Question 1
Which of the following endocrine hormones acts on bones and stimulates the process of bone resorption (dissolution/demineralisation)?[cite: 10]
✅ Correct Answer: Parathyroid hormone (PTH)
Explanation: According to NCERT, Parathyroid hormone (PTH) is a hypercalcemic hormone[cite: 10]. It acts on bones and stimulates the process of bone resorption (dissolution/demineralisation), thereby increasing blood calcium levels[cite: 10].
Question 2
In an old tree trunk, the dark brown, central region of secondary xylem that is highly resistant to microbial attacks is called:[cite: 10]
✅ Correct Answer: Heartwood
Explanation: The central, dark brown region of an old tree trunk is called heartwood[cite: 10]. It comprises dead elements with highly lignified walls and is filled with tannins, resins, and gums, making it highly resistant to microbial attacks[cite: 10]. It provides mechanical support but does not conduct water[cite: 10].
Question 3
The oral contraceptive pill 'Saheli', developed by CDRI Lucknow, prevents pregnancy primarily by:[cite: 10]
✅ Correct Answer: Acting as a non-steroidal preparation that blocks estrogen receptors in the uterus, preventing implantation.
Explanation: 'Saheli' is a non-steroidal oral contraceptive pill containing the chemical centchroman[cite: 10]. It acts as a Selective Estrogen Receptor Modulator (SERM)[cite: 10]. By blocking estrogen receptors in the uterus, it alters the uterine lining, preventing the implantation of a fertilized egg[cite: 10].
Question 4
In the gastric glands of the human stomach, the parietal (oxyntic) cells secrete:[cite: 10]
✅ Correct Answer: Hydrochloric acid (HCI) and intrinsic factor
Explanation: The gastric glands have three major cell types[cite: 10]. The parietal (oxyntic) cells secrete HCI (which provides the acidic pH for pepsin activation) and intrinsic factor (which is essential for the absorption of Vitamin B12)[cite: 10].
Question 5
The core of a eukaryotic cilium or flagellum, called the axoneme, possesses a characteristic arrangement of microtubules described as:[cite: 10]
✅ Correct Answer: 9 peripheral doublets + 2 central singlets
Explanation: The axoneme of a eukaryotic cilium or flagellum usually has nine pairs (doublets) of radially arranged peripheral microtubules, and a pair of centrally located singlet microtubules[cite: 10]. This is famously known as the 9+2 array[cite: 10].
Question 6
The enzyme nitrogenase is highly sensitive to molecular oxygen. In the root nodules of leguminous plants, this enzyme is protected from oxygen poisoning by:[cite: 10]
✅ Correct Answer: Leg-haemoglobin, which acts as an oxygen scavenger.
Explanation: Nitrogenase requires strict anaerobic conditions to function[cite: 10]. The root nodules of legumes contain a pink-colored pigment called leg-haemoglobin[cite: 10]. It binds to oxygen, acting as an oxygen scavenger to protect the nitrogenase enzyme while still supplying enough oxygen for the bacteria's aerobic respiration[cite: 10].
Question 7
After the completion of the biosynthetic stage in a bioreactor, the product undergoes separation and purification before being formulated and marketed. These processes are collectively referred to as:[cite: 10]
✅ Correct Answer: Downstream processing
Explanation: Before a recombinant product is ready for marketing as a finished product, it is subjected to a series of processes including separation and purification[cite: 10]. These processes are collectively known as downstream processing[cite: 10].
Question 8
Human skin colour is controlled by three different genes (A, B, C). A person with genotype AaBbCc will have an intermediate skin colour. This type of inheritance, where the phenotype reflects the additive effect of each dominant allele, is called:[cite: 10]
✅ Correct Answer: Polygenic inheritance
Explanation: Polygenic inheritance occurs when a single trait is controlled by three or more genes[cite: 10]. The phenotype is quantified by the additive effect of all the dominant alleles present[cite: 10]. Human skin color and human height are classic examples[cite: 10].
Question 9
Assertion (A): Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron.
Reason (R): Calcium ions bind to a subunit of troponin on actin filaments, unmasking the active sites for myosin.[cite: 10]
✅ Correct Answer: Both A and R are true but R is not the correct explanation of A.
Explanation: Both statements are factual based on NCERT. Muscle contraction is initiated by a CNS signal (Assertion)[cite: 10]. Calcium does bind to troponin to unmask myosin binding sites (Reason)[cite: 10]. However, the Reason describes a downstream biochemical event at the sarcomere level; it does not explicitly explain why/how the CNS initiates the signal (which involves acetylcholine release at the neuromuscular junction)[cite: 10].
Question 10
Assertion (A): Cleistogamous flowers invariably exhibit autogamy and produce assured seed sets even in the absence of pollinators.
Reason (R): Cleistogamous flowers do not open at all, completely preventing cross-pollination from occurring.[cite: 10]
✅ Correct Answer: Both A and R are true and R is the correct explanation of A.
Explanation: Cleistogamous flowers (like those in Commelina, Viola, Oxalis) never open[cite: 10]. Because the anthers and stigma lie close to each other in a closed floral bud, only self-pollination (autogamy) can occur[cite: 10]. This closed structure perfectly explains why they have an assured seed set even without pollinators[cite: 10].
Question 11
Consider the following statements about fungi belonging to the class Ascomycetes...[cite: 10]
✅ Correct Answer: Both Statement I and Statement II are correct.
Explanation: In Ascomycetes (sac fungi), the asexual spores are conidia, which pinch off exogenously from the tips of conidiophores[cite: 10]. The sexual spores are ascospores, which develop endogenously (inside) sac-like asci[cite: 10]. Both statements align perfectly with NCERT definitions[cite: 10].
