Class 9 Science Chapter 2 Nutrition in Animals MCQ with Answers (30 Solved Questions)

The rationalized CBSE Class 9 curriculum (2024–25) has shifted significantly toward objective questions. In Science, 40–50% of marks often come from MCQs in periodic assessments and unit tests. Why? MCQs test conceptual clarity, not memorization. They force you to distinguish between similar terms (e.g., ingestion vs. digestion vs. egestion), understand cause-and-effect relationships (e.g., why pepsin works only in the stomach's acidic environment), and apply knowledge across scenarios. Assertion-reason MCQs—increasingly common—demand two-level thinking: is the statement true, AND is the reason valid? Chapter 2 MCQs frequently test enzyme action in the human digestive system, the role of bile in fat digestion, rumination in herbivores, and dental adaptation to diet. A single mistake in identifying the correct enzyme or digestive organ can cost 1 mark. By practicing 30 graded MCQs, you internalize the exact wording used in CBSE textbooks and develop speed and confidence for the exam hall.

**1. Which mode of nutrition is shown by animals that eat only plants?** A) Omnivorous B) Herbivorous C) Carnivorous D) Parasitic ✓ **Answer: B** — Herbivorous animals consume only plant matter; cows and goats are classic examples. **2. The process by which food enters the mouth is called:** A) Digestion B) Absorption C) Ingestion D) Egestion ✓ **Answer: C** — Ingestion is the entry of food; digestion breaks it down chemically and mechanically. **3. Which organ secretes hydrochloric acid in humans?** A) Liver B) Pancreas C) Stomach D) Small intestine ✓ **Answer: C** — The stomach lining produces HCl to kill bacteria and activate pepsinogen → pepsin. **4. The enzyme that digests starch in the mouth is:** A) Pepsin B) Amylase C) Lipase D) Trypsin ✓ **Answer: B** — Salivary amylase (ptyalin) breaks down starch into simpler sugars in the mouth. **5. What is the pH of stomach acid?** A) 2–3 (acidic) B) 7 (neutral) C) 8–9 (alkaline) D) 10 (highly alkaline) ✓ **Answer: A** — The stomach's acidic environment (pH 2–3) is optimal for pepsin and HCl action. **6. Which teeth are adapted for cutting and tearing food?** A) Molars B) Premolars C) Incisors and canines D) Wisdom teeth ✓ **Answer: C** — Incisors cut; canines tear. Molars grind. Herbivores have enlarged molars; carnivores have sharp canines. **7. The bile is stored in which organ?** A) Liver B) Pancreas C) Gallbladder D) Duodenum ✓ **Answer: C** — Bile is produced in the liver but stored and concentrated in the gallbladder. **8. Small intestine is the site of:** A) Mechanical digestion only B) Maximum absorption of nutrients C) Secretion of pepsin D) Storage of bile ✓ **Answer: B** — The small intestine (duodenum, jejunum, ileum) absorbs ~90% of nutrients via villi and microvilli. **9. Which enzyme digests proteins in the stomach?** A) Amylase B) Pepsin C) Lipase D) Trypsin ✓ **Answer: B** — Pepsin (secreted as pepsinogen, activated by HCl) breaks proteins into peptides in the acidic stomach. **10. The process of removing undigested waste is called:** A) Ingestion B) Absorption C) Egestion D) Digestion ✓ **Answer: C** — Egestion is the expulsion of feces (undigested food) from the body via the anus.

