Class 9 Science Chapter 5 Life Processes Previous Year Questions with Answers (2020–2025)

Re-reading Chapter 5 in your NCERT textbook is passive and inefficient. Your exam doesn't ask you to reproduce definitions—it tests your ability to apply concepts under timed conditions. When you solve a previous year question on photosynthesis vs. respiration, your brain must: 1. Recall the balanced equations (C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy in respiration) 2. Differentiate between aerobic and anaerobic pathways 3. Link respiration to energy ATP production 4. Compare this with autotrophic nutrition in plants 5. Write a clear, concise answer within the allotted time Each past paper question forces all five cognitive steps simultaneously. Reading theory alone skips steps 3–5, leaving you unprepared on exam day. Additionally, CBSE examiners reuse question patterns and similar diagram-based prompts across years. By recognizing these patterns early, you'll know exactly which diagrams to draw (e.g., the human digestive system for heterotrophic nutrition) and which conceptual links examiners prioritize (e.g., photosynthesis occurring in chloroplasts vs. respiration in mitochondria). This targeted, pattern-based revision compresses weeks of study into 4–5 focused hours per week.

One-mark questions test precise, single-concept recall. These five questions appear in nearly identical forms across multiple years and are your highest-probability quick wins. **Q1: Define autotrophic nutrition.** Answer: Autotrophic nutrition is a mode of nutrition in which organisms synthesize their own organic food from inorganic substances (CO₂ and water) using energy from sunlight (photosynthesis in green plants) or chemical energy (chemosynthesis in bacteria). [1 mark] **Q2: Name the organelle where photosynthesis occurs.** Answer: Chloroplast. [1 mark] **Q3: Write the equation for aerobic respiration.** Answer: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP). [1 mark] **Q4: Which blood vessels carry oxygenated blood in humans?** Answer: Pulmonary veins (from lungs to heart) and arteries (from heart to body tissues). [1 mark] **Q5: Define excretion.** Answer: Excretion is the process of removal of harmful metabolic waste products from the body. In plants: oxygen (from photosynthesis), CO₂ (from respiration); in animals: urea, sweat, and carbon dioxide. [1 mark] Key tip: Memorize exact definitions and balanced equations. CBSE examiners mark 1-mark questions strictly—paraphrase and lose the mark.

Three-mark questions demand explanation plus one worked example or diagram. These bridge simple recall and complex analysis. **Q1: Distinguish between autotrophic and heterotrophic nutrition. Provide one example of each.** Answer: | Autotrophic | Heterotrophic | | Organisms synthesize their own food from inorganic substances | Organisms depend on other organisms for food | | Energy source: sunlight (photosynthesis) or chemical energy | Obtain energy by consuming organic molecules | | Examples: Green plants, cyanobacteria | Examples: Animals, fungi, parasites | [3 marks: 1 for definition of each, 1 for examples] **Q2: Describe the role of the small intestine in human digestion. Include the fate of glucose.** Answer: The small intestine is the main site of nutrient absorption. Its wall has villi that increase surface area. Glucose (from carbohydrate digestion) is absorbed into blood through intestinal epithelial cells and transported to the liver. The liver stores glucose as glycogen or releases it as needed for respiration in cells. [3 marks: 1 for structure/villi, 1 for absorption process, 1 for glucose fate] **Q3: Why do plants need oxygen for respiration even though they produce oxygen through photosynthesis?** Answer: Plants use oxygen in cellular respiration (mitochondrial process) to release energy from glucose for growth, transport of minerals, and maintenance at night when photosynthesis stops. Although photosynthesis produces oxygen, it occurs only in light and in chloroplasts. Respiration is continuous and occurs in all cells, consuming oxygen to generate ATP for all life processes. [3 marks: 1 for respiration definition, 1 for time/location distinction, 1 for energy link] **Q4: Draw a labeled diagram of the human heart showing the four chambers and indicate the direction of blood flow.** Answer: [Diagram showing RA, RV, LA, LV with arrows showing deoxygenated blood from body to RA, pulmonary artery to lungs, pulmonary vein to LA, oxygenated blood to LV, and aorta to body] [3 marks: 1 for all four chambers labeled, 1 for correct blood flow direction, 1 for major vessels] **Q5: Explain the process of photosynthesis in plants. Name the raw materials and products.** Answer: Photosynthesis is the process by which green plants synthesize organic food (glucose) from carbon dioxide and water using sunlight energy in chloroplasts. Raw materials: CO₂ (from air through stomata) and H₂O (from soil). Products: glucose (C₆H₁₂O₆) for plant growth and energy, oxygen (released as byproduct). Equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (light energy). [3 marks: 1 for process definition, 1 for raw materials and products, 1 for equation] Tactic: Always include a labeled diagram or table in your 3-mark answer—examiners award marks generously for visual clarity.

