Transport of Oxygenated Blood:
Oxygenated blood from the lungs enters the left atrium. When the left atrium contracts, blood moves to the left ventricle, which then pumps it to the rest of the body through arteries.

Transport of Deoxygenated Blood:
Deoxygenated blood from the body enters the right atrium. It then passes to the right ventricle, which pumps it to the lungs for oxygenation.

This is called double circulation — blood passes through the heart twice in one complete cycle. The separation of oxygenated and deoxygenated blood ensures a highly efficient supply of oxygen to the body.

Source: Life Processes, Section 5.4.1

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• Examiners expect you to trace both pathways clearly: lungs → left side → body, and body → right side → lungs.
• Mention the chambers (atria and ventricles) by name — this fetches marks.
• The term double circulation is a key term that must appear for full marks.
• Avoid writing long paragraphs; two short labelled sections (oxygenated/deoxygenated) make the answer neat and easy to evaluate.

The enzyme present in saliva (the fluid in the mouth cavity) is salivary amylase. It is produced by the salivary glands.

If the salivary glands stop secreting this enzyme, starch would not be broken down into simple sugars in the mouth. Digestion of carbohydrates would be delayed, beginning only from the small intestine.

Source: Life Processes, Section 5.2.4

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• The question has three parts — name the enzyme, name the gland, state the consequence — so address all three clearly.
• "Salivary amylase" and "salivary glands" are the exact terms from the textbook; use them.
• For the consequence, note that starch digestion would not begin in the mouth, but it is not completely stopped (pancreatic amylase in the small intestine can still act) — so say digestion is delayed/incomplete at this stage, not fully absent.

(c) Assertion (A) is true, but Reason (R) is false.

Amoeba does use finger-like extensions (pseudopodia) to take in food, but not all unicellular organisms take in food by the entire surface — Paramoecium, for example, takes in food at a specific spot.

• A is true: The passage explicitly states "Amoeba takes in food using temporary finger-like extensions of the cell surface."
• R is false: The passage says food may be taken in by the entire surface in single-celled organisms, but Paramoecium (also unicellular) takes food in at a specific spot — disproving the absolute claim in R.
• Examiners expect you to spot the word "all" in the Reason as the flaw; generalisations like "all unicellular organisms" are often incorrect in assertion-reason questions.

(b) nucleus, chloroplast, vacuole, guard cell

In a closed stoma, (1) nucleus, (2) chloroplast, (3) vacuole, and (4) guard cell are the correct labels respectively.

In a standard diagram of stomata, the guard cells are the outermost bean-shaped structures (label 4), with the nucleus, chloroplast, and vacuole visible inside them. When the stoma is closed, the vacuoles are small (less turgid). Memorise the internal-to-external order: nucleus → chloroplast → vacuole → guard cell. Option (b) follows this standard labelling pattern used in NCERT Life Processes diagrams.

(i) The internal energy reserve in plants is starch, and in animals it is glycogen. These are used as sources of energy when needed.

(ii) Desert plants keep their stomata closed during the day to prevent water loss. They take in CO₂ at night and store it in the form of organic compounds (as malic acid). During the day, this stored CO₂ is used for photosynthesis when sunlight is available, even though stomata remain closed.

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• (i) This is a direct factual point — starch (plants) and glycogen (animals) are the standard expected terms. One mark.
• (ii) This describes CAM (Crassulacean Acid Metabolism) plants, though the term is not required at this level. Key idea: CO₂ is absorbed at night → stored as organic acid → released during day for photosynthesis. Two marks — mention both the night CO₂ absorption and daytime use clearly.
• Note: The source passages provided do not cover these topics directly; these answers are based on NCERT Class 10 Life Processes (Chapter 6) standard textbook content.

(i) ATP acts as the energy currency of the cell. The energy released during cellular respiration is used to synthesise ATP from ADP and inorganic phosphate. This ATP is then broken down to release energy (30.5 kJ/mol) to drive all endothermic reactions and life processes in the cell.

(ii) In plants, large intercellular spaces ensure that all cells remain in contact with air. Gases are exchanged through stomata. This ensures sufficient exchange of gases throughout the plant body.

(iii) The direction of diffusion of gases in plants depends upon:

• The environmental conditions, and
• The requirements of the plant (e.g., at night, CO₂ is released; during the day, O₂ is released as CO₂ is used in photosynthesis).

Source: Chapter 5, Section 5.3 Respiration

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• For (i), the key phrase examiners look for is "energy currency" and the idea that ATP stores and releases energy for cellular activities.
• For (ii), mention stomata and intercellular spaces — both are expected.
• For (iii), state both factors clearly: environmental conditions and plant's requirements. Giving the day/night example strengthens the answer and is directly from the textbook.

Nephrons are found in the kidneys.

Structure: Each nephron consists of a cup-shaped Bowman's capsule that encloses a cluster of thin-walled blood capillaries (glomerulus). The capsule leads into a long coiled tubule.

Function: Blood is filtered in the glomerulus. The filtrate enters the tubule, where useful substances like glucose, amino acids, salts and water are selectively reabsorbed. The remaining waste (urine) passes into the ureter.

Source: Chapter 5, Section 5.5.1

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Although the question says 2 marks, it asks three things (location, structure, function), so keep each part brief — one–two lines each. Examiners look for: kidneys as the location, Bowman's capsule + capillary cluster for structure, and filtration + selective reabsorption for function. Do not skip any of the three parts or you lose marks.

Breakdown of glucose in a cell:

Glucose (6-carbon)
↓ (Glycolysis — in cytoplasm)
Pyruvate (3-carbon)

(i) In the presence of oxygen (Aerobic respiration):

Pyruvate → (mitochondria, using O₂) → CO₂ + H₂O + Energy (ATP) (large amount)

(ii) In lack of oxygen (Anaerobic respiration):

• In yeast: Pyruvate → Ethanol + CO₂ + Energy (ATP)
• In muscle cells: Pyruvate → Lactic acid + Energy (ATP)

Source: Chapter 5, Section 5.3 — Respiration

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• The examiner expects a flow chart / schematic, not a paragraph. Use arrows to show the pathway.
• The common first step — glucose → pyruvate (glycolysis, in cytoplasm) — must be shown for full marks.
• Two anaerobic pathways are expected: yeast (ethanol + CO₂) and muscle cells (lactic acid). Mentioning both strengthens the answer.
• Key location details (cytoplasm for glycolysis, mitochondria for aerobic) add precision but are secondary to the pathway itself.
• Keep the flow chart neat and labelled; this is what earns marks in board exams.

(i) Vena cava — Transports deoxygenated blood from the body (various organs/tissues) to the right atrium of the heart.

(ii) Pulmonary artery — Transports deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.

Source: Life Processes, Section 5.4.1

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• The key point examiners look for: both vessels carry deoxygenated blood — a common mistake is assuming arteries always carry oxygenated blood. The pulmonary artery is the exception.
• Always mention source → destination (path) for full marks; naming only the blood type gives half credit.
• "Vena cava is a vein → carries blood to the heart; pulmonary artery carries blood away from the heart to lungs" — this logic confirms direction.

(c) (A) is true, but (R) is false.

Assertion is correct — blood clotting does prevent excessive blood loss. However, clotting is caused by platelets (thrombocytes), not by plasma and white blood cells (WBCs).

Source: Life Processes, Section 5.4.1 (Maintenance by platelets)

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The textbook clearly states: "the blood has platelet cells which circulate around the body and plug these leaks by helping to clot the blood at these points of injury." WBCs fight infection; they do not cause clotting. Plasma transports substances but is not the agent of clotting. Since the Reason incorrectly names WBCs and plasma instead of platelets, R is false, making option (c) correct.

(d) is NOT correct. Water is absorbed from unabsorbed food in the large intestine, not the villi of the small intestine.

Source: Life Processes, Section 5.2.4

The passage clearly states: "The unabsorbed food is sent into the large intestine where its wall absorb more water from this material." The villi of the small intestine function in absorption of digested food, not water from unabsorbed waste. Examiners expect you to distinguish between the roles of the small intestine (digestion + absorption of nutrients) and the large intestine (water absorption from undigested matter).

(d) a fungi, Rhizopus

Fungi like Rhizopus break down food material outside their body and then absorb it. This is saprotrophic nutrition.

The passage in section 5.2.2 explicitly states: "Some organisms break-down the food material outside the body and then absorb it. Examples are fungi like bread moulds, yeast and mushrooms." Rhizopus is a bread mould (fungus), so option (d) is correct. Cuscuta and Tapeworm are parasites; Rhizobium is a symbiotic bacterium — none of these digest food externally before absorbing it.

(a) The glands present in the buccal cavity are salivary glands. Their secretion (saliva) contains salivary amylase (ptyalin) which acts on starch (carbohydrates) and breaks it down into simpler sugars.

(b) The two organs with a sphincter muscle at their exit are:

1. Stomach (pyloric sphincter)
2. Anus (anal sphincter)

(c)
(i) If mucus is not secreted by gastric glands, the inner lining of the stomach will not be protected from the hydrochloric acid and digestive enzymes. This can cause ulcers in the stomach wall.

(ii) If villi are absent in the small intestine, the surface area for absorption of digested food will decrease greatly, leading to poor absorption of nutrients into the blood.

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• (a) Salivary glands and salivary amylase acting on starch is standard textbook content — both parts (gland name + substrate) are needed for full credit.
• (b) Pyloric sphincter (stomach exit) and anal sphincter (anus) are the two key sphincters; examiners look for both organ names.
• (c)(i) Mucus protects stomach lining — ulcers is the key consequence. (c)(ii) Villi increase surface area — their absence means reduced absorption. Each point carries 1 mark.

The process involved is transpiration and transportation through xylem (water transport).

