1. In biological classification, which category includes one or more related orders sharing common characteristics?
Correct Answer: C (Class)
A Class is a taxonomic rank that encompasses one or more related orders (for example, Order Primata and Order Carnivora are placed under Class Mammalia).
A Class is a taxonomic rank that encompasses one or more related orders (for example, Order Primata and Order Carnivora are placed under Class Mammalia).
2. Archaebacteria differ from eubacteria primarily in having:
Correct Answer: B (Distinct cell wall structure and branched-chain membrane lipids)
Archaebacteria lack peptidoglycan (possessing pseudomurein or complex proteins) and have branched ether-linked lipids in their membranes, allowing them to withstand extreme heat, salinity, and pH.
Archaebacteria lack peptidoglycan (possessing pseudomurein or complex proteins) and have branched ether-linked lipids in their membranes, allowing them to withstand extreme heat, salinity, and pH.
3. Which protists possess two flagella, cell wall plates composed of stiff cellulose, and pigments ranging from yellow, green, brown, blue, to red?
Correct Answer: B (Dinoflagellates)
Dinoflagellates are mostly marine, photosynthetic organisms with cell walls containing rigid cellulose plates, one longitudinal flagellum, and one transverse flagellum in a helical groove.
Dinoflagellates are mostly marine, photosynthetic organisms with cell walls containing rigid cellulose plates, one longitudinal flagellum, and one transverse flagellum in a helical groove.
4. The vegetative body of a fungus consisting of a network of interwoven filamentous hyphae is termed:
Correct Answer: B (Mycelium)
The network of tubular, branched filamentous units (hyphae) constituting the vegetative body of a true fungus is called a mycelium.
The network of tubular, branched filamentous units (hyphae) constituting the vegetative body of a true fungus is called a mycelium.
5. Red algae (Rhodophyceae) are predominantly marine and thrive at great ocean depths because:
Correct Answer: B (r-phycoerythrin efficiently absorbs blue-green light)
The accessory pigment r-phycoerythrin absorbs blue-green wavelengths that penetrate deep into the water column, allowing red algae to inhabit both well-lit surfaces and deep marine zones.
The accessory pigment r-phycoerythrin absorbs blue-green wavelengths that penetrate deep into the water column, allowing red algae to inhabit both well-lit surfaces and deep marine zones.
6. In pteridophytes, the dominant, vascularized, independent phase of the life cycle is represented by the:
Correct Answer: B (Diploid sporophyte)
Unlike bryophytes (where the gametophyte is dominant), pteridophytes have a dominant, free-living diploid sporophyte containing true xylem and phloem.
Unlike bryophytes (where the gametophyte is dominant), pteridophytes have a dominant, free-living diploid sporophyte containing true xylem and phloem.
7. The branched stem condition is observed in which of the following gymnosperms?
Correct Answer: B (Pinus and Cedrus)
In gymnosperms, the stem may be unbranched (as in Cycas) or branched (as in Pinus and Cedrus).
In gymnosperms, the stem may be unbranched (as in Cycas) or branched (as in Pinus and Cedrus).
8. Bioluminescence is well-marked and an exclusive property of which animal phylum?
Correct Answer: C (Ctenophora)
Bioluminescence (the ability of a living organism to emit light) is a prominent characteristic of all ctenophores (e.g., Pleurobrachia and Ctenoplana).
Bioluminescence (the ability of a living organism to emit light) is a prominent characteristic of all ctenophores (e.g., Pleurobrachia and Ctenoplana).
9. Which of the following molluscs is commonly known as the “Cuttlefish”?
Correct Answer: B (Sepia)
Sepia is commonly called the Cuttlefish, Loligo is the Squid, Octopus is the Devilfish, and Aplysia is the Sea hare.
Sepia is commonly called the Cuttlefish, Loligo is the Squid, Octopus is the Devilfish, and Aplysia is the Sea hare.
10. Cold-blooded (poikilothermic) animals having a 3-chambered heart (2 atria, 1 ventricle) and performing external fertilization in water belong to class:
Correct Answer: B (Amphibia)
Amphibians are poikilotherms with moist scaleless skin, a 3-chambered heart (with sinus venosus and conus arteriosus), and external fertilization in aquatic environments.
Amphibians are poikilotherms with moist scaleless skin, a 3-chambered heart (with sinus venosus and conus arteriosus), and external fertilization in aquatic environments.
11. In Calotropis and Guava, a pair of leaves arises at each node and lies opposite to each other, representing:
Correct Answer: B (Opposite phyllotaxy)
In opposite phyllotaxy (e.g., Calotropis, Guava), two leaves arise at each node facing opposite directions. In alternate phyllotaxy (China rose, mustard), a single leaf arises at each node.
In opposite phyllotaxy (e.g., Calotropis, Guava), two leaves arise at each node facing opposite directions. In alternate phyllotaxy (China rose, mustard), a single leaf arises at each node.
12. A sterile pistil that fails to produce viable seeds is called a:
Correct Answer: B (Pistillode)
A sterile or non-functional pistil is termed a pistillode. A sterile stamen is called a staminode.
A sterile or non-functional pistil is termed a pistillode. A sterile stamen is called a staminode.
13. In family Solanaceae, the persistent calyx that often enlarges along with the developing fruit is seen in:
Correct Answer: A (Physalis and Brinjal)
Family Solanaceae is characterized by a gamosepalous, persistent calyx that remains attached to mature fruits (e.g., Brinjal, Tomato, and accrescent in Physalis).
Family Solanaceae is characterized by a gamosepalous, persistent calyx that remains attached to mature fruits (e.g., Brinjal, Tomato, and accrescent in Physalis).
14. Which dead sclerenchymatous cells are short, spherical or cylindrical with heavily thickened lignified walls and narrow lumens, commonly found in nut shells and tea leaves?
Correct Answer: B (Sclereids)
Sclereids are isometric or cylindrical sclerenchyma cells with very thick lignified secondary walls and branched pit canals, providing hardness to nutshells (walnut, almond) and grit to pear/guava pulp.
