Step 1: Understanding the Concept:

Genetic disorders are caused by abnormalities in the genome that are heritable.

Infectious diseases are caused by pathogens like bacteria, viruses, or parasites.


Step 2: Detailed Explanation:

1. Friend P: Colour blindness is genetic, but Malaria is a protozoan disease.

2. Friend Q: Albinism is genetic, but Cholera is a bacterial disease.

3. Friend R: Both Haemophilia (X-linked) and Colour blindness (X-linked) are genetic disorders.

4. Friend S: Both Haemophilia and Albinism (autosomal recessive) are genetic disorders.


Step 3: Final Answer:

Since friends R and S listed only genetic disorders, option (b) is correct.
Quick Tip: Always distinguish between "hereditary" (genetic) and "communicable" (infectious) diseases. Malaria, Cholera, and Tuberculosis are never genetic.

Step 1: Understanding the Concept:

Ventricular systole is the phase where the ventricles contract to pump blood out of the heart into the main arteries.


Step 2: Detailed Explanation:

To ensure unidirectional flow of blood:

1. The Atrioventricular (AV) valves (tricuspid and bicuspid) must close to prevent blood from flowing back into the atria.

2. The Semilunar valves (pulmonary and aortic) must open to allow blood to exit the ventricles into the pulmonary artery and aorta.


Step 3: Final Answer:

Therefore, P = close and Q = open.
Quick Tip: The closing of the AV valves during ventricular systole creates the first heart sound, "LUBB".

Step 1: Understanding the Concept:

Transpiration is the loss of water vapor from plants. Xerophytes (desert plants) adapt to minimize this.


Step 2: Detailed Explanation:

1. Assertion (A): A thick, waxy cuticle on the leaf epidermis serves as a physical barrier that restricts water evaporation. This is True.

2. Reason (R): Desert plants actually have small, thick leaves or leaves reduced to spines to minimize surface area for water loss. Large, thin leaves would be disastrous in a desert. This is False.


Step 3: Final Answer:

Since Assertion is true but Reason is false, option (a) is correct.
Quick Tip: Xerophytic adaptations: Thick cuticle, sunken stomata, and reduced leaf surface area (spines).

Step 1: Understanding the Concept:

Based on Chargaff's rule, in a double-stranded DNA, the amount of Purines equals Pyrimidines: \( [A] = [T] \) and \( [G] = [C] \).


Step 2: Detailed Explanation:

The question states 300 base pairs. However, usually in such MCQ contexts, if 75 is the answer, it refers to a calculation based on 300 total bases.

If Total Bases = 300:

1. Given \( G = 75 \).

2. Then \( C = 75 \) (as \( G = C \)).

3. \( G + C = 75 + 75 = 150 \).

4. Remaining bases for A and T = \( 300 - 150 = 150 \).

5. Since \( A = T \), then \( T = 150 / 2 = 75 \).


Step 3: Final Answer:

The number of Thymine bases is 75.
Quick Tip: If \( G = X \), then \( C = X \). If \( A = Y \), then \( T = Y \). In DNA calculations, knowing one base quantity allows you to find the others if the total is known.

Step 1: Understanding the Concept:

Abscisic Acid (ABA) is widely known as the "stress hormone" in plants.


Step 2: Detailed Explanation:

1. Assertion (A): During drought, ABA levels increase, causing guard cells to lose turgor and close the stomatal pore. This is True.

2. Reason (R): By closing stomata, the plant reduces transpiration, which is essential to survive water scarcity. This is True.

3. Logic: The reason correctly justifies why the hormone acts to close the stomata.


Step 3: Final Answer:

Both statements are true and the reason explains the assertion.
Quick Tip: ABA is the "Antagonist" to Gibberellins. While others promote growth, ABA helps in survival and dormancy.

Step 1: Understanding the Concept:

Confusion often arises between names starting with "Leuko-" (white).


Step 2: Detailed Explanation:

1. Assertion (A): Blood cancer is biologically termed Leukemia. Leukoderma (vitiligo) is a skin condition causing white patches due to loss of melanin. This is False.

2. Reason (R): Leukemia is indeed a cancer of blood-forming tissues, resulting in the overproduction of abnormal White Blood Cells (WBCs). This is True.


Step 3: Final Answer:

Assertion is false, but Reason is true.
Quick Tip: "-derma" refers to skin (like epidermis), while "-emia" refers to blood (like anemia or leukemia).

Step 1: Understanding the Concept:

Visually engaging methods rely on sight to convey a message effectively.


Step 2: Detailed Explanation:

1. P. Posters: Use images and graphics (Visual).

2. Q. Loudspeakers: Use sound only (Auditory).

3. R. Film shows: Use moving images (Visual).

4. S. Street plays: Use live performance and costumes (Visual).


Step 3: Final Answer:

P, R, and S are visually engaging, making option (a) correct.
Quick Tip: In mass communication, "visual" refers to anything you see, while "audio" refers to what you hear. Street plays are considered audio-visual.

Step 1: Understanding the Concept:

Colour blindness is an X-linked recessive disorder. Sons inherit the Y from the father and one X from the mother.


Step 2: Detailed Explanation:

Mother: \( X^C X \) (Carrier)

Father: \( XY \) (Normal)

Offspring possibilities:

1. \( X^C X \) (Carrier daughter)

2. \( XX \) (Normal daughter)

3. \( X^C Y \) (Affected son)

4. \( XY \) (Normal son)


Step 3: Final Answer:

Among the sons (\( X^C Y \) and \( XY \)), one out of two is affected. Probability = 50%.
Quick Tip: For any X-linked recessive trait, if the mother is a carrier, 50% of her sons will be affected regardless of the father's phenotype.

Step 1: Understanding the Concept:

The sympathetic nervous system triggers the "fight or flight" response during stress.


Step 2: Detailed Explanation:

1. Bronchodilation: Dilation of bronchioles allows more oxygen intake for energy. This is a sympathetic action.

2. Coronary arteries: Sympathetic stimulation actually causes dilation to supply more blood to the heart muscle.

3. Respiration: Respiration rate increases during stress.


Step 3: Final Answer:

Bronchodilation is the correct physiological effect of the sympathetic system here.
Quick Tip: Sympathetic = Stress (Increases heart rate, dilates pupils, dilates bronchi).
Parasympathetic = Peace (Decreases heart rate, constricts pupils).

Step 1: Understanding the Concept:

Double circulation consists of Pulmonary (Heart-Lungs-Heart) and Systemic (Heart-Body-Heart) circuits.


Step 2: Detailed Explanation:

1. Deoxygenated blood: Right Atrium \(\rightarrow\) Right Ventricle \(\rightarrow\) Pulmonary Artery \(\rightarrow\) Lungs.

2. Oxygenated blood: Pulmonary Veins \(\rightarrow\) Left Atrium \(\rightarrow\) Left Ventricle \(\rightarrow\) Aorta \(\rightarrow\) Body tissues.


