, FADH2, and GTP/ATP are produced from ONE molecule of Acetyl-CoA?
Correct Answer: A (3 NADH, 1 FADH2, and 1 GTP/ATP)
One turn of the Krebs cycle per Acetyl-CoA generates 3 NADH, 1 FADH2, and 1 GTP (substrate-level phosphorylation), alongside 2 CO2 molecules.
One turn of the Krebs cycle per Acetyl-CoA generates 3 NADH, 1 FADH2, and 1 GTP (substrate-level phosphorylation), alongside 2 CO2 molecules.
38. In the mitochondrial electron transport system, Cytochrome c is a small mobile protein located on the:
Correct Answer: B (Outer surface of the inner mitochondrial membrane)
Cytochrome c is a mobile electron carrier on the outer face of the inner mitochondrial membrane that shuttles electrons from Complex III to Complex IV.
Cytochrome c is a mobile electron carrier on the outer face of the inner mitochondrial membrane that shuttles electrons from Complex III to Complex IV.
39. The synthetic auxin widely utilized as a selective herbicide to eradicate broad-leaved dicot weeds in cereal monocot lawns is:
Correct Answer: C (2,4-D)
2,4-D is a synthetic auxin used to eliminate broad-leaved dicot weeds without harming mature monocotyledonous grass and cereal crops.
2,4-D is a synthetic auxin used to eliminate broad-leaved dicot weeds without harming mature monocotyledonous grass and cereal crops.
40. The plant growth regulator that promotes cell division, delays leaf senescence, and helps overcome apical dominance by stimulating lateral buds is:
Correct Answer: B (Cytokinin)
Cytokinins promote cytokinesis, overcome auxin-induced apical dominance by activating axillary buds, and delay senescence (Richmond-Lang effect).
Cytokinins promote cytokinesis, overcome auxin-induced apical dominance by activating axillary buds, and delay senescence (Richmond-Lang effect).
41. Inspiration occurs when intra-pulmonary pressure falls below atmospheric pressure, initiated by the:
Correct Answer: A (Contraction of diaphragm and external intercostal muscles)
Diaphragm contraction flattens it antero-posteriorly, and external intercostal contraction elevates ribs and sternum dorso-ventrally, increasing thoracic volume and lowering intra-pulmonary pressure.
Diaphragm contraction flattens it antero-posteriorly, and external intercostal contraction elevates ribs and sternum dorso-ventrally, increasing thoracic volume and lowering intra-pulmonary pressure.
42. Functional Residual Capacity (FRC) in the human respiratory system equals:
Correct Answer: B (ERV + RV)
Functional Residual Capacity is the volume of air remaining in the lungs after a normal tidal expiration, consisting of ERV (~1000 mL) + RV (~1200 mL) = ~2200 mL.
Functional Residual Capacity is the volume of air remaining in the lungs after a normal tidal expiration, consisting of ERV (~1000 mL) + RV (~1200 mL) = ~2200 mL.
43. The second heart sound (‘dub’) is produced at the beginning of ventricular diastole due to the:
Correct Answer: B (Closure of aortic and pulmonary semilunar valves)
As ventricles relax and pressure drops below arterial pressure, backflow closes the aortic and pulmonary semilunar valves, producing the higher-pitched ‘dub’ sound.
As ventricles relax and pressure drops below arterial pressure, backflow closes the aortic and pulmonary semilunar valves, producing the higher-pitched ‘dub’ sound.
44. A person with blood group AB is called a universal recipient because their blood contains:
Correct Answer: B (Both A and B antigens on RBCs, and no antibodies in plasma)
AB individuals express both A and B agglutinogens on erythrocytes and lack anti-A/anti-B agglutinins in plasma, allowing them to receive red cells from any ABO blood group.
AB individuals express both A and B agglutinogens on erythrocytes and lack anti-A/anti-B agglutinins in plasma, allowing them to receive red cells from any ABO blood group.
45. In human nephrons, the ascending limb of Henle’s loop is:
Correct Answer: B (Impermeable to water and transports electrolytes)
The ascending limb prevents water passage while transporting NaCl out into the medullary interstitium, diluting the tubular filtrate as it ascends toward the cortex.
The ascending limb prevents water passage while transporting NaCl out into the medullary interstitium, diluting the tubular filtrate as it ascends toward the cortex.