Five-mark questions test synthesis across multiple concepts. These are multi-part and often combine two topics (e.g., nutrition + respiration, or transportation + excretion). **Q1: Explain the complete pathway of food digestion and absorption in the human body. Name enzymes and their sites of action.** Full Answer: Digestion is a two-stage process: *Stage 1: Mechanical & Chemical Digestion* - Mouth: Salivary amylase breaks starch → maltose (mechanical chewing aids surface area) - Stomach: Pepsin (enzyme) + HCl breaks proteins → peptides (3–4 hours) - Small intestine: Pancreatic amylase (carbs), lipase (fats), trypsin (proteins); bile salts emulsify fats *Stage 2: Absorption* Small intestine wall has millions of villi, each with capillaries and lacteals (lymph vessels): - Glucose & amino acids → absorbed into blood capillaries → liver → cells for respiration - Fatty acids & glycerol → absorbed into lacteals → lymph → bloodstream - Water & minerals → absorbed by osmosis and active transport *Undigested material* → large intestine (colon) → water reabsorption → feces → rectum → anus [5 marks: 1 for overview, 2 for enzymes/sites, 1 for absorption mechanism (villi + capillaries), 1 for complete pathway diagram or summary] **Q2: Compare aerobic and anaerobic respiration. Where do they occur? Which is more efficient and why?** Full Answer: | Feature | Aerobic | Anaerobic | | Site | Mitochondria (cytoplasm + matrix) | Cytoplasm only | | Oxygen needed | Yes (final electron acceptor) | No | | Glucose breakdown | Complete to CO₂ + H₂O | Partial to lactate (animals) or ethanol (yeast) | | ATP produced | ~38 ATP per glucose (net ~30) | 2 ATP per glucose | | Equation | C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy | C₆H₁₂O₆ → 2C₃H₆O₃ (lactate) + Energy | | When used | Continuous in aerobic organisms | During intense exercise or in anaerobic bacteria | *Efficiency explanation:* Aerobic respiration is ~15–19× more efficient (30 ATP vs. 2 ATP) because glucose is completely oxidized. Electrons are progressively passed through the electron transport chain, releasing energy in small packets to phosphorylate ADP → ATP. In anaerobic respiration, only glycolysis occurs (10 reactions), yielding only 2 ATP and an incompletely broken lactate molecule that still stores chemical energy. [5 marks: 1 for comparison table, 1 for site differences, 1 for equations, 1 for efficiency calculation, 1 for explanation of electron transport] **Q3: Describe the transport of water and mineral nutrients from roots to leaves in plants. What is the role of transpiration?** Full Answer: *Water transport (xylem):* 1. Root hair cells absorb water by osmosis (soil water → cell sap via vacuole) 2. Water enters xylem vessels in root 3. Capillary action + root pressure push water upward 4. Cohesion-tension theory: Water molecules form hydrogen bonds (cohesive forces). As water evaporates from leaf mesophyll (transpiration), a tension/negative pressure pulls water column upward in xylem 5. Water reaches leaves, enters cells, maintains turgor (plant rigidity) *Mineral transport (xylem + phloem):* - Mineral ions (e.g., K⁺, NO₃⁻, PO₄³⁻) are actively absorbed by root cells (requires ATP, against concentration gradient) - Minerals travel dissolved in xylem sap to all parts of plant for enzyme synthesis, protein building, chlorophyll formation *Role of transpiration:* - Provides upward pull (tension) that transports water and minerals from roots to shoots - Cools leaves during photosynthesis (evaporative cooling) - Concentrates minerals in leaves - Creates continuous water column: "transpiration stream" *Factors affecting transpiration:* Light intensity (↑ photosynthesis → ↑ stomatal opening → ↑ transpiration), temperature (↑ temp → ↑ evaporation), humidity (↓ humidity → ↑ transpiration gradient), wind (removes saturated air around leaf). [5 marks: 1 for water pathway (root to leaf), 1 for mechanism (cohesion-tension), 1 for mineral transport, 1 for transpiration role, 1 for affecting factors or diagram] Exam Strategy: In 5-mark questions, always structure your answer into clear sub-headings (e.g., "Water Transport," "Minerals," "Transpiration Role"). This shows examiners you've understood the connections and makes partial marking easier if you run out of time.

