1. The term ‘Systematics’ refers to the:
Correct Answer: B (Systematic arrangement of organisms and their evolutionary relationships)
Derived from the Latin word ‘systema’, Systematics deals with the diversity of organisms, their identification, naming, classification, and their phylogenetic (evolutionary) relationships.
Derived from the Latin word ‘systema’, Systematics deals with the diversity of organisms, their identification, naming, classification, and their phylogenetic (evolutionary) relationships.
2. Which archaebacterial group thrives in extremely hot and acidic environments (e.g., hot sulfur springs)?
Correct Answer: B (Thermoacidophiles)
Thermoacidophiles thrive in high-temperature, low-pH environments (sulfur springs). Halophiles inhabit hyper-saline conditions, and methanogens live in anaerobic marshy environments and animal rumens.
Thermoacidophiles thrive in high-temperature, low-pH environments (sulfur springs). Halophiles inhabit hyper-saline conditions, and methanogens live in anaerobic marshy environments and animal rumens.
3. Entamoeba histolytica moves and captures prey using pseudopodia, classifying it as a/an:
Correct Answer: A (Amoeboid protozoan)
Amoeboid protozoans live in freshwater, sea water, or moist soil and capture prey by extending pseudopodia (false feet), as seen in Amoeba and the parasite Entamoeba.
Amoeboid protozoans live in freshwater, sea water, or moist soil and capture prey by extending pseudopodia (false feet), as seen in Amoeba and the parasite Entamoeba.
4. In bread mold (Rhizopus) and Albugo (parasitic fungus on mustard), the mycelium is:
Correct Answer: B (Aseptate and coenocytic)
Phycomycetes (such as Mucor, Rhizopus, and Albugo) have continuous, multinucleated, aseptate hyphae (coenocytic mycelium).
Phycomycetes (such as Mucor, Rhizopus, and Albugo) have continuous, multinucleated, aseptate hyphae (coenocytic mycelium).
5. Volvox, Ulothrix, and Spirogyra store food primarily as starch inside specialized cellular structures called:
Correct Answer: A (Pyrenoids)
Chlorophyceae (green algae) possess one or more storage bodies called pyrenoids located in chloroplasts, consisting of a central protein core wrapped in a starch sheath.
Chlorophyceae (green algae) possess one or more storage bodies called pyrenoids located in chloroplasts, consisting of a central protein core wrapped in a starch sheath.
6. Gemmae are green, multicellular, asexual reproductive buds produced in small cups located on the thallus of:
Correct Answer: C (Marchantia)
Marchantia produces specialized green, multicellular asexual buds called gemmae inside gemma cups on the dorsal surface of the thallus that detach to form new individuals.
Marchantia produces specialized green, multicellular asexual buds called gemmae inside gemma cups on the dorsal surface of the thallus that detach to form new individuals.
7. The largest tree species (giant redwood tree) is a gymnosperm belonging to the genus:
Correct Answer: C (Sequoia)
Sequoia sempervirens (the giant redwood tree) is one of the tallest living gymnosperm tree species in the world.
Sequoia sempervirens (the giant redwood tree) is one of the tallest living gymnosperm tree species in the world.
8. Which of the following sponge species is commonly called the “Bath sponge”?
Correct Answer: C (Euspongia)
Euspongia is known as the bath sponge due to its soft skeleton of spongin fibers. Sycon is Scypha, and Spongilla is the freshwater sponge.
Euspongia is known as the bath sponge due to its soft skeleton of spongin fibers. Sycon is Scypha, and Spongilla is the freshwater sponge.
9. Presence of an open circulatory system, segmented body with head, thorax, and abdomen, and respiration via trachea is characteristic of:
Correct Answer: C (Insecta)
Insects have bodies divided into head, thorax, and abdomen, three pairs of jointed legs, Malpighian tubules for excretion, and a tracheal respiratory network.
Insects have bodies divided into head, thorax, and abdomen, three pairs of jointed legs, Malpighian tubules for excretion, and a tracheal respiratory network.
10. Metamerism (true segment-by-segment internal and external body division) is characteristically present in which three phyla?
Correct Answer: C (Annelida, Arthropoda, and Chordata)
True metameric segmentation occurs in Annelida (earthworms), Arthropoda (insects), and Chordata (vertebral column, ribs, myotomes).
True metameric segmentation occurs in Annelida (earthworms), Arthropoda (insects), and Chordata (vertebral column, ribs, myotomes).
11. In Alstonia, more than two leaves arise at each node to form a whorl, exhibiting:
Correct Answer: C (Whorled phyllotaxy)
When more than two leaves develop at each node arranged in a circle, it is whorled phyllotaxy (e.g., Alstonia, Nerium). China rose has alternate, and Calotropis has opposite phyllotaxy.
When more than two leaves develop at each node arranged in a circle, it is whorled phyllotaxy (e.g., Alstonia, Nerium). China rose has alternate, and Calotropis has opposite phyllotaxy.
12. A sterile stamen incapable of producing fertile pollen is termed a:
Correct Answer: B (Staminode)
A staminode is an underdeveloped, abortive, or non-functional sterile stamen. A sterile pistil is called a pistillode.
A staminode is an underdeveloped, abortive, or non-functional sterile stamen. A sterile pistil is called a pistillode.
13. In a caryopsis fruit (typical of Gramineae/Poaceae like wheat and maize):
Correct Answer: A (The pericarp is fused with the seed coat)
A caryopsis (grain) is a simple, dry, indehiscent one-seeded fruit where the ovarian wall (pericarp) is inseparable and fused with the seed coat.
A caryopsis (grain) is a simple, dry, indehiscent one-seeded fruit where the ovarian wall (pericarp) is inseparable and fused with the seed coat.
14. Phloem in gymnosperms differs from angiosperm phloem in lacking:
Correct Answer: B (Sieve tubes and Companion cells)
Gymnosperms possess albuminous cells (Strasburger cells) and sieve cells; they lack the specialized sieve tubes and companion cells characteristic of angiosperms.