46. Glomerular capillary blood pressure causes filtration of blood through three structural layers comprising the:
Correct Answer: A (Endothelium, basement membrane, and podocyte slit pores)
The filtration membrane comprises the fenestrated capillary endothelium, the acellular basement membrane, and the visceral Bowman’s layer of podocytes with filtration slits.
The filtration membrane comprises the fenestrated capillary endothelium, the acellular basement membrane, and the visceral Bowman’s layer of podocytes with filtration slits.
47. The total number of pairs of floating ribs that are not attached ventrally to the sternum in humans is:
Correct Answer: C (2 pairs: 11th and 12th ribs)
The 11th and 12th rib pairs attach dorsally to thoracic vertebrae but remain unattached ventrally, protecting the kidneys as floating ribs.
The 11th and 12th rib pairs attach dorsally to thoracic vertebrae but remain unattached ventrally, protecting the kidneys as floating ribs.
48. Saltatory nerve impulse conduction occurs in myelinated nerve fibers because action potentials:
Correct Answer: B (Jump from one Node of Ranvier to the next)
Myelin acts as an insulator; ionic depolarization occurs exclusively at unmyelinated Nodes of Ranvier, speeding up impulse transmission.
Myelin acts as an insulator; ionic depolarization occurs exclusively at unmyelinated Nodes of Ranvier, speeding up impulse transmission.
49. The blind spot in the human eye retina is the anatomical region where:
Correct Answer: B (Optic nerve exits and photoreceptors are absent)
The blind spot (optic disc) lacks rods and cones because ganglion cell axons converge here to form the optic nerve, rendering it insensitive to light.
The blind spot (optic disc) lacks rods and cones because ganglion cell axons converge here to form the optic nerve, rendering it insensitive to light.
50. The fight-or-flight hormones (emergency hormones) Epinephrine and Norepinephrine are secreted by the:
Correct Answer: B (Adrenal medulla)
The adrenal medulla secretes catecholamines (adrenaline/epinephrine and noradrenaline/norepinephrine) in response to sympathetic activation during stress.
The adrenal medulla secretes catecholamines (adrenaline/epinephrine and noradrenaline/norepinephrine) in response to sympathetic activation during stress.
51. The phenomenon where the pollen tube enters the ovule through the integuments or funiculus instead of the micropyle is called:
Correct Answer: C (Mesogamy)
Pollen tube entry through the micropyle is Porogamy, through the chalaza is Chalazogamy (Casuarina), and through the integuments or funiculus is Mesogamy (Cucurbita).
Pollen tube entry through the micropyle is Porogamy, through the chalaza is Chalazogamy (Casuarina), and through the integuments or funiculus is Mesogamy (Cucurbita).
52. Perisperm represents persistent nutritive tissue derived from the remnants of the:
Correct Answer: B (Nucellus)
While nucellar tissue is typically consumed during seed maturation, in black pepper and sugar beet it persists as a dry nutritive perisperm outside the endosperm.
While nucellar tissue is typically consumed during seed maturation, in black pepper and sugar beet it persists as a dry nutritive perisperm outside the endosperm.
53. In flowering plants, self-incompatibility is a genetic mechanism that prevents self-pollen from fertilizing the ovules by:
Correct Answer: B (Inhibiting pollen germination or tube growth in the pistil)
Self-incompatibility is an outbreeding adaptation governed by multiple S-alleles that halts self-pollen germination or retards style tube growth.
Self-incompatibility is an outbreeding adaptation governed by multiple S-alleles that halts self-pollen germination or retards style tube growth.
54. During human spermatogenesis, the morphological transformation of non-motile haploid spermatids into functional spermatozoa is termed:
Correct Answer: B (Spermiogenesis)
Spermiogenesis transforms spherical spermatids into flagellated spermatozoa. Spermiation is the subsequent release of mature spermatozoa from Sertoli cells into the seminiferous tubule lumen.
Spermiogenesis transforms spherical spermatids into flagellated spermatozoa. Spermiation is the subsequent release of mature spermatozoa from Sertoli cells into the seminiferous tubule lumen.
55. Which layer of the mammalian Graafian follicle is vascularized and secretes estrogen?
Correct Answer: B (Theca interna)
The theca interna is the cellular, vascular inner layer of the mature ovarian follicle that produces androgens, which are converted to estrogen by granulosa cells.