1. Water absorbed by roots from the soil enters the root hair cells by osmosis.
2. This water is conducted upward through xylem vessels to all parts of the plant, including the topmost leaves.
3. In the leaves, water evaporates through stomata — this is called transpiration.
4. Transpiration creates a suction pull (transpiration pull), which draws water continuously upward from roots to leaves against gravity.

Thus, a continuous column of water moves from roots to the topmost leaves through the xylem due to transpiration pull.

Source: Chapter 5, Life Processes — Transportation in Plants

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• The examiner expects three key terms: osmosis (root absorption), xylem (conduction), and transpiration pull (driving force).
• Many students forget to mention the mechanism that drives water upward — always state "transpiration pull/suction pull created by transpiration."
• Keep the steps in logical order: soil → roots (osmosis) → xylem → leaves → stomata → transpiration pull.
• 3 marks = 3 distinct points; one mark each for absorption, xylem conduction, and transpiration pull.

Option C: (b) and (c)

Statement (b) is correct — left atrium transfers oxygenated blood to left ventricle, which pumps it to the body. Statement (c) is correct — right atrium receives deoxygenated blood via vena cava.

Statement (a) is wrong because pulmonary veins (not arteries) bring oxygenated blood to the left atrium. Statement (d) is wrong because oxygenated blood goes from the left ventricle to the aorta, not directly from the left atrium. Examiners test whether students know which vessel carries oxygenated/deoxygenated blood and the correct sequence of chambers.

(i) The movements that occur all along the gut are called peristaltic movements. The muscular walls of the alimentary canal contract and relax alternately, pushing the food forward. This helps in thorough mixing of food with digestive juices and moves it along the digestive tract for complete digestion and absorption.

(ii) Bile juice is stored in a sac-like organ called the gall bladder.

Two roles of bile juice:

1. It makes the acidic food coming from the stomach alkaline, so that pancreatic enzymes can act on it.
2. It emulsifies fats — breaks large fat globules into smaller droplets, increasing the surface area for enzyme action.

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• "Peristalsis/peristaltic movements" is the exact term examiners expect for (i) — always name it, then explain the mechanism and its role.
• For (ii), both parts are needed: storage location (gall bladder) + two distinct roles. Emulsification of fats and making the medium alkaline are the two standard points from the NCERT Life Processes chapter. Writing "helps in digestion of fats" alone is too vague — specify emulsification.

(i) Alveoli are richly supplied with blood capillaries to provide a large surface area for rapid exchange of gases (oxygen and carbon dioxide) between air in the alveoli and the blood.

(ii) Haemoglobin (respiratory pigment) has a high affinity for oxygen, so it combines with oxygen to form oxyhaemoglobin and transports it to body cells. Carbon dioxide is mostly transported dissolved in plasma or as bicarbonate ions, not by haemoglobin.

(iii) During anaerobic respiration in humans, there is incomplete breakdown of glucose (pyruvate). Due to lack of oxygen, pyruvate is converted to lactic acid (3-carbon molecule) in the muscle cells instead of being fully oxidised to CO₂ and water.

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• For (i): Link alveolar structure to function — large surface + rich blood supply = efficient gas exchange.
• For (ii): Stress haemoglobin's affinity for O₂, not CO₂. Mention CO₂ transport via plasma/bicarbonate to show contrast.
• For (iii): Key point is incomplete breakdown and no oxygen → pyruvate → lactic acid (3C). Avoid confusing with yeast (which gives ethanol + CO₂). Examiners expect "lactic acid" and "muscle cells" explicitly.

The process involved is translocation, carried out by phloem (vascular tissue).

Food (sucrose) prepared in leaves during photosynthesis is transported to all other parts of the plant — roots, stem, fruits, and seeds — through the phloem. This transport occurs in both upward and downward directions as per the plant's needs.

Source: Life Processes, Chapter 5 (Transport in Plants)

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• The question has two parts: name the process (translocation via phloem) and explain it. Award one mark each.
• Do not confuse phloem (food transport) with xylem (water/mineral transport) — a common error.
• Key points examiners look for: the word phloem, the word translocation, bidirectional movement, and that food reaches all parts of the plant.

(B) lifted ribs and flattened diaphragm.

When a person breathes in (inhalation), the ribs are lifted upward and outward by intercostal muscles, and the diaphragm contracts and flattens, increasing chest cavity volume and allowing air to rush in.

During inhalation, both the ribs moving up/out AND the diaphragm flattening work together to increase the volume of the thoracic cavity, reducing air pressure inside so air flows in. Option (A) is wrong because dome-shaped diaphragm occurs during exhalation. Options (C) and (D) describe exhalation. The key is: inhalation = ribs lifted + diaphragm flattened.

(C) (b) and (c)

Statement (b) is correct — left atrium transfers oxygenated blood to left ventricle, which pumps it to the body. Statement (c) is correct — right atrium receives deoxygenated blood via vena cava.

From the passage: "Oxygen-rich blood from the lungs comes to… the left atrium… the left ventricle contracts… the blood is pumped out to the body. De-oxygenated blood comes from the body to… the right atrium." Statement (a) is wrong because oxygenated blood comes via pulmonary veins, not pulmonary artery. Statement (d) is wrong because the left ventricle (not left atrium) pumps blood into the aorta.

(i) In large multicellular organisms, diffusion alone cannot supply oxygen to all cells. Respiratory pigments (e.g., haemoglobin) carry oxygen from the lungs to oxygen-deficient tissues and release it there.

(ii)
(a) Rings of cartilage are present in the throat to ensure that the air-passage does not collapse, keeping it open at all times for continuous airflow.

(b) Lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for carbon dioxide to be released, ensuring continuous gas exchange.

(c) When we breathe in, lifting the ribs and flattening the diaphragm increases the chest cavity volume, causing air to be sucked into the lungs to fill the expanded alveoli.

(d) The extensive network of blood vessels in alveolar walls facilitates efficient exchange of gases — oxygen is absorbed into the blood and carbon dioxide is released into the alveoli.

Source: Chapter 5 — Life Processes, Section 5.3 Respiration

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• (i) directly comes from the "More to Know" paragraph on respiratory pigments — mention diffusion being insufficient and haemoglobin's role.
• For (ii), all four reasons are explicitly stated in the textbook passage on the human respiratory system. Quote or closely paraphrase the text; examiners look for these exact points.
• Avoid adding extra detail; each sub-point needs only 1–2 lines since the whole (ii) part carries 2 marks total (½ mark each reason).

(i) Hydrochloric acid: Creates an acidic medium in the stomach which facilitates the action of the enzyme pepsin.

(ii) Villi: Finger-like projections on the inner lining of the small intestine that increase surface area for absorption of digested food.

(iii) Anal sphincter: Regulates the exit of undigested/unabsorbed waste material from the body through the anus.

(iv) Lipase: Secreted in pancreatic juice; breaks down emulsified fats into fatty acids and glycerol.

Source: Chapter 5, Section 5.2.4 – Nutrition in Human Beings

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• This 2-mark question has 4 parts, so award roughly ½ mark each — keep each answer to one line only.
• Examiners look for the key function word: "acidic medium/pepsin" for HCl; "increase surface area/absorption" for villi; "regulates exit of waste" for anal sphincter; "breaks down emulsified fats" for lipase.
• Avoid vague answers like "helps in digestion" — be specific about what is digested or what process is aided.

(c) Assertion (A) is true, but Reason (R) is false.

The amount of dissolved oxygen in water is far less than the oxygen present in air, so aquatic organisms must breathe faster to meet their oxygen needs.

The Assertion is correct — aquatic organisms do breathe faster. However, the Reason is wrong because oxygen dissolved in water is actually much lower (not higher) than oxygen in air. This low availability of O₂ in water forces aquatic animals to increase their breathing rate. Since the Reason is factually incorrect, option (c) is the right choice.

(c) (ii) and (iii)

A stoma closes when the plant does not need CO₂ for photosynthesis, and when water flows out of the guard cells, causing them to shrink.

Source: Life Processes, Section 5.2.1

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The textbook clearly states: "the plant closes these pores when it does not need carbon dioxide for photosynthesis" and "the pore closes if the guard cells shrink" (which happens when water flows out). Option (iv) is wrong — water flowing in causes the pore to open, not close.

(i) Oxygenated blood is brought to the heart by the pulmonary veins (from the lungs).

(ii) Deoxygenated blood is brought to the heart by the venae cavae (from the body).

The right atrium receives deoxygenated blood. When the right atrium contracts, the blood passes into the right ventricle, which then pumps it to the lungs through the pulmonary artery for oxygenation.

Source: Life Processes, Section 5.4.1

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• Examiners expect all three parts: name both vessels, name the chamber, and explain the mechanism of sending blood to lungs.
• Common mistakes: calling pulmonary veins "arteries" (they carry oxygenated blood but are still veins), or forgetting to mention the right ventricle's role in pumping blood to the lungs.
• The path is: Right atrium → contracts → Right ventricle → pumps → Pulmonary artery → Lungs.
• 1 mark each for (i) & (ii), and 1 mark for the chamber + mechanism together.

(C) Assertion (A) is true, but Reason (R) is false.

Xylem transports water and minerals from roots to all parts of the plant; it is present throughout the plant — roots, stem, and leaves — not only in roots.

The Assertion is correct (xylem = water + mineral transport). The Reason is false because xylem forms a continuous vascular network through roots, stem, and leaves. Since A is true but R is false, option (C) is correct. Examiners expect you to evaluate both statements independently before choosing.

(B) Hydrochloric acid, Pepsin, Mucus

The gastric glands in the stomach wall release hydrochloric acid, a protein-digesting enzyme called pepsin, and mucus.

Source: Life Processes, Section 5.2.4

The passage clearly states: "These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus." Bile is secreted by the liver (not gastric glands), trypsin and lipase come from the pancreas, and salivary amylase is from salivary glands — so options A, C, and D are wrong. Always associate gastric glands specifically with HCl + pepsin + mucus.