Gymnosperms possess albuminous cells (Strasburger cells) and sieve cells; they lack the specialized sieve tubes and companion cells characteristic of angiosperms.
15. In isobilateral (monocotyledonous) leaves:
Correct Answer: B (Stomata distributed equally on both surfaces)
Isobilateral monocot leaves have stomata on both surfaces (amphistomatic) and an undifferentiated mesophyll, whereas dorsiventral dicot leaves have more stomata on the lower abaxial epidermis.
Isobilateral monocot leaves have stomata on both surfaces (amphistomatic) and an undifferentiated mesophyll, whereas dorsiventral dicot leaves have more stomata on the lower abaxial epidermis.
16. Dense irregular connective tissue with fibroblasts and randomly oriented collagen bundles is predominantly found in:
Correct Answer: C (Skin dermis)
Dense irregular connective tissue contains interwoven collagen fibers capable of withstanding multidirectional tension, forming the tough dermal layer of skin.
Dense irregular connective tissue contains interwoven collagen fibers capable of withstanding multidirectional tension, forming the tough dermal layer of skin.
17. The bilobed, muscular tongue of the frog is attached to the:
Correct Answer: B (Anterior front of the lower jaw, with a free posterior bifurcated end)
A frog’s tongue is attached at the front of the lower jaw; its sticky, bifid posterior end flips out rapidly to capture insects.
A frog’s tongue is attached at the front of the lower jaw; its sticky, bifid posterior end flips out rapidly to capture insects.
18. The erythrocytes (RBCs) of a frog differ from adult human RBCs in being:
Correct Answer: B (Nucleated, oval, and biconvex)
Frog red blood cells are oval, biconvex, and contain a central nucleus along with hemoglobin, whereas mature human RBCs are enucleated and biconcave discs.
Frog red blood cells are oval, biconvex, and contain a central nucleus along with hemoglobin, whereas mature human RBCs are enucleated and biconcave discs.
19. In male frogs, the yellow-colored finger-like projections attached to the anterior end of each kidney that store nutrient energy are:
Correct Answer: B (Fat bodies)
Fat bodies are branched, yellowish lipid-storing structures above the kidneys that provide reserve energy during hibernation, aestivation, and gametogenesis.
Fat bodies are branched, yellowish lipid-storing structures above the kidneys that provide reserve energy during hibernation, aestivation, and gametogenesis.
20. The structural membrane on the outer surface of a frog’s head that receives sound vibrations from the air is the:
Correct Answer: B (Tympanic membrane)
Frogs lack external ears (pinnae); a circular exposed tympanic membrane (tympanum) sits behind each eye to receive atmospheric sound waves.
Frogs lack external ears (pinnae); a circular exposed tympanic membrane (tympanum) sits behind each eye to receive atmospheric sound waves.
21. The middle lamella that cements adjacent plant cell walls together is composed predominantly of:
Correct Answer: B (Calcium and Magnesium pectates)
The middle lamella is an amorphous intercellular cementing layer made largely of calcium and magnesium pectate. Fruit ripening softens fruits as pectate dissolves.
The middle lamella is an amorphous intercellular cementing layer made largely of calcium and magnesium pectate. Fruit ripening softens fruits as pectate dissolves.
22. Which cell organelle is known as the “polymorphic organelle” and exists as primary, secondary, residual bodies, and autophagic vacuoles?
Correct Answer: B (Lysosome)
Lysosomes exhibit polymorphism, transitioning between primary lysosomes (fresh enzymes), secondary lysosomes (phagolysosomes), residual bodies, and autophagic vacuoles.
Lysosomes exhibit polymorphism, transitioning between primary lysosomes (fresh enzymes), secondary lysosomes (phagolysosomes), residual bodies, and autophagic vacuoles.
23. In mitochondria and chloroplasts, 70S ribosomes and circular naked DNA molecules are located within their:
Correct Answer: B (Matrix and Stroma respectively)
Mitochondrial matrix and chloroplast stroma house their circular prokaryotic-like dsDNA genomes, RNA molecules, and 70S ribosomes (semi-autonomous organelles).
Mitochondrial matrix and chloroplast stroma house their circular prokaryotic-like dsDNA genomes, RNA molecules, and 70S ribosomes (semi-autonomous organelles).
24. Microbodies containing catalase and urate oxidase enzymes involved in peroxide metabolism and photorespiration in plants are:
Correct Answer: B (Peroxisomes)
Peroxisomes contain catalase and peroxidase enzymes that neutralize toxic hydrogen peroxide (H2O2) and participate in glycolate metabolism during C2 photorespiration.
Peroxisomes contain catalase and peroxidase enzymes that neutralize toxic hydrogen peroxide (H2O2) and participate in glycolate metabolism during C2 photorespiration.
25. Zwitterion formation is a property of amino acids where at a specific isoelectric pH:
Correct Answer: B (Amino group is protonated and carboxyl group is deprotonated, carrying zero net charge)
Amino acids form dipolar zwitterions in aqueous solutions because the basic amino group gains a proton (-NH3+) while the acidic carboxyl group loses one (-COO-).
Amino acids form dipolar zwitterions in aqueous solutions because the basic amino group gains a proton (-NH3+) while the acidic carboxyl group loses one (-COO-).
26. In the double-helical structure of DNA, the two antiparallel polynucleotide chains run in polarities of:
Correct Answer: A (5′ -> 3′ on one strand and 3′ -> 5′ on the complementary strand)
The two phosphodiester backbones run in opposite directions (antiparallel orientation): one strand runs 5′ to 3′, and the other runs 3′ to 5′.
The two phosphodiester backbones run in opposite directions (antiparallel orientation): one strand runs 5′ to 3′, and the other runs 3′ to 5′.