The theca interna is the cellular, vascular inner layer of the mature ovarian follicle that produces androgens, which are converted to estrogen by granulosa cells.
56. The degeneration of the corpus luteum into a fibrotic white scar called the corpus albicans occurs when:
Correct Answer: A (Fertilization does not occur and LH levels decline)
In the absence of fertilization and hCG signaling, the corpus luteum regresses into a non-functional fibrous corpus albicans, triggering progesterone drop and menstruation.
In the absence of fertilization and hCG signaling, the corpus luteum regresses into a non-functional fibrous corpus albicans, triggering progesterone drop and menstruation.
57. The fast block to polyspermy during mammalian fertilization is caused by:
Correct Answer: B (Depolarization of the oocyte plasma membrane)
Initial sperm-egg fusion causes an influx of Na+ that depolarizes the oolemma (fast electrical block), followed by Ca2+-mediated cortical granule exocytosis that hardens the zona pellucida (slow block).
Initial sperm-egg fusion causes an influx of Na+ that depolarizes the oolemma (fast electrical block), followed by Ca2+-mediated cortical granule exocytosis that hardens the zona pellucida (slow block).
58. The hormone Relaxin, which softens the pubic symphysis to facilitate parturition, is secreted during late pregnancy by the:
Correct Answer: B (Ovary and Placenta)
Relaxin is secreted by the corpus luteum and placenta during late gestation to loosen pelvic ligaments and dilate the cervix for delivery.
Relaxin is secreted by the corpus luteum and placenta during late gestation to loosen pelvic ligaments and dilate the cervix for delivery.
59. Sterilization in human females accomplished by cutting and ligating a small segment of the fallopian tubes is:
Correct Answer: B (Tubectomy)
Tubectomy is surgical female sterilization where a small part of both fallopian tubes is excised or tied off to block ovum transport and prevent fertilization.
Tubectomy is surgical female sterilization where a small part of both fallopian tubes is excised or tied off to block ovum transport and prevent fertilization.
60. In severe cases of male factor infertility characterized by extremely low sperm counts or poor motility, the preferred laboratory ART method is:
Correct Answer: B (ICSI)
In ICSI, a single selected sperm is micro-injected directly into the cytoplasm of an ovum in vitro, overcoming severe oligozoospermia or asthenozoospermia.
In ICSI, a single selected sperm is micro-injected directly into the cytoplasm of an ovum in vitro, overcoming severe oligozoospermia or asthenozoospermia.
61. When a cross is made between tall yellow pea plants (TtYy) and dwarf green pea plants (ttyy), the phenotypic ratio of offspring is:
Correct Answer: B (1 : 1 : 1 : 1)
A dihybrid test cross between a heterozygous double dominant (TtYy) and homozygous double recessive (ttyy) yields a 1:1:1:1 phenotypic and genotypic ratio.
A dihybrid test cross between a heterozygous double dominant (TtYy) and homozygous double recessive (ttyy) yields a 1:1:1:1 phenotypic and genotypic ratio.
62. T.H. Morgan observed 1.3% recombination between the genes for yellow body and white eyes in Drosophila, which indicated that these two genes are:
Correct Answer: B (Tightly linked on the same X chromosome)
A low recombination frequency (1.3%) indicates that the genes for yellow body and white eyes are located physically close together on the X chromosome, showing strong genetic linkage.
A low recombination frequency (1.3%) indicates that the genes for yellow body and white eyes are located physically close together on the X chromosome, showing strong genetic linkage.
63. Phenylketonuria (PKU) is an inborn error of metabolism caused by a deficiency in which hepatic enzyme?
Correct Answer: B (Phenylalanine hydroxylase)
PKU is an autosomal recessive pleiotropic disorder caused by mutations in the PAH gene, preventing conversion of phenylalanine to tyrosine and leading to toxic phenylpyruvic acid accumulation and mental impairment.
PKU is an autosomal recessive pleiotropic disorder caused by mutations in the PAH gene, preventing conversion of phenylalanine to tyrosine and leading to toxic phenylpyruvic acid accumulation and mental impairment.
