Complete Solutions and Summary of How do Organisms Reproduce? – NCERT Class 10, Science, Chapter 7 – Summary, Questions, Answers, Extra Questions
Comprehensive summary and explanation of Chapter 7 'How do Organisms Reproduce?', covering importance of reproduction, DNA copying, types of reproduction (asexual and sexual), modes of asexual reproduction like fission, budding, vegetative propagation, spore formation, sexual reproduction in flowering plants and humans, reproductive health, puberty changes, contraception methods, and practical activities—paired with all question answers and extra questions from NCERT Class X Science.
Updated: 8 months ago
How do Organisms Reproduce?
Chapter 7: Science - Ultimate Study Guide | NCERT Class 10 Notes, Questions, Activities, Diagrams & Quiz 2025
Full Chapter Summary & Detailed Notes - How do Organisms Reproduce Class 10 NCERT
Overview & Key Concepts
- Chapter Goal: Understand reproduction mechanisms. Not vital for individual survival but for species continuity. Exam Focus: Modes, variations, diagrams, human system. 2025 Updates: Links to biotech, evolution. Fun Fact: Variations from DNA errors drive evolution. Diagrams: Fission, budding, human reproduction. Core Idea: Reproduction creates similar yet varied individuals for survival. Real-World: Biodiversity, family planning.
- Wider Scope: Evolution, health, ecology, population dynamics.
Introduction: Why Do Organisms Reproduce?
- Basic question: Reproduction isn't needed for individual life (unlike nutrition/respiration).
- Energy-intensive process; individual could save energy without it.
- Yet organisms reproduce to create more individuals, increasing species visibility.
- Similar appearance defines species; reproduction makes look-alikes.
7.1 Do Organisms Create Exact Copies of Themselves?
- Similar body designs from similar DNA blueprints.
- DNA in nucleus: Info for protein synthesis, body design.
- Basic event: DNA copy via chemical reactions; copies separate with cellular apparatus.
- Cells similar but not identical due to copying variations (no reaction 100% reliable).
- Drastic variations: Cell dies; mild: Subtle differences, basis for evolution.
7.1.1 The Importance of Variation
- Populations occupy niches; DNA consistency maintains design.
- Variations aid survival if niche alters (e.g., temperature rise, heat-resistant bacteria survive).
- Reproduction links to population stability.
Questions from Page 114
- 1. Importance of DNA copying: Creates body design blueprints.
- 2. Variation beneficial for species (survival in changes) but not necessarily individual.
7.2 Modes of Reproduction Used by Single Organisms
- Asexual: Single individual; modes depend on body design.
- Activity 7.1: Yeast in sugar solution; observe budding under microscope.
- Activity 7.2: Mould on bread; observe hyphae growth.
- Compare yeast (buds) and mould (hyphae).
7.2.1 Fission
- Unicellular: Cell division creates new individuals.
- Binary: Two cells (Amoeba any plane; Leishmania oriented to whip-structure).
- Multiple: Many cells (Plasmodium).
- Activity 7.3: Amoeba slides; compare normal/binary fission.
7.2.2 Fragmentation
- Simple multi-cellular: Breaks into pieces upon maturation (Spirogyra).
- Activity 7.4: Lake water filaments; observe Spirogyra tissues.
- Not for complex organisms (specialized tissues/organs).
7.2.3 Regeneration
- Fully differentiated: Grow from parts (Hydra, Planaria).
- Specialized cells proliferate, develop into tissues.
- Sequence: Development; not primary reproduction.
7.2.4 Budding
- Regenerative cells: Outgrowth at site (Hydra bud develops, detaches).
7.2.5 Vegetative Propagation
- Plant parts (root/stem/leaf) develop new plants (sugarcane, roses).
- Activity 7.5: Potato notches/buds; buds give shoots/roots.
- Activity 7.6: Money-plant cuttings; leaves grow new.
- Advantages: Faster flowering/fruits, propagate seedless (banana/orange), genetic similarity.
- Tissue Culture: Cells in medium form callus, differentiate to plantlets (disease-free ornamentals).
7.2.6 Spore Formation
- Simple multi-cellular: Specific parts (Rhizopus hyphae non-reproductive; sporangia with spores).
- Spores: Thick walls, grow on moist surface.
Questions from Page 119
- 1. Binary vs multiple fission: Two vs many cells.
- 2. Spores benefit: Protected till favourable conditions.
- 3. Complex organisms no regeneration: Specialized tissues.
- 4. Vegetative for some plants: Faster, seedless.
- 5. DNA copying essential: Basic event for blueprints.
7.3 Sexual Reproduction
- Two individuals needed (males/females for calves/chicks).
