Second Year syllabus Test-1

Explanation: A

Explanation: D
Magnetic field, Magnetic induction and magnetic field All define same quantity represented by symbol “B” And have SI unit of tesla
1 Tesla= 10⁴ Gauss.
Magnetic field density → Not a standard physical quantity. There is no such defined quantity as “magnetic field density.”

Explanation: A
A capacitor allows current to pass only when the voltage changes with time (i.e., AC).
For DC, once fully charged, no further current flows — it acts as a perfect insulator.
So, it blocks DC and passes AC.

Explanation: C
Output of rectifier circuit is always pulsating DC.

Explanation: B
Last line is emitted when electron makes transition from infinite shell to the lower shell of respective series. Photon emitted as a result of this transition has the maximum frequency and the minimum wavelength.
• First line of a series: n₂ = n₁ + 1 → smallest energy difference → longest wavelength.
• Last line of a series: n₂ → ∞ → maximum energy difference → shortest wavelength.
Thus, last line has lesser wavelength than the first line.

Explanation: D

Explanation: B
Force on a current-carrying conductor
F=I(L×B)
Current direction → North (upward on the page).
Magnetic field → into the page (denoted by × symbol).
Force → given by cross product I×B
Use right-hand rule for cross product
Point index finger (current) upward (North).
Point middle finger (magnetic field) into the page.
Then thumb shows force direction.
Result: Force is towards the West.

Explanation: A
Reactance of inductor is given by X_L = ωL = 2πf × L. It is clear from equation that more the frequency the more will be reactance. The more the reactance the lesser the current.

Explanation: C
V_output or V_dc of half wave rectifier = V_peak/π = 310/3.14 ≈ 100 V.

Explanation: D
A. Activity increases with increase in number of atoms
Yes, because A ∝ N. More atoms → more disintegrations per second.
B. Activity decreases with increase in number of half-lives
Longer half-life → smaller decay constant λ → smaller activity.
C. Activity of an element having small half-life has more activity
Shorter half-life → larger λ → higher activity.

Explanation: D

Explanation: C
Radius of cyclotron: r = P/qB , so if P is same, r is same
For proton we will use right hand rule for direction (positive charge)
For electron we will use left hand rule (negative charge), Therefore they will move in opposite direction.

Explanation: C

Explanation B
The input AC signal has a frequency of 60 Hz.
A half-wave rectifier only allows one half-cycle of the AC signal, so the output frequency remains 60 Hz.
A full-wave rectifier (whether bridge or center-tapped) inverts the negative half-cycles, so the output waveform frequency becomes double the input → 120 Hz.
A half-wave rectifier with a capacitor filter smooths the waveform but still follows the fundamental frequency of 60 Hz.
A center-tapped half-wave rectifier is not a standard name — with a center-tapped transformer you usually make a full-wave rectifier, not half-wave.
Since the oscilloscope shows 120 Hz, the circuit must be a full-wave rectifier.
So the correct answer is: B. Full-wave bridge rectifier.

Explanation: B
In forward bias, applying positive voltage reduces the barrier potential.
As the applied voltage nears the knee voltage (~0.7 V for silicon), the depletion region becomes narrower because majority carriers are pushed across the junction.
This narrowing lowers the resistance of the junction, allowing a sharp rise in current.

Explanation C
For an infinite plane sheet of uniform charge density (σ), the electric field intensity at any point is given by:
E=σ/(2ε₀)
• Here, σ= surface charge density.
• ε₀= permittivity of free space.
This formula comes from Gauss’s Law, applied to a cylindrical Gaussian surface (pillbox) intersecting the plane sheet.
Notice that E does not depend on the distance ( r ) from the sheet.
• Unlike a point charge (∝ 1/r²) or a line charge (∝ 1/r), the field of an infinite plane sheet remains constant everywhere.
Thus, the electric field intensity due to a uniformly charged infinite non-conducting plane sheet is independent of the distance.

Explanation: A
Magnetic flux is a Scalar quantity because it is a dot product of magnetic field and vector area. SI unit of magnetic flux is Weber

Explanation: C
During 1^st quarter = positive
During 2^nd quarter = negative
During 3^rd quarter = positive
During 4^th quarter = negative
During half cycle = 0
During full cycle = 0.

Explanation: D
Question demands half of maximum and not half of Comptons wavelength
Maximum Comptons effect occurs at 180 degrees and is equal to 2 times of Comptons wavelength
For half of maximum comptons effect =  h/mc (1 – cos90) = h/mc (Comptons wavelength).