27. An enzyme without its required non-protein cofactor is catalytically inactive and called an:
Correct Answer: B (Apoenzyme)
The protein portion of a conjugated enzyme is the apoenzyme. Combining the apoenzyme with its non-protein cofactor forms the catalytically active holoenzyme.
The protein portion of a conjugated enzyme is the apoenzyme. Combining the apoenzyme with its non-protein cofactor forms the catalytically active holoenzyme.
28. At which checkpoint of the eukaryotic cell cycle does the cell determine whether to commit irreversibly to DNA replication or enter G0?
Correct Answer: A (G1 / S checkpoint)
The G1/S restriction checkpoint evaluates cell size, nutrient availability, growth factors, and DNA integrity before committing to S-phase replication.
The G1/S restriction checkpoint evaluates cell size, nutrient availability, growth factors, and DNA integrity before committing to S-phase replication.
29. The stage of meiosis during which homologous chromosome pairs align along the equatorial plate in two parallel rows is:
Correct Answer: B (Metaphase I of meiosis)
In Metaphase I, paired bivalent homologous chromosomes align along a double equatorial plate. In mitotic metaphase and Metaphase II, single univalents align on a single plate.
In Metaphase I, paired bivalent homologous chromosomes align along a double equatorial plate. In mitotic metaphase and Metaphase II, single univalents align on a single plate.
30. Meiosis is biologically significant because it:
Correct Answer: B (Conserves chromosome numbers and introduces genetic variations)
Meiosis reduces diploid chromosome counts by half to generate haploid gametes, ensuring species chromosome stability after fertilization while driving genetic diversity through crossing over.
Meiosis reduces diploid chromosome counts by half to generate haploid gametes, ensuring species chromosome stability after fertilization while driving genetic diversity through crossing over.
31. In non-cyclic photophosphorylation, electrons lost by the reaction center P680 of PS II are continuously replenished by electrons from:
Correct Answer: B (Photolysis of Water molecules)
Oxidized P680 pulls replacement electrons from water splitting catalyzed by the oxygen-evolving complex ($2H_2O \rightarrow 4H^+ + O_2 + 4e^-$).
Oxidized P680 pulls replacement electrons from water splitting catalyzed by the oxygen-evolving complex ($2H_2O \rightarrow 4H^+ + O_2 + 4e^-$).
32. The reduction phase of the Calvin cycle involves converting 3-PGA into triose phosphate (G3P/PGAL), consuming:
Correct Answer: A (2 ATP and 2 NADPH per CO2 fixed)
Per CO2 molecule, reduction uses 2 ATP and 2 NADPH to produce triose phosphate. Regeneration of RuBP consumes an additional 1 ATP (totalling 3 ATP + 2 NADPH per CO2).
Per CO2 molecule, reduction uses 2 ATP and 2 NADPH to produce triose phosphate. Regeneration of RuBP consumes an additional 1 ATP (totalling 3 ATP + 2 NADPH per CO2).
33. C4 plants (e.g., Maize, Sugarcane) are photosynthetically more efficient than C3 plants in bright tropical sunlight because C4 plants:
Correct Answer: B (High CO2-concentrating mechanism and lack photorespiration)
The C4 dicarboxylic acid pathway pumps CO2 into bundle sheath cells, maintaining high local CO2:O2 ratios that suppress RuBisCO oxygenase activity and photorespiration.
The C4 dicarboxylic acid pathway pumps CO2 into bundle sheath cells, maintaining high local CO2:O2 ratios that suppress RuBisCO oxygenase activity and photorespiration.
34. In photosynthesis, the carbon dioxide saturation point for C3 and C4 plants occurs at approximately:
Correct Answer: B (450 ppm for C3 and 360 ppm for C4)
C4 plants saturate at lower CO2 concentrations (~360 ppm) due to PEPcase efficiency. C3 plants saturate around 450 ppm, responding with increased productivity under CO2 enrichment.
C4 plants saturate at lower CO2 concentrations (~360 ppm) due to PEPcase efficiency. C3 plants saturate around 450 ppm, responding with increased productivity under CO2 enrichment.
35. In glycolysis, how many net ATP molecules are directly synthesized by substrate-level phosphorylation from one molecule of glucose?
Correct Answer: B (4 ATP gross, giving 2 net ATP)
Glycolysis uses 2 ATP in the preparatory phase (hexokinase and PFK-1) and produces 4 ATP in the payoff phase via substrate-level phosphorylation, yielding a net gain of 2 ATP.
Glycolysis uses 2 ATP in the preparatory phase (hexokinase and PFK-1) and produces 4 ATP in the payoff phase via substrate-level phosphorylation, yielding a net gain of 2 ATP.
36. The respiratory pathway is considered an amphibolic pathway rather than purely catabolic because:
Correct Answer: B (Intermediates used in both catabolic and anabolic pathways)
Respiratory intermediates act as substrates for biosynthesis (e.g., Acetyl-CoA for fatty acids, alpha-ketoglutarate/oxaloacetate for amino acids), making the pathway amphibolic.
Respiratory intermediates act as substrates for biosynthesis (e.g., Acetyl-CoA for fatty acids, alpha-ketoglutarate/oxaloacetate for amino acids), making the pathway amphibolic.
37. In the mitochondrial electron transport chain, Complex I and Complex III are named respectively:
Correct Answer: A (NADH dehydrogenase and Cytochrome bc1 complex)
Complex I is NADH dehydrogenase; Complex II is Succinate dehydrogenase; Complex III is Cytochrome bc1 complex; Complex IV is Cytochrome c oxidase; Complex V is ATP synthase.
Complex I is NADH dehydrogenase; Complex II is Succinate dehydrogenase; Complex III is Cytochrome bc1 complex; Complex IV is Cytochrome c oxidase; Complex V is ATP synthase.