(A) Nephron

The nephron is the basic filtration unit of the kidney. Each kidney contains large numbers of nephrons packed together that filter nitrogenous wastes from the blood.

The passage clearly states: "Each kidney has large numbers of these filtration units called nephrons packed close together." Urethra carries urine out of the body; urinary bladder stores urine; neuron is a nerve cell — all distractors unrelated to filtration.

(a) The respiratory pigment in human beings is haemoglobin, found in red blood cells. Its function is to transport oxygen from the lungs to all body tissues.

(b) Lungs always retain a residual volume of air so that there is sufficient time for oxygen to be absorbed into the blood and carbon dioxide to be released, ensuring a continuous exchange of gases even between breaths.

(c) ATP (Adenosine Triphosphate) is called the energy currency of living beings because energy released during the breakdown of glucose is stored in ATP molecules. This stored energy is then used to power various cellular reactions whenever required — just like currency is used for different transactions.

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• For (a), name haemoglobin explicitly and state it carries O₂ — examiners expect both.
• For (b), the key idea is continuity of gas exchange; without residual air, the alveoli would collapse between breaths, stopping diffusion entirely.
• For (c), link ATP to both storage of energy (from respiration) and utilisation (for cellular reactions) — the "currency" analogy must be explained, not just stated.

(a) X is the Bowman's capsule (cup-shaped end of the nephron). It collects the filtrate from the glomerular capillaries. Blood is filtered here under pressure — the first step of urine formation called filtration.

(b) Useful substances such as glucose, amino acids, salts and water are selectively reabsorbed so that they are not lost from the body. Only waste products (e.g., urea) are retained in the filtrate to be excreted as urine.

Source: Chapter 5, Section 5.5.1 – Excretion in Human Beings

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• (a) The diagram's arrow points to the cup-shaped structure around the glomerulus — that is Bowman's capsule. Always name it and state its role: collecting filtrate / ultrafiltration.
• (b) The key idea is that the body must conserve useful substances. Simply write which substances are reabsorbed and why (to prevent loss of valuable materials). One sentence each is enough for 1 mark.
• Examiners look for correct terminology: "Bowman's capsule," "filtrate," "selective reabsorption."

Formation of Lymph: When blood flows through capillaries, some plasma along with proteins leaks out into the spaces between cells, forming tissue fluid. This tissue fluid enters lymph capillaries and becomes lymph.

Function: Lymph carries digested and absorbed fat from the small intestine to the blood. It also drains excess tissue fluid back into the bloodstream.

The source passages provided do not cover this topic (they relate to reproduction), but this question is from the Life Processes chapter (Chapter 6 – Circulatory System). Examiners expect:

• One clear sentence on how lymph is formed (plasma leaking out of capillaries → tissue fluid → lymph).
• One clear sentence on its function (transport of fats/digested food; return of excess fluid to blood).
• For 2 marks, one mark is typically awarded for formation and one for function. Keep it concise.

Option D: Cytoplasm and Mitochondria

Breakdown of glucose to pyruvate occurs in the cytoplasm, and further breakdown of pyruvate to carbon dioxide (aerobic respiration) occurs in the mitochondria.

The textbook (Section 5.3) clearly states: "The first step is the break-down of glucose into pyruvate — this takes place in the cytoplasm. Break-down of pyruvate using oxygen takes place in the mitochondria." This is a frequently asked fact; remember the sequence: Cytoplasm → Mitochondria for aerobic respiration.

Answer: B — (iii), (ii), (iv), (i), (v)

Correct sequence: finger-like extensions form → food vacuole forms → complex substances broken down → simple nutrients diffuse into cytoplasm → undigested material thrown out.

The passage clearly states the order: temporary finger-like extensions fuse over food → food vacuole forms → complex substances broken to simpler ones inside the vacuole → diffuse into cytoplasm → undigested material thrown out. Option B matches this exactly. Students often confuse steps (iv) and (i) — digestion (iv) must happen before diffusion (i) can occur.

(i) Saliva:
Enzyme: Salivary amylase
Function: Breaks down starch (complex carbohydrate) into simple sugars.

(ii) Bile Juice:
Component: Bile salts (no enzyme)
Function: Makes the acidic food alkaline for pancreatic enzymes to act, and emulsifies large fat globules into smaller ones, increasing efficiency of enzyme action.

(iii) Pancreatic Juice:
Enzymes: Trypsin and Lipase
Function: Trypsin digests proteins; Lipase breaks down emulsified fats into fatty acids and glycerol.

Source: Chapter 5, Section 5.2.4 – Nutrition in Human Beings

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• Bile juice has no enzyme — a common mistake. It contains bile salts that emulsify fats. Examiners specifically look for this distinction.
• For pancreatic juice, name both enzymes (trypsin + lipase) and state both functions to score full marks.
• The keyword for bile's role is emulsification — breaking large fat globules into smaller ones.
• Keep the format neat: name the enzyme/salt first, then its function — this matches the question's demand and makes awarding marks easy for the examiner.

Plants use various techniques to excrete waste:

1. Transpiration — excess water is removed as water vapour through stomata.
2. Stored in vacuoles — waste products are stored in cellular vacuoles.
3. Stored in leaves — wastes accumulate in leaves which then fall off.
4. Resins and gums — wastes are stored as resins and gums in old xylem.
5. Excreted into soil — some waste substances are released into the surrounding soil.

(Any four accepted)

Source: Chapter 5, Section 5.5.2 – Excretion in Plants

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The question is from 5.5.2 Excretion in Plants. Examiners expect students to list distinct methods with a brief description of each. For 2 marks, four points are asked but only two are typically awarded (½ mark each) — write all four clearly to be safe. Avoid mixing up animal excretion details here. Key terms like transpiration, vacuoles, resins and gums, and leaf fall must appear.

(d) Assertion (A) is false, but Reason (R) is true.

In large animals, oxygen cannot easily reach all body parts by simple diffusion; a transport system with respiratory pigments (like haemoglobin) is needed. The Reason correctly states that respiratory pigments carry oxygen to body tissues.

The Assertion is false because large/complex animals have a problem with oxygen delivery — diffusion alone is insufficient over large distances, which is why they evolved circulatory systems and respiratory pigments. The Reason is true: haemoglobin (a respiratory pigment in RBCs) picks up oxygen in the lungs and carries it to tissues. Since A is false and R is true, option (d) is correct.

(b) B and D

Lymph contains plasma, proteins, and blood cells (not specifically RBCs), and lymph vessels finally open into larger veins, not arteries.

Source: Life Processes, Section 5.4.1

The textbook states: "some amount of plasma, proteins and blood cells escape… to form lymph" (ruling out C, which incorrectly says only red blood cells) and "large lymph vessels… finally open into larger veins" (ruling out A, which says arteries). So B and D are both correct.

(b) Nitrogen

Nitrogen is the essential element taken up from the soil by plants to synthesize proteins.

Proteins contain nitrogen as a key element. Plants absorb nitrogen from the soil (as nitrates/nitrites) to build amino acids and proteins. The other options — phosphorus, iron, and magnesium — serve different functions and are not the primary element for protein synthesis. This is a straightforward factual question; just recall that proteins = nitrogen.

(a) Activity: Take a small piece of bread and chew it for 2-3 minutes without swallowing. Initially it has no taste, but after some time it starts to taste sweet.

This happens because saliva contains an enzyme called salivary amylase (ptyalin) which breaks down starch present in the bread into simple sugars (maltose). This shows that saliva acts on the starch in food and begins its chemical digestion in the mouth.

(b) Bile juice is secreted by the liver and stored in the gall bladder. It does not contain any digestive enzymes but is important because it makes the acidic food coming from the stomach alkaline, so that pancreatic enzymes can act on it. It also helps in the emulsification of fats, breaking large fat globules into smaller droplets, which increases the surface area for enzyme action.

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• For part (a), the examiner expects a named activity (chewing bread/starch) + naming salivary amylase + stating starch → sugar. This is a standard 2-mark activity-based answer.
• For part (b), two key points must be mentioned: (i) making medium alkaline and (ii) emulsification of fats. Missing either loses a mark.
• Do not confuse bile with pancreatic juice — bile has no digestive enzymes.

Two protein-digesting enzymes secreted during digestion:

1. Pepsin — secreted by the gastric glands present in the walls of the stomach.
2. Trypsin — secreted by the pancreas (in pancreatic juice) into the small intestine.

Source: Life Processes, Section 5.2.4

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The question specifically asks for protein-digesting enzymes, so do not include salivary amylase (digests starch) or lipase (digests fats). Examiners expect both the enzyme name and the secreting gland for full marks — one mark per enzyme-gland pair. Note that intestinal juice also converts proteins to amino acids, but the question asks for named enzymes with named glands; pepsin + gastric glands and trypsin + pancreas are the clearest, textbook-stated pairs.

Leaves help in excretion in two ways:

1. Storing waste in vacuoles: Waste materials are stored in the cell vacuoles of leaves.
2. Removal through falling leaves: Waste products accumulated in leaves are removed when the plant sheds its leaves (leaf fall).

Source: Life Processes, Chapter 5

The textbook specifically states that plants get rid of waste by storing it in cell-vacuoles or removing it in falling leaves. Examiners expect both points to be clearly linked to leaves (not gums/resins or soil excretion, which relate to other plant parts). Each point is worth 1 mark — name the method and briefly explain it.

The following events take place during photosynthesis in sequence:

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
3. Reduction of carbon dioxide to carbohydrates.

Source: Chapter 5, Section 5.2.1 Autotrophic Nutrition

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The examiner expects these three steps listed in order using the exact phrasing from the textbook. Writing them as a numbered list is ideal for a sequence-based question. Avoid mixing up step 2 and 3 — light reactions (splitting of water) come before carbon fixation (reduction of CO₂). Both marks are awarded for all three steps in correct sequence.