Step 3: Final Answer:

Option (a) correctly describes the sequence for both circulations.
Quick Tip: Blood always flows from Atrium to Ventricle. The Right side handles deoxygenated blood and the Left side handles oxygenated blood.

Step 1: Understanding the Concept:

Pupillary constriction is a reflex action controlled by the brainstem.


Step 2: Detailed Explanation:

While the midbrain is primarily responsible for visual reflexes, in general anatomy questions where midbrain is not provided, the Medulla oblongata (part of the brainstem) is the only neurological center listed associated with vital reflex control. The lens and ligaments are for focusing, not reflex constriction.


Step 3: Final Answer:

The inability to constrict pupils indicates damage to the brain's reflex control centers, represented by (b).
Quick Tip: Pupillary light reflex testing is a standard medical procedure to check brainstem function in unconscious patients.

Step 1: Understanding the Concept:

Healthy kidneys filter out waste but keep large molecules like proteins in the blood.


Step 2: Detailed Explanation:

1. Albuminuria: Presence of albumin (protein) in urine.

2. Haematuria: Blood in urine.

3. Glycosuria: Glucose in urine.


Step 3: Final Answer:

Presence of protein in urine is Albuminuria.
Quick Tip: Protein in urine is a key indicator of glomerular damage in the nephrons.

Step 1: Understanding the Concept:

Swachh Bharat Abhiyan is a national cleanliness mission.


Step 2: Detailed Explanation:

The campaign aims to create a clean India by improving sanitation facilities and managing solid waste effectively.


Step 3: Final Answer:

Option (c) is the primary goal of the mission.
Quick Tip: "Swachh" means "Clean". Focus on options promoting environmental health.

Step 1: Understanding the Concept:

High salt concentration acts as a preservative via osmosis.


Step 2: Detailed Explanation:

1. D: Salt creates a hypertonic solution outside the food.

2. B: Water is drawn out of microbial cells by exosmosis (plasmolysis), which inhibits growth.


Step 3: Final Answer:

The combination of B and D is correct.
Quick Tip: Preservation by salting or sugaring works on the principle of plasmolysis.

Step 1: Understanding the Concept:

The menstrual cycle involves shedding and rebuilding of the uterine lining.


Step 2: Detailed Explanation:

The menstrual phase (Days 1-5) is characterized by the breakdown of the endometrial lining of the uterus and its exit through the vagina as blood and tissue.


Step 3: Final Answer:

Shedding occurs during the menstrual phase.
Quick Tip: Day 1 of the menstrual cycle is defined as the first day of bleeding (menstrual phase).

Step 1: Understanding the Concept:

Tropic movements are directional growth movements of plant parts in response to an external stimulus.


Step 2: Detailed Explanation:

When the tendrils of a climbing plant like a pea come into contact with a physical support, the side of the tendril in contact grows slower than the side away from the support.

This unequal growth rate is triggered by the touch stimulus, causing the tendril to coil or twine around the object.

The prefix "thigmo-" refers to touch, thus the technical term is thigmotropism.


Step 3: Final Answer:

The biological term is Thigmotropism.
Quick Tip: Remember: Photo = Light, Geotropism = Gravity, Hydro = Water, and Thigmo = Touch.

Step 1: Understanding the Concept:

Visual defects occur when light does not focus properly on the retina due to irregularities in the eye's shape or refractive components.


Step 2: Detailed Explanation:

Astigmatism is a common vision condition that causes blurred vision.

It occurs when the cornea or the lens has an irregular curvature (it is shaped more like a football than a round basketball).

This irregularity prevents light from focusing at a single point on the retina, resulting in some parts of the image being sharp while others are distorted or blurred.


Step 3: Final Answer:

The biological term is Astigmatism.
Quick Tip: Astigmatism is corrected using cylindrical lenses which compensate for the uneven curvature of the eye.

Step 1: Understanding the Concept:

Waste management categorizes materials based on their source and potential hazards to health and the environment.


Step 2: Detailed Explanation:

Hospitals and laboratories produce waste such as used syringes, bandages, biological samples, and chemicals.

This waste is potentially infectious or toxic and is technically termed "Biomedical waste".

It requires specialized disposal methods like incineration or autoclaving to prevent the spread of diseases.


Step 3: Final Answer:

The technical term is Biomedical waste.
Quick Tip: Biomedical waste is often segregated using color-coded bins (Yellow, Red, White, Blue) for safe handling and treatment.

Step 1: Understanding the Concept:

Surgical sterilization is a permanent method of contraception that involves blocking the passage of gametes.


Step 2: Detailed Explanation:

In females, the surgical procedure involves cutting and tying (ligating) a small part of both fallopian tubes.

This prevents the egg from meeting the sperm, thus preventing fertilization.

This specific procedure is biologically known as "Tubectomy".


Step 3: Final Answer:

The surgical technique is Tubectomy.
Quick Tip: Remember: \textbf{T}ubectomy involves Fallopian \textbf{T}ubes (females), while \textbf{V}asectomy involves \textbf{V}as deferens (males).

Step 1: Understanding the Concept:

Evolution involves changes in the heritable characteristics of biological populations over successive generations.


Step 2: Detailed Explanation:

When populations of a species become isolated (geographically or reproductively) and undergo genetic divergence due to natural selection or genetic drift, they may become distinct.

The final outcome where these populations can no longer interbreed to produce fertile offspring is the formation of a new species.

This entire biological process is called "Speciation".


Step 3: Final Answer:

The biological term is Speciation.
Quick Tip: Isolation (reproductive or geographic) is the most critical factor leading to speciation.

Step 1: Understanding the Concept:

A human sperm is a microscopic, motile male gamete consisting of a head, neck, middle piece, and tail.


Step 2: Detailed Explanation:

The anterior portion of the sperm head is covered by a cap-like structure.

This structure is the acrosome, which is derived from the Golgi apparatus during spermiogenesis.


Step 3: Final Answer:

The organelle is the Acrosome.
Quick Tip: The acrosome acts like a chemical "drill" to help the sperm penetrate the egg's outer layers.

Step 1: Understanding the Concept:

Fertilization requires the sperm to penetrate protective layers around the ovum, such as the corona radiata and zona pellucida.


Step 2: Detailed Explanation:

The acrosome contains hydrolytic enzymes known as sperm lysins.

The primary enzyme is hyaluronidase, which breaks down the hyaluronic acid holding the follicular cells (corona radiata) together.

Amylase is a digestive enzyme found in saliva and pancreatic juice, not in sperm.


Step 3: Final Answer:

The enzyme is Hyaluronidase.
Quick Tip: Sperm lysins like hyaluronidase are essential for the "acrosome reaction" during fertilization.

Step 1: Understanding the Concept:

Gametes (sperm and egg) are produced through meiosis to ensure the chromosome number is halved.


Step 2: Detailed Explanation:

Human somatic (body) cells have 46 chromosomes (diploid).