38. The Respiratory Quotient (RQ) for pure proteins during aerobic respiration is:
Correct Answer: C (~0.9)
Respiratory Quotient ($RQ = \text{CO}_2 \text{ evolved} / \text{O}_2 \text{ consumed}$) is 1.0 for carbohydrates, 0.7 for fats (tripalmitin), and ~0.9 for proteins.
Respiratory Quotient ($RQ = \text{CO}_2 \text{ evolved} / \text{O}_2 \text{ consumed}$) is 1.0 for carbohydrates, 0.7 for fats (tripalmitin), and ~0.9 for proteins.
39. The bioassay used to detect the activity of Gibberellins based on enzyme induction in cereal grains is the:
Correct Answer: B (Barley endosperm alpha-amylase induction test)
Gibberellins trigger the aleurone layer in germinating barley grains to synthesize hydrolytic alpha-amylase enzymes, breaking down endosperm starch into maltose.
Gibberellins trigger the aleurone layer in germinating barley grains to synthesize hydrolytic alpha-amylase enzymes, breaking down endosperm starch into maltose.
40. The plant hormone responsible for accelerating the malting process in the brewing industry and increasing sugarcane stem yield by up to 20 tonnes/acre is:
Correct Answer: B (Gibberellic acid)
Spraying sugarcane with gibberellins elongates stem internodes to increase sugar yield by 20 tonnes/acre, and GA3 speeds up industrial barley malting.
Spraying sugarcane with gibberellins elongates stem internodes to increase sugar yield by 20 tonnes/acre, and GA3 speeds up industrial barley malting.
41. The maximum volume of air a person can breathe in after a forced expiration is designated as:
Correct Answer: B (Vital Capacity)
Vital Capacity is the maximum volume of air exhaled after maximal inhalation (or inhaled after maximal exhalation), comprising ERV + TV + IRV (~3500–4500 mL).
Vital Capacity is the maximum volume of air exhaled after maximal inhalation (or inhaled after maximal exhalation), comprising ERV + TV + IRV (~3500–4500 mL).
42. In systemic tissues, the unloading of oxygen from oxyhemoglobin is promoted by:
Correct Answer: A (Low pO2, High pCO2, High H+ concentration, and High temperature)
Elevated pCO2, acidity, and temperature reduce hemoglobin’s oxygen affinity, shifting the dissociation curve rightward to promote oxygen delivery to active tissues.
Elevated pCO2, acidity, and temperature reduce hemoglobin’s oxygen affinity, shifting the dissociation curve rightward to promote oxygen delivery to active tissues.
43. Normal human plasma contains approximately what percentage of water and proteins?
Correct Answer: B (90–92% water and 6–8% proteins)
Plasma is a straw-colored viscous fluid constituting 55% of blood volume; 90–92% is water, and 6–8% consists of plasma proteins (fibrinogen, globulin, albumin).
Plasma is a straw-colored viscous fluid constituting 55% of blood volume; 90–92% is water, and 6–8% consists of plasma proteins (fibrinogen, globulin, albumin).
44. On a standard ECG recording, repolarization of the atria is:
Correct Answer: C (Masked within the larger QRS complex)
Atrial repolarization occurs simultaneously with ventricular depolarization, so its electrical signal is obscured by the much larger QRS complex.
Atrial repolarization occurs simultaneously with ventricular depolarization, so its electrical signal is obscured by the much larger QRS complex.
45. Podocytes with interdigitating pedicels forming filtration slits are specialized epithelial cells lining the:
Correct Answer: B (Visceral inner layer of Bowman’s capsule)
Podocytes line the inner visceral wall of Bowman’s capsule, wrapping foot processes around glomerular capillaries to form filtration slits (slit pores).
Podocytes line the inner visceral wall of Bowman’s capsule, wrapping foot processes around glomerular capillaries to form filtration slits (slit pores).
46. The hormone Aldosterone acts on the distal convoluted tubules and collecting ducts of nephrons to promote:
Correct Answer: A (Reabsorption of Na+ and water, and excretion of K+ and phosphate)
Secreted by the adrenal cortex under RAAS activation, aldosterone increases distal tubule Na+/K+ ATPase activity, retaining sodium and water to maintain blood pressure.
Secreted by the adrenal cortex under RAAS activation, aldosterone increases distal tubule Na+/K+ ATPase activity, retaining sodium and water to maintain blood pressure.
47. The H-zone in the center of the skeletal muscle sarcomere corresponds to the:
Correct Answer: B (Central region of thick myosin filaments not overlapped by thin actin filaments)
The H-zone is the central lighter region of the A-band containing thick myosin filaments unoverlapped by thin actin filaments at rest; it narrows during contraction.
The H-zone is the central lighter region of the A-band containing thick myosin filaments unoverlapped by thin actin filaments at rest; it narrows during contraction.
48. A gout attack is caused by joint inflammation triggered by the deposition of:
Correct Answer: B (Monosodium Uric acid crystals)
Gout is a metabolic inflammatory arthritis resulting from hyperuricemia, which leads to needle-like sodium urate crystal deposits in synovial joint cavities.
Gout is a metabolic inflammatory arthritis resulting from hyperuricemia, which leads to needle-like sodium urate crystal deposits in synovial joint cavities.
49. The generation of an action potential in a neuron involves opening voltage-gated Na+ channels, which depolarizes the axon interior from:
Correct Answer: A (-70 mV to approximately +30 mV)
Threshold stimuli open voltage-gated Na+ channels, allowing rapid Na+ influx that reverses membrane potential from resting -70 mV to positive +30 mV.
Threshold stimuli open voltage-gated Na+ channels, allowing rapid Na+ influx that reverses membrane potential from resting -70 mV to positive +30 mV.
50. The master circadian pacemaker that secretes melatonin to regulate sleep-wake cycles and seasonal biological rhythms is the:
Correct Answer: C (Pineal gland)
Located on the dorsal side of the forebrain, the pineal gland secretes melatonin, regulating circadian sleep-wake cycles, body temperature, and seasonal rhythms.
