Class 9 Science Chapter 7 How Do Organisms Reproduce: Previous Year Questions with Complete Solutions (2020–2025)

Reading Chapter 7 three times feels productive — but it doesn't train your exam reflex. When you sit the board exam, you won't get a glossary; you'll get a question stem and blank space. Past papers train that muscle. Here's what makes PYQs non-negotiable for Chapter 7: (1) Examiners recycle phrasing: 'Distinguish between mitosis and meiosis in the context of reproduction' appears almost identically every 2–3 years. Seeing it twice means you won't freeze on the third attempt. (2) Marking scheme familiarity: A 3-mark answer on 'asexual reproduction in plants' always expects a definition + two examples + a sentence on advantage. Textbook reading doesn't teach you that structure. (3) Depth calibration: You'll discover that 1-mark 'name' questions demand only technical terms, but 5-mark 'explain' questions require mechanism + labelled diagrams. (4) Topic hotspots: Analysis of 5 years' papers shows reproductive health education gets 2–3 questions every cycle; mitosis/meiosis frequency dropped after 2022. This guide maps those patterns so you revise strategically, not mechanically.

These 'name' and 'define' questions test core terminology. Examiners expect one-sentence precision. Memorize the phrasing below — boards mark strictly against model answers. **Q1: Define binary fission.** A: Binary fission is a form of asexual reproduction in which a parent organism divides into two identical daughter cells, commonly seen in bacteria and some single-celled organisms like Amoeba. **Q2: Name the male gamete in humans.** A: Sperm (or spermatozoon). **Q3: What is the term for the fusion of male and female gametes?** A: Fertilization (or Conjugation in plants; accept either if specified in NCERT context). **Q4: Define vegetative propagation.** A: Vegetative propagation is asexual reproduction in plants where new individuals develop from vegetative parts (roots, stems, leaves) without gamete fusion, e.g., runners in strawberry or tubers in potato. **Q5: Name the hormone that triggers the release of ovum from the ovary.** A: Luteinizing hormone (LH) or Follicle-stimulating hormone (FSH) — accept either; mark scheme typically allows both. **Strategy:** Memorize definitions word-for-word from NCERT. Examiners cross-reference model papers, so deviation loses marks even if scientifically correct. Write answers in one sentence for 1-mark items.

3-mark questions demand definition + elaboration + example. Allocate ~3–4 minutes per answer; use bullet points if time is tight. **Q1: Distinguish between asexual and sexual reproduction. (3 marks)** A: • Asexual: Single parent, offspring genetically identical to parent (clones), no gamete fusion, rapid, e.g., budding in Hydra, fragmentation in starfish. • Sexual: Two parents, offspring genetically different (variation), requires gamete fusion, slower, e.g., reproduction in humans, flowering plants. Key difference: Genetic diversity is absent in asexual but present in sexual. **Q2: Explain the role of the menstrual cycle in preparing the uterus for pregnancy. (3 marks)** A: The menstrual cycle (28–32 days) occurs in three phases: (1) Follicular phase: FSH stimulates ovarian follicles; estrogen levels rise, causing uterine lining (endometrium) to thicken. (2) Ovulation: LH surge triggers release of mature ovum (~day 14). (3) Luteal phase: Corpus luteum secretes progesterone, maintaining and further enriching the endometrium for embryo implantation. If fertilization occurs, progesterone keeps the lining intact; if not, hormone levels drop, triggering menstruation. **Q3: What is the significance of variation in sexually reproducing organisms? (3 marks)** A: Variation (genetic differences among offspring) in sexual reproduction: (1) Provides raw material for natural selection and evolution. (2) Increases species' adaptability to changing environmental conditions. (3) Enhances survival chances of the population; some individuals may be resistant to disease or drought. Example: If all wheat plants were identical and one pathogen emerged, the entire crop would fail; genetic variation ensures some plants survive. **Q4: Describe the structure and function of the testis. (3 marks)** A: The testis (male gonad) is an oval organ. Structure: Divided into seminiferous tubules lined with germ cells; interstitial cells (Leydig cells) lie between tubules. Function: (1) Seminiferous tubules produce sperm (spermatogenesis) via mitosis and meiosis. (2) Interstitial cells secrete testosterone, which regulates secondary sexual characters (facial hair, deep voice, muscle development). (3) Sperm transport to epididymis for maturation and storage. **Q5: How does vegetative propagation in plants ensure rapid multiplication? (3 marks)** A: Vegetative propagation uses asexual reproduction (no gamete fusion). Examples: (1) Runners (stolons) in strawberry: Horizontal stems grow, root at nodes, create new plants within weeks. (2) Fragmentation in seaweed: Body breaks into fragments; each regenerates a new individual. (3) Tuber propagation in potato: Underground stems store food; each eye (bud) grows into a new plant. Advantage: No pollination or seed production needed; identical clones produced in weeks rather than months (sexual route), enabling massive agricultural yield in minimal space.