Explanation: C
An alpha particle = He nucleus (2 protons + 2 neutrons).
When emitted:
Atomic mass number decreases by 4.
Atomic number decreases by 2 (because 2 protons are lost).
But, Losing 2 protons changes the element itself → it becomes a different element, not just an isotope of the same one.

Explanation: A

Explanation: A

Explanation: D
In AC, the bulb glows (or blinks) twice in each cycle: once in the positive half cycle and once in the negative half cycle.
So, Number of blinks per second = 2 × Frequency.
Blinks per second = 100/2 = 50 Blinks/second
50 = 2f  ⇒  f = 25 Hz.

Explanation: C
Pair production can only occur in vicinity of heavy nucleus as it necessary to absorb the recoil energy. As there is no heavy nucleus in space pair production cannot occur.

Explanation: A

Explanation: A

Explanation: D
Transformer works on the principle of Mutual induction, that is an application of Faraday law which in turn explains electromagnetic induction

Explanation: C
Cobalt-60 is a source of gamma rays and is used in medicine.

Explanation: B
If coefficient = 0 (ideal material 》No change in resistance)
If coefficient = positive (Metals 》Increase in resistance)
If coefficient = negative (semiconductors 》Decrease in resistance).

Explanation: B
When applied current decreases, induced current in order to oppose its cause (decreasing current) will flow in a way to oppose the cause and therefore will flow in the direction of applied current and net current will be sum of induced and applied current
In short when current increases
I_net= I_applied – I_induced
When current decreases
I_net = I_applied + I_induced..

Explanation: C

When wire is bend into circle 10ohm will be divided into two 5-ohm resistors connected in parallel as shown above for similar resistors connected parallel
R_n = R/n = 5/2 = 2.5 Ohm.

Explanation B
Faraday’s Law of Electromagnetic Induction states that an emf is induced in a circuit whenever the magnetic flux through it changes.
The induced emf always opposes the change in flux (Lenz’s Law).
This opposition ensures that no energy is created or destroyed in the process
— it only gets converted (for example, mechanical work → electrical energy).
Thus, Faraday’s law is a direct consequence of the law of conservation of energy.

Explanation C
A. In electromagnetic waves, the oscillating electric and magnetic fields are perpendicular to the direction of propagation, making them transverse.
B. EM waves are transverse, their electric field component can be oriented in specific directions (polarization).
C. Unlike sound waves, electromagnetic waves do not need a material medium. They can travel through vacuum (e.g., sunlight reaching Earth).D. In EM waves, the electric and magnetic fields oscillate mutually perpendicular and also perpendicular to the direction of wave propagation.

Explanation B
Formula: V=E−Ir
As current (I) increases, drop across
Ir increases → terminal voltage falls.
At very high current, V→0.
Option A is wrong → Voltage does not increase; it decreases.
Option C is wrong → Terminal voltage = emf only when no current flows (open circuit).
Option D is wrong → Terminal voltage becomes zero only when
I=r/E , not always.

Explanation: B
As the ring approaches the South pole of the magnet:
The magnetic flux through the ring increases (since it’s moving closer to the magnet’s field).
Faraday’s Law:
A current is induced in the ring to oppose this increase in flux.
Lenz’s Law:
To oppose the approach of the magnet’s South pole, the side of the ring facing the magnet must behave like a North pole.
Result:
The induced North pole of the ring faces the South pole of the magnet.
North and South poles attract, but remember, the attraction is in the opposite direction of the motion (because it’s resisting the change).
This produces an upward magnetic force opposing gravity.
Net Effect on Motion:
Gravity pulls the ring down with force = mg.
Magnetic repulsion/attraction (depending on direction of flux change) acts upward.
Therefore, net acceleration < g.

Explanation: C
Polarization shows wave nature of photon
All other options show matter (particle) nature of photon

Explanation: B
Recombinant DNA technology inserts human genes into bacteria or yeast to mass-produce proteins like insulin.

Explanation: C
Hemoglobin can bind with maximum 4 oxygen molecules, so for obtaining 50% saturation only 2 molecules of oxygen should be bound to hemoglobin.

Explanation: D
Glomerulus is not a part of renal medulla.

Explanation: A
Calcium ions play a critical role in muscle contraction by binding to the troponin molecules present on the thin filaments. When calcium ions bind to troponin, it induces a conformational change in the troponin-tropomyosin complex. This change exposes the myosin-binding sites on the actin filaments, allowing the myosin heads to form cross-bridges and initiate muscle contraction. 