During spermatogenesis, cells undergo reduction division (meiosis) to produce haploid sperm cells.

Therefore, a human sperm contains 23 chromosomes.


Step 3: Final Answer:

The number of chromosomes is 23.
Quick Tip: The fusion of a 23-chromosome sperm and a 23-chromosome egg restores the diploid number of 46 in the zygote.

Step 1: Understanding the Concept:

Cellular movement requires energy in the form of ATP (Adenosine Triphosphate).


Step 2: Detailed Explanation:

The middle piece of the sperm contains numerous spiral mitochondria.

Mitochondria are the "powerhouses of the cell" that perform cellular respiration to produce energy.

This energy powers the tail's lashing movement for swimming. Chloroplasts are only found in plant cells.


Step 3: Final Answer:

The middle piece contains Mitochondria.
Quick Tip: Sperm have a very high metabolic rate because they must travel a long distance relative to their size to reach the egg.

Step 1: Understanding the Concept:

Ejaculation involves the discharge of a complex fluid containing gametes and secretory products.


Step 2: Detailed Explanation:

Semen is the milky white organic fluid that contains sperm.

It includes secretions from the seminal vesicles, prostate gland, and bulbourethral glands.

These fluids provide nutrients and a medium for sperm transport. Hymen is a membrane that partially covers the vaginal opening in females.


Step 3: Final Answer:

The mixture is called Semen.
Quick Tip: The seminal vesicles provide about 60% of the total volume of semen, containing fructose for energy.

Step 1: Understanding the Concept:

Biological classification based on the site of production and target organism.


Step 2: Detailed Explanation:

1. Auxin, Gibberellin, and Cytokinin are all hormones produced by plants to regulate growth and development.

2. Oxytocin is a hormone produced in the hypothalamus and released by the posterior pituitary gland in humans. It is an animal hormone.


Step 3: Final Answer:

The odd one is Oxytocin. The others are Phytohormones.
Quick Tip: Phytohormones include Auxins, Gibberellins, Cytokinins, Ethylene, and Abscisic acid.

Step 1: Understanding the Concept:

The pituitary gland (hypophysis) has two distinct lobes: the adenohypophysis (anterior) and neurohypophysis (posterior).


Step 2: Detailed Explanation:

1. Growth Hormone (GH), Thyroid Stimulating Hormone (TSH), and Gonadotropic Hormone (GTH) are all synthesized and secreted by the anterior lobe of the pituitary gland.

2. Vasopressin (Antidiuretic hormone) is synthesized in the hypothalamus and released by the posterior lobe of the pituitary gland.


Step 3: Final Answer:

The odd one is Vasopressin. The others are anterior pituitary hormones.
Quick Tip: The posterior pituitary only stores and releases two hormones: Oxytocin and Vasopressin (ADH).

Step 1: Understanding the Concept:

Excretion involves the removal of metabolic waste products from the body.


Step 2: Detailed Explanation:

1. Urea and Uric acid are nitrogenous metabolic wastes excreted in human urine.

2. Urochrome is the pigment responsible for the yellow color of urine.

3. Nucleic acids (DNA/RNA) are complex macromolecular structures inside cells and are not standard excretory products in urine.


Step 3: Final Answer:

The odd one is Nucleic acid. The others are constituents of urine.
Quick Tip: Urochrome is derived from the breakdown of hemoglobin (bilirubin) in the liver.

Step 1: Understanding the Concept:

Anatomical structures are specific to different organ systems.


Step 2: Detailed Explanation:

1. Chordae Tendinea, Papillary Muscles, and Sinoatrial node (SA node) are all vital components of the human circulatory system (heart).

2. Cervix is the lower, narrow part of the uterus that opens into the vagina in the female reproductive system.


Step 3: Final Answer:

The odd one is Cervix. The others are parts of the heart.
Quick Tip: Chordae tendinea are the "heart strings" that connect papillary muscles to the AV valves.

Step 1: Understanding the Concept:

Embryology studies the development of an embryo from the fertilization of the ovum to the fetus stage.


Step 2: Detailed Explanation:

1. Morula, Blastocyst, and Foetus are successive developmental stages of a new individual after fertilization.

2. Oviduct (Fallopian tube) is an anatomical structure in the female reproductive tract where fertilization occurs, but it is not a stage of the organism itself.


Step 3: Final Answer:

The odd one is Oviduct. The others are stages of development.
Quick Tip: Sequence: Zygote \(\rightarrow\) Morula \(\rightarrow\) Blastocyst \(\rightarrow\) Embryo \(\rightarrow\) Foetus.

Step 1: Understanding the Concept:

Hormonal disorders often result from the hyposecretion (under-production) or hypersecretion (over-production) of specific hormones.


Step 2: Detailed Explanation:

A consistently high level of glucose in the blood (hyperglycemia) is the hallmark symptom of the disease known as "Diabetes mellitus".

This differs from Diabetes insipidus, which involves water imbalance and lacks high blood sugar.


Step 3: Final Answer:

The disorder is Diabetes mellitus.
Quick Tip: "Mellitus" comes from the Latin word for honey, referring to the sweet taste of sugar in the urine.

Step 1: Understanding the Concept:

Blood glucose levels are strictly regulated by antagonistic hormones produced in the pancreas.


Step 2: Detailed Explanation:

Insulin is the hormone that lowers blood sugar levels by promoting the uptake of glucose into cells for energy or storage as glycogen in the liver and muscles.

A deficiency or insufficient action of insulin leads to high blood sugar levels.


Step 3: Final Answer:

The hormone is Insulin.
Quick Tip: Insulin is secreted when blood sugar is high (after meals), while Glucagon is secreted when blood sugar is low.

Step 1: Understanding the Concept:

The pancreas is a dual-purpose organ (heterocrine gland) having both exocrine and endocrine functions.


Step 2: Detailed Explanation:

The endocrine part of the pancreas consists of clusters of cells called the Islets of Langerhans.

Within these islets, Beta (\(\beta\)) cells are specifically responsible for the production and secretion of insulin.


Step 3: Final Answer:

The organ is the Pancreas.
Quick Tip: Islets of Langerhans make up only about 1-2% of the pancreas' total mass.

Step 1: Understanding the Concept:

Elevated blood glucose levels impact the body's osmotic balance and kidney function.


Step 2: Detailed Explanation:

When blood sugar is very high, the kidneys cannot reabsorb all the glucose, and it is excreted in the urine (glycosuria).

Glucose is osmotically active and carries water with it, leading to excessive urination (Polyuria).

The loss of fluid leads to dehydration and intense thirst (Polydipsia).


Step 3: Final Answer:

A common symptom is excessive urination or excessive thirst.
Quick Tip: The "3 P's" of diabetes are Polyuria, Polydipsia, and Polyphagia (increased hunger).

Step 1: Understanding the Concept:

Lifestyle modifications can significantly help in managing non-communicable metabolic disorders.