Question 12
Consider the following statements regarding the Hershey-Chase experiment...[cite: 10]
✅ Correct Answer: Statement I is correct, Statement II is incorrect.
Explanation: Statement I is true because phosphorus is a structural component of DNA, not proteins[cite: 10]. Statement II is false because sulfur is a constituent of proteins (specifically amino acids like cysteine and methionine), not DNA[cite: 10]. The phages grown on 35S had radioactive protein coats, proving DNA is the genetic material when only 32P entered the bacterial cells[cite: 10].
Question 13
A healthy adult male goes for a spirometry test. His Tidal Volume is 500 mL, his Inspiratory Reserve Volume is 3000 mL, and his Expiratory Reserve Volume is 1100 mL. Based on these values, what is his Vital Capacity (VC)?[cite: 10]
✅ Correct Answer: 4600 mL
Explanation: Vital Capacity (VC) is the maximum volume of air a person can breathe in after a forced expiration (or breathe out after a forced inspiration)[cite: 10]. Formula: $VC = ERV + TV + IRV$[cite: 10]. $VC = 1100 \text{ mL} + 500 \text{ mL} + 3000 \text{ mL} = 4600 \text{ mL}$[cite: 10].
Question 14
An artificial circular plasmid consists of exactly 500 base pairs. How many total phosphodiester bonds are present in this double-stranded circular DNA molecule?[cite: 10]
✅ Correct Answer: 1000
Explanation: A DNA molecule of 500 base pairs contains 1000 total nucleotides (500 on each strand)[cite: 10]. In a linear DNA strand of 'n' nucleotides, there are (n-1) phosphodiester bonds[cite: 10]. However, in a circular DNA molecule (like a plasmid), the two ends join, forming an additional bond[cite: 10]. Therefore, a circular strand of 'n' nucleotides has 'n' phosphodiester bonds[cite: 10]. Two strands of 500 nucleotides each = $500 + 500 = 1000$ phosphodiester bonds[cite: 10].
Question 15
In a Mendelian trihybrid cross involving independent assortment ($AaBbCc \times AaBbCc$), what is the exact probability of obtaining offspring with the genotype $AabbCc$?[cite: 10]
✅ Correct Answer: $1/16$
Explanation: Because the genes assort independently, we treat this as three separate monohybrid crosses[cite: 10]. For $Aa \times Aa$: Probability of '$Aa$' = $2/4 = 1/2$[cite: 10]. For $Bb \times Bb$: Probability of '$bb$' = $1/4$[cite: 10]. For $Cc \times Cc$: Probability of '$Cc$' = $2/4 = 1/2$[cite: 10]. Multiply the individual probabilities: $(1/2) \times (1/4) \times (1/2) = 1/16$[cite: 10].
Question 16
Match the hominid in Column I with its approximate cranial capacity in Column II:[cite: 10]
✅ Correct Answer: a-iii, b-i, c-ii
Explanation: According to NCERT data on human evolution: Homo habilis had a cranial capacity of 650-800 cc (iii)[cite: 10]. Homo erectus had a larger brain around 900 cc (i)[cite: 10]. Neanderthal man had a brain size of 1400 cc (ii)[cite: 10].
Question 17
A botanist observes a flower and notes the following characteristics: actinomorphic symmetry, bisexual nature, 5 united sepals, 5 united petals, 5 epipetalous stamens, and a bicarpellary syncarpous superior ovary with swollen placenta. This describes the floral formula of which plant family?[cite: 10]
✅ Correct Answer: Solanaceae
Explanation: The described traits (actinomorphic, $K(5) C(5) A5 G(2)$ with epipetalous stamens and swollen placenta) perfectly match the potato family, Solanaceae[cite: 10]. Fabaceae is zygomorphic[cite: 10]. Liliaceae is a monocot family characterized by a perianth (tepals) and trimerous flowers[cite: 10].
Question 18
A person consumes a large volume of pure water on a hot day without exercising. Which of the following physiological responses will occur immediately to maintain blood osmolarity?[cite: 10]
✅ Correct Answer: The posterior pituitary suppresses the release of ADH (Vasopressin), leading to diuresis.
Explanation: Drinking excess pure water dilutes the blood, dropping blood osmolarity[cite: 10]. This inhibits the osmoreceptors in the hypothalamus[cite: 10]. As a result, the posterior pituitary stops releasing Antidiuretic Hormone (ADH/Vasopressin)[cite: 10]. Without ADH, the collecting ducts become impermeable to water, resulting in the excretion of a large volume of dilute urine (diuresis)[cite: 10].
Question 19
In his historic experiment, T.W. Engelmann illuminated a green alga (Cladophora) with a continuous spectrum of light and observed the accumulation of aerobic bacteria. The bacteria aggregated predominantly in which regions of the spectrum?[cite: 10]
✅ Correct Answer: Blue and Red light regions
Explanation: Engelmann used a prism to split light into its spectral components and illuminated Cladophora[cite: 10]. He used aerobic bacteria to detect the sites of maximum oxygen evolution[cite: 10]. The bacteria accumulated mainly in the blue and red regions of the spectrum, forming the first described action spectrum of photosynthesis[cite: 10].
Question 20
Diatoms are major producers in the oceans. Their cell walls form two thin overlapping shells, which fit together as in a soap box. These walls are practically indestructible because they are embedded with:[cite: 10]
✅ Correct Answer: Silica
Explanation: Diatoms belong to the kingdom Protista (Chrysophytes)[cite: 10]. Their cell walls overlap to fit together like a soap box[cite: 10]. The walls are embedded with silica, making them virtually indestructible[cite: 10]. Over billions of years, this leaves behind massive accumulations known as 'diatomaceous earth'[cite: 10].
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