Located on the dorsal side of the forebrain, the pineal gland secretes melatonin, regulating circadian sleep-wake cycles, body temperature, and seasonal rhythms.
51. The exine of a pollen grain has distinct circular germ pores where sporopollenin is:
Correct Answer: B (Completely absent, allowing the pollen tube to emerge)
Germ pores are specialized apertures in the pollen exine devoid of sporopollenin, through which the intine emerges to form the pollen tube during germination.
Germ pores are specialized apertures in the pollen exine devoid of sporopollenin, through which the intine emerges to form the pollen tube during germination.
52. Which of the following is a true albuminous (endospermic) dicot seed that retains endosperm tissue at maturity?
Correct Answer: C (Castor)
While most dicot seeds are non-endospermic (e.g., peas, beans), castor and cotton are dicot seeds that retain nutritive endosperm at maturity.
While most dicot seeds are non-endospermic (e.g., peas, beans), castor and cotton are dicot seeds that retain nutritive endosperm at maturity.
53. Development of a fruit without fertilization of the ovary is called ______; development of an embryo without fertilization is called ______:
Correct Answer: B (Parthenocarpy; Apomixis)
Parthenocarpy produces seedless fruit without ovary fertilization (e.g., banana). Apomixis produces asexual seeds without fertilization (e.g., Asteraceae, grasses).
Parthenocarpy produces seedless fruit without ovary fertilization (e.g., banana). Apomixis produces asexual seeds without fertilization (e.g., Asteraceae, grasses).
54. In human males, the temperature of the scrotum is maintained below core body temperature by:
Correct Answer: B (2 to 2.5°C)
The scrotum regulates testicular temperature 2–2.5°C below core body temperature, which is essential for viable spermatogenesis.
The scrotum regulates testicular temperature 2–2.5°C below core body temperature, which is essential for viable spermatogenesis.
55. During human oogenesis, the secondary oocyte arrested at Metaphase II completes its second meiotic division upon:
Correct Answer: B (Contact and entry of a fertilizing spermatozoon)
Sperm entry triggers $Ca^{2+}$ release and degrades MPF, allowing the secondary oocyte to complete Meiosis II, yielding a second polar body and an ootid/ovum.
Sperm entry triggers $Ca^{2+}$ release and degrades MPF, allowing the secondary oocyte to complete Meiosis II, yielding a second polar body and an ootid/ovum.
56. Which hormone secreted by the corpus luteum is responsible for converting the endometrium into a secretory phase to support pregnancy?
Correct Answer: B (Progesterone)
During the luteal phase (days 15–28), the corpus luteum secretes progesterone, preparing the vascular, glandular endometrium for blastocyst implantation.
During the luteal phase (days 15–28), the corpus luteum secretes progesterone, preparing the vascular, glandular endometrium for blastocyst implantation.
57. The embryo at the 8-to-16-celled solid mulberry-like stage before blastocoel formation is the:
Correct Answer: A (Morula)
Successive cleavage divisions produce a solid sphere of 8–16 blastomeres called the morula, which travels through the fallopian tube toward the uterus.
Successive cleavage divisions produce a solid sphere of 8–16 blastomeres called the morula, which travels through the fallopian tube toward the uterus.
58. The fetal ejection reflex in human parturition stimulates the maternal neurohypophysis to release:
Correct Answer: B (Oxytocin)
Signals from the mature fetus and placenta trigger the fetal ejection reflex, stimulating maternal oxytocin release from the posterior pituitary to drive uterine contractions.
Signals from the mature fetus and placenta trigger the fetal ejection reflex, stimulating maternal oxytocin release from the posterior pituitary to drive uterine contractions.
59. “Lippes Loop” is an example of which category of contraceptive device?
Correct Answer: A (Non-medicated IUD)
Lippes Loop is a non-medicated plastic IUD that induces a localized foreign-body reaction, promoting macrophage phagocytosis of spermatozoa in the uterus.
Lippes Loop is a non-medicated plastic IUD that induces a localized foreign-body reaction, promoting macrophage phagocytosis of spermatozoa in the uterus.
60. In an IVF-ET program, transferring an early embryo with up to 8 blastomeres into the fallopian tube is termed:
Correct Answer: A (ZIFT)
Transfer of a zygote or early embryo (up to 8 blastomeres) into the fallopian tube is ZIFT. Embryos beyond 8 blastomeres are transferred into the uterus via IUT.
Transfer of a zygote or early embryo (up to 8 blastomeres) into the fallopian tube is ZIFT. Embryos beyond 8 blastomeres are transferred into the uterus via IUT.
61. In human genetics, red-green colour blindness is an X-linked recessive disorder. A carrier woman ($X^C X^c$) married to a normal man ($X^C Y$) has what probability of having a colour-blind SON?
Correct Answer: B (50% of sons will be colour-blind)
Male offspring receive either $X^C$ (normal, 50%) or $X^c$ (colour-blind, 50%) from their carrier mother; thus, half (50%) of all male children will be colour-blind.
Male offspring receive either $X^C$ (normal, 50%) or $X^c$ (colour-blind, 50%) from their carrier mother; thus, half (50%) of all male children will be colour-blind.
62. An individual with Klinefelter’s Syndrome possesses which karyotype and characteristic phenotypic features?
Correct Answer: B (47, XXY; tall sterile male with gynaecomastia)
Klinefelter’s syndrome results from an extra X chromosome in males (44 autosomes + XXY = 47), leading to testicular dysgenesis, azoospermia, and gynaecomastia.
Klinefelter’s syndrome results from an extra X chromosome in males (44 autosomes + XXY = 47), leading to testicular dysgenesis, azoospermia, and gynaecomastia.
63. Sickle-cell anemia is an autosomal recessive hemoglobin disorder caused by a transversion point mutation in the beta-globin gene, resulting in a codon shift from:
Correct Answer: A (GAG to GUG at position 6)
A point mutation substitutes adenine with thymine in the DNA template, changing codon 6 from GAG (Glutamic acid) to GUG (Valine), causing HbS polymerization under hypoxia.