Step 2: Detailed Explanation:

Since Mohit leads a sedentary life, increasing physical activity is a vital change.

Exercise helps muscles use glucose for energy even without extra insulin and improves the body's sensitivity to insulin.

Dietary changes, like reducing intake of simple sugars and carbohydrates, are also effective.


Step 3: Final Answer:

Regular exercise or a balanced diet low in sugar.
Quick Tip: Sedentary lifestyles are a major risk factor for Type 2 Diabetes even in individuals with normal weight.

Step 1: Understanding the Concept:

The anatomy of the kidney correlates directly with the stages of urine formation (Ultrafiltration, Reabsorption, Secretion).


Step 2: Detailed Explanation:

1. Renal Cortex: This outer layer contains the Malpighian capsules (Glomerulus + Bowman's capsule) where filtration begins. Match: (a).

2. Renal Medulla: The inner part is divided into pyramids and contains the tubular parts of nephrons, specifically the Loops of Henle. Match: (d).

3. Renal Artery: This vessel brings oxygenated, unfiltered blood from the aorta to the kidney. Match: (b).

4. Renal Vein: This vessel carries deoxygenated, filtered blood away from the kidney to the inferior vena cava. Match: (e).

5. Pelvis: The funnel-shaped central cavity that collects urine from the collecting ducts before it enters the ureter. Match: (f).

6. Ureter: The long tube that carries the formed urine down to the urinary bladder. Match: (c).


Step 3: Final Answer:

Renal Cortex matches (a); Renal Medulla matches (d); Renal Artery matches (b); Renal Vein matches (e); Pelvis matches (f); Ureter matches (c).
Quick Tip: Think of the Cortex as the "starting line" (filtration) and the Medulla as the "processing center" (concentration via Henle's loop).

Step 1: Understanding the Concept:

The cell cycle consists of two main phases: Interphase and the M-phase (Mitotic phase).

Interphase is the period between two successive cell divisions.


Step 2: Detailed Explanation:

Interphase was traditionally called the "resting stage" because no visible changes in chromosome structure are seen under a microscope.

However, it is biochemically the most active stage because the cell prepares for division by:

1. Synthesizing proteins and RNA.

2. Replicating its DNA (during the S-phase).

3. Increasing in size and accumulating energy.

It comprises three sub-stages: \( G_1 \), S, and \( G_2 \).


Step 3: Final Answer:

The resting but metabolically active stage is the Interphase.
Quick Tip: Remember: Interphase is the "Preparation Phase" and accounts for nearly 95% of the total duration of the cell cycle.

Step 1: Understanding the Concept:

Binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings.


Step 2: Detailed Explanation:

In binocular vision, the visual fields of the two eyes overlap.

This overlap allows the brain to process two slightly different images of the same object, resulting in:

1. Stereopsis: The ability to perceive the world in three dimensions (3D).

2. Depth Perception: Accurate estimation of how far away an object is.

For a predator like an eagle, this is crucial for precisely locating and striking prey while flying at high speeds.


Step 3: Final Answer:

The primary advantage is precise depth perception and the ability to judge distances accurately.
Quick Tip: Predators usually have binocular vision (eyes in front) for hunting, while prey animals often have monocular vision (eyes on sides) for a wider field of view to spot danger.

Step 1: Understanding the Concept:

A normal human somatic (body) cell is diploid, containing a total of 46 chromosomes (23 pairs).


Step 2: Detailed Explanation:

These 46 chromosomes are categorized into two types:

1. Autosomes: These are chromosomes that determine general body characteristics (somatic traits) and are identical in both males and females. There are 22 pairs, totaling 44 chromosomes.

2. Allosomes: Also known as sex chromosomes, they determine the biological sex of the individual. There is 1 pair, totaling 2 chromosomes (XX in females and XY in males).


Step 3: Final Answer:

A human body cell contains 44 autosomes and 2 allosomes.
Quick Tip: In a gamete (sperm or egg), the numbers are halved: 22 autosomes and 1 allosome.

Step 1: Understanding the Concept:

Wilting occurs when plant cells lose their turgidity (internal water pressure) causing the leaves and stems to droop.


Step 2: Detailed Explanation:

Transpiration is the loss of water vapor from the aerial parts of the plant.

When the rate of water loss (transpiration) exceeds the rate of water absorption by the roots, the cells lose water.

This leads to the loss of turgor pressure in the leaf cells, a condition known as wilting.


Step 3: Final Answer:

The phenomenon is excessive transpiration.
Quick Tip: Wilting can be "temporary" (recovers at night) or "permanent" (reaches a point of no return if the soil is dry).

Step 1: Understanding the Concept:

The rate of transpiration is affected by various external environmental factors such as light, humidity, wind, and temperature.


Step 2: Detailed Explanation:

In the given experiment, the two plants are identical and are kept in brightly lit rooms (light is constant).

The only varying factor is the temperature (\( 15^\circC \) vs \( 38^\circC \)).

Higher temperatures increase the rate of evaporation and reduce the relative humidity of the air, thereby significantly increasing the rate of transpiration.


Step 3: Final Answer:

The factor being tested is temperature.
Quick Tip: Temperature and Transpiration are directly proportional: as temperature increases, the transpiration rate increases.

Step 1: Understanding the Concept:

Prophase is the first and longest stage of mitosis where the cell prepares for the separation of sister chromatids.


Step 2: Detailed Explanation:

Key features to include in the diagram:

1. Nuclear Membrane: Draw it as a dashed or breaking line to show it is disappearing.

2. Nucleolus: Usually shown as disappearing or absent.

3. Centrioles: Two pairs of centrioles moving towards opposite poles.

4. Spindle Fibers/Astral Rays: Radiating from the centrioles.

5. Chromosomes: Draw exactly four distinct X-shaped structures representing the condensed chromatin. Each 'X' consists of two chromatids held by a centromere.

6. Labeling: Label Centrioles, Centromere, Chromatids, and Disappearing Nuclear Membrane.


Step 3: Final Answer:

A correctly drawn animal cell in prophase must show the centrioles, astral rays, and 4 chromosomes with a fragmenting nuclear envelope.
Quick Tip: In animal cell mitosis, always remember to draw 'astral rays' around the centrioles (Amphiastral mitosis), which are absent in plant cells (Anastral mitosis).

Step 1: Understanding the Concept:

Scientific names follow the binomial nomenclature system established by Carl Linnaeus.


Step 2: Detailed Explanation:

The name consists of two parts:

1. Genus: \textit{Homo (must always be capitalized).

2. Specific Epithet (Species): \textit{sapiens (must always be in lowercase).

When handwritten, the two names should be underlined separately.


Step 3: Final Answer:

The scientific name is \textit{Homo sapiens.
Quick Tip: Always capitalize the Genus name and use lowercase for the species name to follow standard biological naming rules.