Sclereids are isometric or cylindrical sclerenchyma cells with very thick lignified secondary walls and branched pit canals, providing hardness to nutshells (walnut, almond) and grit to pear/guava pulp.
15. In monocotyledonous stems, which tissue is completely absent in the vascular bundles?
Correct Answer: C (Phloem parenchyma and Cambium)
Monocot stems have closed conjoint vascular bundles lacking vascular cambium, and their phloem characteristically lacks phloem parenchyma.
Monocot stems have closed conjoint vascular bundles lacking vascular cambium, and their phloem characteristically lacks phloem parenchyma.
16. The specialized cell junctions that prevent substances from leaking across an epithelial tissue barrier are:
Correct Answer: A (Tight junctions)
Tight junctions fuse the outer plasma membranes of adjacent epithelial cells to create an impermeable seal that prevents fluid and ion leakage across epithelial sheets.
Tight junctions fuse the outer plasma membranes of adjacent epithelial cells to create an impermeable seal that prevents fluid and ion leakage across epithelial sheets.
17. In the digestive tract of frogs, food is propelled through the esophagus into the stomach by muscular contractions known as:
Correct Answer: B (Peristalsis)
Food swallowed whole by the frog is moved through the short esophagus into the stomach via coordinated rhythmic contractions of circular and longitudinal smooth muscles (peristalsis).
Food swallowed whole by the frog is moved through the short esophagus into the stomach via coordinated rhythmic contractions of circular and longitudinal smooth muscles (peristalsis).
18. The total number of spinal nerve pairs emerging from the spinal cord in a frog is:
Correct Answer: A (10 pairs)
In frogs (Rana tigrina), 10 pairs of cranial nerves arise from the brain and 10 pairs of spinal nerves emerge through intervertebral foramina from the spinal cord.
In frogs (Rana tigrina), 10 pairs of cranial nerves arise from the brain and 10 pairs of spinal nerves emerge through intervertebral foramina from the spinal cord.
19. In male frogs, the paired testes are attached to the upper part of the kidneys by a double fold of peritoneum termed the:
Correct Answer: A (Mesorchium)
The male frog testes are suspended from the antero-ventral surface of the kidneys by a specialized peritoneal fold called the mesorchium, through which vasa efferentia pass.
The male frog testes are suspended from the antero-ventral surface of the kidneys by a specialized peritoneal fold called the mesorchium, through which vasa efferentia pass.
20. In frogs, during periods of aestivation (summer sleep) and hibernation (winter sleep), gaseous exchange is carried out exclusively through the:
Correct Answer: C (Moist vascular skin)
During dormant periods (hibernation and aestivation), frogs remain buried underground and rely entirely on cutaneous respiration via dissolved oxygen diffusing across their vascular skin.
During dormant periods (hibernation and aestivation), frogs remain buried underground and rely entirely on cutaneous respiration via dissolved oxygen diffusing across their vascular skin.
21. The fluid mosaic model of cell membranes was proposed by Singer and Nicolson in:
Correct Answer: B (1972)
S.J. Singer and G.L. Nicolson formulated the widely accepted Fluid Mosaic Model in 1972, describing biological membranes as dynamic protein icebergs floating in a sea of fluid phospholipids.
S.J. Singer and G.L. Nicolson formulated the widely accepted Fluid Mosaic Model in 1972, describing biological membranes as dynamic protein icebergs floating in a sea of fluid phospholipids.
22. Which cell organelle contains the highest concentration of hydrolytic digestive enzymes capable of breaking down all biological macromolecules at acidic pH?
Correct Answer: B (Lysosome)
Lysosomes contain acid hydrolases (lipases, proteases, carbohydrases, nucleases) that function optimally at ~pH 5.0 to digest phagocytosed materials and autophagic debris.
Lysosomes contain acid hydrolases (lipases, proteases, carbohydrases, nucleases) that function optimally at ~pH 5.0 to digest phagocytosed materials and autophagic debris.
23. In plant chloroplasts, non-pigmented plastids specialized for storing starch reserves (e.g., in potato tubers) are:
Correct Answer: A (Amyloplasts)
Leucoplasts are non-pigmented storage plastids: Amyloplasts store starch (carbohydrates), Elaioplasts store oils/fats, and Aleuroplasts store proteins.
Leucoplasts are non-pigmented storage plastids: Amyloplasts store starch (carbohydrates), Elaioplasts store oils/fats, and Aleuroplasts store proteins.
24. The axoneme of eukaryotic cilia and flagella is composed of microtubules arranged in which ultrastructural array?
Correct Answer: B (9 + 2 array)
Cilia and flagella contain an axoneme consisting of nine peripheral doublet microtubules surrounding a central pair of single microtubules (9 + 2 pattern) enclosed in a central sheath.
Cilia and flagella contain an axoneme consisting of nine peripheral doublet microtubules surrounding a central pair of single microtubules (9 + 2 pattern) enclosed in a central sheath.
25. Palmitic acid is a saturated fatty acid that possesses how many total carbon atoms including the terminal carboxyl carbon?
Correct Answer: B (16 carbons)
Palmitic acid is a 16-carbon saturated fatty acid (CH3(CH2)14COOH). Arachidonic acid has 20 carbons including the carboxyl carbon.
Palmitic acid is a 16-carbon saturated fatty acid (CH3(CH2)14COOH). Arachidonic acid has 20 carbons including the carboxyl carbon.
26. In the beta-pleated sheet secondary structure of proteins, adjacent polypeptide chains are held together laterally by:
Correct Answer: B (Intermolecular Hydrogen bonds)
In beta-pleated sheets, extended polypeptide strands run parallel or antiparallel and are stabilized by intermolecular hydrogen bonds between backbone C=O and N-H groups.
In beta-pleated sheets, extended polypeptide strands run parallel or antiparallel and are stabilized by intermolecular hydrogen bonds between backbone C=O and N-H groups.
27. An inorganic metallic ion tightly bound to an apoenzyme that is indispensable for its catalytic activity (e.g., Iron in Cytochrome oxidase) is a:
Correct Answer: B (Metal ion cofactor / Prosthetic group)
Enzyme cofactors comprise organic coenzymes (NAD, FAD), tightly bound prosthetic groups (heme), and inorganic metal ions (e.g., Fe2+, Mg2+, Zn2+) coordinating with active site residues.