A point mutation substitutes adenine with thymine in the DNA template, changing codon 6 from GAG (Glutamic acid) to GUG (Valine), causing HbS polymerization under hypoxia.
64. In eukaryotic nuclei, transcriptionally active and loosely packed chromatin that stains light is designated as:
Correct Answer: B (Euchromatin)
Euchromatin is loosely packed, light-staining, transcriptionally active chromatin. Heterochromatin is densely packed, dark-staining, and transcriptionally inactive.
Euchromatin is loosely packed, light-staining, transcriptionally active chromatin. Heterochromatin is densely packed, dark-staining, and transcriptionally inactive.
65. Meselson and Stahl proved semiconservative DNA replication in E. coli using heavy isotope 15N and density gradient centrifugation with:
Correct Answer: B (Cesium Chloride)
Meselson and Stahl separated hybrid ($^{15}\text{N}/^{14}\text{N}$) and light ($^{14}\text{N}/^{14}\text{N}$) DNA duplexes using CsCl equilibrium density-gradient centrifugation.
Meselson and Stahl separated hybrid ($^{15}\text{N}/^{14}\text{N}$) and light ($^{14}\text{N}/^{14}\text{N}$) DNA duplexes using CsCl equilibrium density-gradient centrifugation.
66. In the genetic code dictionary, which amino acid is coded by ONLY a single triplet codon?
Correct Answer: B (Methionine and Tryptophan)
Among the 20 amino acids, only Methionine (AUG) and Tryptophan (UGG) are specified by a single codon. All other amino acids are encoded by 2 to 6 degenerate codons.
Among the 20 amino acids, only Methionine (AUG) and Tryptophan (UGG) are specified by a single codon. All other amino acids are encoded by 2 to 6 degenerate codons.
67. In the lac operon, the structural gene ‘y’ encodes the enzyme:
Correct Answer: B (Permease)
In the lac operon: gene ‘z’ encodes Beta-galactosidase, gene ‘y’ encodes Permease (which facilitates lactose entry), and gene ‘a’ encodes Transacetylase.
In the lac operon: gene ‘z’ encodes Beta-galactosidase, gene ‘y’ encodes Permease (which facilitates lactose entry), and gene ‘a’ encodes Transacetylase.
68. Industrial melanism observed in the Peppered Moth (Biston betularia) in England following the Industrial Revolution is an example of:
Correct Answer: B (Natural selection in action)
Soot deposition darkened tree bark, providing camouflage for melanic (black) moths against predatory birds, demonstrating directional natural selection.
Soot deposition darkened tree bark, providing camouflage for melanic (black) moths against predatory birds, demonstrating directional natural selection.
69. In a population in Hardy-Weinberg equilibrium, if the frequency of dominant allele ‘p’ is 0.7, what is the frequency of homozygous recessive individuals ($q^2$)?
Correct Answer: C (0.09)
Given $p = 0.7$, then $q = 1 – p = 0.3$. The frequency of homozygous recessive individuals ($q^2$) is $(0.3)^2 = 0.09$ (or 9%).
Given $p = 0.7$, then $q = 1 – p = 0.3$. The frequency of homozygous recessive individuals ($q^2$) is $(0.3)^2 = 0.09$ (or 9%).
70. The evolutionary transition of vertebrates from aquatic to terrestrial life is linked to lobe-finned coelacanth fish caught in South Africa in:
Correct Answer: A (1938)
In 1938, a live coelacanth (Latimeria) was caught off South Africa, proving that lobe-finned ancestors evolved into the first land-dwelling amphibians.
In 1938, a live coelacanth (Latimeria) was caught off South Africa, proving that lobe-finned ancestors evolved into the first land-dwelling amphibians.
72. The diagnostic Widal test for clinical confirmation of Typhoid detects serum antibodies against:
Correct Answer: B (Salmonella typhi O and H antigens)
The Widal agglutination test identifies typhoid by detecting patient serum antibodies against the somatic ‘O’ and flagellar ‘H’ antigens of Salmonella typhi.
The Widal agglutination test identifies typhoid by detecting patient serum antibodies against the somatic ‘O’ and flagellar ‘H’ antigens of Salmonella typhi.
72. Which primary lymphoid organ is situated near the heart beneath the breastbone and gradually atrophies with advancing age?
Correct Answer: B (Thymus)
The thymus is a primary lymphoid organ where T-lymphocytes mature; it is prominent at birth and gradually atrophies into adipose tissue by old age.
The thymus is a primary lymphoid organ where T-lymphocytes mature; it is prominent at birth and gradually atrophies into adipose tissue by old age.
73. Human Immunodeficiency Virus (HIV) preferentially attaches to and infects helper T-cells via which cell-surface receptor?
Correct Answer: B (CD4 receptor)
The HIV envelope glycoprotein gp120 binds to host CD4 receptors on helper T-lymphocytes and macrophages, initiating viral entry and infection.
The HIV envelope glycoprotein gp120 binds to host CD4 receptors on helper T-lymphocytes and macrophages, initiating viral entry and infection.
74. The biological property of normal cells that halts their proliferation upon touching neighboring cells and is lost in cancer cells is:
Correct Answer: B (Contact inhibition)
Contact inhibition arrests normal cell division once adjacent cells touch. Neoplastic cancer cells lose this property, forming multi-layered tumor masses.
Contact inhibition arrests normal cell division once adjacent cells touch. Neoplastic cancer cells lose this property, forming multi-layered tumor masses.
75. “Crack” or “Coke” (Cocaine) is an alkaloid obtained from the leaves of the South American plant:
Correct Answer: C (Erythroxylum coca)
Cocaine is extracted from Erythroxylum coca; it inhibits dopamine reuptake in the central nervous system, inducing stimulation and euphoria.