Explanation: C
Each testis has 250 – 300 lobules.

Explanation: A
When the sperm count exceeds set limits, The hormone inhibits GnRH and FSH, decreasing the activity of the Sertoli cells. It inhibits the synthesis and
release of the follicle-stimulating hormone in the pituitary gland and reduces the hypothalamic LH – releasing hormone content.

Explanation: B
Option B is correct since the number of linkage groups in humans is equal to the haploid number of chromosomes. The linkage groups refer to all the genes on a single chromosome. These groups are inherited together in an individual. The chromosomes in humans are 46 and their haploid number is 23. So linkage groups are also 23. Option A is incorrect since it states 1/21 which is wrong. Option C is incorrect since it states 1/23 which is wrong. Option D is incorrect since it states 1/24 which is wrong.

Explanation: A
The answer is heritable. Natural selection can only amplify or diminish variations that are passed on from parents to offspring. Heritable traits are those that are encoded in the genes of an organism. These traits are passed on from parents to offspring through the process of reproduction.

Explanation: D
Most synapses in humans are chemical, where neurotransmitters carry the signal across a wider synaptic cleft (>20 nm).

Explanation: D
“Alveoli do not collapse even after forceful expiration because a certain amount of air always remains in the lungs. This is called residual volume (~1200 mL). It keeps the alveoli partially inflated and ensures continuous gaseous exchange.

Explanation: B
Level of ADH during dehydration increases in order to conserve more water in body.

Explanation: D
A–band of sarcomere can polarize visible light. The A–band of a sarcomere consists of an overlap between light and heavy (actin and myosin) protein filaments. As a result, this band is denser and appears darker than surrounding regions under polarized light visualization

Explanation B
Spirochete Treponema pallidum is responsible for causing syphilis.

Explanation: A
The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens. The seminiferous tubules of the testis open into the vasa efferentia through rete testis. The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis. So if vasa efferentia gets blocked, the gametes will not be transported from testes to epididymis.

Explanation: C
Pisum sativum, the common Pea, normally has seven pairs of chromosomes at meiosis.

Explanation: B
In the human kidney, about 70–80% of nephrons are cortical nephrons, which are located primarily in the renal cortex and have shorter loops of Henle. The remaining 20–30% are juxtamedullary nephrons. These nephrons are located closer to the corticomedullary junction and have long loops of Henle extending deep into the medulla. This structural feature plays a crucial role in concentrating urine by establishing the medullary osmotic gradient.

Explanation: C
The myelin sheath insulates the axon and forces the action potential to jump from one Node of Ranvier to the next, making conduction faster.

Explanation: A
Explanation of each option:
A. C- Alveoli- Thin-walled vascular bag-like structures for exchange of gases (Correct Option): The alveoli are indeed thin-walled, vascular, and resemble tiny sacs or “bag-like” structures. They are responsible for the primary function of gas exchange in the respiratory system. Oxygen is taken up by the bloodstream, and carbon dioxide is released into the alveoli to be exhaled. The thin walls and extensive vascularization of alveoli facilitate efficient gas exchange.
B. D- Lower end of lungs- Diaphragm pulls it down during inspiration: The lower end of the lungs is not directly pulled down by the diaphragm during inspiration. Instead, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity and allowing the lungs to expand and fill with air during inspiration. The diaphragm plays a crucial role in the mechanics of breathing. 
C. A- Trachea- Long tube supported by complete cartilaginous rings for conducting inspired air: The trachea is indeed a long tube in the human respiratory system, but it is not supported by “complete cartilaginous rings.” Instead, the trachea is supported by C-shaped cartilaginous rings. These C-shaped rings provide support to the trachea while allowing flexibility for swallowing and neck movement. The main function of the trachea is to conduct inspired air from the upper respiratory tract (nose and mouth) into the lower respiratory tract (lungs).
D. B- Pleural membrane- Surround ribs on both sides to provide cushion against rubbing: The pleural membrane does not primarily surround the ribs. Instead, it forms a double-layered sac that surrounds the lungs and lines the inner surface of the chest wall. It consists of two layers: the visceral pleura (which covers the lungs) and the parietal pleura (which lines the chest wall). The pleural membrane’s main function is to create a sealed, fluid-filled space between the layers, reducing friction and enabling the smooth movement of the lungs during breathing.
Summary: The correct option is (A) C. Alveoli are indeed thin-walled, vascular, and responsible for gas exchange in the respiratory system. The other options provide explanations but do not accurately describe the main function or characteristics of the labeled structures.