Enzyme cofactors comprise organic coenzymes (NAD, FAD), tightly bound prosthetic groups (heme), and inorganic metal ions (e.g., Fe2+, Mg2+, Zn2+) coordinating with active site residues.
28. The specialized stage of meiotic Prophase I where crossing over between non-sister chromatids of homologous chromosomes is completed is:
Correct Answer: C (Pachytene)
Pachytene is the tetrad stage where recombinase-mediated crossing over and genetic recombination occur between non-sister chromatids of homologous pairs.
Pachytene is the tetrad stage where recombinase-mediated crossing over and genetic recombination occur between non-sister chromatids of homologous pairs.
29. The alignment of all cellular chromosomes in a single plane across the spindle equator (metaphase plate) defines:
Correct Answer: B (Metaphase)
During metaphase, kinetochore spindle microtubules pull chromosomes to align their centromeres along the equatorial metaphase plate.
During metaphase, kinetochore spindle microtubules pull chromosomes to align their centromeres along the equatorial metaphase plate.
30. If a diploid organism has 2n = 16 chromosomes, how many bivalents (tetrads) will be observed during Zygotene/Pachytene of Meiosis I?
Correct Answer: B (8 bivalents)
Each bivalent consists of a pair of synapsed homologous chromosomes. For 2n = 16, the number of bivalents is n = 8.
Each bivalent consists of a pair of synapsed homologous chromosomes. For 2n = 16, the number of bivalents is n = 8.
31. In photosynthetic light reactions, Photosystem II (P680) is located predominantly in the:
Correct Answer: A (Appressed granal thylakoid membranes)
Photosystem II and its water-splitting complex are concentrated in the stacked (appressed) regions of grana thylakoids, whereas Photosystem I and ATP synthase occupy non-appressed stroma lamellae.
Photosystem II and its water-splitting complex are concentrated in the stacked (appressed) regions of grana thylakoids, whereas Photosystem I and ATP synthase occupy non-appressed stroma lamellae.
32. The primary stable 3-carbon carboxylated product in the C3 Calvin cycle is:
Correct Answer: B (3-Phosphoglyceric acid)
Melvin Calvin used 14CO2 in Chlorella to demonstrate that the first stable product of photosynthetic carbon fixation is 3-phosphoglyceric acid (3-PGA).
Melvin Calvin used 14CO2 in Chlorella to demonstrate that the first stable product of photosynthetic carbon fixation is 3-phosphoglyceric acid (3-PGA).
33. In C4 plants, the enzyme responsible for regenerating phosphoenolpyruvate (PEP) from pyruvate in mesophyll chloroplasts is:
Correct Answer: B (Pyruvate phosphate dikinase)
Pyruvate returned to mesophyll cells is phosphorylated to PEP by pyruvate phosphate dikinase (PPDK), converting ATP to AMP and consuming 2 high-energy phosphate equivalents.
Pyruvate returned to mesophyll cells is phosphorylated to PEP by pyruvate phosphate dikinase (PPDK), converting ATP to AMP and consuming 2 high-energy phosphate equivalents.
34. Photorespiration (C2 cycle) does NOT produce:
Correct Answer: A (ATP or NADPH)
Photorespiration is a wasteful process: it consumes energy (ATP) and fixed carbon, releasing CO2 in mitochondria without generating ATP, NADPH, or sugars.
Photorespiration is a wasteful process: it consumes energy (ATP) and fixed carbon, releasing CO2 in mitochondria without generating ATP, NADPH, or sugars.
35. The pathway of Glycolysis (EMP pathway) consists of a sequential series of how many enzymatic steps?
Correct Answer: C (10 enzymatic reactions)
Glycolysis (formulated by Embden, Meyerhof, and Parnas) consists of 10 cytosolic reactions: 5 in the preparatory investment phase and 5 in the energy-conserving payoff phase.
Glycolysis (formulated by Embden, Meyerhof, and Parnas) consists of 10 cytosolic reactions: 5 in the preparatory investment phase and 5 in the energy-conserving payoff phase.
36. In cellular respiration, the link reaction (oxidative decarboxylation of pyruvate to Acetyl-CoA) takes place in the:
Correct Answer: B (Mitochondrial matrix)
Pyruvate synthesized in the cytoplasm is transported into the mitochondrial matrix, where pyruvate dehydrogenase converts it into Acetyl-CoA, CO2, and NADH.
Pyruvate synthesized in the cytoplasm is transported into the mitochondrial matrix, where pyruvate dehydrogenase converts it into Acetyl-CoA, CO2, and NADH.
37. In the Krebs cycle, the only 5-carbon dicarboxylic intermediate formed during the pathway is:
Correct Answer: C (Alpha-ketoglutaric acid)
Alpha-ketoglutaric acid is the solitary 5-carbon intermediate of the Krebs cycle, formed by the oxidative decarboxylation of 6-carbon isocitrate.
Alpha-ketoglutaric acid is the solitary 5-carbon intermediate of the Krebs cycle, formed by the oxidative decarboxylation of 6-carbon isocitrate.
38. In the mitochondrial electron transport chain, Complex II is biochemically identical to which Krebs cycle enzyme?
Correct Answer: B (Succinate dehydrogenase)
Complex II of the ETS is the enzyme succinate dehydrogenase (succinate:ubiquinone oxidoreductase), which oxidizes succinate to fumarate while reducing FAD to FADH2 in the inner membrane.
Complex II of the ETS is the enzyme succinate dehydrogenase (succinate:ubiquinone oxidoreductase), which oxidizes succinate to fumarate while reducing FAD to FADH2 in the inner membrane.
39. The natural plant hormone identified and isolated from human urine of pellagra patients and later shown to be Indole-3-acetic acid (IAA) is:
Correct Answer: A (Auxin)
Auxin was first isolated from human urine by Kogl and Haagen-Smit (1934) and subsequently confirmed to be indole-3-acetic acid (IAA), the principal natural plant auxin.
