Class 9 Science Chapter 6 Control and Coordination Previous Year Questions (2020–2025)

Reading your textbook twice won't improve your exam score. Past papers do. Here's why: (1) **Question patterns**: CBSE examiners repeat certain question types. For example, 'Name the hormone that controls blood glucose' or 'Draw and label a reflex arc' appear almost every year—but students who've only read theory often miss the exact wording CBSE expects. (2) **Time management**: Exams are timed. Working PYQs teaches you to answer a 1-mark question in 1–2 minutes, a 3-mark in 5 minutes, and a 5-mark in 8 minutes. (3) **Marking patterns**: CBSE reward specific keywords. For instance, in a 3-mark question on reflex action, you must mention 'sensory neuron → relay neuron → motor neuron' in sequence. Reading theory doesn't guarantee you'll write it that way. (4) **Confidence under pressure**: When you've solved the same question type three times before your exam, you walk in knowing exactly what to expect. (5) **Weak spots surface fast**: A PYQ reveals whether you truly understand plant hormones vs. animal hormones, or if you've just skimmed the chapter. Our curated list of 13 questions covers all marks—1, 3, and 5—so you're never surprised on exam day.

1-mark questions test immediate recall and definition. These five have appeared (or been rephrased) in multiple CBSE papers: **Q1: Which of the following is a plant hormone?** (a) Insulin (b) Auxin (c) Adrenaline (d) Testosterone **Answer: (b) Auxin** — Auxin promotes cell elongation and phototropism. Insulin, adrenaline, and testosterone are animal hormones. **Q2: The reflex arc does not involve the:** (a) Spinal cord (b) Brain (c) Sensory neuron (d) Motor neuron **Answer: (b) Brain** — A reflex arc is a direct sensory → spinal cord → motor pathway that bypasses the brain, allowing instant response (e.g., pulling your hand from a hot object). **Q3: Which gland secretes adrenaline?** (a) Pancreas (b) Thyroid (c) Adrenal (d) Pituitary **Answer: (c) Adrenal** — The adrenal medulla releases adrenaline during fight-or-flight responses. The pancreas secretes insulin; thyroid secretes thyroxine. **Q4: Gibberellins are plant hormones that promote:** (a) Root growth (b) Seed germination (c) Leaf fall (d) Stomatal closure **Answer: (b) Seed germination** — Gibberellins break dormancy and trigger seed sprouting. Abscisic acid (not gibberellin) promotes leaf fall. **Q5: The junction between two neurons is called:** (a) Axon (b) Dendrite (c) Synapse (d) Ganglion **Answer: (c) Synapse** — A synapse is the gap where neurotransmitters transmit signals from one neuron to the next.

3-mark questions demand explanation, examples, and structure. These five types recur in CBSE term exams: **Q1: Explain the reflex arc with a diagram. Why is it faster than a voluntary action?** **Answer:** A reflex arc is the pathway: Receptor → Sensory neuron → Spinal cord (relay neuron) → Motor neuron → Effector. When you touch a hot plate, sensory receptors send signals directly to the spinal cord, which immediately sends signals to muscles to pull your hand away—all without waiting for the brain to process. Voluntary actions (e.g., deciding to pick up a pencil) must travel from sensory organs → brain → motor cortex → muscles, adding extra steps and time. Thus, reflex actions take ~0.05 seconds; voluntary actions take ≥ 0.5 seconds. This protects organs from sudden harm. **Q2: Name three plant hormones and state one function of each.** **Answer:** (1) **Auxin** – Promotes cell elongation and controls phototropism (bending towards light). (2) **Gibberellin** – Promotes seed germination and stem elongation. (3) **Abscisic acid (ABA)** – Promotes stomatal closure during drought and dormancy in seeds. [Alternative: Ethylene – promotes fruit ripening; Cytokinin – promotes cell division.] **Q3: How do nervous and endocrine systems differ in terms of speed and duration of response?** **Answer:** The **nervous system** acts via electrical signals and neurotransmitters—responses are rapid (milliseconds to seconds) but short-lived. Example: adrenaline surge when you see danger; you react instantly but calm down within minutes. The **endocrine system** acts via hormones released into the bloodstream—responses are slower (seconds to minutes) but long-lasting. Example: growth hormone steadily increases height over months/years. The nervous system is like an emergency alarm; the endocrine system is like a slow thermostat. **Q4: A student's pancreas does not produce insulin. What will happen to her blood glucose levels and why?** **Answer:** Blood glucose will rise above normal (hyperglycemia) because insulin's role is to lower blood glucose by promoting uptake into cells and storage as glycogen. Without insulin, glucose accumulates in the blood and is excreted in urine (condition: diabetes mellitus type 1). Cells cannot access glucose for energy despite high blood levels. **Q5: Describe the role of the synapse in nerve impulse transmission.** **Answer:** A synapse is the junction between two neurons. When an impulse reaches the axon terminal (presynaptic neuron), neurotransmitters are released into the synaptic cleft (gap). These chemicals diffuse across and bind to receptors on the dendrite of the next neuron (postsynaptic), generating a new impulse. Synapses ensure one-way transmission, allow for signal amplification or dampening, and enable modulation of nerve signals. Some synapses are excitatory (promote firing); others are inhibitory (suppress firing).