Explanation: B
Each A band has a lighter stripe in its mid-section called H-zone (H stands for “hele” mean bright). The H-zone is bisected by dark line called M – line. The I bands have mid line called Z-line (Z for Zwishen means between).

Explanation C

Explanation: B
Reference: Text Book.

Explanation: C
“Hemophilia A is an X-linked recessive disorder. Affected males (like Ahmed) have the defective gene on their single X chromosome. They cannot pass this X to their sons (sons inherit father’s Y chromosome), but they always pass it to their daughters. Thus, daughters become carriers and can transmit the gene to their own sons (Ahmed’s grandsons).
Therefore, Ahmed passed the trait to his grandson through his daughter.

Explanation: B
Let allele for blue phenotype [dominant] =B, Let allele for white phenotype [recessive] =b, Parental phenotypes =Bb[heterozygous] *bb [homozygous], Phenotypic probability of white phenotypes=[1+1]/4=0.5 =50%

Explanation: B
The ascending limb actively transports Na⁺, Cl⁻, and K⁺ but does not allow water reabsorption.

Explanation: C
CSF is formed by various processes including diffusion, pinocytosis, and active transport from the blood vessels of the brain and spinal cord.

Explanation: C
The transport of oxygen and carbon dioxide in blood mainly occurs through red blood cells (RBCs) and blood plasma.
• Oxygen (O₂): About 98% of oxygen is carried by RBCs, where it binds with hemoglobin to form oxyhemoglobin. The remaining 2% is dissolved directly in plasma.
• Carbon dioxide (CO₂): About 70% of CO₂ is transported as bicarbonate ions in plasma, around 23% binds with hemoglobin in RBCs (as carbaminohemoglobin), and the remaining 7% is dissolved in plasma.

Explanation: C
Bone consists of three types of cells:
⟹ Osteoblast ⟶ Bone forming cells.
⟹ Osteoclast ⟶ Bone dissolving cells.
⟹ Osteocytes ⟶ bone cells.

Explanation: A
The tough outer layer of tissue that covers and protects the brain and spinal cord and is closest to the skull. The dura mater is one of the three layers that form the meninges.

Explanation: A
In oogenesis, diploid oogonium goes through mitosis until one develops into a primary oocyte, which will begin the first meiotic division, but then arrest; it will finish this division as it develops in the follicle, giving rise to a haploid secondary oocyte and a smaller polar body. Thus, “Option A” is the correct answer.

Explanation: B
To understand and solve this, you can divide your thinking into two. For character 1. When genes are passed down to offspring, when the genes of this character pass down, the Dominant gene will always be present, so only one phenotype is possible from this character. For character 2. Three genotypes are possible, RR, Rr, and rr. RR and Rr are one phenotype and rr another. Total 2 So 2 × 1=2 total phenotypes

Explanation: A
Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the surviving individuals. Those individuals whose inherited characteristics it them best to their environment are likely to leave more offspring than the less-it individuals.

Explanation: B
DCT has osmoregulatory role and secretes hydrogen ions to regulate blood pH.

Explanation: C
The midbrain is involved in spatial awareness and processes visual and auditory information.

Explanation: A
Surfactants is a lipoprotein layer inside alveoli, which reduce surface tension between water molecules to increase gases exchange. 

Explanation: A
Calcium ion plays an important role in muscle contraction. Calcium ions bind to troponin causing a change in its shape and position. Thus, in turn alters shape and position of tropomyosin to
which troponin binds. This shift exposes the active sites on F–actin molecules. Hence, myosin cross bridges are then able to bind to these active sites.  

Explanation: A
In action membrane potential, charges are reversed. The inner side of the cell membrane has excess of positive ions (thus positive charges) at its internal surface, and the outer surface becomes more negative.

Explanation: D
“In human females, oogenesis begins before birth, and primary oocytes are arrested in prophase I until puberty. Each month, during ovulation, one oocyte resumes meiosis and is arrested again at metaphase II. The oocyte will only complete meiosis II if a sperm penetrates it.
Thus, oocytes are held in second metaphase until fertilization.