Step 1: Understanding the Concept:

Nervous tissue in the brain and spinal cord is organized into grey matter and white matter.


Step 2: Detailed Explanation:

In the Cerebrum:

1. The outer portion is the Cerebral Cortex, which is composed of Grey Matter. This area is packed with cell bodies (Cytons) and dendrites.

2. The inner portion is the Cerebral Medulla, which is composed of White Matter. This area primarily contains myelinated nerve fibers (Axons).


Step 3: Final Answer:

In the cerebrum, cytons are located on the outside (Grey matter) and axons are located on the inside (White matter).
Quick Tip: Mnemonic: For the brain (Cerebrum/Cerebellum), think "G.O. W.I." -> Grey Outside, White Inside.

Step 1: Understanding the Concept:

The arrangement of nervous tissue in the spinal cord is the reverse of that in the brain.


Step 2: Detailed Explanation:

In the Spinal Cord:

1. The inner portion is H-shaped or butterfly-shaped and is composed of Grey Matter. It contains the Cytons (cell bodies) of motor and associative neurons.

2. The outer portion surrounds the grey matter and consists of White Matter. It contains bundles of myelinated Axons forming ascending and descending tracts.


Step 3: Final Answer:

In the spinal cord, cytons are on the inside (Grey matter) and axons are on the outside (White matter).
Quick Tip: Mnemonic: For the Spinal Cord, think "W.O. G.I." -> White Outside, Grey Inside. It's the opposite of the brain!

Step 1: Understanding the Concept:

Evolutionary theories explain the origin and diversification of species over time.


Step 2: Detailed Explanation:

The Theory of Natural Selection was proposed by the English naturalist Charles Darwin (and independently by Alfred Russel Wallace).

The core idea is that individuals with traits better suited to their environment are more likely to survive and reproduce, passing those advantageous traits to the next generation.


Step 3: Final Answer:

Charles Darwin proposed the theory.
Quick Tip: Darwin's famous book "On the Origin of Species" (1859) detailed this theory.

Step 1: Understanding the Concept:

Industrial Melanism is a classic example of natural selection observed in nature due to environmental changes caused by industrial pollution.


Step 2: Detailed Explanation:

The organism is the Peppered Moth.

Before the Industrial Revolution in England, light-colored moths were more common because they were camouflaged against lichen-covered trees.

After industrialization, soot darkened the trees, and the light-colored moths were easily spotted by birds. Dark-colored (melanic) moths survived better and their population increased.


Step 3: Final Answer:

The organism is the Peppered Moth or \textit{Biston betularia.
Quick Tip: Industrial Melanism proves that natural selection favors whichever phenotype provides the best camouflage in the current environment.

Step 1: Understanding the Concept:

These processes are results of osmosis (movement of water through a semi-permeable membrane).


Step 2: Detailed Explanation:

1. Plasmolysis:

- Occurs when a plant cell is placed in a hypertonic solution (more concentrated than the cell sap).

- Water moves out of the cell (exosmosis).

- The protoplasm shrinks and pulls away from the cell wall.

2. Deplasmolysis:

- Occurs when a recently plasmolysed cell is placed in a hypotonic solution (less concentrated than the cell sap).

- Water moves into the cell (endosmosis).

- The protoplasm swells and returns to its original position against the cell wall.


Step 3: Final Answer:

Plasmolysis involves water loss and shrinkage in hypertonic media, while deplasmolysis involves water gain and recovery in hypotonic media.
Quick Tip: Remember: Plasmolysis \(\rightarrow\) Hypertonic (Outward movement). Deplasmolysis \(\rightarrow\) Hypotonic (Inward movement).

Step 1: Understanding the Concept:

The prostate gland is a male accessory reproductive gland.


Step 2: Detailed Explanation:

It is a single, walnut-sized gland located at the base of the urinary bladder.

It surrounds the prostatic urethra, which is the tube through which both urine and semen pass.


Step 3: Final Answer:

The prostate gland is located just below the urinary bladder.
Quick Tip: Because of its location surrounding the urethra, an enlarged prostate often causes difficulty in urination.

Step 1: Understanding the Concept:

Sperm require a specific pH range to remain motile and viable.


Step 2: Detailed Explanation:

The prostate gland secretes a thin, milky, alkaline fluid.

This alkalinity serves two purposes:

1. It neutralizes the acidic residue of urine in the male urethra.

2. It neutralizes the naturally acidic environment of the female vagina, which would otherwise kill the sperm.


Step 3: Final Answer:

The alkaline secretion neutralizes acids to protect the sperm and maintain their motility.
Quick Tip: Prostatic fluid also contains enzymes and citric acid to nourish and activate sperm.

Step 1: Understanding the Concept:

Control of urination is achieved by circular muscles that act like valves.


Step 2: Detailed Explanation:

The urethral sphincter is a circular muscle located at the junction of the bladder and the urethra.

When contracted, it keeps the urethra closed, holding urine in the bladder. When it relaxes, urine is allowed to flow out (micturition).

Damage to this muscle or the nerves controlling it during surgery leads to incontinence (leakage).


Step 3: Final Answer:

The structure is the urethral sphincter.
Quick Tip: There are two sphincters: the internal (involuntary) and the external (voluntary).

Step 1: Understanding the Concept:

Mature mammalian Red Blood Cells (RBCs) lose their nucleus and other organelles (mitochondria, ribosomes) during development.


Step 2: Detailed Explanation:
This structural adaptation offers three main advantages:

1. Increased Space: The absence of a nucleus provides more internal volume for hemoglobin, maximizing the oxygen-carrying capacity.

2. Surface Area: It allows the cell to assume a biconcave shape, which increases the surface area to volume ratio for faster gas exchange.

3. Flexibility: Without a rigid nucleus, RBCs are highly flexible, allowing them to squeeze through narrow capillaries.


Step 3: Final Answer:

The primary advantage is maximizing the space for hemoglobin to carry oxygen efficiently.
Quick Tip: Also, the lack of mitochondria ensures that the RBC does not consume the oxygen it is transporting!

Step 1: Understanding the Concept:

A food chain shows the linear flow of energy from producers to various levels of consumers.


Step 2: Detailed Explanation:

1. Producer: Algae (photosynthetic).

2. Primary Consumer: Mosquito larvae (feed on algae).

3. Secondary Consumer: Small fish (feed on larvae).

4. Tertiary Consumer: Kingfisher (feeds on small fish).


Step 3: Final Answer:

Algae \(\rightarrow\) Mosquito larvae \(\rightarrow\) Small fish \(\rightarrow\) Kingfisher.
Quick Tip: Always start with the organism that produces its own food (the producer) and end with the top predator.

Step 1: Understanding the Concept:

Energy flow always begins with the producer in a grazing food chain.