5-mark questions test deep understanding, comparisons, and integration. These three are high-frequency: **Q1: With a labeled diagram, explain the reflex arc. Include the role of the spinal cord and why this mechanism is important for survival.** **Full Solution:** [Diagram expected: Touch (receptor) → Sensory neuron (carries impulse to spinal cord) → Relay neuron (in spinal cord) → Motor neuron (carries impulse to muscle) → Muscle contraction (effector/response)] The reflex arc is an involuntary, automatic response to a stimulus without conscious brain involvement. **Pathway:** When you touch a sharp object, pain receptors send signals via sensory (afferent) neurons to the spinal cord. The spinal cord contains relay neurons that immediately synapse with motor (efferent) neurons. Motor neurons carry the signal to arm muscles, causing instant withdrawal—all within ~50 milliseconds. **Role of spinal cord:** Acts as a reflex center; processes and relays impulses without waiting for brain approval. **Survival importance:** (1) Protects organs from immediate harm (hand from flame, eye from dust). (2) Faster than voluntary action—no time wasted. (3) Occurs even in unconscious states. Example: A person in coma pulls hand away from pain. This is an evolutionary adaptation ensuring survival despite cognitive delays. **Q2: Compare nervous and endocrine control systems. In what situations would each be more effective?** **Full Solution:** | **Aspect** | **Nervous System** | **Endocrine System** | |---|---|---| | **Transmission** | Electrical signals + neurotransmitters | Hormones via blood | | **Speed** | Very fast (milliseconds) | Slow (seconds to minutes) | | **Duration** | Short-lived (seconds to minutes) | Long-lasting (hours to months) | | **Reach** | Localized to specific neurons/organs | Widespread to all cells with receptors | | **Control** | Precise, conscious & involuntary | General, involuntary | **When nervous system is better:** (1) Sudden danger (fight-or-flight reflex). (2) Precise movements (typing, surgery). (3) Quick adjustments (balance, pupil dilation in darkness). (4) Coordinated sensory-motor responses (catching a falling object). **When endocrine system is better:** (1) Sustained changes (growth over years via growth hormone). (2) Metabolism regulation (thyroid hormone controls metabolic rate for months). (3) Reproductive cycles (menstrual cycle controlled by estrogen and progesterone over weeks). (4) Long-term stress response (cortisol maintains elevated blood glucose during prolonged hardship). In reality, both systems work together—the nervous system triggers endocrine release, and hormones modulate nerve sensitivity. **Q3: Explain the role of insulin and glucagon in maintaining blood glucose homeostasis. What happens when these hormones fail?** **Full Solution:** **Normal homeostasis:** Blood glucose should stay 80–120 mg/100 mL. - **After eating (high blood glucose):** Pancreatic beta cells (β-cells) detect glucose ↑ and secrete **insulin**. Insulin opens GLUT4 channels on muscle and fat cells, allowing glucose uptake. Excess is stored as glycogen in liver and muscle, or fat in adipose tissue. Blood glucose normalizes. - **During fasting (low blood glucose):** Pancreatic alpha cells (α-cells) detect glucose ↓ and secrete **glucagon**. Glucagon activates liver enzymes to break glycogen into glucose and release it into blood. Blood glucose rises back to normal. **Negative feedback:** Once glucose is controlled, insulin/glucagon secretion stops, preventing over-correction. **When these hormones fail:** 1. **Insulin deficiency (Type 1 diabetes):** Glucose cannot enter cells. Blood glucose rises dangerously (hyperglycemia, up to 300+ mg/100 mL). Muscles starve of energy; patient becomes weak, thirsty, urinates frequently. Excess glucose spills into urine. Ketones accumulate (diabetic ketoacidosis—life-threatening). 2. **Glucagon deficiency (rare):** During fasting, blood glucose drops too low (hypoglycemia). Brain cells (which need glucose) malfunction, causing confusion, seizures, coma, or death. 3. **Insulin resistance (Type 2 diabetes):** Cells ignore insulin signals. Glucose accumulates; pancreas overworks, eventually failing. **Treatment:** Type 1 requires insulin injections; Type 2 managed by diet, exercise, and medication. This illustrates how a single hormone imbalance threatens survival.