Explanation: A
The principle of segregation states that each individual has two alleles for each gene, and these alleles segregate during gamete formation, with each gamete receiving only one allele. A 3:1 ratio in the F2 generation of a monohybrid cross suggests that the trait being studied is controlled by a single gene with two alleles and follows a dominant and recessive pattern of inheritance. The dominant allele is expressed in the phenotype of individuals that are homozygous dominant or heterozygous, while the recessive allele is only expressed in individuals that are homozygous recessive. Therefore, the mode of inheritance for the trait being studied is likely to be Mendel’s law of segregation.

Explanation: B
The processes of natural selection thus cause an increase of favourable alleles and a decrease of unfavourable alleles within the population, Over succeeding generations, individual members become better adapted to local conditions, thus, leading to the evolution of new species

Explanation: B
The opposite flow of filtrate in ascending and descending limbs of loop of Henle helps concentrate solutes in medulla (counter current mechanism).

Explanation: A
The base-pairing principle ensures that probes only bind to sequences complementary to their own.

Explanation: D
•The rate of breathing is primarily regulated by the respiratory centers in the medulla oblongata and pons, which respond to chemical signals from the chemoreceptors in the aorta and carotid arteries. These chemoreceptors are sensitive to changes in the levels of carbon dioxide (CO₂) partial pressure, hydrogen ion (H+) concentration (pH), and oxygen (O₂) partial pressure in the blood.
•Blood glucose level, on the other hand, does not directly influence the rate of breathing through the chemoreceptors in the medulla oblongata, aorta, and carotid artery. Instead, blood glucose levels are primarily regulated by hormones such as insulin and glucagon, and they play a crucial role in maintaining glucose homeostasis in the body. However, glucose levels can indirectly affect breathing in cases of severe hypoglycemia or hyperglycemia, which may lead to altered levels of consciousness or metabolic imbalances that can impact respiratory function. But it is not a direct regulator of the rate of breathing through the chemoreceptors mentioned.

Explanation: C
Fibrous joints are also called fixed or immovable joints because they do not allow any movement. These joints are immovable as they have no joint cavity or space present between the bones. They are connected via fibrous connective tissue. There are three types of fibrous joints: sutures, syndesmoses, and gomphoses. Sutures are found only in the skull, an example of a syndesmosis is the joint of the tibia and fibula in the ankle, Gomphoses occur between teeth and their sockets.
So, the correct answer is ‘Fibrous joint’
A. Synovial joints are freely moveable joints.
B. Ball and socket joint are example of freely moveable joints.
D. These joints allow little movement like pubic symphysis, intervertebral disc and coastal cartilage. 

Explanation: B
Consecutive neurons are so arranged that the axon endings of one neuron are connected to the dendrites of the next neuron. There is no cytoplasmic connection between the two neurons and microscopic gaps are left between them.

Explanation: D
The correct sequence for transport of sperm cells in male reproductive system is Seminiferous tubules → Rete testis → Vasa efferentia → Epididymis → Vas deferens → Ejaculatory duct → Urethra → Urethral meatus.

Explanation: C
According to the law of segregation, when two pure breeds are crossed (e.g. RR and rr), all of the F1 generation has the dominant trait and their genotype is Rr. They are called Hybrids. When hybrids are crossed, resulting F2 generation has the phenotypic ratio of 3:1 and their genotypic ratio is 1:2:1. So, the correct Option is C.

Explanation: D
The main points of Darwin’s theory of evolution are “Descent with Modification,” “Natural Selection,” “Adaptation”. These concepts collectively form the foundation of his theory and provide an explanation for how species evolve and adapt to their environments over time.

Explanation: B
Probes carry fluorescent or radioactive tags and bind specifically to complementary viral genetic material.

Explanation: B
Reflex actions bypass the brain and occur through the spinal cord for a fast response.

Explanation: D
During inspiration muscles of ribs and diaphragm contract due to which ribs are elevated and diaphragm become less dome shaped. The space in chest cavity is increased.

Explanation: A
A neuron that transmits a stimulus to muscle tissue is called motor neuron. A motor unit consists of a single motor neuron (nerve cell) and the muscle fibers it innervates. The portion of the muscle plasma membrane (sarcolemma) that lies beneath the nerve endings (axon terminals) is called the motor end plate. The axon terminals and the motor end plate together constitute the neuromuscular junction or neuromotor junction. 
B. Sarcolemma of muscle fiber penetrates deep into the cell to form a hollow elongated tube called transverse tubule.
C. Muscle fibers of skeletal muscles are composed of myofibrils which are further of two types thick and thin myofibrils.
D. Endoplasmic reticulum of muscles is called sarcoplasmic reticulum.