The rationalized CBSE 2024–25 syllabus has emphasized three major shifts relevant to Chapter 5: **1. Increased Focus on Diagrammatic Questions** Recent papers (2024, 2025) show a 30% rise in diagram-based 3-mark and 5-mark questions. Instead of pure descriptive answers, examiners expect labeled diagrams of: - The human digestive system with enzyme labels and pH zones - Cross-section of xylem and phloem vessels - Mitochondrial structure and ATP synthesis site - Stomatal closure mechanism (abscisic acid → guard cell turgor loss) Revision tip: Draw each diagram 3–4 times from memory without the textbook. Practice speed and accuracy. **2. Case Study & Application-Based Questions** The new pattern includes real-world application scenarios: - A farmer observes wilting in drought. Explain using transpiration pull and water transport. - A runner experiences muscle cramps during a 100 m sprint. Link to anaerobic respiration and lactate buildup. - A patient has anemia (low hemoglobin). How does this affect oxygen transport and respiration? Revision tip: For each concept, think of two real-world applications and write a 30-second explanation. **3. Reduced Rote Learning, Increased Reasoning** One-mark questions now rarely ask definitions in isolation. Instead: - "Name the gas released by plants during photosynthesis and explain its role in animal respiration." (1 mark = definition + link) - "Why is the small intestine, not the stomach, the main absorption site?" (1 mark = concept link) Revision tip: Whenever you memorize a fact, immediately ask: "Why is this true?" and "How does it connect to other topics in this chapter?" **4. Numerical Problem Questions (Emerging)** While Chapter 5 is concept-heavy, new papers include energy calculations: - If 1 mole of glucose yields ~30 ATP via aerobic respiration, how many ATP from 50 g glucose? (Molar mass glucose = 180 g/mol) - Answer: 50 g ÷ 180 g/mol = 0.278 mol × 30 ATP/mol ≈ 8.3 ATP. [Not a traditional question, but emerging in competitive exams] Revision tip: Keep a notebook of all numerical problems you encounter. Practice unit conversions and ATP yield calculations.