(d) Assertion (A) is false, but Reason (R) is true.

The Assertion is false — ventricles have thicker walls than atria. The Reason is true — ventricles pump blood to various organs at high pressure.

Source: Chapter 5, Section 5.4.1 (Transportation in Human Beings)

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The textbook clearly states: "ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do." So the Assertion incorrectly swaps the relationship — it's the ventricles that are thick-walled, not the atria. The Reason correctly explains why ventricles need thick walls. Hence option (d) is correct.

(b) faster because the amount of dissolved oxygen in water is fairly low.

Aquatic organisms must breathe faster to extract sufficient oxygen, as water contains much less dissolved oxygen than air.

The key concept is that dissolved oxygen in water is present in very small amounts compared to oxygen in air. To meet their oxygen needs, aquatic organisms (e.g., fish) must process a larger volume of water rapidly, making their breathing rate faster than that of terrestrial organisms. Option (d) is a distractor — while technically related, the reason given in the textbook focuses on the low amount of dissolved oxygen, not the limited capacity of water to dissolve air. Option (a) is wrong because it implies aquatic animals need more oxygen, which is not the stated reason.

(b) transpiration and temperature regulation.

Loss of water vapour from aerial parts of plants is transpiration, which helps in temperature regulation of the plant.

Transpiration is specifically the loss of water in vapour form from aerial parts (leaves, stems) through stomata. The textbook notes that plants lose large amounts of water through stomata; this evaporative loss cools the plant surface, regulating its temperature. Option (c) and (d) describe translocation, not transpiration. Option (a) is a distractor — photosynthesis requires water but transpiration does not directly "help" photosynthesis.

(i) Double Circulation:
When blood passes through the heart twice during one complete cycle through the body, it is called double circulation. Blood goes once to the lungs (pulmonary circulation) and once to the rest of the body (systemic circulation).

(ii) Separation of right and left sides:
The separation prevents oxygenated and de-oxygenated blood from mixing, allowing a highly efficient supply of oxygen to the body.

Birds and mammals are warm-blooded — they constantly use energy to maintain body temperature. This requires a continuous, efficient oxygen supply. The complete separation of the two sides of the heart ensures oxygen-rich blood is always pumped to body tissues without dilution, meeting their high energy demands.

Source: Chapter 5, Section 5.4.1

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• Part (i) is worth ~1 mark: one crisp definition focusing on "twice through the heart" and naming both circuits.
• Part (ii) is worth ~2 marks: state the purpose (no mixing → efficient O₂ supply) and then specifically link to birds/mammals being warm-blooded with high energy needs. Examiners expect both the general benefit and the specific application to warm-blooded animals.

(A)(i) In Paramecium, food is taken in at a specific spot on the cell. Cilia covering the entire surface of the cell move and direct food particles to this spot, where they are ingested.

(ii)
(a) Hydrochloric acid – Creates an acidic medium in the stomach that facilitates the action of the enzyme pepsin.

(b) Trypsin – A pancreatic enzyme that digests proteins in the small intestine.

(c) Muscular walls of stomach – Help in mixing food thoroughly with digestive juices.

(d) Salivary amylase – Breaks down starch (complex carbohydrate) into simple sugars in the mouth.

Source: Chapter 5, Section 5.2.3 and 5.2.4

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• For Paramecium, the key points are: definite shape, food taken at a specific spot, and role of cilia — all three should be mentioned.
• For part (ii), each sub-point is worth roughly ½ mark, so one crisp line per item is enough.
• Examiners look for the correct enzyme–substrate pair: amylase→starch, trypsin→proteins, pepsin (activated by HCl)→proteins.
• Avoid confusing pepsin (stomach) with trypsin (pancreas/small intestine).

The plant kept in dark could not perform photosynthesis as sunlight is essential for it. Without photosynthesis, no carbohydrates (food) were produced. The plant used up all its stored starch for respiration and, with no energy reserve left, it could not survive longer. The plant in sunlight continued photosynthesis and stayed alive.

Source: Life Processes, Section 5.2.1 Autotrophic Nutrition

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• The key idea is that sunlight is essential for photosynthesis, which produces carbohydrates that serve as energy reserve (stored as starch).
• The plant in dark exhausts its stored starch through respiration with no way to replenish it — this is the direct cause of death.
• Mention both: no photosynthesis → no food/energy to get full marks. Saying only "no sunlight" without linking to energy/food loss will lose a mark.

(i) Renal Artery: It supplies oxygenated blood (containing nitrogenous wastes) to the kidneys for filtration.

(ii) Urethra: It carries urine from the urinary bladder to the outside of the body for elimination.

(iii) Glomerulus: It is a cluster of thin-walled capillaries where filtration of blood takes place — waste products and other substances are filtered out of the blood into the Bowman's capsule.

(iv) Tubular part of nephron: It selectively reabsorbs useful substances such as glucose, amino acids, salts and a major amount of water from the filtrate back into the blood.

Source: Life Processes, Chapter 5, Section 5.5.1

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• These are standard 1-mark-each parts; one clear function per organ is enough — no elaboration needed.
• Examiners look for key terms: filtration (glomerulus), reabsorption (tubule), elimination/passage of urine (urethra), supply of blood for filtration (renal artery).
• Do not confuse ureter (carries urine from kidney to bladder) with urethra (bladder to outside).
• The tubular reabsorption point is directly stated in the textbook: "glucose, amino acids, salts and a major amount of water are selectively re-absorbed."

(i) Renal Artery: It carries oxygenated blood (with nitrogenous wastes) from the aorta to the kidneys for filtration.

(ii) Urethra: It carries urine from the urinary bladder to the outside of the body for its elimination.

(iii) Glomerulus: It is a cluster of thin-walled blood capillaries where filtration of blood takes place under pressure; the filtrate (containing urea, glucose, salts, water) is collected into the Bowman's capsule.

(iv) Tubular part of nephron: It selectively re-absorbs useful substances such as glucose, amino acids, salts and a major amount of water from the filtrate back into the blood, so that only waste-concentrated urine passes forward.

Source: Chapter 5, Section 5.5.1 – Excretion in Human Beings

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• Examiners expect one specific function per organ — one crisp sentence each is enough for 1 mark per part.
• The renal artery is part of the blood supply bringing waste-laden blood to the kidney; do not confuse it with the renal vein (which carries filtered blood away).
• "Glomerulus" and "Bowman's capsule" together form the filtration unit; the question focuses on the glomerulus specifically — filtration is the key word.
• For the tubular part, the key term is selective reabsorption — examiners look for this phrase.

(i) Renal Artery: It supplies oxygenated blood (containing nitrogenous wastes) to the kidneys for filtration.

(ii) Urethra: It carries urine from the urinary bladder to the outside of the body for expulsion.

(iii) Glomerulus: It is a cluster of capillaries where filtration of blood takes place — waste products, water, glucose, salts are filtered out of the blood into the Bowman's capsule.

(iv) Tubular part of nephron: It selectively re-absorbs useful substances such as glucose, amino acids, salts and a major amount of water from the filtrate back into the blood.

Source: Chapter 5, Section 5.5.1 – Excretion in Human Beings

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• Examiners expect one specific function per organ — do not describe structure.
• Key terms to use: filtration (glomerulus), reabsorption (tubule), expulsion/release (urethra), blood supply with wastes (renal artery).
• The tubule's role in selective reabsorption is a frequently tested point — mention at least two substances reabsorbed.
• Keep each point to one sentence; these are likely 1-mark each.

(i) Renal Artery: It supplies oxygenated blood (containing nitrogenous wastes like urea) to the kidneys for filtration.

(ii) Urethra: It carries urine from the urinary bladder to the outside of the body for elimination.

(iii) Glomerulus: It is a cluster of thin-walled capillaries where filtration of blood takes place — water, urea, glucose, salts pass into the Bowman's capsule.

(iv) Tubular part of nephron: It performs selective reabsorption — useful substances like glucose, amino acids, salts and water are reabsorbed back into the blood from the filtrate.

Source: Chapter 5, Section 5.5.1 – Excretion in Human Beings

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• Each part carries 1 mark, so one clear, specific function per part is enough — no elaboration needed.
• Examiners look for the key function word: filtration (glomerulus), reabsorption (tubule), elimination/passage of urine (urethra), supply of blood with wastes (renal artery).
• Don't confuse ureter (carries urine from kidney to bladder) with urethra (bladder to outside).
• "Selective reabsorption" is the expected term for the tubular part — use it.

(c) (A) is true but (R) is false.

Assertion is correct — villi are finger-like projections richly supplied with blood vessels. However, the Reason is false — villi increase surface area for absorption of digested food, not for completing digestion.

The textbook clearly states: "The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption." Digestion is completed by intestinal enzymes in the intestinal juice — villi play no role in digestion itself. Examiners specifically test this distinction between absorption and digestion. Always check whether the Reason correctly explains the Assertion and is factually accurate.

(b) Movement of water in and out of the guard cells.

When guard cells absorb water, they become turgid and stomata open; when they lose water, they become flaccid and stomata close. This is the standard NCERT explanation for stomatal movement.

Steps for experimental verification that sunlight is essential for photosynthesis:

1. Take a healthy potted plant and keep it in a dark room for three days so that all existing starch is used up (destarch the plant).
2. Cover a portion of a leaf on both sides with black paper strips to block sunlight, while leaving the rest of the leaf exposed.
3. Place the plant in bright sunlight for about six hours.
4. Pluck the leaf; remove the black paper.
5. Boil the leaf in water, then in alcohol (using a water-bath) to remove chlorophyll.
6. Dip the leaf in dilute iodine solution.
7. Observation: The exposed (sunlit) area turns blue-black (starch present); the covered area remains brown (no starch).
8. Conclusion: Sunlight is essential for photosynthesis, as starch is produced only in areas that received light.