**11. The small intestine receives secretions from two glands. Name them:** A) Liver and stomach B) Pancreas and gallbladder C) Liver and pancreas D) Salivary glands and liver ✓ **Answer: C** — The small intestine receives pancreatic juice (enzymes: trypsin, lipase, amylase) and bile from the liver. **12. Why is bile important in fat digestion?** A) It digests fats into fatty acids B) It emulsifies fats, increasing surface area for lipase action C) It neutralizes stomach acid D) It produces lipase ✓ **Answer: B** — Bile salts break large fat globules into smaller droplets (emulsification), allowing pancreatic lipase to act efficiently. **13. A cow is a ruminant because it:** A) Eats only grass B) Has four stomachs C) Regurgitates and re-chews food D) Has molars instead of canines ✓ **Answer: C** — Ruminants like cows regurgitate partially digested food (bolus), rechew it (rumination), and re-digest it. This allows efficient extraction of nutrients from cellulose. **14. The stomach of a cow has four chambers. Which chamber stores food temporarily?** A) Rumen B) Reticulum C) Omasum D) Abomasum ✓ **Answer: A** — The rumen is the largest chamber where food is stored and initially fermented by bacteria that digest cellulose. **15. Small intestine is longer in herbivores than carnivores because:** A) Herbivores need more time for absorption B) Plant material is harder to digest and requires extended fermentation C) Carnivores have larger livers D) Herbivores drink more water ✓ **Answer: B** — Plant cells have cellulose (undigestible by animal enzymes); herbivores have longer small intestines and rely on bacterial fermentation in the cecum or rumen. **16. Trypsin works best in which environment?** A) Acidic (pH 2–3) B) Neutral (pH 7) C) Alkaline (pH 8–9) D) Highly alkaline (pH 10+) ✓ **Answer: C** — Trypsin (pancreatic protease) is activated in the alkaline small intestine by enterokinase; pepsin works in acidic stomach. **17. The enzyme lipase digests fats into:** A) Glucose and fructose B) Amino acids C) Glycerol and fatty acids D) Maltose and sucrose ✓ **Answer: C** — Lipase breaks the ester bonds in triglycerides, producing glycerol and fatty acids for absorption. **18. The protein that transports oxygen in red blood cells is absorbed in the small intestine as:** A) Whole protein B) Amino acids (from digested protein) C) Peptides only D) Polypeptides ✓ **Answer: B** — Proteins are completely digested into amino acids in the small intestine via trypsin, chymotrypsin, and carboxypeptidases. Amino acids are then absorbed. **19. Carnivores have a short small intestine and a reduced cecum because:** A) They don't need to absorb nutrients B) Meat is easily digested; no bacterial fermentation of plant cellulose is needed C) They have larger livers D) They only eat at night ✓ **Answer: B** — Meat (animal protein) is readily digested by pepsin and trypsin without need for microbial fermentation. Carnivores retain food for less time. **20. Which of the following is NOT a function of the large intestine?** A) Absorption of water B) Secretion of mucus for lubrication C) Digestion of carbohydrates by bacterial action D) Secretion of digestive enzymes ✓ **Answer: D** — The large intestine absorbs water and minerals, secretes mucus, and hosts bacteria that produce vitamins (e.g., B12, K). It does NOT secrete digestive enzymes.

**21. Assertion: Pepsin can work optimally in the small intestine.** Reason: The small intestine provides a more acidic pH than the stomach. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: C** — Pepsin denatures (becomes inactive) above pH 6; the small intestine is alkaline (pH 8–9). Pepsin works ONLY in the stomach (pH 2–3). R is false. **22. Assertion: Bile salts are enzymes that break down fats.** Reason: They are secreted by the pancreas into the duodenum. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is false; R is false D) A is true; R is false ✓ **Answer: C** — Bile salts are NOT enzymes; they emulsify fats. Bile is secreted by the LIVER (stored in gallbladder), not the pancreas. Both A and R are false. **23. Assertion: Ruminants have a four-chambered stomach because they are herbivores.** Reason: Plant material contains cellulose, which requires time and microbial fermentation for digestion. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: A** — Herbivores evolved multi-chambered stomachs to house cellulolytic bacteria. The reason directly explains the assertion. **24. Assertion: A person with a damaged pancreas will fail to digest fats and proteins in the small intestine.** Reason: The pancreas secretes lipase and trypsin into the small intestine. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: A** — Without pancreatic enzymes (lipase, trypsin, amylase), fat and protein digestion severely impairs. R directly explains A. **25. Assertion: Herbivores need longer small intestines than carnivores.** Reason: Herbivores consume plant material with a lower nutrient density per unit mass. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is false; R is true D) A is true; R is false ✓ **Answer: A** — Herbivores require extended transit time and increased surface area for absorbing nutrients from less digestible plant matter. R logically explains A. **26. Assertion: Incisors in humans are adapted for cutting plant material.** Reason: Humans are primarily omnivorous and have relatively flat incisors. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: B** — Both statements are true, but R does NOT explain A. Flat incisors cut; the reason is omnivory, not tooth shape. They are independent truths. **27. Assertion: The small intestine has villi and microvilli to increase surface area for nutrient absorption.** Reason: The small intestine is the primary site of nutrient absorption in the digestive system. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: A** — The small intestine absorbs ~90% of nutrients. Villi and microvilli increase surface area for this function. R explains A. **28. Assertion: Salivary amylase is re-secreted in the pancreas as pancreatic amylase.** Reason: Both enzymes have the same function (breaking α-1,4-glycosidic bonds in starch). A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is false; R is true D) A is true; R is false ✓ **Answer: B** — Both enzymes break starch, but they are distinct proteins synthesized in different organs (salivary glands vs. pancreas). R does NOT explain A; they are separate molecules. **29. Assertion: Carnivores have a highly acidic stomach (pH ~2) and a short esophagus.** Reason: Meat is rich in protein and requires strong pepsin action for rapid digestion. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is false; R is true D) A is true; R is false ✓ **Answer: A** — Carnivores have acidic stomachs for efficient protein digestion. The short esophagus is an adaptation, but the reason (high protein diet) logically supports the assertion. **30. Assertion: A person with no gallbladder can still digest fats, but less efficiently.** Reason: The liver can still secrete bile into the duodenum even without gallbladder storage. A) Both A and R are true; R explains A B) Both A and R are true; R does NOT explain A C) A is true; R is false D) A is false; R is true ✓ **Answer: A** — Bile is continuously produced by the liver. Without the gallbladder (storage/concentration), bile release is continuous but dilute, reducing fat emulsification efficiency. R explains A.