Explanation: B
Calcium channels reside in the surface membrane of the presynaptic nerve terminal. Inside the terminal, Ca²⁺ ions rapidly bind to endogenous intracellular buffers and could trigger Ca²⁺ release from internal Ca²⁺ stores. Inside the terminal, Ca²⁺ ions rapidly bind to endogenous intracellular buffers and could trigger Ca²⁺ release from internal Ca²⁺ stores

Explanation: A
Following menstruation, the proliferative phase begins. It usually lasts from around day 6 to day 14 of a 28-day cycle, but the exact timing can vary. During this phase: Follicle-stimulating hormone (FSH) stimulates the development of ovarian follicles, each containing an immature egg (oocyte). Rising levels of estrogen, produced by the developing follicles, stimulate the growth and proliferation of the endometrial lining in the uterus. 

Explanation: A
The father transmits his “X-chromosome” to the daughter while the sons receive “Y-chromosome” from the father. Since only the daughter and none of the sons are affected, the trait is X-linked. Daughters get the second copy of X-chromosomes from the mother who is normal and hence does not carry the affected allele of the trait. The trait is expressed in daughters under heterozygous conditions, hence it is an X-linked dominant trait. The correct option is A.

Explanation: B
Charles Darwin is widely recognized as the person who argued for evolution with strong evidence and is most famous for his theory of evolution by natural selection. Darwin’s work, particularly his book “On the Origin of Species,” is a foundational contribution to the field of evolutionary biology. He provided substantial evidence for the idea of species evolving over time through the mechanism of natural selection.

Explanation: B
Struvite stones (15–20% of cases) form due to infections by urease-producing bacteria such as Proteus, Klebsiella, etc.

Explanation: B
Haemophilia B is a genetic disorder where the body lacks or has low levels of blood clotting factor IX, which is essential for normal blood clotting. This leads to prolonged bleeding.
Key point: 
• Haemophilia A → Factor VIII 
• Haemophilia B → Factor IX 
• Haemophilia C → Factor XI
So, the correct answer is B.

Explanation: B
The larynx is a cartilaginous segment of the respiratory tract located in the anterior aspect of the neck. The primary function of the larynx in humans and other vertebrates is to protect the lower respiratory tract from aspirating food into the trachea while breathing.

Explanation: B
Cartilage is an important component of skeleton. It consists of a firm matrix containing collagen and elastin fibres and cells in fluidfilled lacunae. Cartilage has many types.

Explanation: B
“A nerve or muscle fiber remains at resting potential until stimulated.
A sub-threshold stimulus is too weak to produce an action potential.
A threshold stimulus is the minimum strength required to depolarize the membrane to its critical level, thereby generating an action potential.
Stronger stimuli beyond the threshold do not increase the size of the action potential (all-or-none law).
Hence, a stimulus capable of producing an action potential is called a threshold stimulus.”

Explanation: C
Between the seminiferous tubules in the testes are interstitial cells, also known as Leydig cells. Leydig cells are responsible for secreting the male sex hormone testosterone. Testosterone plays a crucial role in the development and maintenance of male reproductive tissues and the expression of male secondary sexual characteristics. It influences the development of the testes, promotes the production of sperm in the seminiferous tubules, and is involved in the development of male secondary sexual characteristics such as facial hair, deepening of the voice, and increased muscle mass.

Explanation: B
The gene responsible for color blindness is located on the X chromosome. In other words, red-green color blindness is an X-linked recessive condition. If a female inherits one normal color vision gene and one mutated gene, she won’t be red-green color blind, because it’s a recessive trait.

Explanation: A
Lamarck believed that organisms can change over time through the inheritance of acquired characteristics. Theories proposed by other scientists are mentioned under their name.

Explanation: C
Hyperuricemia is characterized by high uric acid in blood, predisposing to uric acid stones.

Explanation: C
Gene linkage refers to the tendency of genes located on the same chromosome to be inherited together during genetic crosses.

Explanation: B
Hypothalamus is the brain part which has homeostatic thermostat.

Explanation: B
Cardiac and smooth muscles are involuntary in action, while skeletal muscles are voluntary in their functions.

Explanation: B
Myelin insulates axons and enables saltatory conduction between nodes of Ranvier, making nerve impulses travel faster and more efficiently. It doesn’t store nutrients, help cells divide, or synthesize neurotransmitters.