Source: Life Processes, Section 5.2.1 (Activity based on Activities 5.1 & 5.2)

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• Examiners expect the answer as sequential steps — destarching → partial covering → sunlight exposure → destaining in alcohol → iodine test → observation → conclusion.
• Key terms to include: destarch, black paper, alcohol (chlorophyll removal), iodine test, blue-black colour.
• The contrast between covered and uncovered portions is the core proof — always state both results.
• "Water-bath" for alcohol heating is a safety detail that can earn an extra half-mark.

(a)(i) The first step in the breakdown of glucose — in both aerobic and anaerobic respiration — is the splitting of glucose (a six-carbon molecule) into pyruvate (a three-carbon molecule). This process is called glycolysis and it takes place in the cytoplasm of the cell.

(a)(ii) ATP is called the energy currency of the cell because energy released during respiration is stored in ATP molecules. Whenever the cell needs energy for activities like muscle contraction, protein synthesis, or nerve impulse conduction, ATP is broken down to release a fixed, usable amount of energy (~30.5 kJ/mol).

(a)(iii) Residual volume is the volume of air that always remains in the lungs even after breathing out. It ensures sufficient time for oxygen to be absorbed into the blood and for carbon dioxide to be released from the blood into the alveoli.

Source: Chapter 5, Section 5.3 — Respiration

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• (i) Examiners expect the term "pyruvate/pyruvic acid," mention that it is a 3-carbon molecule, and the location — cytoplasm. Many students forget to say it applies to BOTH aerobic and anaerobic respiration.
• (ii) The key idea is that ATP stores and releases energy in fixed amounts for diverse cellular activities. Quoting the analogy to a battery or mentioning ~30.5 kJ/mol adds precision.
• (iii) "Residual volume" must be linked to its purpose (time for gas exchange), not just defined as leftover air — that's what earns the mark.

(a) Birds and mammals are warm-blooded animals that maintain a constant high body temperature. This requires a lot of energy, so they need highly efficient oxygen supply. Mixing of oxygenated and deoxygenated blood would reduce the efficiency of oxygen delivery to tissues, making them unable to sustain the high metabolic rate needed.

(b) Amphibians and reptiles can tolerate some mixing of the two blood streams. Their body temperature depends on the temperature of the environment (they are cold-blooded/poikilothermic).

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• The key concept for (a) is the link between warm-bloodedness, high energy demand, and the need for pure oxygenated blood.
• For (b), examiners expect the names amphibians and reptiles and the term environmental temperature (or that they are cold-blooded/ectothermic). These points come from Chapter 7 (Control and Coordination / Life Processes context) of the NCERT textbook. Note: the source passages provided are from other chapters, but this is standard NCERT Biology content for Class 10, Chapter 6 (Life Processes).

(c) Lactic acid

During vigorous exercise, anaerobic respiration occurs in muscle cells, converting pyruvate to lactic acid. Its accumulation causes painful muscle cramps.

The key concept is anaerobic respiration in animals: when oxygen is insufficient (vigorous exercise), pyruvate → lactic acid (not ethanol, which occurs in yeast/plants). Lactose is a sugar, not a respiration product. Glucose is the starting material, not a product of pyruvate breakdown.

(d) II

The guard cells (region II) surround the stomatal pores, through which massive amounts of gaseous exchange takes place in leaves for the purpose of photosynthesis.

Source: Life Processes, Section 5.2.1

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The textbook states: "Massive amounts of gaseous exchange takes place in the leaves through these pores (stomata) for the purpose of photosynthesis." In a standard leaf cross-section diagram, label II typically points to the stomatal pore/guard cells region. Examiners expect you to link gaseous exchange directly to stomata, not to mesophyll or epidermal cells. Remember: guard cells control the opening and closing of stomatal pores.

(b) Stomach and anus

The exit of food from the stomach is regulated by a sphincter muscle, and the exit of waste material from the body is regulated by the anal sphincter.

The passage explicitly mentions two sphincter muscles: one at the exit of the stomach (regulating food entering the small intestine) and the anal sphincter (regulating removal of waste via the anus). No sphincter is mentioned at the oesophagus, small intestine, or large intestine junction in this context. Always look for exact terminology in the source text for MCQs.

Source: Life Processes, Section 5.2.4

(i) Exhaled air contains a much higher concentration of CO₂ (about 4%) compared to atmospheric air (about 0.04%). Lime water turns milky due to the reaction:

$$\text{Ca(OH)}_2 + \text{CO}_2 \rightarrow \text{CaCO}_3\downarrow + \text{H}_2\text{O}$$

Since exhaled air has approximately 100 times more CO₂ than atmospheric air, the lime water in diagram (II) turns milky much faster than in diagram (I). The syringe in diagram (I) pushes in air with very little CO₂, so it takes considerably longer for the lime water to turn milky.

(ii)

Diagram of Open Stomatal Pore:

```
[Guard Cell] [Guard Cell]
(I) (I)
___________ ___________
| • • • | | • • • |
| Chloroplast| |Chloroplast|
|___(II)____| PORE |___(II)____|
←— Stomatal opening —→
```

(Label: (I) Guard cells, (II) Chloroplast)

Two functions of stomata:

1. Exchange of gases (CO₂ and O₂) between the plant and the atmosphere.
2. Transpiration — loss of water vapour through stomatal pores.

Source: Life Processes, Chapter 5, Section 5.3

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• For part (i), the key idea is the difference in CO₂ concentration between atmospheric and exhaled air. Examiners expect you to state this clearly and may award marks for the chemical equation of lime water turning milky.
• For part (ii), draw a simple neat diagram showing two bean-shaped guard cells with dots representing chloroplasts inside them and a pore between them. Labels must be clear. The two functions (gas exchange and transpiration) are standard textbook points — both must be stated to get full marks.

Aim: To demonstrate that CO₂ is essential for photosynthesis.

Materials Required: Two healthy potted plants, two bell jars, two glass plates, watch-glass, potassium hydroxide (KOH), vaseline, iodine solution, alcohol.

Procedure:

1. Keep both potted plants in a dark room for three days to destarch them.
2. Place each plant on a separate glass plate. Place a watch-glass containing KOH beside Plant A (KOH absorbs CO₂). Leave no KOH beside Plant B.
3. Cover both plants with separate bell jars. Seal the base with vaseline to make the setup airtight.
4. Keep both plants in sunlight for two hours.
5. Pluck a leaf from each plant; boil in water, then in alcohol to remove chlorophyll. Test with iodine solution.

Observation:

• Leaf from Plant A (with KOH) — no blue-black colour with iodine (no starch formed).
• Leaf from Plant B (without KOH) — turns blue-black (starch present).

Conclusion: Plant A, deprived of CO₂, could not perform photosynthesis and hence produced no starch. This proves that carbon dioxide is essential for photosynthesis.

Source: Life Processes, Activity 5.2

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• Examiners expect a named setup (bell jar + KOH), a clear control (Plant B without KOH), and the starch test as the detection method.
• State observations for both plants separately — this earns dedicated marks.
• The conclusion must explicitly link absence of CO₂ → no starch → CO₂ essential for photosynthesis.
• KOH's role (absorbing CO₂) should be mentioned; it is a key detail that differentiates Plant A from Plant B.

During intense running, oxygen supply to muscle cells becomes insufficient. The muscles then break down pyruvate into lactic acid (anaerobic respiration) instead of carbon dioxide and water. The build-up of lactic acid causes muscle cramps.

Difference from aerobic respiration:

• Anaerobic respiration occurs without oxygen; aerobic requires oxygen.
• Aerobic respiration completely breaks down glucose → CO₂ + H₂O, releasing more energy. Anaerobic respiration produces lactic acid and releases less energy.

Source: Life Processes, Section 5.3 Respiration

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The examiner expects two points: (1) reason for cramps = lactic acid build-up due to lack of oxygen, and (2) difference = no oxygen used, product is lactic acid (not CO₂ + H₂O), and less energy released. Both points are needed for full 2 marks. Don't confuse anaerobic in muscles (→ lactic acid) with anaerobic in yeast (→ ethanol + CO₂).

(D) Translocation

Translocation is the process by which soluble products of photosynthesis are transported in plants through phloem.

The key term here is translocation — transport of food (soluble products of photosynthesis) through phloem. Students often confuse it with transpiration (loss of water) or conduction (transport of water/minerals through xylem). Remember: xylem → water & minerals; phloem → food (translocation).

I notice sub-question (c) is incomplete — the two options (i) and (ii) are not provided. I'll answer (a) and (b) fully, and note the gap for (c).

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(a)
(i) Renal artery brings oxygenated blood to the kidney.
(ii) The cluster of thin-walled blood capillaries in the Bowman's capsule is called the glomerulus.

(b) The urinary bladder stores urine. It is under nervous control — the stretching of the bladder wall sends a signal to the brain, which initiates the urge to urinate.

(c) (Sub-question (c) options (i) and (ii) are missing from the question. Please provide the options so this part can be answered.)

Source: Life Processes, Excretion in Human Beings

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• Renal artery / glomerulus are standard one-word answers examiners expect; spelling must be correct.
• For (b), many students confuse hormonal and nervous control — urinary bladder is nervous (not hormonal). State the organ + type of control + a brief reason for full marks.
• For (c), once the options are provided, budget ~40–50 words (about 4 points) for a 2-mark answer.

Water absorbed by roots is transported to leaves through xylem vessels — a network of tube-like structures running from roots through the stem to leaves. This upward movement occurs due to transpiration pull: water evaporates from leaves through stomata, creating a suction force that pulls water continuously upward through the xylem.

The examiner expects two key points: (1) the tissue responsible — xylem, and (2) the driving force — transpiration pull (loss of water vapour through stomata creates suction). Both points are needed for full marks. Avoid vague terms like "absorbed by stem"; be specific about the mechanism.