Step 2: Detailed Explanation:

1. Producer: Green leaves.

2. Primary Consumer: Snail (herbivore).

3. Secondary Consumer: Frog (carnivore, eats snail).

4. Tertiary Consumer: Crow (eats frog).


Step 3: Final Answer:

Green leaves \(\rightarrow\) Snail \(\rightarrow\) Frog \(\rightarrow\) Crow.
Quick Tip: In any food chain, the arrow always points from the "eaten" to the "eater" (the direction of energy flow).

Step 1: Understanding the Concept:

The placenta is a temporary organ that connects the developing fetus to the uterine wall.


Step 2: Detailed Explanation:
Key functions include:

1. Nutritional: It allows the transport of glucose, amino acids, and vitamins from maternal blood to fetal blood.

2. Excretory: It removes urea and \( CO_2 \) from the fetal blood into the mother's blood.

3. Endocrine: It secretes hormones like Progesterone and Estrogen to maintain pregnancy.


Step 3: Final Answer:

The placenta facilitates the exchange of oxygen, nutrients, and wastes between the mother and the fetus.
Quick Tip: Note that maternal and fetal blood vessels are very close but their blood never actually mixes!

Step 1: Understanding the Concept:

The fetus requires a physical link for the transport of materials to and from the placenta.


Step 2: Detailed Explanation:

The umbilical cord is a tube-like structure containing two umbilical arteries and one umbilical vein.

It connects the navel of the fetus to the placenta.


Step 3: Final Answer:

The structure is the umbilical cord.
Quick Tip: Umbilical arteries carry deoxygenated blood to the placenta, and the umbilical vein carries oxygenated blood to the fetus (opposite of normal adult circulation).

Step 1: Understanding the Concept:

Secondary sexual characteristics are physical traits that emerge during puberty but are not directly part of the reproductive system.


Step 2: Detailed Explanation:

In males, these changes are driven by the hormone testosterone:

1. Voice: The larynx (Adam's apple) enlarges, causing the voice to become deeper/low-pitched.

2. Hair: Growth of hair on the face (beard/mustache), chest, armpits, and pubic region.

3. Body Build: Increased muscle mass and widening of shoulders.


Step 3: Final Answer:

Two characteristics are: 1. Deepening of the voice. 2. Growth of facial hair.
Quick Tip: Primary characteristics are present at birth (genitals); secondary characteristics develop during puberty (hormone-driven).

Step 1: Understanding the Concept:

As people age, the eye's ability to focus on nearby objects decreases.


Step 2: Detailed Explanation:

Presbyopia is caused by:

1. Loss of elasticity of the eye lens.

2. Weakening of the ciliary muscles.

This makes it difficult for the lens to become sufficiently convex to focus light from near objects (like a needle) onto the retina.


Step 3: Final Answer:

The disorder is Presbyopia.
Quick Tip: Presbyopia is often confused with Hypermetropia; however, Presbyopia is strictly due to aging and loss of lens flexibility.

Step 1: Understanding the Concept:

Correction of refractive errors involves using lenses to shift the focal point back onto the retina.


Step 2: Detailed Explanation:

Since the eye cannot focus near objects, a convex lens is used to provide the additional convergence needed.

If the person also has myopia (difficulty seeing distant objects), bifocal lenses (concave part for distance and convex part for near) are prescribed.


Step 3: Final Answer:

The defect is corrected using a convex lens of suitable focal length.
Quick Tip: Convex lenses "converge" light rays, helping eyes that can't bend light enough on their own.

Step 1: Understanding the Concept:

Blurry vision occurs when light rays do not converge exactly on the retina.


Step 2: Detailed Explanation:

In Presbyopia (and Hypermetropia), the lens is too weak to bend the incoming divergent light rays from a near object.

Consequently, the light rays would converge at a point behind the retina. This results in a blurred image on the retina itself.


Step 3: Final Answer:

The image of near objects is formed behind the retina.
Quick Tip: Remember: \textbf{My}opia (Near-sighted) = Image in \textbf{front} of retina. \textbf{H}ypermetropia/\textbf{P}resbyopia = Image \textbf{behind} retina.

Step 1: Understanding the Concept:

Population density is a measurement of population per unit land area.


Step 2: Detailed Explanation:

It is usually expressed as:
\[ Population Density = \frac{Total number of individuals}{Total area of the region} \]

For humans, it is commonly measured as the number of persons per square kilometer (\( persons/km^2 \)). It indicates how crowded a specific geographical area is.


Step 3: Final Answer:

Population density is the total number of people living in a specific unit of area.
Quick Tip: Factors like urbanization, availability of resources, and climate affect population density significantly.

Step 1: Understanding the Concept:

The adrenal cortex secretes several types of hormones, including small amounts of sex hormones (gonadocorticoids).


Step 2: Detailed Explanation:

Adrenal Virilism is a clinical condition caused by the hypersecretion of androgens (male-like sex hormones) from the adrenal cortex.

While both males and females have these hormones, excessive production in females leads to the development of male secondary sexual characteristics.


Step 3: Final Answer:

Hypersecretion of Androgens results in Adrenal Virilism.
Quick Tip: Overproduction of adrenal hormones can also lead to Cushing's Syndrome or Addison's disease (if under-produced).

Step 1: Understanding the Concept:

High levels of male hormones in females cause "masculinization".


Step 2: Detailed Explanation:

Key symptoms include:

1. Hirsutism: Growth of beard, mustache, and coarse body hair in patterns typically seen in males.

2. Menstrual irregularities: Disruption of the normal ovarian cycle.

3. Voice changes: Deepening of the voice.


Step 3: Final Answer:

A common symptom is Hirsutism (excessive facial hair growth).
Quick Tip: This condition highlights how precise hormonal balance must be for normal physiological function.

Step 1: Understanding the Concept:

Cytokinesis is the division of the cytoplasm after the nucleus has divided.


Step 2: Detailed Explanation:

1. In Animal Cells: Due to the absence of a cell wall, the flexible plasma membrane pinches in to form a cleavage furrow. This furrow deepens until the cell is split into two.

2. In Plant Cells: The rigid cell wall prevents furrowing. Instead, vesicles from the Golgi apparatus align at the equator to form a cell plate. This plate grows outwards to join the existing cell walls, dividing the cell.


Step 3: Final Answer:

Plant cells use cell plate formation, whereas animal cells use cleavage furrowing for cytokinesis.
Quick Tip: Remember: \textbf{P}lant = \textbf{P}late. \textbf{A}nimal = \textbf{F}urrow.

Step 1: Understanding the Concept:

Photosynthesis requires light. Without light, a plant stops making new starch and consumes its stored reserves.


Step 2: Detailed Explanation:

Placing the plant in the dark for 48 hours ensures that any starch present in the leaves at the start is used up by the plant for respiration or translocated to the storage organs (roots/stems).

This "destarching" is essential to ensure that any starch found \textit{after the experiment is purely the result of the experimental conditions.


Step 3: Final Answer:

The plant was placed in the dark to ensure the leaves were completely free of starch (destarched).
Quick Tip: Destarching is a standard preliminary step for almost all photosynthesis experiments to get accurate results.