Auxin was first isolated from human urine by Kogl and Haagen-Smit (1934) and subsequently confirmed to be indole-3-acetic acid (IAA), the principal natural plant auxin.
40. The term ‘Vernalization’ refers to the:
Correct Answer: B (Promotion of flowering by low temperature)
Vernalization is the quantitative or qualitative dependence of flowering on exposure to low chilling temperatures (1–6°C), as observed in winter wheat, rye, and biennials.
Vernalization is the quantitative or qualitative dependence of flowering on exposure to low chilling temperatures (1–6°C), as observed in winter wheat, rye, and biennials.
41. The volume of air inspired or expired with each normal resting breath (Tidal Volume) in a healthy human adult is approximately:
Correct Answer: B (500 mL)
Tidal Volume (TV) is ~500 mL per breath; breathing 12–16 times per minute yields a resting minute ventilation of 6,000–8,000 mL/min.
Tidal Volume (TV) is ~500 mL per breath; breathing 12–16 times per minute yields a resting minute ventilation of 6,000–8,000 mL/min.
42. What are the partial pressures of Oxygen (pO2) in deoxygenated blood and oxygenated blood respectively (in mm Hg)?
Correct Answer: A (40 mm Hg and 95 mm Hg)
In systemic circulation, deoxygenated venous blood has a pO2 of 40 mm Hg (and pCO2 of 45 mm Hg), while oxygenated arterial blood has a pO2 of 95 mm Hg (and pCO2 of 40 mm Hg).
In systemic circulation, deoxygenated venous blood has a pO2 of 40 mm Hg (and pCO2 of 45 mm Hg), while oxygenated arterial blood has a pO2 of 95 mm Hg (and pCO2 of 40 mm Hg).
43. The specialized agranulocytes that transform into phagocytic macrophages in peripheral tissues are:
Correct Answer: C (Monocytes)
Monocytes (6–8% of WBCs) are large kidney-shaped agranulocytes that circulate in blood before entering tissues to differentiate into resident macrophages and dendritic cells.
Monocytes (6–8% of WBCs) are large kidney-shaped agranulocytes that circulate in blood before entering tissues to differentiate into resident macrophages and dendritic cells.
44. On a standard clinical ECG recording, what does the T-wave represent?
Correct Answer: C (Repolarization of ventricles)
The P-wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T-wave marks ventricular repolarization (ventricular diastole recovery).
The P-wave represents atrial depolarization, the QRS complex represents ventricular depolarization, and the T-wave marks ventricular repolarization (ventricular diastole recovery).
45. In the Renin-Angiotensin-Aldosterone System (RAAS), the substrate Angiotensinogen is produced by the:
Correct Answer: B (Liver)
The plasma protein angiotensinogen is synthesized and secreted by the liver; renal renin cleaves it into Angiotensin I, which ACE in pulmonary endothelium converts to Angiotensin II.
The plasma protein angiotensinogen is synthesized and secreted by the liver; renal renin cleaves it into Angiotensin I, which ACE in pulmonary endothelium converts to Angiotensin II.
46. The thin structural filament of skeletal muscle myofibrils is composed of which three proteins?
Correct Answer: A (F-Actin, Tropomyosin, and Troponin)
Each thin filament consists of two helically wound strands of filamentous actin (F-actin), two strands of regulatory tropomyosin, and complex troponin units bound at regular intervals.
Each thin filament consists of two helically wound strands of filamentous actin (F-actin), two strands of regulatory tropomyosin, and complex troponin units bound at regular intervals.
47. How many total pairs of ribs form the human thoracic rib cage?
Correct Answer: B (12 pairs)
The human thorax contains 12 rib pairs: 1–7 are vertebrosternal (true ribs), 8–10 are vertebrochondral (false ribs), and 11–12 are vertebral (floating ribs).
The human thorax contains 12 rib pairs: 1–7 are vertebrosternal (true ribs), 8–10 are vertebrochondral (false ribs), and 11–12 are vertebral (floating ribs).
48. The autoimmune inflammatory disorder characterized by antibodies attacking joint synovial membranes, causing synovial hypertrophy and erosion of articular cartilage, is:
Correct Answer: B (Rheumatoid Arthritis)
Rheumatoid arthritis is an autoimmune condition where autoantibodies (Rheumatoid Factor) attack synovial joints, forming an inflammatory pannus that erodes cartilage.
Rheumatoid arthritis is an autoimmune condition where autoantibodies (Rheumatoid Factor) attack synovial joints, forming an inflammatory pannus that erodes cartilage.
49. The cerebral hemisphere white matter tract that connects the left and right cerebral hemispheres is the:
Correct Answer: B (Corpus callosum)
The left and right cerebral hemispheres are interconnected by a thick transverse band of commissural myelinated nerve fibers called the corpus callosum.
The left and right cerebral hemispheres are interconnected by a thick transverse band of commissural myelinated nerve fibers called the corpus callosum.
50. Destruction of the adrenal cortex causing deficiency of glucocorticoids and mineralocorticoids leads to Addison’s disease, characterized by:
Correct Answer: B (Extreme weakness, fatigue, low blood pressure, and bronze skin)
Addison’s disease results from adrenal cortical hyposecretion; lack of cortisol and aldosterone causes hypoglycemia, hyponatremia, hypotension, and melanocyte-stimulating hyperpigmentation.
Addison’s disease results from adrenal cortical hyposecretion; lack of cortisol and aldosterone causes hypoglycemia, hyponatremia, hypotension, and melanocyte-stimulating hyperpigmentation.
51. The phenomenon of “Double Fertilization” in angiosperms involves two distinct fusion events:
Correct Answer: A (Syngamy and Triple Fusion)
Double fertilization is unique to angiosperms: one sperm fertilizes the egg to yield a diploid zygote (2n), while the second sperm fuses with two polar nuclei to yield a triploid primary endosperm nucleus (3n).
Double fertilization is unique to angiosperms: one sperm fertilizes the egg to yield a diploid zygote (2n), while the second sperm fuses with two polar nuclei to yield a triploid primary endosperm nucleus (3n).