64. In a DNA nucleotide strand, adjacent deoxyribose sugar units are linked to each other by:
Correct Answer: C (3′-5′ Phosphodiester bonds)
Nucleotides within a single DNA strand are covalently linked by 3′-5′ phosphodiester bonds between the 3′-OH of one sugar and the 5′-phosphate group of the adjacent sugar.
Nucleotides within a single DNA strand are covalently linked by 3′-5′ phosphodiester bonds between the 3′-OH of one sugar and the 5′-phosphate group of the adjacent sugar.
65. In prokaryotic transcription, the core RNA polymerase enzyme holoenzyme consists of which subunit composition?
Correct Answer: B (Alpha2, Beta, Beta-prime, Omega + Sigma factor)
The E. coli RNA polymerase core enzyme has 5 subunits (alpha2, beta, beta-prime, omega). Association with the initiation sigma factor forms the complete functional holoenzyme.
The E. coli RNA polymerase core enzyme has 5 subunits (alpha2, beta, beta-prime, omega). Association with the initiation sigma factor forms the complete functional holoenzyme.
66. The catalytic ribozyme present in the 50S large ribosomal subunit of prokaryotes responsible for peptide bond synthesis is:
Correct Answer: B (23S rRNA)
The 23S rRNA component of the prokaryotic 50S ribosomal subunit acts as a ribozyme (peptidyl transferase), catalyzing peptide bond formation between amino acids.
The 23S rRNA component of the prokaryotic 50S ribosomal subunit acts as a ribozyme (peptidyl transferase), catalyzing peptide bond formation between amino acids.
67. The total number of base pairs in the haploid human genome and the estimated average number of genes documented by the Human Genome Project are:
Correct Answer: A (3 x 10^9 base pairs and ~30,000 genes)
The human haploid genome contains 3.1647 billion base pairs (~3 x 10^9 bp) coding for roughly 25,000–30,000 functional genes.
The human haploid genome contains 3.1647 billion base pairs (~3 x 10^9 bp) coding for roughly 25,000–30,000 functional genes.
68. The biochemical evidence that all living organisms share a common evolutionary ancestor is demonstrated by the universal occurrence of:
Correct Answer: B (Similar genetic code, ATP, and Cytochrome c)
The universality of the triplet genetic code, identical ATP-based energetic pathways, and homologous proteins like Cytochrome c point to a single common origin of life.
The universality of the triplet genetic code, identical ATP-based energetic pathways, and homologous proteins like Cytochrome c point to a single common origin of life.
69. The evolutionary phenomenon where two morphologically extreme phenotypes are favored over the intermediate average phenotype in a population is:
Correct Answer: C (Disruptive selection)
Disruptive selection selects against mean traits and favors both phenotypic extremes, producing a bimodal distribution curve and potentially splitting the population into two sub-species.
Disruptive selection selects against mean traits and favors both phenotypic extremes, producing a bimodal distribution curve and potentially splitting the population into two sub-species.
70. The hominid ancestor known as “Java Man” who lived around 1.5 million years ago and was the first to use fire belongs to:
Correct Answer: B (Homo erectus)
Homo erectus fossils found in Java (1891) had a cranial capacity of ~900 cc, walked fully upright, and showed evidence of both meat consumption and controlled fire use.
Homo erectus fossils found in Java (1891) had a cranial capacity of ~900 cc, walked fully upright, and showed evidence of both meat consumption and controlled fire use.
71. In human filariasis (Elephantiasis), chronic inflammation leads to swelling of the scrotum and lower limbs because the nematode parasite lodges inside:
Correct Answer: B (Lymphatic vessels)
Adult Wuchereria bancrofti worms reside in the lymphatic channels of the lower extremities and groin, causing lymphatic obstruction, lymphedema, and gross deformities.
Adult Wuchereria bancrofti worms reside in the lymphatic channels of the lower extremities and groin, causing lymphatic obstruction, lymphedema, and gross deformities.
72. Which type of immunity is developed when ready-made antibodies are injected directly into a patient to neutralize snake venom?
Correct Answer: B (Passive artificial immunity)
Antivenom contains preformed neutralizing antibodies raised in donor animals, providing immediate passive artificial protection against lethal snake toxins.
Antivenom contains preformed neutralizing antibodies raised in donor animals, providing immediate passive artificial protection against lethal snake toxins.