Step 1: Understanding the Concept:

Chlorophyll is the green pigment in leaves. Its color can interfere with the color change of the iodine test.


Step 2: Detailed Explanation:

Boiling the leaf in ethyl alcohol (ethanol) dissolves the chlorophyll.

The leaf becomes pale or white. This allows the blue-black color (indicating starch) to be clearly visible when iodine is added later.

Note: The leaf is first boiled in water to kill the cells and make the membrane permeable.


Step 3: Final Answer:

Boiling in alcohol removes the green pigment chlorophyll to allow clear observation of the starch-iodine color reaction.
Quick Tip: Warning: Never boil alcohol directly over a flame as it is highly inflammable; always use a water bath!

Step 1: Understanding the Concept:

The spinal cord has a distinct internal anatomy visible in cross-section.


Step 2: Detailed Explanation:

The diagram shows the classic butterfly-shaped internal structure of the spinal cord.

1. Grey Matter: The inner dark region consisting of cell bodies. It is shaped like an 'H' or a butterfly.

2. White Matter: The outer pale region consisting of myelinated axons.

3. Central Canal: The small hole in the middle which contains cerebrospinal fluid.


Step 3: Final Answer:

The structure is the T.S. of the spinal cord. Grey matter is the inner core, and white matter is the outer layer.
Quick Tip: In the spinal cord, the Grey matter is on the inside, which is exactly the opposite of the Cerebrum.

Step 1: Understanding the Concept:

Photosynthesis is the process by which green plants convert light energy into chemical energy stored in glucose.


Step 2: Key Formula or Approach:

The reaction requires Carbon dioxide and Water as reactants, with Light and Chlorophyll as essential conditions.


Step 3: Detailed Explanation:
\[ 6CO_2 + 12H_2O \xrightarrow[Chlorophyll]{Light Energy} C_6H_{12}O_6 + 6H_2O + 6O_2 \]

- \( CO_2 \): Carbon Dioxide

- \( H_2O \): Water

- \( C_6H_{12}O_6 \): Glucose

- \( O_2 \): Oxygen (released as a byproduct)


Step 4: Final Answer:

The balanced chemical equation is \( 6CO_2 + 12H_2O \rightarrow C_6H_{12}O_6 + 6H_2O + 6O_2 \).
Quick Tip: Always include the \( 12H_2O \) on the reactant side and \( 6H_2O \) on the product side to correctly show that water is both used and produced in the process.

Step 1: Understanding the Concept:

NADP is a coenzyme that acts as a universal electron carrier in metabolic processes.


Step 2: Detailed Explanation:

In photosynthesis, \( NADP^+ \) is reduced to NADPH during the light-dependent reactions (Photolysis of water). NADPH then provides reducing power in the Calvin Cycle (Dark Reaction) to produce glucose.


Step 3: Final Answer:

NADP stands for Nicotinamide Adenine Dinucleotide Phosphate.
Quick Tip: In photosynthesis, think of NADPH as a "hydrogen-carrying truck" traveling from the Light phase to the Dark phase.

Step 1: Understanding the Concept:

ADP is a nucleotide consisting of adenine, ribose, and two phosphate groups.


Step 2: Detailed Explanation:

It is the lower-energy form of the cell's energy currency. By adding a third phosphate group (\( ADP + P_i \rightarrow ATP \)), the cell stores energy. This process is called phosphorylation.


Step 3: Final Answer:

ADP stands for Adenosine Diphosphate.
Quick Tip: ADP is like a partially charged battery; ATP is the fully charged version!

Step 1: Understanding the Concept:

Neurons are not physically connected. Communication between them requires a specialized junction.


Step 2: Detailed Explanation:

A synapse is the junction between the axon terminal of one neuron (pre-synaptic) and the dendrite of the next neuron (post-synaptic).

Transmission across the synapse is typically chemical, involving the release of neurotransmitters which diffuse across the gap to trigger a new impulse.


Step 3: Final Answer:

A synapse is the point of communication between two neurons.
Quick Tip: Information flow across a synapse is always \textbf{unidirectional} (one way).

Step 1: Understanding the Concept:

Neurotransmitters are chemical messengers released by synaptic vesicles at the axon terminal.


Step 2: Detailed Explanation:

The most common neurotransmitter in the peripheral nervous system and at neuromuscular junctions is Acetylcholine.

When an impulse reaches the axon end, acetylcholine is released into the synaptic cleft, binds to receptors on the next neuron, and initiates a new electrical impulse.


Step 3: Final Answer:

The most widely cited neurotransmitter is Acetylcholine.
Quick Tip: Once its job is done, enzymes like acetylcholinesterase quickly break it down to prevent continuous stimulation.

Step 1: Understanding the Concept:

Leydig cells (Interstitial cells) are endocrine cells located in the testes.


Step 2: Detailed Explanation:

They are found in the connective tissue \textit{between the seminiferous tubules.

Under the influence of Luteinizing Hormone (LH), they synthesize and secrete Testosterone, which is responsible for male secondary sexual characteristics and stimulating spermatogenesis.


Step 3: Final Answer:

The role of Leydig cells is to produce and secrete testosterone.
Quick Tip: Remember: Leydig = Interstitial cells (the spaces between the tubes).

Step 1: Understanding the Concept:

The seminiferous tubules are the functional units of the testes.


Step 2: Detailed Explanation:

These highly coiled tubes are lined with germinal epithelium.

Through the process of meiosis (specifically spermatogenesis), the germ cells divide and mature into spermatozoa (sperm cells). They also contain Sertoli cells which provide nourishment to the developing sperm.


Step 3: Final Answer:

The role of seminiferous tubules is the production and initial development of sperm.
Quick Tip: If all the seminiferous tubules in one testis were uncoiled and laid end to end, they would stretch for several hundred meters!

Step 1: Understanding the Concept:

Greenery acts as a natural buffer and filtration system for cities.


Step 2: Detailed Explanation:

Reduction in urban greenery leads to:

1. Poor Air Quality: Fewer trees mean less \( CO_2 \) absorption and less oxygen production, leading to higher smog levels.

2. Increased Temperature: The "Urban Heat Island" effect occurs because concrete absorbs heat, while trees would have provided cooling through shade and transpiration.

3. Flooding: Less unpaved ground means more surface runoff during rain.


Step 3: Final Answer:

A major problem is the significant increase in air pollution and ambient temperatures.
Quick Tip: Trees are often called the "lungs of a city" because of their role in purifying air.

Step 1: Understanding the Concept:

Green plants perform gas exchange through their stomata.


Step 2: Detailed Explanation:

During the day, plants take in Carbon dioxide (\( CO_2 \)) for photosynthesis. This removes a major greenhouse gas from the atmosphere.

Simultaneously, they release Oxygen (\( O_2 \)) as a byproduct, which is essential for the survival of all aerobic life forms.