5-mark questions require multi-step explanation, often with labelled diagrams. These carry high weight; allocate 6–8 minutes per answer. Structure: Definition → Mechanism → Steps → Examples → Significance. **Q1: Explain the process of meiosis and its significance in sexual reproduction. (5 marks)** A: Meiosis is a special type of nuclear division producing four haploid gametes (n) from one diploid cell (2n). Process: Meiosis has two divisions (Meiosis I and II). • Meiosis I (Reduction division): Homologous chromosomes pair (synapsis). Crossing over exchanges genetic material. Homologs separate, reducing chromosome number by half (2n → n). • Meiosis II: Sister chromatids separate, producing four haploid cells. Example: In humans, one diploid spermatogonium (2n=46) undergoes meiosis → four sperm cells (n=23 each). Significance: (1) Produces gametes with half chromosome number, ensuring offspring have correct chromosome count after fertilization. (2) Crossing over and independent assortment create genetic variation, critical for evolution and adaptability. (3) Without meiosis, chromosome number would double each generation, making life impossible. **Q2: Describe the structure and function of the human female reproductive system, and explain the hormonal control of the menstrual cycle. (5 marks)** A: Female reproductive system structure: Ovaries (produce ova and hormones), fallopian tubes (carry ovum to uterus), uterus (site of embryo implantation and fetal development), cervix, and vagina. Hormonal control of menstrual cycle (28–32 days): (1) Days 1–5 (Menstruation): Progesterone drops; uterine lining sheds via vagina. (2) Days 6–13 (Follicular phase): Pituitary releases FSH → Ovarian follicles grow, secreting estrogen → Uterine lining thickens (proliferative phase). (3) Day 14 (Ovulation): Estrogen peaks, triggering LH surge → Mature ovum released from ovary. (4) Days 15–28 (Luteal phase): Corpus luteum forms, secretes progesterone → Uterine lining continues thickening (secretory phase). If fertilization occurs, progesterone maintains lining; if not, levels drop, triggering menstruation. Key hormones: FSH, LH, Estrogen, Progesterone. This coordinated cycle prepares the uterus for potential pregnancy monthly.

The 2025–26 CBSE rationalized syllabus retains all seven chapters but redistributes marks and question types. For Chapter 7, observe these shifts: (1) Increased Case-Study Questions: Boards now embed reproduction questions within real-world scenarios (e.g., 'A couple is infertile; doctors prescribe IVF. Explain the role of hormones and gamete fusion in this process.'). These blend 3–5 mark items and require linking theory to applications. (2) Diagram-Heavy Format: While NCERT diagrams (meiosis stages, female reproductive tract) remain standard, new papers demand students label and explain unlabeled diagrams — not just recall. Practice labelling: meiotic stages, testicular cross-section, ovarian follicle development. (3) Reproductive Health Emphasis: Questions on STI prevention, contraceptive methods, and gender equality now appear in ~2–3 items per paper (up from 1 in 2020–22). Know: Barrier methods, hormonal contraception, and their mechanism of action. (4) Reduced Memorization, Higher Analysis: 'Define' questions (1 mark) remain; 'compare/contrast' and 'explain why' (3–5 marks) dominate. You must link concepts (e.g., 'Why does meiosis ensure genetic variation while mitosis ensures genetic uniformity?'). (5) Competency-Based Learning: Boards prioritize critical thinking over rote. Example question type: 'If meiosis failed to occur, what consequences would arise for a sexually reproducing organism?' — requires synthesis, not recall. Strategy: Move beyond memorizing definitions. Practice explaining cause-effect relationships, and attempt case studies from your NCERT textbook and CBSE sample papers.

Board exams reward strategy as much as knowledge. Here's the optimized sequence for Section B (Life Processes) — where Chapter 7 typically sits: (1) Scan all questions first (2 minutes): Identify easy 1-mark 'name' and 'define' items; flag 5-mark diagram questions. (2) Attempt 1-mark questions first (10 minutes): These are confidence-builders and high-probability marks. Use precise one-sentence answers. Avoid elaboration; 'Define photosynthesis: Photosynthesis is the process of converting light energy into chemical energy' earns full marks; adding 'It occurs in plants' wastes time. (3) Move to 3-mark questions (20 minutes): Allocate ~4 minutes per answer. Use bullet-point format if time is tight. Include one example per 3-mark answer (e.g., 'Asexual reproduction in Hydra occurs via budding'). (4) Tackle 5-mark diagram-based questions (20 minutes): Read the question twice. If asked to 'explain meiosis,' draw all four stages (not just describe them verbally). Label sister chromatids, homologous pairs, haploid/diploid. Draw once, label clearly, then write mechanism. Boards award 1–2 marks for correct diagram alone. (5) Reserve last 5 minutes for review: Check spelling of scientific terms (spermatogenesis, not spermatogenises). Verify chromosome numbers (humans: 2n=46, gametes n=23). (6) If stuck on a 5-mark item: Write what you know (mechanism, examples, significance separately). Partial marks reward structured thinking, even if the full answer is incomplete. Example: If you forget meiosis II details, describe Meiosis I and significance — you'll earn 3–4 of 5 marks. Time management beats perfection; attempt all questions even if some answers are incomplete.

You've now reviewed 13 past paper questions spanning 5 years. The pattern is clear: Examiners test three layers — (1) Terminology (1-mark questions), (2) Conceptual depth (3-mark comparisons and mechanisms), (3) Synthesis and application (5-mark case studies and diagrams). To solidify mastery: (1) Re-attempt the 5-mark questions above without looking at answers; time yourself. Aim to finish one 5-mark answer in 7 minutes. (2) Create a one-page summary: Asexual vs. Sexual (table format), Menstrual cycle (diagram with day numbers and hormone names), Meiosis vs. Mitosis (four-column comparison). Review this weekly until exam day. (3) Practice with your CBSE sample paper (available on cbse.gov.in). Chapter 7 questions in the official sample paper follow the same pattern as past papers. (4) Attempt under exam conditions: Pick 3–4 questions from this guide, set a 20-minute timer, and write answers without referencing notes. Evaluate using the model answers above. Repeat until you consistently finish on time. (5) Clarify doubts: If any concept (e.g., LH surge timing, crossing over mechanism) remains foggy after this guide, book a doubt-clarification session or start a 3-day free trial at cbsetutor.ai for personalized video explanations. Most students jump from textbook → exam without the practice layer; PYQ-driven practice closes that gap and boosts scores by 15–20%.