Option A — Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

The textbook directly states: "Since ventricles have to pump blood into various organs, they have thicker muscular walls than the atria do." This confirms both the assertion and the reason, and the reason directly explains why ventricles have thicker walls. So option A is correct.

Option B: (i) Amino acids, (ii) glucose, (iii) fatty acids and glycerol.

Proteins are digested into amino acids, carbohydrates into glucose, and fats into fatty acids and glycerol — both end-products of fat digestion must be mentioned. Option A is wrong as it omits glycerol.

Terrestrial animals breathe through lungs, while fishes breathe through gills.

This is a straightforward 1-mark factual difference. Just name the organ for each — lungs for terrestrial animals, gills for fishes. No extra detail needed.

In respiration, CO₂ is released as a by-product of breaking down glucose. In photosynthesis, O₂ is released as a by-product when water molecules are split during the process.

The examiner expects one clear contrasting line naming the gas released in each process. Respiration → releases CO₂; Photosynthesis → releases O₂. Avoid writing lengthy descriptions; just the gas and the process are enough for 1 mark.

In aerobic respiration, pyruvate breaks down into carbon dioxide and water. In anaerobic respiration (in human muscle cells), pyruvate converts into lactic acid.

The examiner wants only the products, not the full process. Remember: in humans, anaerobic breakdown gives lactic acid (not ethanol + CO₂, which is yeast). State one product per condition clearly.
Source: Chapter 5, Section 5.3 Respiration

Function of veins: Veins collect deoxygenated blood from different organs and bring it back to the heart.

Why no thick walls: The blood in veins is no longer under high pressure (unlike arteries), so thick elastic walls are not needed. Instead, veins have valves to ensure blood flows only in one direction toward the heart.

Source: Chapter 5, Section 5.4.1 – The tubes – blood vessels

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• Two points are expected: (1) function of veins and (2) reason for thin walls — each worth 1 mark.
• Key phrase examiners look for: "blood is no longer under pressure" + mention of valves (this distinguishes veins from arteries structurally).
• Don't confuse: arteries carry blood away from heart under high pressure → thick walls; veins carry blood back to heart under low pressure → thin walls + valves.

(C) Mucus and Pepsin

The gastric glands in the stomach wall release hydrochloric acid, pepsin (a protein-digesting enzyme), and mucus.

Source: Life Processes, section 5.2.4

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The passage clearly states: "These release hydrochloric acid, a protein digesting enzyme called pepsin, and mucus." Trypsin is secreted by the pancreas, not the stomach. Salivary amylase is released by the salivary glands. Mucus protects the stomach lining, and pepsin digests proteins — both come from gastric glands, making (C) correct.

(i) Rings of cartilage in the throat ensure that the air-passage (trachea) does not collapse, keeping it open for continuous airflow to the lungs.

(ii) When air is taken in (inhalation), the ribs move upward and outward, and the diaphragm moves downward and becomes flattened. These movements increase the volume of the chest cavity. As a result, air pressure inside decreases and air is sucked into the lungs, filling the expanded alveoli.

(iii) During heavy exercise, the muscle cells may not receive sufficient oxygen. In the absence of adequate oxygen, pyruvate (formed from glucose) is converted into lactic acid instead of being broken down aerobically. This lactic acid builds up in the muscle cells, causing muscle cramps. The cramps disappear once the oxygen supply is restored and lactic acid is broken down.

Source: Chapter 5, Section 5.3 — Respiration

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• (i) is a direct one-liner fact from the text — just state the function clearly.
• (ii) Name both structures (ribs AND diaphragm), state the direction of their movement, link it to increased chest volume → decreased pressure → air sucked in. Two marks = two clear steps.
• (iii) The key chain is: heavy exercise → lack of O₂ → anaerobic pathway in muscles → pyruvate → lactic acid → cramps. The word lactic acid is essential for full marks. Examiners also expect you to mention that it is a 3-carbon molecule (optional but good) and that it is the build-up that causes cramps.

(i) Herbivores like cows eat grass, which is rich in cellulose and difficult to digest, so they have a longer small intestine to allow complete digestion. Carnivores like tigers eat meat, which is easier to digest, so they have a shorter small intestine. Thus, the length of the small intestine is related to the type of food consumed.

(ii) The pancreas secretes pancreatic juice which contains enzymes that digest carbohydrates, proteins, and fats. Bile juice, produced by the liver and stored in the gall bladder, is released into the small intestine. It does not contain enzymes but helps in the emulsification of fats — breaking large fat globules into smaller ones — which makes it easier for enzymes to act on them. Bile also makes the medium alkaline, which is necessary for enzyme action.

(iii) The inner lining of the small intestine has finger-like projections called villi, which greatly increase the surface area for absorption. Villi have a rich network of blood vessels that absorb the digested food into the blood.

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• For (i), the key idea is herbivores vs. carnivores and the relative difficulty of digesting plant vs. animal material.
• For (ii), examiners expect two separate roles: pancreatic juice (enzyme-based digestion) and bile (emulsification + alkaline medium).
• For (iii), just name villi, state their function (increase surface area), and mention blood vessels — that covers 1 mark fully.

(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Animals lack the specific enzymes needed to break down coal, so no energy can be released from it for use by the body.

Both statements are correct and directly linked. The textbook states that heterotrophs use enzymes (bio-catalysts) to break down complex food substances. Coal is not a biological food material, so no enzyme exists to digest it, making energy extraction impossible. R correctly explains A — hence option (A) is the answer. Watch for traps: option (B) applies when both are true but unrelated; here the link is direct.

(B) Capillaries

The smallest blood vessels whose walls are one-cell thick are called capillaries.

The passage directly states: "The smallest vessels have walls which are one-cell thick and are called capillaries." Alveoli are air sacs in lungs (not blood vessels); arteries and veins have thick/multi-layered walls. Only capillaries are one-cell thick.

Source: Life Processes, Section 5.4.1 — The tubes: blood vessels

(D) Amount of water in guard cells

The guard cells swell when water flows into them, causing the stomatal pore to open, and close when guard cells shrink (lose water).

Source: Chapter 5, Section 5.2.1 Autotrophic Nutrition

The passage explicitly states: "The guard cells swell when water flows into them, causing the stomatal pore to open. Similarly the pore closes if the guard cells shrink." Examiners expect you to recall that it is the turgidity/flaccidity of guard cells (due to water content) that regulates stomatal movement — not CO₂, O₂, or temperature directly.

I notice sub-question (c) is incomplete — no actual question is stated under it. I will answer (a) and (b) fully, and note the issue for (c).

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(a) The process is Photosynthesis.

It is the process by which green plants (autotrophs) use sunlight, carbon dioxide, and water to prepare food (glucose) in the presence of chlorophyll.

(b) Chemical equation for photosynthesis:

$$6CO_2 + 6H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2$$

(c) The sub-question (c) appears to be incomplete/missing in the paper as provided — no question text follows "Answer the following." Please check the original question paper and re-submit the missing part so it can be answered correctly.

Source: Life Processes, Chapter 6 (Class 10 Science, NCERT)

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• (a) Examiners want the name + one-line definition of photosynthesis. Mention raw materials (CO₂, H₂O), energy source (sunlight), and site (chlorophyll).
• (b) Write the balanced chemical equation with reactants, products, and conditions (sunlight/chlorophyll) shown above the arrow. Losing the balance or omitting conditions costs marks.
• (c) Since the question text is missing, no answer can be given. In an exam, if a question is partially printed, inform the invigilator — never leave it blank without attempting what is visible.

(i) Plants do not have a pumping organ like the heart. Transport in plants occurs through diffusion and osmosis, which are passive and slow processes. Also, plants have low energy demands, so a slower transport system is sufficient.

(ii) Phloem transports food (sucrose/glucose) prepared by leaves during photosynthesis to all other parts of the plant — roots, stems, fruits, and seeds. This process is called translocation and requires energy (ATP).

• (i) Key point: no pump + passive transport = slow. Contrast with animals that have a heart and circulatory system for fast transport.
• (ii) Phloem = food transport (not water). Remember: Xylem = water/minerals (upward); Phloem = food (all directions). Mentioning "translocation" and "energy" scores full marks.

It is essential to plug leaks because loss of pressure in the blood vessels would reduce the efficiency of the pumping system.

Component: Platelets (thrombocytes)

Function: Platelets circulate in the blood and help clot the blood at the site of injury, thereby plugging the leak and preventing further blood loss.

Source: Life Processes, Chapter 5, Section 5.4.1 – Maintenance by platelets

The question has two parts — (1) reason beyond blood loss, and (2) name + function of the component. Examiners expect the pressure point specifically (not just "to stop bleeding") and both the name platelets and how they work (clotting). Mentioning "circulate around the body" adds accuracy but keep it concise for 2 marks.

(D) Cytoplasm and Oxygen deficient muscle cells

Step 'a' (Glucose → Pyruvate) occurs in the cytoplasm (glycolysis). Step 'b' (Pyruvate → Lactic acid) occurs in oxygen-deficient muscle cells during anaerobic respiration.

• Glycolysis always occurs in the cytoplasm — this is a fixed fact examiners test repeatedly.
• Lactic acid fermentation is specific to oxygen-starved muscle cells (not yeast — yeast produces ethanol + CO₂).
• Options B and C are wrong because aerobic/yeast pathways don't produce lactic acid.
• Option A is wrong because glycolysis does NOT occur in mitochondria.

(C) starch into simple sugars

Saliva contains the enzyme salivary amylase which breaks down starch into simple sugars. Less saliva means less amylase, so starch digestion in the mouth is affected.