**Trap 1: Confusing Enzymes with Their Functions** Example: "Pepsin digests carbohydrates" (FALSE—pepsin is a protease). Students often memorize enzyme names without remembering their substrate. Always verify: pepsin → protein, amylase → starch, lipase → fat, cellulase → cellulose (secreted by bacteria, NOT animals). **Trap 2: Reversing Enzyme-pH Relationships** Example: "Trypsin works best in acidic pH" (FALSE—it works in alkaline pH 8–9). Pepsin works in acidic pH 2–3. Students confuse these. Create a mental rule: stomach = acid + pepsin; small intestine = alkaline + trypsin/lipase/amylase. **Trap 3: Mixing Up Organ Locations and Functions** Example: "Bile is secreted by the pancreas" (FALSE—it's made by the liver, stored in gallbladder). Or "Trypsin is secreted by the stomach" (FALSE—it comes from the pancreas). Always link: liver → bile; pancreas → enzymes + bicarbonate; stomach → HCl + pepsinogen. **Trap 4: Overgeneralizing Herbivore vs. Carnivore Traits** Example: "All herbivores have four-chambered stomachs" (FALSE—some have single-chambered with a cecum, like horses). Ruminants (cows, sheep, goats) have four chambers. Non-ruminant herbivores have different adaptations. Never assume all herbivores share the same anatomy. **Trap 5: Assertion-Reason Pitfalls** Example: Both statements are true, but "R does NOT explain A." Many students pick (A) automatically if both seem correct. Always ask: Does the reason logically support the assertion? E.g., "Bile is important (true) because it is produced by the pancreas (false)." Both parts must be correct AND causally linked for answer (A). **Trap 6: Confusing Complete vs. Partial Digestion** Example: "Cellulose is completely digested in the human large intestine" (FALSE—humans lack cellulase enzymes; bacteria ferment it, but we cannot fully absorb it). Only animals with symbiotic bacteria (ruminants, some herbivores) "digest" cellulose efficiently. **Trap 7: Misinterpreting Tooth Adaptation** Example: "Canines in herbivores are large and sharp for tearing plants" (FALSE—herbivores have reduced canines; carnivores have large, sharp canines for tearing meat). Always match tooth morphology to diet: sharp canines → meat-eater; flat molars → plant-eater. **Trap 8: Overlooking the Role of Bacteria** Example: "The stomach digests all proteins enzymatically, no bacterial help needed" (PARTIALLY TRUE in humans, but INCOMPLETE). Humans rely on pepsin in the stomach and trypsin in the small intestine. Ruminants and herbivores rely heavily on bacterial fermentation for plant matter. Don't ignore microbial digestion in herbivores.

**Step 1: Read the Question Stem First (Not Options)** Spend 5–7 seconds understanding what the question asks. Is it asking for a definition, a function, an example, or a cause-and-effect relationship? Avoid jumping to options—they are designed to confuse. Example: "Why is the small intestine longer in herbivores?" Know you're looking for a reason related to digestion difficulty, not water absorption. **Step 2: Predict the Answer Before Reading Options** If you know pepsin works in the stomach at low pH, mentally say "pepsin = acidic stomach" before reading A, B, C, D. This prevents options from anchoring your thinking. **Step 3: Eliminate Obviously Wrong Options (Hard Negation)** In a typical MCQ, 1–2 options are clearly wrong. Example: "Amylase is secreted by the pancreas" — if you know amylase is secreted by salivary glands AND the pancreas, eliminate "salivary glands only." Each elimination narrows to 50–75% accuracy, fast. **Step 4: For Assertion-Reason MCQs, Evaluate Independently** — First, is the Assertion true? (Yes/No) — Second, is the Reason true? (Yes/No) — Third, does Reason CAUSE/EXPLAIN Assertion? (Yes/No) If all three are "yes," pick (A). If A is true but R is false, pick (C). Treat them as two separate statements first, then link them. **Step 5: Allocate Time Strategically** — Easy MCQs (like questions 1–10): 30–40 seconds each. Total: 5–7 minutes. — Medium MCQs (like questions 11–20): 50–70 seconds each. Total: 10–12 minutes. — Hard/Assertion-Reason MCQs (like questions 21–30): 80–100 seconds each. Total: 13–17 minutes. — Buffer/Review: 3–5 minutes to revisit flagged questions. **Total for 30 MCQs: ~25–30 minutes (realistic for a 90-minute exam block).** **Step 6: Flag & Revisit** If stuck on a question after 60 seconds, mark it with a mental flag and move on. Complete all MCQs, then return. Often, later questions prompt recall of earlier concepts. **Step 7: Use Process of Elimination for Guesses** If genuinely uncertain between two options, eliminate based on: (a) which organ/enzyme is more commonly tested? (b) Which matches the textbook language most closely? Example: Between "small intestine" and "duodenum," both are correct for nutrient absorption, but "small intestine" is the broader, safer answer unless the question specifically asks for the first region. **Practice Tip**: Solve these 30 MCQs under timed conditions (30 minutes for all 30). Repeat weekly until your accuracy reaches ≥85% and time drops to 25 minutes. Speed and accuracy together = exam readiness.