Explanation: C
Correct option: C Mendel’s laws, which describe patterns of inheritance, can be explained by the behavior of chromosomes during meiosis. Meiosis is the cell division process that produces gametes (sex cells), and it involves the recombination and segregation of chromosomes. The segregation of alleles during meiosis corresponds to Mendel’s Law of Segregation, while the independent assortment of chromosomes corresponds to Mendel’s Law of Independent Assortment. Therefore, option C, chromosomes behavior in meiosis, provides an explanation for Mendel’s laws.

Explanation: C
Herbert Spencer was the first person to use the term “survival of the fittest”. He did so in his 1864 book Principles of Biology. Spencer was a philosopher and sociologist who was influenced by Darwin’s work on evolution. He used the term “survival of the fittest” to describe the process by which organisms that are better adapted to their environment are more likely to survive and reproduce.

Explanation: B
Overactive parathyroid glands increase blood calcium (hypercalcemia), leading to calcium oxalate or phosphate stone formation.

Explanation: C
Only parental types (no recombinants) indicate complete or tight linkage, meaning the genes are very close on the chromosome and do not cross over.

Explanation: B
Self explanatory.

Explanation: A
When a muscle is at rest, tropomyosin is a regulatory protein that covers the myosin-binding sites on the actin filament. This covering prevents the myosin heads from attaching to actin, effectively inhibiting muscle contraction. Tropomyosin’s position is controlled by the troponin complex in response to calcium levels. 

Explanation: A
⇒ The head of the sperm contain lysosome like acrosome is produced by Golgi apparatus. It contain hydrolytic enzyme Hyaluronidase.

Explanation: B
The breakdown of the endometrium during menstruation is due to a decrease in the levels of the hormone progesterone. This hormone is responsible for maintaining the lining of the uterus, and when its levels decrease, the lining begins to break down. So, option B is correct.

Explanation: C
Luteinizing hormone (LH) is a hormone produced by the anterior pituitary gland. It plays a crucial role in the female reproductive system by triggering ovulation. Ovulation is the process in which a mature follicle in the ovary releases an egg (oocyte) into the fallopian tube, where it can potentially be fertilized by sperm. Hence, option C is correct.

Explanation: D
In a homozygous pea plant, axial flowers (A) are dominant over terminal flowers (a)

Explanation: D
Chris Lyell was a great geologist of his time. His theory of uniformitarianism inspired Darwin. According to Lyell, the geologic processes that were around at the beginning of time were the same ones that were happening in the present as well and they worked the same way. He believed the Earth developed through a series of slow changes that built up over time.

Explanation: B  
When the body overheats, it tries to cool down by increasing sweat production (more sweating), which helps release heat through evaporation. At the same time, the body reduces urine output (less urination) to conserve water, as more is being lost through sweat. This is part of thermoregulation in humans.

Explanation: B
Their specificity makes monoclonal antibodies valuable in detecting and targeting unique antigens such as those in pathogens or cancer cells.

Explanation: C
NH₃ is a group 5 compound with a donatable lone pair of electrons.

Explanation: D
The α-carbon is the carbon atom directly attached to the halogen atom in alkyl halides.
In primary, secondary, and tertiary alkyl halides, this α-carbon is always bonded to four atoms (halogen + hydrogens or carbons).
Since it forms four σ-bonds, its hybridization is sp³.
Primary alkyl halide → α-carbon bonded to 1 carbon + 2 hydrogens + 1 halogen → sp³
Secondary alkyl halide → α-carbon bonded to 2 carbons + 1 hydrogen + 1 halogen → sp³
Tertiary alkyl halide → α-carbon bonded to 3 carbons + 1 halogen → sp³
Therefore, in all types of alkyl halides, the α-carbon is sp³ hybridized.

Explanation: D
Nitrile (–C≡N): Contains a cyano group, which has a carbon–nitrogen triple bond, but no carbonyl (C=O) group.

Explanation B
Correct Match: Hemoglobin is an iron-containing protein found in red blood cells. Its primary function is to transport oxygen from the lungs to the rest of the body’s tissues. It also carries some carbon dioxide from the tissues back to the lungs.

Explanation: C
1,2-Dichloroethene has a C=C double bond where each carbon atom is bonded to one hydrogen atom and one chlorine atom. This satisfies the conditions for cis-trans isomerism.

Explanation: C
Ethanol is a primary alcohol that gives positive Lucas’s test on heating
3° alcohol → Immediate cloudiness
2° alcohol → 5–10 min
1° alcohol (like ethanol) → Only on heating.