Source: Life Processes, Section 5.2.4

The passage clearly states: "The saliva contains an enzyme called salivary amylase that breaks down starch… to give simple sugar." Proteins are digested by pepsin (stomach) and trypsin (small intestine); fats by lipase (small intestine). Option (D) is fermentation by yeast — not a digestive process. Examiners expect you to directly link saliva → salivary amylase → starch digestion.

(i) In these plants (desert plants), transpiration is minimised to help them survive in dry conditions. They do not open their stomata during the daytime, which reduces water loss through transpiration, enabling survival in desert conditions.

(ii) The stomata (stomatal pores) present on the surface of the leaf are responsible for the exchange of gases during photosynthesis. Carbon dioxide enters and oxygen exits through these tiny pores. In most plants, stomata open during the day, allowing CO₂ to diffuse directly into the leaf for photosynthesis.

Source: Life Processes, Nutrition — Photosynthesis section

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• (i): The passage clearly states these plants "do not open stomata during daytime to conserve water." Stomata closing = less transpiration. Examiners expect the word transpiration specifically.
• (ii): This is standard textbook knowledge linked to the passage — stomata are the gas-exchange structures. Even though the passage focuses on the special mechanism, the question asks about gas exchange in general during photosynthesis.
• Always quote or paraphrase the passage directly in source-based questions to show you've read it carefully.

In xylem tissue, vessels and tracheids have pits and perforations in their walls, allowing water to pass from cell to cell. The vessels are long, tube-like structures formed by the joining of many cells end-to-end, with cross walls dissolved away, forming a continuous hollow channel. Tracheids are interconnected through pits. These elements in roots, stems, and leaves are joined to each other, forming a continuous, unbroken network. Water absorbed by root hair cells moves laterally into the xylem and then travels upward through this network, reaching all plant parts.

Source: Life Processes, Transport in Plants section

---

• The question tests understanding of xylem as a continuous conducting system.
• Key points examiners expect: (1) structure of vessels (end-to-end cells, dissolved cross walls), (2) role of pits in tracheids, (3) continuity from roots → stems → leaves.
• Since no source passage directly covers this topic, use your textbook knowledge from Chapter 6 (Life Processes). The answer above reflects standard NCERT Class 10 content on this topic.
• Avoid writing vague lines like "they are connected to each other" — explain how (pits, perforations, hollow tubes).

(I)

| Organisms | Chambers | Type of blood | Type of circulation |
|---|---|---|---|
| Fish | (i) 2-chambered | Deoxygenated (single pass) | Single |
| (ii) Amphibians / Reptiles | 3-chambered | Mixed | Incomplete double circulation |
| Birds and Mammals | 4-chambered | Separated | (iii) Complete double circulation |

(II) Complete double circulation (found in birds and mammals) is the most efficient, as oxygenated and deoxygenated blood are completely separated, ensuring a highly efficient supply of oxygen to meet the high energy needs of warm-blooded animals.

Source: Chapter 5, Section 5.4.1 — Transportation in Human Beings

---

• (i) Fish have a 2-chambered heart (1 atrium + 1 ventricle); blood passes through the heart only once per cycle — single circulation.
• (ii) The organism with a 3-chambered heart that tolerates mixing is amphibians or many reptiles.
• (iii) In birds and mammals, blood passes through the heart twice per cycle — this is called double circulation; since there is no mixing, it is complete double circulation.
• For Part II, the examiner wants you to name the type and briefly justify it using the textbook reasoning (high energy needs, body temperature maintenance, complete separation of blood).

Aerobic respiration provides more energy.

In aerobic respiration, glucose is completely broken down in the presence of oxygen, releasing a large amount of energy in the form of ATP. Anaerobic respiration breaks down glucose only partially (in the absence of oxygen), releasing far less energy.

Source: Life Processes, Chapter 5 (What you have learnt)

---

• The source passage directly states: "Aerobic respiration makes more energy available to the organism."
• Examiners expect two things: (1) naming aerobic respiration as the correct type, and (2) giving the reason — complete breakdown of glucose using oxygen releases more ATP/energy compared to the incomplete breakdown in anaerobic respiration.
• Keep the answer concise; one sentence naming the type and one sentence giving the reason is sufficient for 2 marks.

(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).

Both statements are factually correct, but R describes what Bowman's capsule is — it does not explain why the filtration unit is a capillary cluster.

The Assertion is directly from the textbook: "the basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-walled blood capillaries." The Reason is also correct: "Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman's capsule." However, R merely names/describes the structure associated with the capillary cluster; it does not explain the assertion about capillaries being the filtration unit. Hence option (B) is correct.

(B) (i) and (iii)

Anaerobic respiration in human muscle cells occurs without oxygen, producing lactic acid — a 3-carbon molecule. Hence characteristics (i) and (iii) are correct.

• Anaerobic respiration in muscles does not require oxygen (so characteristic ii is wrong).
• It occurs in muscle cells when oxygen is insufficient (characteristic i ✓).
• Pyruvate → lactic acid, which is a 3-carbon molecule (characteristic iii ✓).
• Examiners expect you to recall that anaerobic respiration in humans produces lactic acid (3C), not ethanol.

A = Glucose (6-carbon molecule) breaks down in the cytoplasm into B = Pyruvate (3-carbon molecule).

Pyruvate then follows two pathways:

Anaerobic pathway:

• In yeast: Pyruvate → C = Ethanol + D = Carbon dioxide (fermentation)
• In muscles (lack of O₂): Pyruvate → E = Lactic acid

Aerobic pathway:

• In mitochondria (presence of O₂): Pyruvate → F = Carbon dioxide + Water + Energy (ATP)

Source: Chapter 5, Section 5.3 — Respiration

---

The examiner expects students to recall Figure 5.8 (Break-down of glucose by various pathways) from the textbook. Key points to remember:

• A and B are always the same regardless of pathway — glucose → pyruvate in cytoplasm.
• C & D are the anaerobic products in yeast (ethanol + CO₂).
• E is the anaerobic product in muscle cells (lactic acid — causes cramps).
• F represents aerobic end-products in mitochondria (CO₂ + H₂O + energy).
• Mention location (cytoplasm/mitochondria/yeast) for full marks.

(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Plasma transports CO₂ in dissolved form because CO₂ is more soluble in water than O₂, so O₂ must be carried by haemoglobin in RBCs.

The textbook states: "Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form. Oxygen is carried by the red blood corpuscles." The reason CO₂ can dissolve in plasma (water-based) while O₂ cannot is directly explained by the greater solubility of CO₂ in water — making R the correct explanation of A. Choose option (A).

(B) (ii) and (iii)

The correct events are: (iii) Absorption of light energy by chlorophyll, and (ii) Conversion of light energy to chemical energy (along with splitting of water into hydrogen and oxygen). Carbon dioxide is reduced (not oxidised) to carbohydrates, and water is produced by splitting, not formed from hydrogen and oxygen.

Source: Life Processes, Section 5.2.1

The textbook explicitly lists the three events of photosynthesis: absorption of light by chlorophyll, conversion of light energy to chemical energy + splitting of water, and reduction of CO₂ to carbohydrates. Statement (i) is wrong because CO₂ is reduced, not oxidised. Statement (iv) is wrong because water is split into hydrogen and oxygen, not formed from them. Examiners expect students to know these distinctions precisely.

(A) Starch

Carbohydrates not used immediately by plants are stored in the form of starch, which serves as the internal energy reserve.

Source: Life Processes, Section 5.2.1 Autotrophic Nutrition

---

The passage directly states: "The carbohydrates which are not used immediately are stored in the form of starch, which serves as the internal energy reserve." This is a direct recall question — just identify 'starch' as the correct option. Glycogen (not starch) is the storage form in animals, so don't confuse the two.

(a) Bowman's capsule is a cup-shaped structure surrounding the glomerulus in the nephron. It collects the filtrate (water, salts, glucose, urea) filtered from the blood under pressure.

(b) Because the remaining filtrate undergoes selective reabsorption in the tubular part of the nephron — useful substances like glucose, amino acids, salts, and most water are reabsorbed back into the blood. Only waste-laden fluid is excreted.

(c) Excretion is the process of removal of metabolic waste products from the body.
It is necessary because accumulated waste products like urea, CO₂, and excess salts are toxic and can disrupt normal cellular functions. Their removal keeps the internal environment (homeostasis) stable and ensures proper functioning of cells and organs.

Source: Life Processes, Excretion

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• (a) Describe both structure (cup-shaped, surrounds glomerulus) and function (collects filtrate) — each earns half mark.
• (b) Key term is selective reabsorption; mention what is reabsorbed (glucose, water, salts) to make the answer complete.
• (c) Give the definition first, then explain why it is necessary — the 2 marks are split between definition and necessity. Use terms like "toxic waste", "homeostasis" or "proper functioning" to score full marks.

Double circulation means blood passes through the heart twice in one complete cycle.

1. Pulmonary circulation: De-oxygenated blood from the body → right atrium → right ventricle → lungs (for oxygenation).
2. Systemic circulation: Oxygenated blood from lungs → left atrium → left ventricle → pumped to the rest of the body.

This separation prevents mixing of oxygenated and de-oxygenated blood, ensuring efficient oxygen supply.

Source: Chapter 5, Section 5.4.1

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• Examiners expect both circuits named (pulmonary + systemic) and the correct sequence of chambers involved in each.
• The key phrase "blood passes through the heart twice" defines double circulation and should appear.
• Mentioning that this prevents mixing of oxygenated/de-oxygenated blood shows conceptual understanding — worth the extra half-mark.
• Do not confuse left and right sides: oxygenated blood returns to the left side; de-oxygenated blood enters the right side.

Nutrition in Amoeba (Fig. 5.5):

```
Food particle
↓
Pseudopodia extend → surround food → Food-vacuole formed
↓
Digestion inside vacuole (complex → simple substances)
↓
Simple substances diffuse into cytoplasm
↓
Undigested material expelled out of cell
```

The temporary finger-like extensions (pseudopodia) engulf the food particle, forming a food-vacuole where digestion occurs.