52. A true fruit (eucarp) is defined biologically as a:
Correct Answer: B (Mature, ripened ovary developed exclusively following fertilization)
A true fruit (eucarp, e.g., mango, tomato) develops solely from the fertilized ovarian wall, whereas false fruits incorporate floral parts like the thalamus or calyx.
A true fruit (eucarp, e.g., mango, tomato) develops solely from the fertilized ovarian wall, whereas false fruits incorporate floral parts like the thalamus or calyx.
53. In an anatropous (inverted) ovule (the most common angiosperm ovule type), the micropyle lies:
Correct Answer: A (Close to the hilum and funiculus facing downwards)
In anatropous ovules (found in >80% of angiosperms), the ovule body curves through 180° such that the micropyle comes to lie immediately adjacent to the hilum and funiculus.
In anatropous ovules (found in >80% of angiosperms), the ovule body curves through 180° such that the micropyle comes to lie immediately adjacent to the hilum and funiculus.
54. In human males, the coiled tubular duct resting along the posterior surface of each testis where spermatozoa undergo functional maturation and motility acquisition is the:
Correct Answer: C (Epididymis)
The epididymis is a tightly coiled 6-meter duct on the posterior testis where spermatozoa spend ~2 weeks acquiring forward motility and membrane glycoproteins.
The epididymis is a tightly coiled 6-meter duct on the posterior testis where spermatozoa spend ~2 weeks acquiring forward motility and membrane glycoproteins.
55. During human oogenesis, the unequal meiotic division of the primary oocyte produces a large secondary oocyte and a tiny:
Correct Answer: A (First Polar Body)
Meiosis I in oogenesis is asymmetric, retaining virtually all cytoplasm in the functional secondary oocyte while casting off a tiny, non-functional first polar body.
Meiosis I in oogenesis is asymmetric, retaining virtually all cytoplasm in the functional secondary oocyte while casting off a tiny, non-functional first polar body.
56. The hormone responsible for maintaining the corpus luteum and stimulating continuous progesterone secretion during early pregnancy is:
Correct Answer: C (human Chorionic Gonadotropin)
Trophoblast cells of the implanted blastocyst secrete hCG, an LH-analog that rescues the corpus luteum from regression to sustain progesterone output through the first trimester.
Trophoblast cells of the implanted blastocyst secrete hCG, an LH-analog that rescues the corpus luteum from regression to sustain progesterone output through the first trimester.
57. The process of attachment of the blastocyst to the uterine endometrial wall is known as:
Correct Answer: C (Implantation)
Implantation occurs around day 6–7 post-fertilization when the trophoblast layer of the blastocyst embeds into the secretory endometrium of the uterus.
Implantation occurs around day 6–7 post-fertilization when the trophoblast layer of the blastocyst embeds into the secretory endometrium of the uterus.
58. The neuroendocrine reflex that induces vigorous uterine contractions during human labor is termed the:
Correct Answer: A (Fetal Ejection Reflex)
The fetal ejection reflex is initiated by signals from the mature fetus and placenta, triggering cervical stretching that stimulates posterior pituitary oxytocin release via a positive feedback loop.
The fetal ejection reflex is initiated by signals from the mature fetus and placenta, triggering cervical stretching that stimulates posterior pituitary oxytocin release via a positive feedback loop.
59. “Saheli”, the oral contraceptive pill developed by CDRI Lucknow, is chemically:
Correct Answer: B (A non-steroidal selective estrogen receptor modulator taken once a week)
Saheli (centchroman / ormeloxifene) is a non-steroidal oral contraceptive taken once weekly that antagonizes uterine estrogen receptors to block blastocyst implantation with minimal hormonal side effects.
Saheli (centchroman / ormeloxifene) is a non-steroidal oral contraceptive taken once weekly that antagonizes uterine estrogen receptors to block blastocyst implantation with minimal hormonal side effects.
60. In an In Vitro Fertilization (IVF) clinic, the laboratory procedure where a semen sample with very low sperm count (oligozoospermia) is introduced directly into the female partner’s uterus is:
Correct Answer: C (Intra-Uterine Insemination)
In Intra-Uterine Insemination (IUI), concentrated washed sperm from the husband or donor is deposited directly into the uterine cavity near the time of ovulation.
In Intra-Uterine Insemination (IUI), concentrated washed sperm from the husband or donor is deposited directly into the uterine cavity near the time of ovulation.
61. In a monohybrid cross displaying complete dominance (e.g., Tall x Dwarf pea plants), what is the expected genotypic ratio in the F2 generation?
Correct Answer: B (1 TT : 2 Tt : 1 tt)
Selfing the heterozygous F1 generation (Tt × Tt) produces a phenotypic ratio of 3 Tall : 1 Dwarf and a genotypic ratio of 1 homozygous dominant (TT) : 2 heterozygous (Tt) : 1 homozygous recessive (tt).
Selfing the heterozygous F1 generation (Tt × Tt) produces a phenotypic ratio of 3 Tall : 1 Dwarf and a genotypic ratio of 1 homozygous dominant (TT) : 2 heterozygous (Tt) : 1 homozygous recessive (tt).
62. Which aneuploid chromosomal condition in humans results from the presence of an additional copy of the X chromosome in males (47, XXY)?
Correct Answer: B (Klinefelter’s syndrome)
Klinefelter’s syndrome (44 autosomes + XXY = 47) results from non-disjunction of sex chromosomes, producing tall sterile males with underdeveloped testes and gynaecomastia.
Klinefelter’s syndrome (44 autosomes + XXY = 47) results from non-disjunction of sex chromosomes, producing tall sterile males with underdeveloped testes and gynaecomastia.
63. In human genetics, Thalassemia is an autosomal recessive disorder caused by:
Correct Answer: A (Reduced synthesis or deletion of alpha or beta globin chains)
Thalassemia is a quantitative hemoglobinopathy caused by gene deletions/mutations on chromosome 16 (α-thalassemia) or chromosome 11 (β-thalassemia) that reduce globin chain output.
Thalassemia is a quantitative hemoglobinopathy caused by gene deletions/mutations on chromosome 16 (α-thalassemia) or chromosome 11 (β-thalassemia) that reduce globin chain output.