Cocaine is extracted from Erythroxylum coca; it inhibits dopamine reuptake in the central nervous system, inducing stimulation and euphoria.
76. The organic acid produced by the fungus Aspergillus niger via industrial aerobic fermentation is:
Correct Answer: A (Citric acid)
Aspergillus niger produces citric acid; Acetobacter aceti yields acetic acid, Clostridium butylicum yields butyric acid, and Lactobacillus yields lactic acid.
Aspergillus niger produces citric acid; Acetobacter aceti yields acetic acid, Clostridium butylicum yields butyric acid, and Lactobacillus yields lactic acid.
77. The blood-cholesterol lowering agent Statin acts therapeutically by:
Correct Answer: B (Competitively inhibiting HMG-CoA reductase)
Statins (produced by Monascus purpureus) act as competitive inhibitors of HMG-CoA reductase, suppressing endogenous cholesterol biosynthesis in the liver.
Statins (produced by Monascus purpureus) act as competitive inhibitors of HMG-CoA reductase, suppressing endogenous cholesterol biosynthesis in the liver.
78. Methanogenic bacteria present in the anaerobic sludge digesters of sewage plants belong to:
Correct Answer: B (Archaebacteria)
Methanobacterium species are obligate anaerobic archaebacteria that convert organic sludge into biogas ($CH_4 + CO_2 + H_2S$).
Methanobacterium species are obligate anaerobic archaebacteria that convert organic sludge into biogas ($CH_4 + CO_2 + H_2S$).
79. The microbial biocontrol agent used to control insect larvae without causing environmental toxicity is:
Correct Answer: A (Bacillus thuringiensis)
Bacillus thuringiensis produces crystalline Cry delta-endotoxins that selectively kill insect larvae (caterpillars, beetles, flies) without harming non-target organisms.
Bacillus thuringiensis produces crystalline Cry delta-endotoxins that selectively kill insect larvae (caterpillars, beetles, flies) without harming non-target organisms.
80. A non-leguminous woody tree (e.g., Alnus) forms symbiotic root nodules to fix atmospheric nitrogen with the actinomycete:
Correct Answer: B (Frankia)
The filamentous actinomycete Frankia forms nitrogen-fixing root nodules in non-leguminous woody plants such as Alnus and Casuarina. Rhizobium nodulates legumes.
The filamentous actinomycete Frankia forms nitrogen-fixing root nodules in non-leguminous woody plants such as Alnus and Casuarina. Rhizobium nodulates legumes.
81. The palindromic recognition sequence of the restriction endonuclease EcoRI is:
Correct Answer: A (5′-GAATTC-3′ and 3′-CTTAAG-5′)
EcoRI recognizes the 6-bp palindrome 5′-GAATTC-3′ and cuts between G and A, generating single-stranded 5′-AATT sticky ends.
EcoRI recognizes the 6-bp palindrome 5′-GAATTC-3′ and cuts between G and A, generating single-stranded 5′-AATT sticky ends.
82. In recombinant DNA technology, the enzyme that covalently seals nicks between adjacent 3′-OH and 5′-phosphate ends of DNA fragments is:
Correct Answer: B (T4 DNA Ligase)
DNA ligase acts as molecular glue, forming covalent phosphodiester bonds to join complementary cohesive sticky ends or blunt-ended DNA fragments.
DNA ligase acts as molecular glue, forming covalent phosphodiester bonds to join complementary cohesive sticky ends or blunt-ended DNA fragments.
83. In the Polymerase Chain Reaction (PCR), the correct temperature profile for Denaturation, Annealing, and Extension steps is roughly:
Correct Answer: A (~94°C, ~55°C, and ~72°C respectively)
PCR cycles through Denaturation at ~94°C (unwinding DNA), Primer Annealing at ~50–60°C, and Primer Extension by Taq polymerase at ~72°C.
PCR cycles through Denaturation at ~94°C (unwinding DNA), Primer Annealing at ~50–60°C, and Primer Extension by Taq polymerase at ~72°C.
84. The tumor-inducing (Ti) plasmid used as a cloning vector for introducing genes into dicot plant cells is naturally found in:
Correct Answer: B (Agrobacterium tumefaciens)
Agrobacterium tumefaciens carries the Ti-plasmid, which transfers T-DNA into the plant genome. Disarmed versions serve as primary cloning vectors for plant genetic engineering.
Agrobacterium tumefaciens carries the Ti-plasmid, which transfers T-DNA into the plant genome. Disarmed versions serve as primary cloning vectors for plant genetic engineering.
85. The cryIAc and cryIIAb genes introduced into genetically modified cotton confer resistance against:
Correct Answer: A (Cotton bollworms)
Proteins encoded by cryIAc and cryIIAb control cotton bollworm infestations, while cryIAb controls the corn borer.
Proteins encoded by cryIAc and cryIIAb control cotton bollworm infestations, while cryIAb controls the corn borer.
86. In RNA interference (RNAi), the enzyme complex that binds siRNAs and cleaves complementary cellular target mRNA is:
Correct Answer: B (RISC)
Dicer cleaves dsRNA into siRNAs, which assemble into the RNA-Induced Silencing Complex (RISC) to target and degrade complementary viral or cellular mRNA transcripts.
Dicer cleaves dsRNA into siRNAs, which assemble into the RNA-Induced Silencing Complex (RISC) to target and degrade complementary viral or cellular mRNA transcripts.
87. Recombinant human insulin (Humulin) was first commercially produced by Eli Lilly in 1983 using:
Correct Answer: B (Escherichia coli)
Eli Lilly synthesized human insulin by cloning and expressing A and B chain DNA sequences separately in E. coli, then joining the purified chains via disulfide bridges.
Eli Lilly synthesized human insulin by cloning and expressing A and B chain DNA sequences separately in E. coli, then joining the purified chains via disulfide bridges.