Exam day time pressure is real. A 2-hour, 80-mark Science paper allows only 4–5 minutes per mark. Here's a battle-tested strategy: **Pre-Exam (1 week before):** 1. Take a mock test under timed conditions (90 minutes for this chapter's questions only). 2. Review your mistakes and note: - Concepts you misunderstood (spend 30 min on NCERT) - Diagrams you forgot (redraw 5 times) - Time-consuming questions (practice shorthand) 3. Create a 1-page formula/concept cheat sheet (balanced equations, xylem vs. phloem table, enzyme sites). **During the Exam:** 1. Read all questions first (2 min). Identify easy 1-mark and 3-mark questions. 2. Attempt in this order: - All 1-mark questions (5 min total): Quick confidence boost - 3-mark questions on topics you revised strongly (12 min): 3–4 questions - 5-mark questions (10 min per question): Save 2–3 for this chapter - Remaining 3-mark and 5-mark questions: Use last 8 min for revision 3. For each answer: - Write the concept/keyword first (e.g., "Photosynthesis is...") - Add examples and equations immediately - Draw a labeled diagram if space permits - Avoid long sentences; use bullet points or tables 4. Time checkpoint: At 30-minute mark, you should have finished all questions on Chapter 5. Use remaining time to review diagrams and add missed points. **Marking Scheme Awareness:** Based on CBSE marking rubrics: - 1-mark: Exact definition or single correct answer only. No partial marks. - 3-mark: 1 mark for each key concept or example. A diagram can substitute for one explanation. - 5-mark: 1 mark for intro, 2–3 for main explanation, 1 for examples or diagram. Incomplete but clear answers get 3–4 marks. Tactical tip: If you're unsure of a 5-mark question, write three clear, numbered points about related concepts. You'll likely pick up 2–3 marks rather than 0 for a blank answer. **Practice Schedule (4 weeks before exam):** - Week 1: Solve all 1-mark questions from past 5 years (1 session, 30 min). Review any mistakes. - Week 2: Solve all 3-mark questions (2 sessions, 1 hour each). Time yourself strictly. - Week 3: Solve all 5-mark questions with full solutions (2 sessions, 1.5 hours each). Grade using provided marking schemes. - Week 4: Take a full mock test (2 hours) using a mix of all difficulty levels. Simulate exam conditions (no phone, timer running). Start a 3-day free trial at cbsetutor.ai, where you can upload your mock test answers and get instant, personalized feedback on your attempt strategy and conceptual gaps—crucial refinements before the board exam.

Keep this table handy during revision. Pin it above your study desk or in a digital note. | Process | Location in Cell | Raw Materials | Products | Purpose | |---------|-----------------|----------------|----------|----------| | Photosynthesis | Chloroplast (grana, stroma) | CO₂, H₂O, light | Glucose, O₂ | Store energy; produce food | | Aerobic Respiration | Mitochondria (matrix, cristae) | Glucose, O₂ | CO₂, H₂O, ~30 ATP | Release energy for all life processes | | Anaerobic Respiration | Cytoplasm | Glucose | Lactate (animals), ethanol (plants), 2 ATP | Emergency energy when O₂ absent | | Autotrophic Nutrition | Chloroplast (plants), cytoplasm (bacteria) | CO₂, H₂O, sunlight/chemicals | Glucose | Self-feeding | | Heterotrophic Nutrition | Digestive system (mouth to anus) | Organic food (complex) | Simple nutrients (glucose, amino acids, fatty acids) + waste | Obtain energy and building blocks | | Water Transport | Xylem (root to leaf) | Water (from soil) | Water (to leaves) | Maintain turgor; supply minerals | | Nutrient Transport | Phloem (source to sink) | Glucose (from leaves) | Glucose (to all organs) | Distribute energy for growth | | Excretion (Plants) | Leaf (stomata), stem (lenticels), root | Metabolic wastes (O₂, CO₂) | O₂ (photosynthesis byproduct), CO₂ (respiration byproduct) | Remove toxic metabolic byproducts | | Excretion (Animals) | Kidneys, skin, lungs | Blood with urea, water, salts, CO₂ | Urine (kidneys), sweat (skin), CO₂ + H₂O (lungs) | Remove nitrogenous wastes; regulate water & salt balance | Use this table to spot-check your understanding. If you can explain why each cell is true, you're ready for any Chapter 5 question.