64. In the Hershey-Chase bacteriophage T2 experiment, radioactive 32P was recovered in the:
Correct Answer: B (Bacterial cell pellet at the bottom)
32P-labeled viral DNA was injected into the host E. coli cells and sedimented with the bacterial pellet, while 35S-labeled protein capsids remained in the supernatant.
32P-labeled viral DNA was injected into the host E. coli cells and sedimented with the bacterial pellet, while 35S-labeled protein capsids remained in the supernatant.
65. The enzyme DNA Ligase joins Okazaki fragments by catalyzing the formation of:
Correct Answer: B (Phosphodiester bonds between adjacent 3′-OH and 5′-phosphate ends)
DNA ligase seals single-strand nicks on the lagging strand by forming covalent phosphodiester bonds between adjacent 3′-hydroxyl and 5′-monophosphate groups using ATP/NAD+.
DNA ligase seals single-strand nicks on the lagging strand by forming covalent phosphodiester bonds between adjacent 3′-hydroxyl and 5′-monophosphate groups using ATP/NAD+.
66. The genetic code is described as “degenerate” because:
Correct Answer: B (Most amino acids are specified by more than one triplet codon)
Because 61 sense codons specify only 20 amino acids, most amino acids (except Methionine and Tryptophan) are encoded by multiple synonymous codons (degeneracy of the code).
Because 61 sense codons specify only 20 amino acids, most amino acids (except Methionine and Tryptophan) are encoded by multiple synonymous codons (degeneracy of the code).
67. The variable number of tandem repeats (VNTRs) used as hybridization probes in DNA fingerprinting belong to which class of satellite DNA?
Correct Answer: B (Minisatellites)
VNTRs are minisatellite sequences (10–60 bp repeats) that show high copy-number polymorphism between individuals and are inherited in a Mendelian fashion.
VNTRs are minisatellite sequences (10–60 bp repeats) that show high copy-number polymorphism between individuals and are inherited in a Mendelian fashion.
68. The forelimbs of humans, cheetahs, whales, and bats share a common basic arrangement of bones (humerus, radius, ulna, carpals, metacarpals, phalanges), exemplifying:
Correct Answer: A (Homology arising from divergent evolution)
Vertebrate forelimbs share identical anatomical bone plans inherited from a common ancestor (homology) that have diverged to serve different locomotory functions (running, swimming, flying).
Vertebrate forelimbs share identical anatomical bone plans inherited from a common ancestor (homology) that have diverged to serve different locomotory functions (running, swimming, flying).
69. In a population in Hardy-Weinberg equilibrium, if the frequency of a recessive allele (q) is 0.2, what is the frequency of the homozygous dominant genotype (p2)?
Correct Answer: C (0.64)
Given q = 0.2, the dominant allele frequency is p = 1 – q = 0.8. The homozygous dominant genotype frequency (p2) is (0.8)2 = 0.64 (or 64%).
Given q = 0.2, the dominant allele frequency is p = 1 – q = 0.8. The homozygous dominant genotype frequency (p2) is (0.8)2 = 0.64 (or 64%).
70. The giant carnivorous dinosaur Tyrannosaurus rex that lived ~65 million years ago reached an estimated height of about:
Correct Answer: B (20 feet)
According to the NCERT biology curriculum, the largest apex predatory dinosaur Tyrannosaurus rex stood ~20 feet tall and possessed 6-inch dagger-like teeth before going extinct 65 million years ago.
According to the NCERT biology curriculum, the largest apex predatory dinosaur Tyrannosaurus rex stood ~20 feet tall and possessed 6-inch dagger-like teeth before going extinct 65 million years ago.
71. Streptococcus pneumoniae and Haemophilus influenzae infect the pulmonary alveoli, causing pneumonia characterized by:
Correct Answer: B (Fluid-filled alveoli, chills, fever, and gray/bluish nails)
Pneumonia pathogens infect alveolar sacs, filling them with inflammatory fluid/pus and impairing gas exchange, leading to hypoxia and cyanotic discoloration of lips and fingernails.
Pneumonia pathogens infect alveolar sacs, filling them with inflammatory fluid/pus and impairing gas exchange, leading to hypoxia and cyanotic discoloration of lips and fingernails.
72. An antibody monomer molecule is structurally represented as H2L2 because it comprises:
Correct Answer: B (Two Heavy and two Light polypeptide chains linked by disulfide bonds)
Each immunoglobulin monomer consists of 4 polypeptide chains (2 identical heavy H-chains and 2 identical light L-chains) covalently cross-linked by interchain disulfide bonds.
Each immunoglobulin monomer consists of 4 polypeptide chains (2 identical heavy H-chains and 2 identical light L-chains) covalently cross-linked by interchain disulfide bonds.
73. Which of the following organs are classified as Primary Lymphoid Organs where immature lymphocytes differentiate and acquire antigen sensitivity?
Correct Answer: B (Bone Marrow and Thymus)
Primary lymphoid organs (bone marrow and thymus) provide microenvironments for the maturation of B-cells and T-cells. Secondary lymphoid organs (spleen, lymph nodes) are sites of antigen presentation.
Primary lymphoid organs (bone marrow and thymus) provide microenvironments for the maturation of B-cells and T-cells. Secondary lymphoid organs (spleen, lymph nodes) are sites of antigen presentation.
74. The most feared biological characteristic of malignant tumors, where cancerous cells detach from primary tumors to establish secondary tumors in distant organs, is:
Correct Answer: B (Metastasis)
Metastasis is the dissemination of malignant cells from primary tumors into blood and lymph vessels to colonize distant tissues, representing the hallmark of cancer progression.
Metastasis is the dissemination of malignant cells from primary tumors into blood and lymph vessels to colonize distant tissues, representing the hallmark of cancer progression.
75. Tobacco smoke contains high concentrations of Carbon Monoxide (CO), which causes tissue hypoxia because CO:
Correct Answer: B (Binds to hemoglobin with 200x higher affinity than oxygen)
Carbon monoxide binds hemoglobin with ~200 times higher affinity than O2, forming carboxyhemoglobin and drastically reducing oxygen transport to peripheral tissues.