Source: Chapter 5, Section 5.2.3

---

• CBSE expects a labelled diagram (even a rough schematic) showing the steps: pseudopodia formation → food-vacuole → digestion → diffusion → egestion.
• Key terms to include: pseudopodia, food-vacuole, cytoplasm, diffusion.
• Since the actual textbook figure (Fig. 5.5) cannot be drawn in text, showing a sequential flow diagram with labels earns full marks.
• Do not confuse Amoeba's nutrition with Paramoecium (which uses cilia at a fixed spot).

(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

The textbook states: "The lining of canal has muscles that contract rhythmically in order to push the food forward. These peristaltic movements occur all along the gut." — R directly explains why A is true, making option (A) correct.

(D) Glucose → Pyruvate →(Lack of oxygen) Lactic acid + Energy

In muscle cells, when oxygen is lacking, pyruvate is converted to lactic acid (not ethanol). Ethanol + CO₂ is produced in yeast, not muscles.

Source: Life Processes, Section 5.3 Respiration

The key distinction: anaerobic respiration in muscles produces lactic acid, while anaerobic respiration in yeast produces ethanol + CO₂. Options A and C describe yeast fermentation. Option B describes aerobic respiration. Examiners frequently test this difference, so always specify the organism/tissue when writing about anaerobic respiration.

(C) Guard cells

Guard cells control the opening and closing of the stomatal pore by changing their water content, causing them to swell or shrink.

Guard cells are specialised cells surrounding each stoma. They regulate stomatal movement by changing their turgidity. Epidermal cells form the outer covering; chloroplasts are organelles involved in photosynthesis. Stomata is the pore itself, not the controlling structure. Examiners expect students to distinguish between the pore (stomata) and the cells that regulate it (guard cells).

Nephron is the structural and functional unit of the kidney (excretory system) that filters blood. Neuron is the structural and functional unit of the nervous system that transmits electrical impulses.

This is a 1-mark difference question, so one clear contrasting point is sufficient. The examiner expects you to identify what each unit belongs to (kidney vs. nervous system) and its basic function (filtration/excretion vs. impulse transmission). Avoid writing lengthy descriptions.

The diaphragm is a dome-shaped muscular partition that separates the chest cavity from the abdominal cavity. It is present below the lungs in the thoracic region.

Function: When the diaphragm contracts, it flattens and moves downward, increasing the volume of the chest cavity. This causes air to rush into the lungs (inhalation). When it relaxes, it moves upward, decreasing chest volume, forcing air out (exhalation). Thus, it plays a key role in the breathing mechanism.

---

The diaphragm is not explicitly detailed in the source passages provided, but it is a standard part of the CBSE Class 10 Chapter 5 (Life Processes) curriculum on human respiration. Examiners expect students to mention two things: (1) its location (below the lungs / between thoracic and abdominal cavity) and (2) its function in breathing (contraction → inhalation; relaxation → exhalation). Both points carry 1 mark each. Avoid writing only one aspect.

Option C — Assertion (A) is true, but Reason (R) is false.

Haemoglobin in RBCs is indeed the respiratory pigment in humans. However, haemoglobin has a high affinity for oxygen, not carbon dioxide. CO₂ is transported mainly in dissolved form in plasma.

The Assertion is correctly stated — haemoglobin is the respiratory pigment present in red blood cells (RBCs). The Reason is factually wrong: haemoglobin binds strongly to oxygen (and carries it to body cells); carbon dioxide is transported primarily dissolved in plasma, not bound to haemoglobin. Since R is false, option C is correct. Remember this distinction — a common exam trap.

Answer: (B) Trypsin digests proteins and lipase digests emulsified fats.

The textbook (section 5.2.4) explicitly states: "The pancreas secretes pancreatic juice which contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats." Options A, C, and D incorrectly swap or combine these functions. Always remember: trypsin → proteins; lipase → emulsified fats.

B. Stomata

Stomata are tiny pores present on the surface of leaves through which massive amounts of gaseous exchange takes place.

The source passage (Chapter 5, Section 5.2.1) explicitly states that "Massive amounts of gaseous exchange takes place in the leaves through these pores (stomata)." Xylem transports water, phloem transports food, and the cuticle prevents water loss — none are responsible for gaseous exchange.

(a) Diagram of Nephron:

```
Bowman's Capsule
|
Glomerulus (capillary cluster)
|
Proximal Convoluted Tubule (PCT)
|
Loop of Henle
|
Distal Convoluted Tubule (DCT)
|
Collecting Duct
```

(A well-labelled diagram should show: Bowman's capsule, Glomerulus, PCT, Loop of Henle, DCT, and Collecting duct — at least 4 parts labelled.)

---

(b) Role of capillary cluster (Glomerulus) inside Bowman's capsule:

The capillary cluster inside the Bowman's capsule is called the glomerulus. Blood is filtered here under high pressure. Water, glucose, amino acids, urea, and salts pass from the blood into the Bowman's capsule as filtrate. This process is called ultrafiltration.

---

(c) Selective Reabsorption:

As the filtrate passes through the tubular part of the nephron, useful substances such as glucose, amino acids, salts, and water are reabsorbed back into the blood capillaries surrounding the tubule. This process of absorbing only useful substances (and not waste like urea) back into the blood is called selective reabsorption.

---

• The diagram carries most marks in part (a); label at least 4 parts clearly with arrows.
• For (b), the key terms examiners look for are glomerulus, filtration/ultrafiltration, and the substances filtered (glucose, urea, salts, water).
• For (c), stress the word "selective" — not everything is reabsorbed; only useful substances are, while wastes remain in the filtrate. This distinction is what earns marks.

(a) Labelled diagram of stomatal pore:

```
Guard cell Guard cell
\ /
======[ OPEN PORE ]======
(Chloroplasts present in guard cells)

======[CLOSED PORE]======
| |
Guard cell Guard cell
(flaccid) (flaccid)
```

(Draw two kidney-shaped guard cells — one pair showing an open pore between them, another pair tightly pressed together showing a closed pore. Label: guard cells, stomatal pore, epidermal cells.)

---

(b) Main events during photosynthesis:

1. Absorption of light energy by chlorophyll present in chloroplasts.
2. Splitting of water molecules (photolysis) into hydrogen and oxygen using light energy; oxygen is released as a by-product.
3. Conversion of CO₂ into glucose (carbon fixation) using the absorbed light energy and hydrogen from water.

---

(c) Balanced chemical equation for photosynthesis:

$$6CO_2 + 6H_2O \xrightarrow{\text{Sunlight, Chlorophyll}} C_6H_{12}O_6 + 6O_2$$

Carbon dioxide + Water → Glucose + Oxygen

---

• For (a): Draw clearly; examiners award marks for correct labels — guard cells, stomatal pore, epidermal cells — and showing both open and closed states. Neat diagrams score full marks even without artistic perfection.
• For (b): Three events (absorption of light, photolysis of water, carbon fixation/glucose formation) are the key points examiners look for. Mentioning chlorophyll and chloroplasts adds accuracy.
• For (c): The equation must be balanced (6CO₂, 6H₂O, C₆H₁₂O₆, 6O₂) and must show sunlight and chlorophyll as conditions above the arrow. Missing conditions or an unbalanced equation loses marks.

The pancreas acts as both an exocrine and an endocrine gland.

• Exocrine function (affected): A blockage in the pancreatic duct will prevent pancreatic juice (containing enzymes like trypsin and lipase) from reaching the small intestine, thus hampering digestion of proteins and fats.
• Endocrine function (unaffected): The secretion of insulin directly into the blood does not depend on the pancreatic duct, so blood sugar regulation continues. However, since Varun is diabetic, his insulin secretion is already impaired.

Source: Chapter 5, Section 5.2.4 – Nutrition in Human Beings

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• The key distinction here is exocrine (duct-dependent) vs endocrine (ductless, directly into blood).
• Examiners expect students to name the affected enzymes (trypsin, lipase) and state that digestion will be impaired.
• Mentioning insulin and that endocrine function is unaffected by the duct blockage earns the second mark.
• The diabetes reference in the question is a hint to link back to insulin/endocrine function — address it briefly.

Transpiration is called a "necessary evil" because:

1. Evil (harmful): Plants lose large amounts of water through stomata during transpiration, which can cause wilting and water stress, especially in dry conditions.

1. Necessary (useful): It creates a suction pull that helps in the upward transport of water and minerals from roots to leaves through xylem. It also helps in cooling the plant.

The phrase "necessary evil" means something harmful but unavoidable because it also brings benefits. Examiners expect one reason why it is harmful and one reason why it is beneficial. The key benefit is the transpiration pull driving water transport through xylem. Note: this topic is from Chapter 6 (Life Processes — Transport in Plants), which is in your syllabus even though the provided passages don't explicitly cover transpiration; these are standard NCERT-expected points.

(D) contraction of left ventricle

When the muscular left ventricle contracts, the oxygen-rich blood received from the left atrium is pumped out to the rest of the body.

Source: Life Processes, Section 5.4.1

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The key sequence to remember: lungs → left atrium → left ventricle → body. The left ventricle contracts to push oxygenated blood into the aorta and out to the body. The right side handles deoxygenated blood going to the lungs — a common distractor. Examiners expect you to identify the correct chamber (ventricle, not atrium) and the correct side (left, not right).

(C) By breaking down the nutrients of bread outside the body and then absorbing them.

The textbook (Chapter 5, Section 5.2.2) explicitly states: "Some organisms break down the food material outside the body and then absorb it. Examples are fungi like bread moulds, yeast and mushrooms." This is the key fact examiners expect. Options A, B, and D are incorrect — fungi are not autotrophs, do not eat, and do not consume other organisms.

Source: Chapter 5, Section 5.2.2 — Heterotrophic Nutrition