73. A diagnostic technique that uses strong magnetic fields and non-ionizing radiation to generate high-resolution 3D images of internal physiological lesions and tumors is:
Correct Answer: B (MRI)
MRI uses magnetic fields and radiofrequency pulses (non-ionizing radiation) to generate high-contrast images of soft tissues, making it effective for tumor diagnosis without radiation hazards.
MRI uses magnetic fields and radiofrequency pulses (non-ionizing radiation) to generate high-contrast images of soft tissues, making it effective for tumor diagnosis without radiation hazards.
74. The cellular oncogenes (c-onc) or proto-oncogenes present in normal human cells can trigger malignant neoplastic transformation when:
Correct Answer: A (Activated or mutated by carcinogens)
Proto-oncogenes regulate normal cellular growth; when mutated or activated by physical, chemical, or biological carcinogens, they become active oncogenes driving uncontrolled division.
Proto-oncogenes regulate normal cellular growth; when mutated or activated by physical, chemical, or biological carcinogens, they become active oncogenes driving uncontrolled division.
75. The psychoactive chemical “Cannabinoid” extracted from Cannabis sativa binds to cannabinoid receptors primarily located in the:
Correct Answer: B (Brain and central nervous system)
Cannabinoids interact with specific cannabinoid receptors located primarily in the brain, altering mood, sensory perception, and cardiovascular function.
Cannabinoids interact with specific cannabinoid receptors located primarily in the brain, altering mood, sensory perception, and cardiovascular function.
76. The industrial production of ethanol from molasses is carried out using the yeast strain:
Correct Answer: A (Saccharomyces cerevisiae)
Saccharomyces cerevisiae (Brewer’s yeast) ferments sugary substrates into ethanol and CO2 in large industrial fermenters.
Saccharomyces cerevisiae (Brewer’s yeast) ferments sugary substrates into ethanol and CO2 in large industrial fermenters.
77. The organic acid produced by the anaerobic bacterium Clostridium butylicum is:
Correct Answer: C (Butyric acid)
Clostridium butylicum produces butyric acid; Aspergillus niger produces citric acid; Acetobacter aceti yields acetic acid; and Lactobacillus yields lactic acid.
Clostridium butylicum produces butyric acid; Aspergillus niger produces citric acid; Acetobacter aceti yields acetic acid; and Lactobacillus yields lactic acid.
78. During the physical primary treatment of municipal sewage water, floating debris and solid soil grit are removed respectively by:
Correct Answer: A (Sequential filtration and sedimentation)
Primary sewage treatment physically removes floating debris via mesh filtration and settles out grit and coarse soil particles in primary settling tanks.
Primary sewage treatment physically removes floating debris via mesh filtration and settles out grit and coarse soil particles in primary settling tanks.
79. Dried spores of the bacterium Bacillus thuringiensis sold in sachets are mixed with water and sprayed to control:
Correct Answer: B (Butterfly caterpillars and insect larvae)
Bt spores sprayed on brassicas or fruit trees are ingested by caterpillars; the alkaline gut environment activates the Cry toxin, killing the larvae.
Bt spores sprayed on brassicas or fruit trees are ingested by caterpillars; the alkaline gut environment activates the Cry toxin, killing the larvae.
80. Free-living soil bacteria capable of fixing atmospheric nitrogen without forming root nodules include:
Correct Answer: C (Azotobacter and Beijerinckia)
Azotobacter (aerobic) and Rhodospirillum (anaerobic) are free-living nitrogen fixers. Rhizobium and Frankia are symbiotic nodule-forming nitrogen fixers.
Azotobacter (aerobic) and Rhodospirillum (anaerobic) are free-living nitrogen fixers. Rhizobium and Frankia are symbiotic nodule-forming nitrogen fixers.
81. In an agarose gel electrophoresis apparatus, DNA fragments load at the cathode (-) and migrate toward the anode (+) because:
Correct Answer: B (The sugar-phosphate backbone carries a net negative charge)
Negatively charged phosphate groups in the DNA backbone cause fragments to migrate toward the positive anode when an electric field is applied across the gel.
Negatively charged phosphate groups in the DNA backbone cause fragments to migrate toward the positive anode when an electric field is applied across the gel.