Explanation: B
Pigments are insoluble and remain as particles, while dyes dissolve and bind chemically.

Explanation: A
Base catalyst in nucleophilic addition reactions of aldehydes & ketones catalyzes the reaction by removing electrophilic portion of reagent & generating a strong nucleophile.

Explanation: D
An ester has the general formula R-CO-OR’. It is formed from a carboxylic acid and an alcohol.
The carbonyl group is the C=O part.
The alkoxide group is the -OR’ part, an oxygen atom bonded to another carbon chain.

Explanation: B
An SN1 (Substitution, Nucleophilic, Unimolecular) reaction proceeds in two steps, with the first and rate-determining step being the formation of a carbocation intermediate. The rate of an SN1 reaction is dependent on the stability of this carbocation. The more stable the carbocation, the faster it forms, and the more reactive the alkyl halide. The stability of carbocations follows this trend:
Tertiary > Secondary > Primary
In 2-Chloro-2-Methyl butane: The chlorine atom is attached to a tertiary carbon. It will form a tertiary carbocation.

Explanation: D
Decarboxylation of carboxylic acids occur in the presence of soda lime to give an alkane with one carbon less than the carbons in carboxylic acid used.

Explanation: B
K gives superoxide on oxidation with oxygen. In group 1 K & below give super oxides, in group 2 Sr & Ba give peroxides.

Explanation: A
Identify the type of hydrogens: First, let’s identify the different types of hydrogen atoms in 2-methylbutane. The structure is:(CH₃-CH(CH₃)-CH₂-CH₃)
There are six equivalent primary hydrogens on the two terminal (CH₃) groups.
There is one tertiary hydrogen on the second carbon atom.
There are two secondary hydrogens on the third carbon atom.
The order of reactivity for a free-radical halogenation reaction is: tertiary > secondary > primary. This is because the more substituted the radical, the more stable it is due to hyperconjugation. Since the tertiary hydrogen is the most reactive, it is the most likely to be substituted by the halogen. The halogen will therefore add to the second carbon, replacing the tertiary hydrogen to give 2-Halo-2-Methyl butane. 

Explanation: A
Excess Br₂ gives a white ppt of Tribromophenol upon reaction with phenol.
C₆H₅OH + 3Br₂ → 2, 4, 6, – C₆H₂Br₃OH (whiteppt) + 3HBr,   

Explanation: B
Esters are reduced using LiAlH₄ to give corresponding alcohols.
Ethyl propionate (CH₃CH₂COOCH₂CH₃):
This is an ester (propanoic acid ethyl ester).
Reduction with LiAlH₄:
LiAlH₄ is a powerful reducing agent.
It reduces esters to two alcohols:
One alcohol comes from the acid part (–COOR → R–CH₂OH).
The other alcohol comes from the alkyl part (–OR → R′–OH).
Breaking it down:
Acid part = propanoate → reduced to propan-1-ol (CH₃CH₂CH₂OH).
Alkoxy part = ethyl (–OCH₂CH₃) → reduced to ethanol (CH₃CH₂OH).
Products: Ethanol, Propanol.

Explanation: C
Benedict’s test (or Fehling’s test / Tollen’s test):
Aldehydes are easily oxidized to carboxylic acids → give positive result (red Cu₂O ppt in Benedict’s / Fehling’s; silver mirror in Tollen’s).
Ketones (except α-hydroxy ketones) do not react.
This is the most reliable reagent to distinguish aldehyde vs ketone.

Explanation: D
Tertiary alcohols undergo dehydration most easily to give alkenes.

Explanation: B
Order of acidity is:
P-nitrophenol > O-nitrophenol > M-nitrophenol > Phenol

Explanation: D

Explanation: A
Lower periods have higher ionization energy & group 5 has greater ionization energy than group 6 elements.
Nitrogen (1s² 2s² 2p³): Half-filled p-orbitals → extra stable, hence very high IE.
Oxygen (1s² 2s² 2p⁴): Just after half-filled → less stable, so IE lower than nitrogen.
Beryllium (1s² 2s²): IE is high (since it’s small, 2nd period), but not as high as nitrogen.
Phosphorus (1s² … 3s² 3p³): Similar to nitrogen (half-filled), but in 3rd period → larger size, so lower IE than nitrogen.

Explanation: D
Alkylation and acylation of benzene is called Friedel-Craft’s reaction.