Carbon monoxide binds hemoglobin with ~200 times higher affinity than O2, forming carboxyhemoglobin and drastically reducing oxygen transport to peripheral tissues.
76. The traditional Indian fermented food “Idli” and “Dosa” dough is fermented by:
Correct Answer: B (Natural lactic acid bacteria)
Rice and black gram batter is fermented by wild lactic acid bacteria (Leuconostoc and Streptococcus) that generate lactic acid and CO2, puffing up the batter.
Rice and black gram batter is fermented by wild lactic acid bacteria (Leuconostoc and Streptococcus) that generate lactic acid and CO2, puffing up the batter.
77. The immunosuppressive medication Cyclosporin A is produced via fungal fermentation using:
Correct Answer: C (Trichoderma polysporum)
Trichoderma polysporum is an ascomycete fungus used to produce Cyclosporin A, an immunosuppressant that selectively blocks calcineurin signaling in T-cells.
Trichoderma polysporum is an ascomycete fungus used to produce Cyclosporin A, an immunosuppressant that selectively blocks calcineurin signaling in T-cells.
78. During the physical primary treatment of municipal sewage, coarse floating debris (plastic bottles, leaves) is removed by:
Correct Answer: A (Sequential wire mesh filtration)
Primary sewage treatment begins with sequential filtration through progressive bar screens and mesh filters to trap and remove floating solid debris.
Primary sewage treatment begins with sequential filtration through progressive bar screens and mesh filters to trap and remove floating solid debris.
79. The biological control agent used to manage root-rot diseases caused by fungal pathogens in the crop rhizosphere is:
Correct Answer: B (Trichoderma species)
Trichoderma species colonize the root rhizosphere, secreting antifungal enzymes (chitinases, glucanases) that parasitize and suppress pathogenic soil fungi (Fusarium, Rhizoctonia).
Trichoderma species colonize the root rhizosphere, secreting antifungal enzymes (chitinases, glucanases) that parasitize and suppress pathogenic soil fungi (Fusarium, Rhizoctonia).
80. The fungal symbiont in a Mycorrhizal association (e.g., Glomus) assists the host plant by:
Correct Answer: B (Absorbing phosphorus from soil and improving drought/pathogen tolerance)
Mycorrhizal networks absorb poorly mobile phosphate ions from the soil and transfer them to the host plant while conferring enhanced drought and salinity tolerance.
Mycorrhizal networks absorb poorly mobile phosphate ions from the soil and transfer them to the host plant while conferring enhanced drought and salinity tolerance.
81. Restriction endonucleases are called “molecular scissors” because they:
Correct Answer: B (Cut double-stranded DNA at specific palindromic sequences)
Type II restriction endonucleases recognize specific palindromic DNA sequences and cleave internal phosphodiester backbones, generating defined sticky or blunt ends.
Type II restriction endonucleases recognize specific palindromic DNA sequences and cleave internal phosphodiester backbones, generating defined sticky or blunt ends.
82. In plasmid pBR322, the origin of replication (‘ori’) sequence is essential because:
Correct Answer: B (Sequence where replication starts and controls copy number)
The ‘ori’ locus is the DNA sequence that recruits host DNA polymerase to initiate replication, determining the copy number of the vector and its recombinant insert per cell.
The ‘ori’ locus is the DNA sequence that recruits host DNA polymerase to initiate replication, determining the copy number of the vector and its recombinant insert per cell.
83. To isolate pure DNA from bacterial cells, RNA and protein contaminants are degraded by adding which enzymes?
Correct Answer: B (RNase and Proteases)
Crude cell lysates are treated with RNase to digest cellular RNA and proteases (e.g., Proteinase K) to digest histones and cellular proteins, leaving purified DNA for ethanol precipitation.
Crude cell lysates are treated with RNase to digest cellular RNA and proteases (e.g., Proteinase K) to digest histones and cellular proteins, leaving purified DNA for ethanol precipitation.
84. The three sequential temperature steps that constitute ONE cycle of Polymerase Chain Reaction (PCR) are:
Correct Answer: A (Denaturation -> Annealing -> Extension)
PCR cycles through: 1) Thermal denaturation of double-stranded template DNA (~94°C); 2) Primer annealing (~50–60°C); and 3) Primer extension by Taq polymerase (~72°C).
PCR cycles through: 1) Thermal denaturation of double-stranded template DNA (~94°C); 2) Primer annealing (~50–60°C); and 3) Primer extension by Taq polymerase (~72°C).
85. Bt cotton plants are protected against target lepidopteran insect larvae (cotton bollworms) because the plant tissues express:
Correct Answer: B (CryIAc and CryIIAb endotoxin proteins)
Bt cotton is genetically engineered with cryIAc and cryIIAb genes from Bacillus thuringiensis, which produce crystal endotoxins that form lytic pores in the midgut of feeding bollworm larvae.
Bt cotton is genetically engineered with cryIAc and cryIIAb genes from Bacillus thuringiensis, which produce crystal endotoxins that form lytic pores in the midgut of feeding bollworm larvae.
86. In tobacco plants transformed by RNA interference (RNAi) against Meloidogyne incognita, the introduced double-stranded RNA (dsRNA) silences:
Correct Answer: B (Specific essential mRNA transcripts of the nematode)
Transgenic plant dsRNA is processed into siRNAs that guide the nematode’s own RISC complex to degrade its essential mRNAs, preventing nematode survival and root-knot pathology.
Transgenic plant dsRNA is processed into siRNAs that guide the nematode’s own RISC complex to degrade its essential mRNAs, preventing nematode survival and root-knot pathology.
87. In 1983, the American pharmaceutical company Eli Lilly commercially synthesized human insulin (Humulin) using recombinant DNA technology by:
Correct Answer: B (Producing chains A and B separately in E. coli and joining them via disulfide bonds)
Eli Lilly synthesized two DNA sequences for insulin A and B chains, expressed them separately in E. coli host cells, and linked the purified peptides in vitro via disulfide bridges.
Eli Lilly synthesized two DNA sequences for insulin A and B chains, expressed them separately in E. coli host cells, and linked the purified peptides in vitro via disulfide bridges.