The 2024–25 rationalized CBSE Class 9 syllabus has refined emphasis on this chapter: **(1) Increased focus on diagrams and labeling:** Expect more 'Draw and label' questions for reflex arc, neuron, and endocrine glands. CBSE now explicitly rewards clarity—synapses, axon terminals, and hormone pathways must be accurately shown. **(2) Application-based scenarios:** Instead of 'Define hormone,' questions now ask: 'A student is scared before an exam. Which hormone is released? Trace its path and effects.' This tests conceptual understanding, not rote memory. **(3) Integration with other chapters:** Chapter 6 is increasingly linked to Chapter 5 (Photosynthesis—plant hormones in light-dependent movements) and Chapter 7 (Reproduction—role of FSH, LH). Multi-chapter PYQs are rising. **(4) Reduced theoretical jargon:** The term 'Neurotransmitter' is now expected to be explained functionally ('chemical messenger at synapses') rather than just named. Simpler, more direct language. **(5) Case studies on disorders:** Questions on diabetes, goiter (thyroid), and hormone imbalances are frequent. Students must connect hormone deficiency to symptoms and treatments. **(6) Shift from 'List' to 'Explain':** 'List three plant hormones' (pure recall) is less common. More: 'Explain how two plant hormones differ in function.' This demands deeper comprehension. **(7) 5-mark questions now emphasize comparison and mechanisms:** Full-mark answers require labeled diagrams + written explanation. Single-sentence answers score 1–2 marks max. **Preparation strategy:** Focus on understanding mechanisms (how reflex arc works, why insulin matters), not just definitions. Practice drawing and labeling repeatedly. Link concepts across chapters. This shift rewards mastery, not memorization.

When you sit down to answer Control and Coordination questions, follow this proven approach: **(1) For 1-mark questions (1–2 minutes each):** - Read the question twice to catch the exact keyword (e.g., 'does NOT involve' vs. 'involves'). - Eliminate two obviously wrong options before guessing if unsure. - Move on immediately; don't get stuck. One 1-mark is not worth 5 minutes. **(2) For 3-mark questions (5–6 minutes each):** - Use a **mini-outline** in the margin: write 'Point 1: ___, Point 2: ___, Point 3: ___' before writing full sentences. This prevents rambling. - Always include a **labeled example** (e.g., hand pulling from hot plate for reflex arc). - If asked to name hormones, list with ONE function each—don't over-explain. - Check: Did I answer *all* sub-parts? (Many 3-mark questions have 2–3 parts.) **(3) For 5-mark questions (8–10 minutes each):** - **Spend 1 minute sketching the diagram** (if needed). A rough but labeled diagram scores marks even if explanation is brief. - **Write 3–4 sentences per main point.** Depth beats length. - Use **comparison tables** for 'differ in' or 'compare' questions—they're faster and clearer than paragraphs. - **State the conclusion.** For example: 'Thus, reflex arcs are survival mechanisms because they bypass the brain.' **(4) Cross-check your answers:** - For 'Name the gland/hormone' questions, match gland ↔ hormone ↔ function (e.g., pancreas ↔ insulin ↔ lowers glucose). - For 'Explain' questions, reread your answer as if you're a student seeing it for the first time—does it make sense? **(5) Time management for the full exam:** - If the paper has 40 marks in 2 hours: 1-mark = 2 min, 3-mark = 6 min, 5-mark = 10 min (with 5-min buffer). - Chapter 6 is often 8–12 marks on a full Science paper. Allocate 15–18 minutes total. **(6) Common mistakes to avoid:** - **Confusing sensory and motor neurons:** Sensory = **afferent** (toward CNS); Motor = **efferent** (away from CNS). - **Mixing up hormones:** Insulin ≠ glucagon (opposite roles); Adrenaline ≠ thyroid hormone (different speeds). - **Incomplete reflex arc diagrams:** Always show receptor → sensory → spinal cord → motor → effector. - **Missing the 'why':** Don't just list; explain causation (e.g., 'Insulin is needed because cells can't take glucose without it'). Start your exam by reading all questions once, then tackle in this order: 1-mark (quick wins), then 3-mark, then 5-mark (hardest last). This builds momentum and prevents panic.

Owning 13 solved questions is step one. Using them *strategically* is step two. Here's a structured 2-week prep plan: **Week 1: Learn and Practice** - Day 1–2: Read Chapter 6 (NCERT) once, taking brief notes on nervous system and reflex arc. - Day 3: Read NCERT on plant hormones (auxin, gibberellins, abscisic acid) and animal hormones (insulin, adrenaline, thyroxine). - Day 4–5: Solve the 5 one-mark questions here. If you score <4/5, reread definitions in your textbook. - Day 6–7: Solve the 5 three-mark questions. Write full sentences; don't just bullet-point. Check your answers against the solutions provided. **Week 2: Mastery and Speed** - Day 8–9: Attempt the 3 five-mark questions without looking at solutions. Time yourself: 8 minutes per question. Compare with the full solutions here. - Day 10: Redo any question you scored <50% on. This time, use the solution as a guide but write your own explanation. - Day 11: **Mix-and-match:** Shuffle the 13 questions randomly. Solve 5–6 in one sitting (mixed marks), as if you're in a real exam. Time yourself strictly. - Day 12–13: Review mistakes. For each error, write the corrected answer once by hand (not typing—handwriting reinforces memory). **Ongoing (post-exam prep):** - Every week, revisit one set (e.g., 1-mark questions). Speed matters—aim to answer all 5 in under 5 minutes. - If your school releases new term exams, add those questions to your question bank and compare with our patterns. - Share confusing questions with peers or a tutor (like those at cbsetutor.ai) to unlock insights you might miss alone. **Pro tip:** Create a **Personal Error Log.** For each wrong answer, note (1) What I thought, (2) What the correct answer is, (3) Why I was wrong, (4) How I'll remember it next time. Review this log 2–3 days before your final exam.