82. The specific vector used to transfer recombinant genes into animal cells that integrates genes into the host chromosome is a disarmed:
Correct Answer: B (Retrovirus)
Disarmed retroviruses deliver therapeutic or recombinant genes into animal and human cells, while disarmed Ti-plasmids of Agrobacterium tumefaciens are used for plant systems.
Disarmed retroviruses deliver therapeutic or recombinant genes into animal and human cells, while disarmed Ti-plasmids of Agrobacterium tumefaciens are used for plant systems.
83. During PCR amplification, oligonucleotide primers bind to single-stranded DNA templates during which thermal step?
Correct Answer: B (Annealing)
In PCR: Denaturation (~94°C) unzips the duplex; Annealing (~50–60°C) allows primers to base-pair with complementary flanking sequences; Extension (~72°C) synthesizes new DNA via Taq polymerase.
In PCR: Denaturation (~94°C) unzips the duplex; Annealing (~50–60°C) allows primers to base-pair with complementary flanking sequences; Extension (~72°C) synthesizes new DNA via Taq polymerase.
84. The continuous culture method in industrial bioreactors maintains cells in their physiologically most active exponential phase by:
Correct Answer: A (Continuously draining spent medium and adding fresh medium)
Continuous culture keeps cells in steady-state exponential (log) growth, maximizing biomass and product yields compared to closed batch systems.
Continuous culture keeps cells in steady-state exponential (log) growth, maximizing biomass and product yields compared to closed batch systems.
85. The cryIAb gene from Bacillus thuringiensis is engineered into crops to provide resistance against:
Correct Answer: B (Corn borer)
The cryIAb gene specifically controls corn borer pests in transgenic maize, whereas cryIAc and cryIIAb control cotton bollworms.
The cryIAb gene specifically controls corn borer pests in transgenic maize, whereas cryIAc and cryIIAb control cotton bollworms.
86. In RNA interference (RNAi), the silencing of specific mRNA molecules is mediated by:
Correct Answer: B (Double-stranded RNA processed into siRNAs)
In RNAi, Dicer processes dsRNA into small interfering RNAs (siRNAs), which guide the RISC complex to cleave complementary target mRNAs, blocking translation.
In RNAi, Dicer processes dsRNA into small interfering RNAs (siRNAs), which guide the RISC complex to cleave complementary target mRNAs, blocking translation.
87. Recombinant human insulin production by Eli Lilly was achieved by synthesizing A and B peptide chains separately in:
Correct Answer: A (Escherichia coli)
Eli Lilly prepared two separate DNA sequences for insulin chains A and B, expressed them in E. coli host cells, and joined the purified chains with disulfide bonds.
Eli Lilly prepared two separate DNA sequences for insulin chains A and B, expressed them in E. coli host cells, and joined the purified chains with disulfide bonds.
88. Adenosine Deaminase (ADA) deficiency can be managed by periodically administering the functional enzyme to patients through:
Correct Answer: B (Enzyme replacement therapy)
In enzyme replacement therapy, purified functional ADA enzyme is periodically injected into the patient. While palliative, it is not a permanent cure (which requires bone marrow stem cell gene therapy).
In enzyme replacement therapy, purified functional ADA enzyme is periodically injected into the patient. While palliative, it is not a permanent cure (which requires bone marrow stem cell gene therapy).
89. The diagnostic technique ELISA (Enzyme-Linked Immunosorbent Assay) relies on:
Correct Answer: B (Antigen-Antibody interactions)
ELISA identifies infections by detecting pathogen-specific antigens or host-generated antibodies using enzyme-linked chromogenic reporter assays.
ELISA identifies infections by detecting pathogen-specific antigens or host-generated antibodies using enzyme-linked chromogenic reporter assays.
90. Commercial exploitation of indigenous bio-resources by multinational corporations without proper authorization or fair benefit sharing is termed:
Correct Answer: C (Biopiracy)
Biopiracy refers to patenting or commercially exploiting traditional bioresources and indigenous knowledge without authorization or compensatory benefit-sharing.
Biopiracy refers to patenting or commercially exploiting traditional bioresources and indigenous knowledge without authorization or compensatory benefit-sharing.
91. The sea anemone and hermit crab association, where the crab gains camouflage and the anemone gets transport and food scraps, is an example of:
Correct Answer: B (Mutualism / Proto-cooperation)
Both partners benefit (+, +): the hermit crab gains protective camouflage and stinging defense from the anemone, while the sea anemone receives mobility and access to food particles.