88. The 1990 clinical gene therapy trial for ADA deficiency used which viral vector to deliver functional ADA cDNA into patient lymphocytes?
Correct Answer: B (Disarmed Retrovirus)
A disarmed retroviral vector transferred functional human ADA cDNA into cultured T-lymphocytes harvested from the 4-year-old patient.
A disarmed retroviral vector transferred functional human ADA cDNA into cultured T-lymphocytes harvested from the 4-year-old patient.
89. Genetically engineered ‘Golden Rice’ addresses dietary malnutrition by synthesizing provitamin A (beta-carotene) in its:
Correct Answer: B (Grain Endosperm)
Transgenes from daffodil and bacteria allow Golden Rice to synthesize beta-carotene (provitamin A) directly in the edible endosperm of the grain.
Transgenes from daffodil and bacteria allow Golden Rice to synthesize beta-carotene (provitamin A) directly in the edible endosperm of the grain.
90. In India, which governmental committee grants biosafety clearances and commercial approval for GM crops?
Correct Answer: B (GEAC)
The Genetic Engineering Appraisal Committee (under MoEFCC) evaluates biosafety, environmental risks, and field-trial permits for genetically modified organisms in India.
The Genetic Engineering Appraisal Committee (under MoEFCC) evaluates biosafety, environmental risks, and field-trial permits for genetically modified organisms in India.
91. The epiphytic orchid growing on the branch of a mango tree is an example of:
Correct Answer: A (Commensalism)
The orchid gains physical support, light access, and rain without taking nutrients from or harming the host mango tree (+, 0 commensal interaction).
The orchid gains physical support, light access, and rain without taking nutrients from or harming the host mango tree (+, 0 commensal interaction).
92. In a growing/expanding population, the age-sex pyramid displays:
Correct Answer: B (A triangular profile with a broad pre-reproductive base)
A broad base of pre-reproductive individuals creates a triangular age pyramid, reflecting high birth rates and rapid population expansion.
A broad base of pre-reproductive individuals creates a triangular age pyramid, reflecting high birth rates and rapid population expansion.
93. In xeric primary ecological succession on bare rocks (Lithosere), the pioneer colonizing species are:
Correct Answer: B (Crustose lichens)
Crustose lichens colonize bare rocks first, secreting organic carbonic acids to weather rock minerals into a primitive soil layer for foliose lichens and mosses.
Crustose lichens colonize bare rocks first, secreting organic carbonic acids to weather rock minerals into a primitive soil layer for foliose lichens and mosses.
94. In an ecosystem, the rate of total organic matter production during photosynthesis by autotrophs is:
Correct Answer: A (Gross Primary Productivity)
Gross Primary Productivity (GPP) is the total rate of organic matter synthesis during photosynthesis. Net Primary Productivity is what remains after respiratory utilization ($NPP = GPP – R$).
Gross Primary Productivity (GPP) is the total rate of organic matter synthesis during photosynthesis. Net Primary Productivity is what remains after respiratory utilization ($NPP = GPP – R$).
95. In any stable natural ecosystem, the ecological pyramid of energy is:
Correct Answer: A (ALWAYS upright)
Due to Lindeman’s 10% law and thermodynamic heat dissipation at each trophic transfer, available energy decreases monotonically from producers upward, so energy pyramids are strictly upright.
Due to Lindeman’s 10% law and thermodynamic heat dissipation at each trophic transfer, available energy decreases monotonically from producers upward, so energy pyramids are strictly upright.
96. In Alexander von Humboldt’s logarithmic species-area equation $\log S = \log C + Z \log A$, the slope of the line ‘Z’ across a small geographic region is:
Correct Answer: A (0.1 to 0.2)
Within normal contiguous regional areas, regression slope Z values fall between 0.1 and 0.2 regardless of taxonomic group. Across whole continents, Z steepens to 0.6–1.2.
Within normal contiguous regional areas, regression slope Z values fall between 0.1 and 0.2 regardless of taxonomic group. Across whole continents, Z steepens to 0.6–1.2.
97. Which factor of the “Evil Quartet” is the single greatest driver of modern species extinctions?
Correct Answer: A (Habitat loss and fragmentation)
Deforestation, habitat destruction, and breaking large habitats into small fragments represent the single greatest cause driving species to extinction worldwide.
Deforestation, habitat destruction, and breaking large habitats into small fragments represent the single greatest cause driving species to extinction worldwide.
98. Parthenium (Carrot grass), Lantana, and Eichhornia (Water hyacinth) represent invasive weeds in India that cause biodiversity loss through:
Correct Answer: B (Alien species invasion)
Invasive alien weed species (Parthenium, Lantana, Eichhornia) outcompete indigenous plant communities, causing decline and local displacement of native flora.
Invasive alien weed species (Parthenium, Lantana, Eichhornia) outcompete indigenous plant communities, causing decline and local displacement of native flora.
99. Which of the following is an In-situ (on-site) biodiversity conservation strategy?
Correct Answer: D (Biosphere Reserve, National Park, and Wildlife Sanctuary)
In-situ conservation preserves endangered species in their native wild ecosystems (National Parks, Sanctuaries, Biosphere Reserves, Sacred Groves). Zoos and seed banks are Ex-situ strategies.
In-situ conservation preserves endangered species in their native wild ecosystems (National Parks, Sanctuaries, Biosphere Reserves, Sacred Groves). Zoos and seed banks are Ex-situ strategies.
100. The Western Ghats, Indo-Burma, and Himalaya are internationally designated as:
Correct Answer: B (Global Biodiversity Hotspots covering India)
Three of the world’s 34 biodiversity hotspots cover India: Western Ghats-Sri Lanka, Indo-Burma, and the Himalayas, each harboring high endemism under severe habitat threat.
Three of the world’s 34 biodiversity hotspots cover India: Western Ghats-Sri Lanka, Indo-Burma, and the Himalayas, each harboring high endemism under severe habitat threat.