**Human Digestive Enzyme Lookup Table** | Enzyme | Source | Works Best In | Breaks Down | Product | |--------|--------|---------------|-------------|----------| | Salivary Amylase (Ptyalin) | Salivary Glands | Mouth (pH 6.8) | Starch (α-1,4 bonds) | Maltose, Glucose | | Pepsinogen → Pepsin | Stomach Lining | Stomach (pH 2–3) | Protein | Peptides, Polypeptides | | Pancreatic Amylase | Pancreas | Small Intestine (pH 8–9) | Starch | Maltose | | Trypsin | Pancreas | Small Intestine (pH 8–9) | Protein | Peptides, Amino Acids | | Chymotrypsin | Pancreas | Small Intestine (pH 8–9) | Protein | Peptides | | Lipase | Pancreas + Stomach | Small Intestine (pH 8–9) | Fat/Triglyceride | Glycerol + Fatty Acids | | Carboxypeptidase | Pancreas | Small Intestine (pH 8–9) | Polypeptides | Amino Acids | **Key Herbivore Adaptation: Cellulase** — Humans cannot produce cellulase (the enzyme that breaks cellulose). Ruminants harbor cellulolytic bacteria in the rumen that ferment plant material. This is why the small intestine of a cow is relatively shorter than expected but fermentation is compensated in the rumen (48–72 hours of microbial action). **Tooth Formula (Human Adult)** — Incisors: 2 per quadrant × 4 = 8 (sharp, for cutting) — Canines: 1 per quadrant × 4 = 4 (pointed, for tearing) — Premolars: 2 per quadrant × 4 = 8 (flat, grinding surface) — Molars: 3 per quadrant × 4 = 12 (flat, grinding surface) — **Total: 32 teeth** This table is a must-memorize reference for Class 9 exams. Screenshot or create flashcards.

You've now worked through 30 graded MCQs spanning all four topics of Chapter 2. Your next actions: 1. **Take the Full Quiz Again (Timed)** Re-solve all 30 MCQs in 30 minutes without looking at answers. Target ≥85% accuracy. If you score <75%, identify which topic (modes of feeding, human digestion, ruminant digestion, teeth) is weak and re-read that section in your NCERT textbook. 2. **Create Flashcard Sets** — Card 1: "Enzyme Name → Substrate, pH, Source" (e.g., Pepsin → Protein, pH 2–3, Stomach) — Card 2: "Organ → Functions" (e.g., Pancreas → secretes enzymes + bicarbonate) — Card 3: "Comparison Cards" (Herbivore vs. Carnivore anatomy) 3. **Link to Chapter 1 (Cell Structure)** Chapter 1 covered cell types. Recall that animal cells have lysosomes (containing hydrolytic enzymes for intracellular digestion). Chapter 2 expands to extracellular digestion in multicellular animals. This connection strengthens conceptual retention. 4. **Use Diagrams Actively** — Draw and label the human digestive system from mouth to anus. Mark where each enzyme works and its pH. — Sketch the four-chambered cow stomach (rumen, reticulum, omasum, abomasum) and trace food flow. — Compare human and carnivore tooth arrangements. Active drawing beats passive reading by 3×. 5. **Practice Assertion-Reason Questions Daily** Assertion-reason MCQs are the new CBSE norm. Spend 10 minutes daily on 2–3 assertion-reason pairs. Develop the habit of separating truth claims from causal relationships. 6. **Mock Exam Simulation** Once you're confident, simulate a full Science periodic test: 30 MCQs from Chapters 1–3, 30 minutes, no breaks. This trains exam stamina and time discipline. Many students excel in isolated practice but falter under exam stress. **Final Tip**: If your school uses a learning management system (LMS) or platform like BYJU'S or Khan Academy, cross-check your answers with their explanations. Different sources sometimes phrase enzyme functions slightly differently; aligning with your teacher's exact textbook language ensures exam compatibility.