Both partners benefit (+, +): the hermit crab gains protective camouflage and stinging defense from the anemone, while the sea anemone receives mobility and access to food particles.
92. In a population with an urn-shaped age pyramid, the birth rate is low and the proportion of pre-reproductive individuals is:
Correct Answer: B (Smaller than the reproductive age group)
An urn-shaped pyramid has a narrow pre-reproductive base, reflecting low birth rates and a declining or negative-growth population.
An urn-shaped pyramid has a narrow pre-reproductive base, reflecting low birth rates and a declining or negative-growth population.
93. The entire sequential series of biological communities that successfully replace one another in a given habitat during succession is called a:
Correct Answer: A (Sere)
The complete sequence of transitional communities that replace each other from pioneer colonization to the stable climax community is known as a sere (or seral stages).
The complete sequence of transitional communities that replace each other from pioneer colonization to the stable climax community is known as a sere (or seral stages).
94. In hydrarch ecological succession in water bodies, the pioneer stage and climax community are respectively:
Correct Answer: B (Phytoplankton and Forest)
Hydrarch succession begins with floating phytoplankton pioneers and progresses through submerged, floating, reed-swamp, marsh-meadow, and scrub stages to reach a mesic forest climax.
Hydrarch succession begins with floating phytoplankton pioneers and progresses through submerged, floating, reed-swamp, marsh-meadow, and scrub stages to reach a mesic forest climax.
95. In an aquatic ecosystem (e.g., lake or pond), the pyramid of biomass is inverted because:
Correct Answer: B (Standing biomass of phytoplankton is smaller)
Microscopic phytoplankton have high metabolic rates, rapid cell division, and short lifespans, so their standing biomass at any moment is smaller than the larger, longer-lived fish they support.
Microscopic phytoplankton have high metabolic rates, rapid cell division, and short lifespans, so their standing biomass at any moment is smaller than the larger, longer-lived fish they support.
96. High species richness in tropical rainforests compared to temperate zones is attributed to:
Correct Answer: B (Evolutionary stability, less seasonality, and high solar energy)
Tropical latitudes have remained unglaciated for millions of years, offering predictable warm climates and abundant solar irradiance that foster speciation.
Tropical latitudes have remained unglaciated for millions of years, offering predictable warm climates and abundant solar irradiance that foster speciation.
97. The catastrophic extinction of hundreds of native cichlid fish species in Lake Victoria following the introduction of an alien predator illustrates:
Correct Answer: B (Alien species invasion)
Introducing the predatory Nile Perch into Lake Victoria caused the extinction of over 200 endemic cichlid fish species due to heavy predation and competition.
Introducing the predatory Nile Perch into Lake Victoria caused the extinction of over 200 endemic cichlid fish species due to heavy predation and competition.
98. Water Hyacinth (Eichhornia crassipes), introduced for its purple flowers and leaf shape, is called the “Terror of Bengal” because it:
Correct Answer: B (Grows rapidly, depleting dissolved oxygen and killing fish)
Eichhornia forms dense floating mats over static water bodies that block sunlight, extract dissolved oxygen, and cause mass fish mortality.
Eichhornia forms dense floating mats over static water bodies that block sunlight, extract dissolved oxygen, and cause mass fish mortality.
99. Which international biodiversity convention treaty came into force following the 1992 Earth Summit in Rio de Janeiro?
Correct Answer: A (Convention on Biological Diversity)
The 1992 Earth Summit in Rio de Janeiro established the Convention on Biological Diversity (CBD) to promote biodiversity conservation and equitable sharing of genetic resources.
The 1992 Earth Summit in Rio de Janeiro established the Convention on Biological Diversity (CBD) to promote biodiversity conservation and equitable sharing of genetic resources.
100. The total number of designated Biodiversity Hotspots in the world that feature exceptional endemism and severe habitat loss is:
Correct Answer: C (34)
Initially, 25 hotspots were identified by Norman Myers; 9 more have been added, bringing the global total to 34 hotspots that cover less than 2% of Earth’s land while harboring over 50% of plant and animal species.
Initially, 25 hotspots were identified by Norman Myers; 9 more have been added, bringing the global total to 34 hotspots that cover less than 2% of Earth’s land while harboring over 50% of plant and animal species.