88. Adenosine Deaminase (ADA) enzyme is crucial for the proper functioning of the human:
Correct Answer: B (Immune system)
ADA deaminates deoxyadenosine in purine salvage; ADA deficiency leads to toxic dATP accumulation that selectively destroys developing T and B lymphocytes, causing SCID.
ADA deaminates deoxyadenosine in purine salvage; ADA deficiency leads to toxic dATP accumulation that selectively destroys developing T and B lymphocytes, causing SCID.
89. Genetically engineered ‘Golden Rice’ is biofortified with genes from daffodil (Narcissus) and bacteria (Erwinia) to synthesize:
Correct Answer: B (Beta-carotene in the edible grain endosperm)
Golden Rice expresses phytoene synthase and carotene desaturase transgenes, directing beta-carotene (provitamin A) biosynthesis into the polished rice endosperm.
Golden Rice expresses phytoene synthase and carotene desaturase transgenes, directing beta-carotene (provitamin A) biosynthesis into the polished rice endosperm.
90. In India, which regulatory statutory committee under the Ministry of Environment, Forest and Climate Change evaluates the biosafety and commercial release of GM crops?
Correct Answer: B (GEAC)
The Genetic Engineering Appraisal Committee (GEAC) is the apex statutory body that evaluates environmental safety, field trials, and commercial approvals for GMOs in India.
The Genetic Engineering Appraisal Committee (GEAC) is the apex statutory body that evaluates environmental safety, field trials, and commercial approvals for GMOs in India.
91. The mutualistic association between roots of higher plants (e.g., Pinus, Orchids) and soil fungi is called:
Correct Answer: B (Mycorrhiza)
Mycorrhiza is an obligate mutualistic association (+, +) where the fungus absorbs soil minerals (especially phosphorus) and water for the plant in exchange for photosynthetic carbohydrates.
Mycorrhiza is an obligate mutualistic association (+, +) where the fungus absorbs soil minerals (especially phosphorus) and water for the plant in exchange for photosynthetic carbohydrates.
92. In a population showing Verhulst-Pearl logistic growth, the population growth curve is:
Correct Answer: B (Sigmoid / S-shaped curve)
Under finite resource conditions, population growth follows a logistic sigmoid curve: initial lag phase → exponential acceleration phase → deceleration → stationary carrying-capacity asymptote (K).
Under finite resource conditions, population growth follows a logistic sigmoid curve: initial lag phase → exponential acceleration phase → deceleration → stationary carrying-capacity asymptote (K).
93. In ecological succession, the stable terminal biological community that is in dynamic equilibrium with the local climate is the:
Correct Answer: C (Climax community)
The climax community is the final self-perpetuating stage in ecological succession that maintains stable species composition and biomass in equilibrium with regional climatic conditions.
The climax community is the final self-perpetuating stage in ecological succession that maintains stable species composition and biomass in equilibrium with regional climatic conditions.
94. In an ecosystem, the rate of biomass production by autotrophic plants available to heterotrophs (NPP) is related to Gross Primary Productivity (GPP) by:
Correct Answer: A (NPP = GPP – R)
Net Primary Productivity (NPP = GPP – R) is the net organic biomass stored by photosynthetic autotrophs after subtracting autotrophic metabolic respiration costs (R).
Net Primary Productivity (NPP = GPP – R) is the net organic biomass stored by photosynthetic autotrophs after subtracting autotrophic metabolic respiration costs (R).
95. In any natural ecosystem, which of the following ecological pyramids can NEVER be inverted under any circumstances?
Correct Answer: C (Pyramid of Energy)
The pyramid of energy is always upright because energy is lost as metabolic heat at each successive trophic level according to the Second Law of Thermodynamics.
The pyramid of energy is always upright because energy is lost as metabolic heat at each successive trophic level according to the Second Law of Thermodynamics.
96. Robert May’s scientifically sound global estimate calculates the total number of species existing on Earth to be approximately:
Correct Answer: B (7 million)
While the IUCN catalog lists ~1.5–1.7 million named species, Robert May’s global statistical extrapolations estimate total planetary species richness at around 7 million.
While the IUCN catalog lists ~1.5–1.7 million named species, Robert May’s global statistical extrapolations estimate total planetary species richness at around 7 million.
97. The introduction of invasive alien Nile Perch into Lake Victoria (East Africa) led to the catastrophic extinction of over 200 endemic species of:
Correct Answer: B (Cichlid fishes)
Introducing the predatory Nile Perch into Lake Victoria caused the extinction of more than 200 native cichlid fish species through heavy predation and competitive exclusion.
Introducing the predatory Nile Perch into Lake Victoria caused the extinction of more than 200 native cichlid fish species through heavy predation and competitive exclusion.
98. Water Hyacinth (Eichhornia crassipes) is called the “Terror of Bengal” because it:
Correct Answer: B (Grows rapidly, draining dissolved oxygen and causing fish mortality)
Eichhornia forms dense floating mats over static freshwater bodies that block sunlight, extract dissolved oxygen, and cause mass fish kills.
Eichhornia forms dense floating mats over static freshwater bodies that block sunlight, extract dissolved oxygen, and cause mass fish kills.
99. Which of the following is an example of an In-situ (on-site) biodiversity conservation area in India?
Correct Answer: C (Kaziranga National Park and Nilgiri Biosphere Reserve)
National Parks, Biosphere Reserves, Wildlife Sanctuaries, and Sacred Groves protect species in their natural habitats (In-situ). Botanical gardens, zoos, and gene banks are Ex-situ facilities.
National Parks, Biosphere Reserves, Wildlife Sanctuaries, and Sacred Groves protect species in their natural habitats (In-situ). Botanical gardens, zoos, and gene banks are Ex-situ facilities.
100. Sacred Groves in Meghalaya that provide inviolable protection to rare endemic flora through tribal cultural traditions are located in the:
Correct Answer: A (Khasi and Jaintia Hills)
The Khasi and Jaintia Hills in Meghalaya host sacred groves protected by tribal custom, preserving relict plant species found nowhere else.
The Khasi and Jaintia Hills in Meghalaya host sacred groves protected by tribal custom, preserving relict plant species found nowhere else.