Additionally, leaves trap dust particles and pollutants on their surfaces.


Step 3: Final Answer:

Plants improve air quality by acting as carbon sinks and oxygen producers.
Quick Tip: Broad-leaved trees are particularly effective at filtering particulate matter (PM 2.5 and PM 10) from the urban air.

Step 1: Understanding the Concept:

Citizen participation is crucial for the success of environmental conservation efforts.


Step 2: Detailed Explanation:

As a citizen, one can:

1. Plant Trees: Participate in "Van Mahotsav" or local plantation drives.

2. Adopt a Green Space: Maintain local parks or create "vertical gardens" in limited spaces.

3. Awareness: Educate others about the importance of trees and report the illegal cutting of trees to authorities.

4. Sustainable Living: Reduce personal carbon footprint to lessen the overall pressure on natural resources.


Step 3: Final Answer:

An active role involves regular plantation and the protection of existing local flora.
Quick Tip: Even small actions, like keeping potted plants on a balcony, help improve the immediate micro-environment!

Step 1: Understanding the Concept:

When a plant cell is placed in a hypotonic solution (like pure water), water enters the cell through the process of endosmosis.


Step 2: Detailed Explanation:

The incoming water fills the central vacuole, causing it to expand.

This expansion pushes the cytoplasm and other cell contents against the rigid cell wall.

The actual hydrostatic pressure exerted by the swollen protoplast against the cell wall is called Turgor Pressure.

In response, the cell wall exerts an equal and opposite pressure called Wall Pressure, which prevents the cell from bursting.


Step 3: Final Answer:

The term is Turgor Pressure.
Quick Tip: Turgor pressure is what keeps herbaceous plants upright and prevents them from wilting.

Step 1: Understanding the Concept:

The Central Nervous System (Brain and Spinal Cord) is protected by three layers of membranes called meninges.


Step 2: Detailed Explanation:

The three layers of meninges are the Dura mater (outer), Arachnoid mater (middle), and Pia mater (inner).

The space between the arachnoid and pia mater is the subarachnoid space.

This space, along with the central canal of the spinal cord, is filled with a clear, colorless alkaline fluid known as Cerebrospinal Fluid (CSF).


Step 3: Final Answer:

The fluid is Cerebrospinal Fluid (CSF).
Quick Tip: CSF acts as a liquid cushion, protecting the delicate nervous tissue from mechanical shocks.

Step 1: Understanding the Concept:

Fluids in the body often serve multiple roles, including protection and metabolic support.


Step 2: Detailed Explanation:

The Cerebrospinal Fluid (CSF) performs the following critical functions:

1. Mechanical Protection: It acts as a shock absorber, protecting the spinal cord and brain from injury during sudden movements or impacts.

2. Buoyancy: It reduces the effective weight of the brain and spinal cord, preventing pressure on blood vessels and nerves.

3. Metabolic Exchange: It helps in the exchange of nutrients (like glucose) and metabolic waste products between the blood and the neurons.


Step 3: Final Answer:

The primary function is to protect the spinal cord from mechanical shocks and to provide nutrients.
Quick Tip: Always mention "shock absorption" as the primary function of CSF in exam answers.

Step 1: Understanding the Concept:

A turgid cell is fully distended with water, where the cell components are pressed tightly against the cell wall.


Step 2: Detailed Explanation:

In the provided diagram:

1. Vacuole: This is the largest organelle in a mature plant cell, shown as the central transparent region. It contains cell sap and pushes other organelles to the periphery.

2. Plasma Membrane: This is the semi-permeable boundary of the cytoplasm. In a turgid cell, it is pushed flush against the Cell Wall (the outermost thick boundary). The line just interior to the cell wall represents the plasma membrane.


Step 3: Final Answer:

Label the large central sac as the Vacuole and the boundary line immediately inside the cell wall as the Plasma membrane.
Quick Tip: In a turgid cell, the plasma membrane is not easily distinguishable from the cell wall unless it is specifically pointed out as the inner layer.

Step 1: Understanding the Concept:

Waste is classified based on its ability to be broken down by biological agents (decomposers) like bacteria and fungi.


Step 2: Detailed Explanation:

1. Biodegradable waste: Substances that can be decomposed naturally into harmless components (e.g., organic matter). In the list:

- Decaying fruits: Organic matter from plants.

- Newspapers: Made from wood pulp (cellulose).

2. Non-biodegradable waste: Substances that cannot be broken down by microorganisms and persist in the environment for a long time. In the list:

- Styrofoam: A synthetic polymer.

- Metallic cans: Inorganic metal.

- Plastic bottles: Synthetic polymers.


Step 3: Final Answer:

The two biodegradable wastes are Decaying fruits and Newspapers.
Quick Tip: Natural products (paper, food, cotton) are usually biodegradable, while man-made chemicals (plastics, glass, metals) are generally non-biodegradable.

Step 1: Understanding the Concept:

The internal ear is the deepest part of the ear, responsible for both hearing and equilibrium.


Step 2: Detailed Explanation:

The entire complex structure of the inner ear is collectively called the Labyrinth.

It consists of two parts:

1. The Bony Labyrinth: A series of cavities in the temporal bone.

2. The Membranous Labyrinth: A series of fluid-filled sacs and tubes found within the bony labyrinth.

This includes the Cochlea (for hearing) and the Vestibular system (for balance).


Step 3: Final Answer:

The collective term is the Labyrinth.
Quick Tip: The term "Labyrinth" perfectly describes the intricate and complex maze-like structure of the inner ear.

Step 1: Understanding the Concept:

Sound waves are converted into electrical impulses in the cochlea by specialized sensory structures.


Step 2: Detailed Explanation:

The cochlea contains a specific sensory organ called the Organ of Corti, which rests on the basilar membrane.

It contains "hair cells" that act as auditory receptors.

Chronic exposure to high-decibel sounds (like drilling and blasting) causes mechanical stress that damages these delicate hair cells.

Once damaged, these cells often do not regenerate, leading to permanent hearing loss even if the eardrum (tympanic membrane) is healthy.


Step 3: Final Answer:

The sensory organ is the Organ of Corti.
Quick Tip: The Organ of Corti is essentially the "microphone" of the body that converts vibrations into nerve signals.

Step 1: Understanding the Concept:

Industrial activities often release various types of pollutants into the surrounding environment.


Step 2: Detailed Explanation:

In a stone quarry, the workers are exposed to:

1. Noise Pollution: Caused by heavy machinery used for digging, drilling, and high-intensity explosives used for blasting. This is the direct cause of Rajat's hearing loss.

2. Air Pollution: Quarrying processes generate huge amounts of suspended particulate matter (dust, silica). This can lead to respiratory diseases like Silicosis.


Step 3: Final Answer:

The workers face Noise Pollution and Air Pollution.
Quick Tip: While noise causes the immediate symptoms described (hearing loss), air pollution is a silent, long-term health hazard in quarries.