- Significance: Overcomes asexual limitations (slow variations).
7.3.1 Why the Sexual Mode of Reproduction?
- DNA copying: Variations source, protect species.
- Mechanisms not 100% accurate; sexual combines from two for novel variants.
- Problem: Double DNA; solved by meiosis (half in germ-cells).
- Gametes: Similar/simple organisms; specialized complex (male motile, female stored).
7.3.2 Sexual Reproduction in Flowering Plants
- Parts: Sepals/petals/stamens/pistil (reproductive).
- Unisexual (papaya) vs bisexual (Hibiscus).
- Stamen: Pollen grains.
- Pistil: Ovary (ovules/egg), style, stigma (sticky).
- Fertilisation: Pollen fuses egg → zygote → embryo/seed/fruit.
- Pollination: Self (same flower), cross (another); agents wind/water/animals.
- Pollen tube grows to ovary.
- Activity 7.7: Soak gram seeds; observe parts/germination.
7.3.3 Reproduction in Human Beings
- Sexual mode; changes from childhood.
- Growth: Height/teeth increase.
- Puberty: Body proportions change, new features (hair, oily skin, pimples).
- Boys: Facial hair, voice crack, erections.
- Girls: Breast increase, nipple darken, menstruation.
- Changes gradual, vary by person; signals maturity.
- Maturation during adolescence as body growth slows.
- Germ-cells join: External (plants) or internal (animals).
7.3.3 (a) Male Reproductive System
- Testes (scrotum, lower temp): Sperms, testosterone (puberty changes).
- Vas deferens + urethra; prostate/seminal vesicles add fluid (transport/nutrition).
- Sperms: Genetic material + tail.
7.3.3 (b) Female Reproductive System
- Ovaries: Eggs, hormones.
- Oviduct/fallopian tube to uterus (cervix to vagina).
- Fertilisation in oviduct; embryo implants in uterus (thick lining, blood-rich).
- Placenta: Nutrition/oxygen from mother, waste removal; villi increase area.
- 9 months development; birth via uterine contractions.
7.3.3 (c) What Happens When the Egg is Not Fertilised?
- Egg lives 1 day; uterus prepares monthly (thick/spongy lining).
- No fertilisation: Lining breaks, exits as blood/mucous (menstruation, 2-8 days).
7.3.3 (d) Reproductive Health
- Maturation gradual; body/mind may not ready for sex/children.
- Pressures: Friends/family/government.
- STDs: Gonorrhoea/syphilis/warts/HIV; condom prevents some.
- Pregnancy demands; contraception: Barrier (condom), hormonal (pills, side-effects), IUD (loop), surgical (vasectomy/tubectomy, infections).
- Unwanted pregnancies: Surgery misused for female foeticide (illegal, declines sex ratio).
- Population: Birth/death rates; size concerns for living standards, but inequality main issue.
What You Have Learnt (Page 126)
- Reproduction not essential individual; DNA copy + apparatus.
- Asexual modes: Fission/regeneration/budding/vegetative/spore.
- Sexual: Two individuals, variations for survival.
- Plants: Pollination/fertilisation.
- Puberty changes; male/female systems.
- Fertilisation in fallopian; contraception methods.
Questions from Page 126
- 1. Pollination vs fertilisation: Pollen transfer vs gamete fusion.
- 2. Seminal vesicles/prostate: Fluid for sperm.
- 3. Girls puberty: Breasts/menstruation.
- 4. Embryo nourishment: Placenta.
- 5. Copper-T for STDs: No.
Exercises (Page 127)
- 1. Asexual budding: (b) Yeast.
- 2. Not female part: (c) Vas deferens.
- 3. Anther: (d) Pollen grains.
- 4. Sexual advantages: Variations, survival.
- 5. Testis functions: Sperms/testosterone.
- 6. Menstruation: No fertilisation.
- 7. Labelled flower: Diagram parts.
- 8. Contraception methods: Condom/pills/IUD/surgery.
- 9. Unicellular/multicellular modes: Simple/complex.
- 10. Reproduction stability: Variations.
- 11. Contraceptive reasons: Health/population/STDs.
Why This Guide Stands Out
Complete chapter coverage: Notes, diagrams, activities, Q&A (all NCERT + extras), quiz. Student-centric, exam-ready for 2025. Free & ad-free.
Key Themes & Tips
- Asexual: Quick, identical, no variation.
- Sexual: Variations, survival advantage.
- Human: Puberty, systems, health.
- Tip: Draw diagrams for 5+ marks; link variations to evolution.
Exam Case Studies
Variation in bacteria; human fertilisation process; activity conclusions.
Project & Group Ideas
- Model asexual modes; simulate pollination; discuss reproductive health.
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